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PHYS THER
Vol. 88, No. 5, May 2008, pp. 567-579
DOI: 10.2522/ptj.20070045

This Article Abstract Full Text (PDF) The Bottom Line Correction (v88,p797) All Versions of this Article: ptj.20070045v1 88/5/567    most recent Submit a response Alert me when this article is cited Alert me when Rapid Responses are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Farquhar, S. J Articles by Snyder-Mackler, L. Search for Related Content PubMed PubMed Citation Articles by Farquhar, S. J Articles by Snyder-Mackler, L. Related Collections Kinesiology/Biomechanics Injuries and Conditions: Knee Social Bookmarking                      What's this?

Research Reports

Persistence of Altered Movement Patterns During a Sit-to-Stand Task 1 Year Following Unilateral Total Knee Arthroplasty

Sara J Farquhar, Darcy S Reisman and Lynn Snyder-Mackler

SJ Farquhar, PT, MPT, is a doctoral student in the Graduate Program in Biomechanics and Movement Science and the Department of Physical Therapy, University of Delaware.
DS Reisman, PT, PhD, is Assistant Professor, Department of Physical Therapy, University of Delaware.
L Snyder-Mackler, PT, ScD, SCS, ATC, FAPTA, is Professor, Department of Physical Therapy, 301 McKinly Laboratory, University of Delaware, Newark, DE 19716 (USA).

Address all correspondence to Dr Snyder-Mackler at: smack{at}udel.edu

Submitted February 5, 2007; Accepted December 28, 2007

 
Background and Purpose: Following total knee arthroplasty (TKA), quadriceps femoris muscle strength (force-generating capacity) and functional test scores improve but continue to be lower than those in people without injury. Analysis of the sit-to-stand (STS) task demonstrated side-to-side differences in subjects with TKA, as well as differences between subjects with TKA and control subjects. It was hypothesized that, when using a self-selected starting position, subjects 1 year following TKA would show improvements in strength and movement patterns but would continue to show asymmetries of angles and moments at the hips and knees.

Subjects and Methods: Twenty-four subjects (12 subjects with unilateral TKA and 12 control subjects) were recruited; those with TKA were tested 3 months and 1 year following surgery. Motion analysis of an STS task was synchronized with 2 force platforms and electromyography. Outcome measures included joint angles and moments, electromyography, vertical ground reaction forces, muscle strength, and functional performance tests.

Results: Subjects with TKA showed improvements in symmetry of motion, strength, and functional performance from 3 months to 1 year following TKA. Compared with control subjects, subjects with TKA relied on increased hip flexion and a larger hip extensor moment to perform the STS task.

Discussion and Conclusion: The increased hip extensor moment demonstrated that subjects adopted a strategy to avoid the use of the quadriceps femoris muscle, yet this strategy persisted as quadriceps femoris muscle strength improved. This pattern may be a learned movement pattern that may not resolve without retraining.

Top Abstract Introduction Method Results Discussion Conclusion References

 
The joint most commonly affected by osteoarthritis (OA) is the knee.^1,2 Total knee arthroplasty (TKA) often is performed to relieve the pain of end-stage knee OA following the failure of nonsurgical management. Over time, most subjects with TKA continue to report functional improvements,^3,4 pain reduction,^3,5,6 and satisfaction with outcomes.⁷ However, subjects with TKA continue to have lower scores than age-matched control subjects without arthritis on functional tests such as the Timed "Up & Go" (TUG) Test, the Stair-Climbing Test (SCT), and the 6-Minute Walk Test (6MWT).^4,8 The strength (force-generating capacity) of the quadriceps femoris muscle has been shown to correlate with results on the 6MWT and the SCT.⁹

Quadriceps femoris muscle weakness in the surgically treated (involved) limb has been reported to persist for 1 year⁴ and for up to 3 years¹⁰ following TKA. At 3 months following TKA, quadriceps femoris muscle strength correlates with both functional performance^9,11 and the symmetry of walking and the sit-to-stand (STS) movement.¹¹ Cross-sectional motion analysis of the STS task demonstrated differences between involved and uninvolved limbs (differences between the sides in subjects with TKA) as well as between control subjects and subjects 3 months,¹¹ 1 year,¹² and up to 6 years¹³ following TKA. Specifically, the hip and knee contralateral to the TKA were shown to bear more load, demonstrating higher extensor moments^11,13 and ground reaction forces.^11,13 Compensation patterns adopted in an effort to avoid pain may lead to altered loading patterns that may place additional stresses on the uninvolved limb¹¹; these patterns may have the long-term consequence of advancing OA in the hip or knee contralateral to the TKA.^14–16

Investigations that test subjects longitudinally often report the results of questionnaires¹⁷ or functional tests or strength.^18,19 Investigations of kinematics have included subjects over a range of years following TKA,¹³ have reported on a mixture of subjects with unilateral and bilateral TKA,^4,13 or have reported differences only at the knee.¹² Although these reports are valuable, they do not provide information about longitudinal changes in movement patterns over discrete time intervals. Thus, little is known about changes in STS task performance over time in subjects following TKA.

Changes in patterns may play a role in the noncognate progression of OA in other joints of the lower extremities.¹⁶ Assessment of subjects at discrete intervals may provide insight into how these movement patterns change over time. Previously, differences between the sides during an STS task were reported in subjects 3 months following TKA¹¹ when the subjects’ knee angle was constrained at 90 degrees of flexion during sitting. Differences in kinematics and kinetics when subjects with TKA are allowed to self-select their starting position are unknown.

Therefore, the purpose of this study was to investigate changes in STS task performance in subjects 3 months and 1 year following TKA and differences between these subjects and control subjects who were healthy. We hypothesized that if subjects 3 months after TKA self-selected their starting position, there would be asymmetries in the motions and moments of the hips and knees relative to the motions and moments in matched control subjects. We hypothesized that quadriceps femoris muscle strength and function would show improvements 1 year after TKA and that strength, function, and movement patterns would be more similar to those of control subjects.

Top Abstract Introduction Method Results Discussion Conclusion References

 
Subjects

Fourteen subjects with unilateral TKA (6 women and 8 men) were recruited in the Wilmington, Del, area from among the patients of a group of orthopedic surgeons who perform tricompartmental, cemented TKA with a medial parapatellar surgical approach, with the proximal incision extending into the quadriceps tendon. Following TKA, all subjects with TKA participated in 6 weeks (3 times per week, for a mean of 17 visits) of rehabilitation. Outpatient physical therapy at the University of Delaware Physical Therapy Clinic included interventions to control pain and swelling and increase range of motion, with an emphasis on quadriceps femoris muscle strengthening, as previously described.²⁰

Subjects participated in functional and strength testing and motion analysis 3 months following surgery and again 1 year following surgery. Twelve of the 14 subjects returned for testing 1 year following surgery; both subjects who did not return were scheduled for TKA on the contralateral knee. Only data for the 12 subjects (6 women and 6 men) who returned for motion analysis and functional and strength testing at 1 year were used in the analyses. All results for subjects 3 months and 1 year following TKA were compared with the results for control subjects. Twelve subjects without injury (5 women and 7 men) were matched by age (±5 years), height (±5%), and body mass index (±5%) to subjects 1 year following TKA (Tab. 1). Subjects with TKA also were matched to control subjects by limb; for example, a subject with a right TKA had a matched control subject with the right limb designated as the so-called involved limb.

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Table 1. Demographic Data for Subjects With Total Knee Arthroplasty (TKA) and Control Subjects

Subjects were excluded if they had evidence of musculoskeletal impairments that limit function (low back pain or hip, knee, or ankle pain scored as greater than 4 out of 10 on a verbal analog scale or surgery in a lower-extremity joint other than the TKA), with the exception of the unilateral TKA in subjects with TKA. Subjects also were excluded if they had a body mass index (weight [in kilograms]/height [in meters squared]) of greater than 40 kg/m² (morbidly obese), uncontrolled blood pressure, diabetes mellitus, neoplasms, neurological disorders (Parkinson disease, impaired sensation, stroke, or head injury), or a flexion contracture in either leg of greater than 5 degrees or if they were unable to rise from a chair without the use of their arms. All subjects completed self-assessment questionnaires and quadriceps muscle strength and functional testing on a separate day from motion analysis testing. All subjects gave written informed consent.

Motion Analysis

Subjects sat on an armless, backless chair, with the chair height set to the knee joint line. No restrictions were placed on the position of the lower extremities, and subjects rose from the chair at a self-selected pace. Subjects were asked to hold the arms across the chest or in the lap and were instructed not to use the arms to assist with rising from the chair.

Motion analysis of the STS task was performed by use of a 3-dimensional, 6-camera motion analysis system (VICON Peak).^* Two forceplates positioned in the floor captured the ground reaction forces under each leg during the STS task. Analog data (forceplate data and electromyography [EMG]) were sampled at 1,080 Hz, and video data were sampled at 120 Hz. Retroreflective markers were placed bilaterally on the heads of the fifth metatarsals, lateral malleoli, lateral femoral condyles, greater trochanters, and iliac crests; 2 markers were placed on the heel counter of each shoe. Rigid thermoplastic shells, each with 4 retroreflective markers glued on, were affixed bilaterally to the lower leg and thigh and over the sacrum by use of elastic wraps (SuperWrap) or double-sided tape to minimize movement artifacts.

Lower-extremity joint kinetics and kinematics were time normalized to 100% of the STS task, as defined from the start to the end of standing. The start of standing and the end of standing are both determined by the angular velocity of the pelvic marker. When the angular velocity moves above zero, the start of standing has begun, and when it returns to zero, the end of standing has been reached. This method was chosen to eliminate reliance on a variable associated with one of the limbs because of the evidence of asymmetry in subjects with TKA. "Seat-off," the instant at which the buttocks leave the seat, was operationally defined as the time of the peak vertical ground reaction force²¹ (Fig. 1).

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Figure 1. (Top) Schematic of the sit-to-stand (STS) task. The individual starts in a seated position (A) and flexes forward at the hips, bringing the body forward, and the buttocks leave the chair (seat-off) (B). The individual begins to stand (C) by extending at the hip and knee and stops when reaching a complete standing position (D). The shaded area represents the ranges for the instant of seat-off. (Middle) Hip flexion angle normalized to 100% of the STS task. Hip flexion increases as the individual begins to stand (B), and then the hips start extending as the individual reaches a standing position (C and D). (Bottom) Vertical ground reaction force (Fz) normalized to 100% of the STS task. The force increases as the individual puts weight through each limb. The Fz peaks at seat-off and then declines as the individual stabilizes the weight between the limbs. Symbols: black line=control limb, solid blue line=involved limb of subjects 1 year following total knee arthroplasty (TKA), dashed blue line=uninvolved limb of subjects 1 year following TKA. Abbreviations: 1YR=1 year following TKA, CTRL=control, CTRL-INV=control limb that was matched to the limb that underwent TKA, HA=hip angle, NON=noninvolved (not surgically treated) limb, OP=involved (surgically treated) limb.

Marker trajectories were filtered with a low-pass filter at 6 Hz, and forceplate data were filtered with a low-pass filter at 40 Hz.²² Forceplate data were normalized to body mass. Sagittal-plane hip, knee, and ankle joint angles were calculated by use of rigid body analysis and Euler angles²³; joint moments were calculated by use of inverse dynamics²³ and were expressed as net internal moments normalized to body mass and height (Visual3D, version 3.77). Customized software (Labview 8)^|| identified flexion and extension, peak internal extensor and flexor moments, and vertical ground reaction forces. Peak data points used for analyses were chosen to coincide with seat-off.

EMG

Electromyographic activity was recorded with a 16-channel system^# interfaced with the VICON system for simultaneous recording. Active surface electrodes (1.2 cm in diameter, interelectrode distance of 1.8 cm) were taped over the mid-muscle belly of the vastus lateralis and the biceps femoris muscles. Elastic bands were wrapped over the electrodes to minimize movement. The subject was positioned on a padded plinth in order to isometrically test each muscle for the verification of electrode placement and to record resting baseline and maximum signals.

The raw EMG data were filtered by use of customized software (Labview 8) that filtered the signals with a 350-Hz low-pass Butterworth filter. Following full-wave rectification, a linear envelope of the signal was created by use of a phase-corrected 20-Hz low-pass Butterworth filter. This linear envelope was normalized to the maximum signal obtained during either the maximal voluntary isometric contraction (MVIC) trial or the dynamic trial. The maximum EMG signal used for normalization was the average of the peak value plus the values at 25 frames before and after the peak value (total of 51 frames) to allow for an accurate representation of the signal. All subsequent EMG data were normalized against this maximum value. Electromyographic data collected during the STS task were analyzed to identify the peak level of muscle activation.

Quadriceps Muscle Strength Measurement

The MVIC of the quadriceps femoris muscle was assessed isometrically.^24–27 In brief, subjects were seated in an electromechanical dynamometer (Kin-Com 500H)^** with the knee flexed to 75 degrees. Subjects performed 2 submaximal contractions and 1 MVIC lasting 2 to 3 seconds each to become familiar with the testing procedure and to warm up the muscle.

After 5 minutes of rest, subjects were instructed to contract the quadriceps femoris muscle maximally for approximately 3 seconds. Verbal encouragement and visual output of their force were used to motivate the subjects to produce an MVIC. The MVIC force was measured and recorded by use of customized software (Labview 4.0.1 and 5.0).^|| A maximum of 3 trials were performed on each leg. The highest volitional force achieved was used for analysis. In subjects with TKA, the uninvolved limb was tested before the involved limb.

Functional Testing

Measures of functional performance included the TUG Test, the SCT, and the 6MWT. The TUG Test measures the time it takes a subject to rise from an armchair (seat height of 46 cm), walk 3 m, turn around, and return to sitting in the same chair.²⁸ The SCT measures the time it takes a subject to ascend and descend a flight of twelve 7-in-high steps; use of one handrail is permitted. The stair-climbing task was found to be sensitive to change with physical activity interventions in people with knee OA.²⁹ One practice test was performed, and the average of 2 tests was used for analysis with both the TUG Test and the SCT.

The 6MWT is a self-paced functional test used to provide an assessment of the extent to which impairments affect mobility. The 6MWT measures the distance a person can walk in 6 minutes. It is a highly reliable measure in healthy, older adult populations (r=.95)³⁰ and is considered to be one of the most responsive measures of function following TKA.^3,31 For all tests, subjects were instructed to walk as quickly and as safely as they were able.

Data Analysis

Joint angles, joint moments, vertical ground reaction forces, and peak magnitudes of muscle activity were analyzed by use of an analysis of variance (ANOVA) with 2 repeated measures comparing subjects with TKA at 3 months and 1 year following surgery (time) and involved versus uninvolved limbs (limb). If an interaction effect was present, then main effects were not investigated. Paired t tests were performed as post hoc tests. Comparisons of control subjects with those with TKA were performed by use of an ANOVA (limb x group) at both 3 months and 1 year following TKA. Independent t tests were used for post hoc comparisons if significant main effects or an interaction was present. The results of the ANOVAs are reported in Tables 2, 3, and 4. The results of the post hoc tests are reported in Figures 2, 3, 4, 5, 6, and 7.

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Table 2. Results of Kinematic and Kinetic Analysesa

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Table 3. Results of Electromyographya

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Table 4. Results of Quadriceps Femoris Muscle Strength Analysisa

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Figure 2. (Top) Post hoc differences in the peak hip flexion angle. There were no differences over time or between limbs (P>.05) in subjects 3 months and 1 year following total knee arthroplasty (TKA). Compared with control subjects, subjects 3 months following TKA had greater flexion (involved limb, P=.01; uninvolved limb, P<.001), which persisted 1 year following TKA (involved limb, P=.025; uninvolved limb, P=.003). (Bottom) Post hoc differences in the peak hip internal extensor moment. Subjects with TKA had a higher moment at 1 year than at 3 months in the involved limb (P=.044) but not the uninvolved limb (P=.281). Compared with control subjects, subjects 3 months following TKA had a higher hip extensor moment (involved limb, P=.002; uninvolved limb, P<.001), which persisted 1 year following TKA (involved limb, P<.001; uninvolved limb, P<.001). Abbreviations: 3 mo=3 months following TKA, 1 y=1 year following TKA, NON=noninvolved (not surgically treated) limb, OP=involved (surgically treated) limb.

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Figure 3. (Top) Post hoc differences in the peak knee flexion angle. There were no differences between subjects 3 months following total knee arthroplasty (TKA) and control subjects (P>.05). (Bottom) Post hoc differences in the peak knee internal extensor moment. At 3 months following TKA, the moment was higher in the uninvolved limb (P=.001) than in the involved limb. By 1 year, there were no differences between the sides (P=.342). At 3 months following TKA, the moment in the involved limb was lower than that in control subjects (P=.006), whereas the uninvolved limb showed no difference (P=.271). By 1 year following TKA, there were no differences (involved limb, P=.161; uninvolved limb, P=.294). Abbreviations: 3 mo=3 months following TKA, 1 y=1 year following TKA, NON=noninvolved (not surgically treated) limb, OP=involved (surgically treated) limb.

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Figure 4. Post hoc differences in the peak magnitude of the vastus lateralis muscle. At 3 months following total knee arthroplasty (TKA), values in the involved limb were lower than those in the uninvolved limb (P<.001). By 1 year, the involved limb showed improvement (P<.069), resulting in no differences between the sides (P=.34). Compared with control subjects, subjects 3 months following TKA had lower values in the involved limb (P=.012) and higher values in the uninvolved limb (P=.011). At 1 year following TKA, there were no differences (involved limb, P=.52; uninvolved limb, P=.914). Abbreviations: 3 mo=3 months following TKA, 1 y=1 year following TKA, NON=noninvolved (not surgically treated) limb, OP=involved (surgically treated) limb, EMG=electromyography.

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Figure 5. Post hoc differences in the peak magnitude of the biceps femoris muscle. At 3 months following total knee arthroplasty (TKA), values in the uninvolved limb were higher than those in the involved limb (P=.015). By 1 year, values in the uninvolved limb decreased (P=.084), resulting in no differences between the sides (P=.253). Compared with control subjects, subjects 3 months following TKA had higher values in the uninvolved limb (P=.070), and there were no differences in the involved limb (P=.945). At 1 year following TKA, there were no differences (involved limb, P=.783; uninvolved limb, P=.74). Abbreviations: 3 mo=3 months following TKA, 1 y=1 year following TKA, NON=noninvolved (not surgically treated) limb, OP=involved (surgically treated) limb, EMG=electromyography.

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Figure 6. Post hoc results for normalized vertical ground reaction forces (Fz). At 3 months following total knee arthroplasty (TKA), Fz for the involved limb were lower than Fz for the uninvolved limb (P=.001). By 1 year, Fz for the involved limb increased (P<.01), resulting in no differences between sides (P=.072). Compared with control subjects, subjects 3 months following TKA had higher Fz for the uninvolved limb (P=.001). At 1 year following TKA, there were no differences (involved limb, P=.77; uninvolved limb, P=.068). Abbreviations: 3 mo=3 months following TKA, 1 y=1 year following TKA, NON=noninvolved (not surgically treated) limb, OP=involved (surgically treated) limb.

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Figure 7. Post hoc results for normalized quadriceps femoris muscle strength. At 3 months following total knee arthroplasty (TKA), the muscle in the involved limb was weaker than that in the uninvolved limb (P=.001). By 1 year, strength in the involved limb improved (P=.016), but this limb continued to be weaker than the uninvolved limb (P=.015). Compared with control subjects, subjects 3 months following TKA had a weaker muscle in the involved limb (P=.001) but not in the uninvolved limb (P=.092). At 1 year following TKA, there were no differences (involved limb, P=.096; uninvolved limb, P=.408). Abbreviations: 3 mo=3 months following TKA, 1 y=1 year following TKA, NON=noninvolved (not surgically treated) limb, OP=involved (surgically treated) limb, BMI=body mass index, MVC=maximal voluntary contraction.

Functional test scores at 3 months and 1 year were compared by use of paired t tests; functional test scores for control subjects and subjects with TKA at 3 months and 1 year were compared by use of independent t tests. The alpha value was set to .05 for all variables except EMG data, for which the alpha value was set to .10 in an effort to avoid a type II error attributable to the high variability of EMG data.^32–34 All analyses were carried out with SPSS software, version 14.0.2.

Top Abstract Introduction Method Results Discussion Conclusion References

 
Differences at the Hip

There were no differences in the hip flexion angle in subjects 3 months and 1 year following TKA (Tab. 2 and Fig. 2). For the hip flexion angle there was an effect of group (Tab. 2), and values from post hoc tests were significantly higher (Fig. 2) for subjects both 3 months and 1 year following TKA than for control subjects. For the hip extensor moment there was an effect of time (Tab. 2), and values from post hoc tests for the involved limb were significantly higher at 1 year than at 3 months following TKA (Fig. 2). For the hip extensor moment at both 3 months and 1 year following TKA there was an effect of group (Tab. 2), and values from post hoc tests were higher for both involved and uninvolved limbs of subjects with TKA than for those of control subjects (Fig. 2).

Differences at the Knee

The peak knee flexion angle did not change over time, nor was it different in subjects with TKA and control subjects (Tab. 2 and Fig. 3). For the knee extensor moment there was an effect of limb (Tab. 2), and at 3 months after TKA, values from post hoc tests were significantly higher for the uninvolved limb than for the involved limb (Fig. 3). At 1 year following TKA, there were no differences between the limbs (Fig. 3). Compared with control subjects, subjects 3 months after TKA showed an interaction effect for both knee angle (Tab. 2) and knee extensor moment (Tab. 2); post hoc tests revealed that only the knee extensor moment of the involved limb was lower than that in control subjects (Fig. 3). Compared with control subjects, subjects 1 year after TKA showed an effect of group for both knee flexion angle (Tab. 2) and knee extensor moment (Tab. 2); however, post hoc tests did not reveal any differences.

EMG Differences

The normalized peak magnitude of the vastus lateralis muscle in subjects 3 months and 1 year following TKA showed a limb x time interaction (Tab. 3). At 3 months following TKA, post hoc tests showed that the normalized peak magnitude was lower on the involved side than on the uninvolved side; by 1 year following TKA, there were no differences between the sides (Fig. 4). Compared with control subjects, subjects 3 months after TKA showed an effect of limb, an effect of group, and an interaction effect (Tab. 3). Post hoc tests revealed that the normalized peak magnitude was higher for the uninvolved limb 3 months following TKA than for control subjects (Fig. 4). Compared with control subjects, subjects 1 year after TKA showed an effect of limb (Tab. 3). There were no differences in the normalized peak magnitude between subjects 1 year following TKA and control subjects (Fig. 4).

The normalized peak magnitude of the biceps femoris muscle in subjects 3 months and 1 year following TKA showed a limb x time interaction (Tab. 3). Values from post hoc tests were higher for the uninvolved side than for the involved side 3 months following TKA (Fig. 5). The peak magnitude for the uninvolved side decreased by 1 year following TKA (Fig. 5), resulting in no differences between the sides. Compared with control subjects, subjects 3 months following TKA showed an effect of limb and an interaction effect (Tab. 3). Values from post hoc tests were higher for the uninvolved limb 3 months following TKA than for control subjects (Fig. 5). At 1 year following TKA, there continued to be an effect of limb (Tab. 3). However, there were no post hoc differences in peak magnitude between subjects 1 year following TKA and control subjects (Fig. 5).

Vertical Ground Reaction Forces

In subjects with TKA, there was a limb x time interaction (Tab. 2). Post hoc tests at 3 months following TKA revealed that vertical ground reaction forces for the involved limb were significantly lower than those for the uninvolved limb (Fig. 6). By 1 year, the vertical ground reaction forces for the involved limb increased significantly, resulting in no differences between the sides (Fig. 6). Compared with control subjects, subjects with TKA showed no effect of limb or group at both times (Tab. 2 and Fig. 6).

Quadriceps Femoris Muscle Strength

Subjects 3 months and 1 year after TKA showed an effect of limb and an effect of time (Tab. 4). At 3 months following TKA, post hoc tests revealed that the involved quadriceps femoris muscle was significantly weaker than the uninvolved quadriceps muscle (Fig. 7). By 1 year, the strength of the involved limb improved, but this limb continued to be weaker than the uninvolved limb (Fig. 7). Compared with control subjects, subjects 3 months following TKA showed an effect of limb (Tab. 4). Post hoc tests revealed that subjects 3 months after TKA were weaker in the involved limb but not in the uninvolved limb than control subjects (Fig. 7). There were no differences in strength between subjects 1 year following TKA and control subjects (Fig. 7).

Functional Testing

Subjects performed significantly better on the SCT but not on the TUG Test or the 6MWT at 1 year following TKA than at 3 months after surgery (Fig. 8). Compared with control subjects, subjects 3 months following TKA performed significantly more slowly on the SCT but not on the TUG Test or the 6MWT. There were no differences between subjects 1 year following TKA and control subjects on the TUG Test, the SCT, or the 6MWT (Fig. 8).

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Figure 8. (Top) Results of the Timed "Up & Go" (TUG) Test and the Stair-Climbing Test (SCT), in which a higher number represents slower performance (worse score). Subjects performed better on the SCT (P=.001) at 1 year following total knee arthroplasty (TKA) than at 3 months, but there were no differences with the TUG Test (P=.289). Compared with control subjects, subjects 3 months following TKA performed more slowly on the SCT (P=.024) but not on the TUG Test (P=.383). At 1 year following TKA, there were no differences (TUG Test, P=.728; SCT, P=.198). (Bottom) Post hoc results of the 6-Minute Walk Test (6MWT). There were no differences over time in subjects with TKA (P=.178) or compared with controls (P>.05). Abbreviations: 3 mo=3 months following TKA, 1 y=1 year following TKA, NON=noninvolved (not surgically treated) limb, OP=involved (surgically treated) limb.

Top Abstract Introduction Method Results Discussion Conclusion References

 
We hypothesized that asymmetries in the motions and moments of the hips and knees at 3 months after TKA in subjects using a self-selected starting position would be different from those in matched control subjects. We hypothesized that by 1 year following TKA, quadriceps femoris muscle strength, performance on functional tests, and movement patterns would be more similar to those in control subjects. Our hypotheses were partially supported by the results. Subjects with TKA demonstrated improvements in quadriceps femoris muscle strength, movement patterns, and performance on functional tests from 3 months to 1 year. However, subjects with TKA did not demonstrate an STS movement pattern similar to that of control subjects. A pattern of reliance on the hip extensor muscles emerged 3 months following TKA and appeared to become more pronounced over time. At 1 year after TKA, quadriceps femoris muscle strength, vertical ground reaction forces, knee moments, and EMG data all were normalized, yet the hip moments had increased further. This movement strategy reduced demand on the knee extensor muscles and persisted 1 year following TKA despite the normalization of weight bearing and strength.

Relationship of Movement Patterns and Strength

At 3 months following TKA, the altered strategy used to complete the STS consisted of unloading of the involved limb with the use of greater hip flexion, which resulted in higher hip extensor moments. At 3 months following TKA, the quadriceps femoris muscles in the involved limb were still weak. Increased hip flexion reduced the demand on the knee extensor muscles, transferring it to the hip extensor muscles³⁵ during the STS task; therefore, an altered movement strategy that places less demand on the knee extensor muscles is logical at 3 months following surgery. However, at 1 year, resolution of the strength asymmetries and asymmetries in STS task performance resulted in a movement pattern that was atypical relative to that in control subjects, suggesting that this pattern is a learned movement pattern that may not resolve without retraining.

At 3 months after TKA, subjects may use hip flexion because they cannot generate the necessary knee extensor muscle torque. In the early phases following surgery, this seems to be a reasonable compensation pattern. Yu et al³⁶ demonstrated that angular motions of the hip contribute to horizontal and vertical velocity during the STS task, in which the angular motion of the knee contributes to horizontal velocity and prevents collapse. This difference in the contributions of the joints may play a role in reliance on the hip extensor muscles in subjects with TKA. The knee extensor muscles continue to act to prevent collapse, but the contribution to horizontal velocity may be reduced. This strategy was likely adopted because of pain or weakness or in an effort to avoid using the knee extensor muscles and is often present in people with OA prior to TKA.

What is the potential impact of the persistence of this abnormal movement pattern after the resolution of the impairments that likely lead to its development? Our subjects following TKA used their hip extensor muscles more than their counterparts who were not injured. Long-term stresses on the hip joints may be a contributing factor in the progression of OA, particularly in the uninvolved hip.^16,37 A large hip extensor moment has been shown to be a contributor to increased wear on the anterior portion of the femur³⁸ and has been implicated in the development of hip OA.^37,38 Therefore, the high stresses present in functional tasks coupled with altered joint loading may be contributing factors in the evolution of OA, particularly in the contralateral hip.

Functional Outcomes

Despite the altered movement strategy for the STS task that persisted at 1 year, subjects 1 year following TKA were not different from control subjects in terms of functional test scores. However, it is important to note that although there was a lack of statistical significance, subjects with TKA had lower scores on all of the functional tests than control subjects. These results indicate that improvements in timed functional test scores, although useful, may not reveal important differences in movement performance that could have future consequences for the development of OA in other joints of the lower extremities.

Physical Therapy Intervention

Why would subjects show improvements in strength, symmetry, and functional performance yet continue to demonstrate an altered STS movement strategy 1 year following TKA? All of our subjects participated in physical therapy at a clinic that focuses its efforts on the symmetry of quadriceps femoris muscle strength, weight bearing, and gait retraining. Our physical therapy protocol²⁰ for subjects following TKA includes measurements of quadriceps muscle strength bilaterally, and efforts are focused on strengthening the involved limb to make it as strong as the uninvolved limb. Weights, neuromuscular electrical stimulation, and functional training are all used to improve strength and functional control of the quadriceps femoris muscles. The criterion for the progression of the exercises is that the subject can complete the exercises correctly but still is maximally fatigued at the end of each set. Standardization of this protocol in our clinic has produced excellent outcomes.^18–20

During physical therapy, it is common for gait to be assessed regularly, even as a subject moves around the clinic to go to different exercise stations. Other functional tasks, such as the STS task and negotiation of stairs, are not assessed or trained with the same regularity. However, the results of the present study indicate the potential importance of including evaluation and training for tasks such as the STS task and negotiation of stairs, particularly because these tasks subject the knee joint to higher stresses and forces than walking.³⁹

The STS task could easily be incorporated as a functional retraining exercise into physical therapy following TKA. Through movement reeducation strategies, a subject could be taught to complete the STS task using a more typical movement pattern. Furthermore, this task could be incorporated into physical therapy rehabilitation as an exercise to improve the use of the involved limb. Given the potential impact of a poor movement strategy during the STS task on the progression of OA in the contralateral limb, functionally reeducating subjects to perform the STS task may be one component of physical therapy rehabilitation that could affect long-term outcomes following TKA.

Potential Limitations

There are limitations to the present investigation. Allowing subjects to self-select their starting position allows insight into how the task is naturally performed. Because we allowed subjects to self-select their starting position, we expected that asymmetries would persist. We were surprised to discover that the self-selected starting position resulted in a lack of differences 1 year after TKA. However, the self-selected starting position contributed to the variability of the results which, in a small sample size, can lead to the underestimation of an effect, or a type II error. In addition, our decision to use an alpha value of .05 for our small sample also increased the risk of a type I error. The risk of a type I error also existed because of the large number of comparisons made in the present study. Thus, the small sample size could have been a limiting factor in the lack of differences between control subjects and subjects 1 year following TKA.

The self-selected starting position likely played a role in the interaction effect when subjects 3 months after TKA were compared with control subjects. All subjects were allowed to select their starting position; the inherent variability in the healthy control subjects,⁴⁰ confounded by the small sample size, played a role in generating this interaction. Chair height also plays a role in STS task performance^13,37; we chose 100% of tibial height in order to standardize that aspect of the task. However, it has been found that chair height primarily affects moments at the knee but minimally affects moments at the hip³⁷; therefore, chair height likely did not account for our results.

Top Abstract Introduction Method Results Discussion Conclusion References

 
At 3 months following TKA, subjects had quadriceps femoris muscle weakness that likely contributed to the compensatory movement strategy observed during the STS task. However, at 1 year following TKA, these impairments were resolved, yet subjects persisted with the abnormal movement strategy of increased hip flexion and larger hip extensor moments. Thus, resolution of the underlying impairments does not automatically lead to a resolution of the compensatory pattern. This finding suggests that the abnormal movement pattern may not resolve without retraining. Attention to retraining of this compensatory movement strategy is important because it may be a potential contributor to the development of future OA.

 
Ms Farquhar and Dr Snyder-Mackler provided concept/idea/research design and data collection. All authors provided writing and data analysis. The authors thank Yuri Yoshida and Ryan Mizner for assistance with data collection.

The Human Subjects Review Board at the University of Delaware approved this study.

These data were presented, in part, at the 2007 Annual Meeting of the Orthopaedic Research Society; March 2–5, 2008; San Francisco, Calif; and at the 2008 Combined Sections Meeting of the American Physical Therapy Association; February 6–9, 2008; Nashville, Tenn.

^* VICON, 14 Minns Business Park, West Park, Oxford, United Kingdom OX2 0JB.

Bertec Corp, 6171 Huntley Rd, Suite J, Columbus, OH 43229.

Fabrifoam Inc, 900 Springdale Dr, Exton, PA 19341.

C-Motion Inc, 15821-A Crabbs Branch Way, Rockville, MD 20855.

^|| National Instruments Corp, 11500 N Mopac Expressway, Austin, TX 78759.

^# Motion Lab Systems Inc, 15045 Old Hammond Hwy, Baton Rouge, LA 70816.

^** Isokinetic International, 6426 Morning Glory Dr, Harrison, TN 37341.

SPSS Inc, 233 S Wacker Dr, Chicago, IL 60606.

Top Abstract Introduction Method Results Discussion Conclusion References

 

1. Cushnaghan J, Dieppe P. Study of 500 patients with limb joint osteoarthritis, I: analysis by age, sex, and distribution of symptomatic joint sites. Ann Rheum Dis. 1991;50:8–13.[Abstract/Free Full Text]
2. Dieppe P, Cushnaghan J, Tucker M, et al. The Bristol "OA500 study": progression and impact of the disease after 8 years. Osteoarthritis Cartilage. 2000;8:63–68.[CrossRef][Web of Science][Medline]
3. Moffet H, Collet JP, Shapiro SH, et al. Effectiveness of intensive rehabilitation on functional ability and quality of life after first total knee arthroplasty: a single-blind randomized controlled trial. Arch Phys Med Rehabil. 2004;85:546–556.[CrossRef][Web of Science][Medline]
4. Walsh M, Woodhouse LJ, Thomas SG, Finch E. Physical impairments and functional limitations: a comparison of individuals 1 year after total knee arthroplasty with control subjects. Phys Ther. 1998;78:248–258.[Abstract/Free Full Text]
5. Fitzgerald JD, Orav EJ, Lee TH, et al. Patient quality of life during the 12 months following joint replacement surgery. Arthritis Rheum. 2004;51:100–109.[CrossRef][Web of Science][Medline]
6. Jones G, Glisson M, Hynes K, Cicuttini F. Sex and site differences in cartilage development: a possible explanation for variations in knee osteoarthritis in later life. Arthritis Rheum. 2000;43:2543–2549.[CrossRef][Web of Science][Medline]
7. Ethgen O, Bruyere O, Richy F, et al. Health-related quality of life in total hip and total knee arthroplasty: a qualitative and systematic review of the literature. J Bone Joint Surg Am. 2004;86:963–974.[Abstract/Free Full Text]
8. Finch E, Walsh M, Thomas SG, Woodhouse LJ. Functional ability perceived by individuals following total knee arthroplasty compared to age-matched individuals without knee disability.J Orthop Sports Phys Ther. 1998;27:255–263.[Web of Science][Medline]
9. Rejeski WJ, Ettinger WH Jr, Schumaker S, et al. Assessing performance-related disability in patients with knee osteoarthritis. Osteoarthritis Cartilage. 1995;3:157–167.[CrossRef][Web of Science][Medline]
10. Berth A, Urbach D, Awiszus F. Improvement of voluntary quadriceps muscle activation after total knee arthroplasty. Arch Phys Med Rehabil. 2002;83:1432–1436.[CrossRef][Web of Science][Medline]
11. Mizner RL, Snyder-Mackler L. Altered loading during walking and sit-to-stand is affected by quadriceps weakness after total knee arthroplasty. J Orthop Res. 2005;23:1083–1090.[CrossRef][Web of Science][Medline]
12. Jevsevar DS, Riley PO, Hodge WA, Krebs DE. Knee kinematics and kinetics during locomotor activities of daily living in subjects with knee arthroplasty and in healthy control subjects. Phys Ther. 1993;73:229–239; discussion 240–242.[Abstract/Free Full Text]
13. Su FC, Lai KA, Hong WH. Rising from chair after total knee arthroplasty. Clin Biomech (Bristol, Avon). 1998;13:176–181.[CrossRef]
14. Mont MA, Mitzner DL, Jones LC, Hungerford DS. History of the contralateral knee after primary knee arthroplasty for osteoarthritis. Clin Orthop Relat Res. December 1995:145–150.
15. Ritter MA, Carr KD, Keating EM, Faris PM. Long-term outcomes of contralateral knees after unilateral total knee arthroplasty for osteoarthritis. J Arthroplasty. 1994;9:347–349.[CrossRef][Medline]
16. Shakoor N, Block JA, Shott S, Case JP. Nonrandom evolution of end-stage osteoarthritis of the lower limbs. Arthritis Rheum. 2002;46:3185–3189.[CrossRef][Web of Science][Medline]
17. Ritter MA, Thong AE, Davis KE, et al. Long-term deterioration of joint evaluation scores. J Bone Joint Surg Br. 2004;86:438–442.[CrossRef][Medline]
18. Mizner RL, Petterson SC, Snyder-Mackler L. Quadriceps strength and the time course of functional recovery after total knee arthroplasty. J Orthop Sports Phys Ther. 2005;35:424–436.[Web of Science][Medline]
19. Mizner RL, Petterson SC, Stevens JE, et al. Preoperative quadriceps strength predicts functional ability one year after total knee arthroplasty. J Rheumatol. 2005;32:1533–1539.[Abstract/Free Full Text]
20. Stevens JE, Mizner RL, Snyder-Mackler L. Neuromuscular electrical stimulation for quadriceps muscle strengthening after bilateral total knee arthroplasty: a case series. J Orthop Sports Phys Ther. 2004;34:21–29.[CrossRef][Web of Science][Medline]
21. Kralj A, Jaeger RJ, Munih M. Analysis of standing up and sitting down in humans: definitions and normative data presentation. J Biomech. 1990;23:1123–1138.[CrossRef][Web of Science][Medline]
22. Antonsson EK, Mann RW. The frequency content of gait. J Biomech. 1985;18:39–47.[CrossRef][Web of Science][Medline]
23. Winter DA. Biomechanics and Motor Control of Human Movement. 3rd ed. Hoboken, NJ: John Wiley & Sons; 2005.
24. Kent-Braun JA, Le Blanc R. Quantitation of central activation failure during maximal voluntary contractions in humans. Muscle Nerve. 1996;19:861–869.[CrossRef][Web of Science][Medline]
25. Chmielewski TL, Stackhouse S, Axe MJ, Snyder-Mackler L. A prospective analysis of incidence and severity of quadriceps inhibition in a consecutive sample of 100 patients with complete acute anterior cruciate ligament rupture. J Orthop Res. 2004;22:925–930.[CrossRef][Web of Science][Medline]
26. Snyder-Mackler L, De Luca PF, Williams PR, et al. Reflex inhibition of the quadriceps femoris muscle after injury or reconstruction of the anterior cruciate ligament. J Bone Joint Surg Am. 1994;76:555–560.[Abstract/Free Full Text]
27. Stevens JE, Mizner RL, Snyder-Mackler L. Quadriceps strength and volitional activation before and after total knee arthroplasty for osteoarthritis. J Orthop Res. 2003;21:775–779.[CrossRef][Web of Science][Medline]
28. Podsiadlo D, Richardson S. The Timed "Up & Go": a test of basic functional mobility for frail elderly persons. J Am Geriatr Soc. 1991;39:142–148.[Web of Science][Medline]
29. Ettinger WH Jr, Burns R, Messier SP, et al. A randomized trial comparing aerobic exercise and resistance exercise with a health education program in older adults with knee osteoarthritis. The Fitness Arthritis and Seniors Trial (FAST). JAMA. 1997;277:25–31.[Abstract/Free Full Text]
30. Harada ND, Chiu V, Stewart AL. Mobility-related function in older adults: assessment with a 6-minute walk test. Arch Phys Med Rehabil. 1999;80:837–841.[CrossRef][Web of Science][Medline]
31. Parent E, Moffet H. Comparative responsiveness of locomotor tests and questionnaires used to follow early recovery after total knee arthroplasty. Arch Phys Med Rehabil. 2002;83:70–80.[CrossRef][Web of Science][Medline]
32. Chmielewski TL, Hurd WJ, Rudolph KS, et al. Perturbation training improves knee kinematics and reduces muscle co-contraction after complete unilateral anterior cruciate ligament rupture. Phys Ther. 2005;85:740–749; discussion 750–754.[Abstract/Free Full Text]
33. Rudolph KS, Snyder-Mackler L. Effect of dynamic stability on a step task in ACL deficient individuals. J Electromyogr Kinesiol. 2004;14:565–575.[CrossRef][Web of Science][Medline]
34. Winter DA, Eng P. Kinetics: our window into the goals and strategies of the central nervous system. Behav Brain Res. 1995;67:111–120.[CrossRef][Web of Science][Medline]
35. Sibella F, Galli M, Romei M, et al. Biomechanical analysis of sit-to-stand movement in normal and obese subjects. Clin Biomech (Bristol, Avon). 2003;18:745–750.[CrossRef]
36. Yu B, Holly-Crichlow N, Brichta P, et al. The effects of the lower extremity joint motions on the total body motion in sit-to-stand movement. Clin Biomech (Bristol, Avon). 2000;15:449–455.[CrossRef]
37. Rodosky MW, Andriacchi TP, Andersson GB. The influence of chair height on lower limb mechanics during rising. J Orthop Res. 1989;7:266–271.[CrossRef][Web of Science][Medline]
38. Hampton SJ, Andriacchi TP, Galante JO. Three dimensional stress analysis of the femoral stem of a total hip prosthesis. J Biomech. 1980;13:443–448.[CrossRef][Web of Science][Medline]
39. Andriacchi TP, Galante JO, Fermier RW. The influence of total knee-replacement design on walking and stair-climbing. J Bone Joint Surg Am. 1982;64:1328–1335.[Free Full Text]
40. Gundersen LA, Valle DR, Barr AE, et al. Bilateral analysis of the knee and ankle during gait: an examination of the relationship between lateral dominance and symmetry. Phys Ther. 1989;69:640–650.[Abstract/Free Full Text]

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