Stephanie C. Petterson

Early Quadriceps Strength Loss After Total Knee Arthroplasty: The Contributions of Muscle Atrophy and Failure of Voluntary Muscle Activation

BACKGROUND While total knee arthroplasty reduces pain and provides a functional range of motion of the knee, quadriceps weakness and reduced functional capacity typically are still present one year after surgery. The purpose of the present investigation was to determine the role of failure of voluntary muscle activation and muscle atrophy in the early loss of quadriceps strength after surgery. METHODS Twenty patients with unilateral knee osteoarthritis were tested an average of ten days before and twenty-seven days after primary total knee arthroplasty. Quadriceps strength and voluntary muscle activation were measured with use of a burst-superimposition technique in which a supramaximal burst of electrical stimulation is superimposed on a maximum voluntary isometric contraction. Maximal quadriceps cross-sectional area was assessed with use of magnetic resonance imaging. RESULTS Postoperatively, quadriceps strength was decreased by 62%, voluntary activation was decreased by 17%, and maximal cross-sectional area was decreased by 10% in comparison with the preoperative values; these differences were significant (p < 0.01). Collectively, failure of voluntary muscle activation and atrophy explained 85% of the loss of quadriceps strength (p < 0.001). Multiple linear regression analysis revealed that failure of voluntary activation contributed nearly twice as much as atrophy did to the loss of quadriceps strength. The severity of knee pain with muscle contraction did not change significantly compared with the preoperative level (p = 0.31). Changes in knee pain during strength-testing did not account for a significant amount of the change in voluntary activation (p = 0.14). CONCLUSIONS Patients who are managed with total knee arthroplasty have profound impairment of quadriceps strength one month after surgery. This impairment is predominantly due to failure of voluntary muscle activation, and it is also influenced, to a lesser degree, by muscle atrophy. Knee pain with muscle contraction played a surprisingly small role in the reduction of muscle activation.

Improved function from progressive strengthening interventions after total knee arthroplasty: A randomized clinical trial with an imbedded prospective cohort

OBJECTIVE To determine the effectiveness of progressive quadriceps strengthening with or without neuromuscular electrical stimulation (NMES) on quadriceps strength, activation, and functional recovery after total knee arthroplasty (TKA), and to compare progressive strengthening with conventional rehabilitation. METHODS A randomized controlled trial was conducted between July 2000 and November 2005 in an academic outpatient physical therapy clinic. Two hundred patients who had undergone primary, unilateral TKA for knee osteoarthritis were randomized to 1 of 2 interventions 4 weeks after surgery, and 41 patients eligible for enrollment who did not participate in the intervention were tested 12 months after surgery (standard of care group). All randomized patients received 6 weeks of outpatient physical therapy 2 or 3 times per week through 1 of 2 intervention protocols: an exercise group (volitional strength training) or an exercise-NMES group (volitional strength training and NMES). Treatment effects were evaluated by a burst superimposition test to assess quadriceps strength and volitional activation 3 and 12 months postoperatively. The Medical Outcomes Study Short Form 36 and Knee Outcome Survey were completed. Knee range of motion, Timed Up and Go, Stair-Climbing Test, and 6-Minute Walk were also measured. RESULTS Strength, activation, and function were similar between the exercise and exercise-NMES groups at 3 and 12 months. The standard of care group was weaker and exhibited worse function at 12 months compared with both treatment groups. CONCLUSION Progressive quadriceps strengthening with or without NMES enhances clinical improvement after TKA, achieving similar short- and long-term functional recovery and approaching the functional level of healthy older adults. Conventional rehabilitation does not yield similar outcomes.

Measuring Functional Improvement after Total Knee Arthroplasty Requires both Performance-Based and Patient-Report Assessments: A Longitudinal Analysis of Outcomes

The purpose was to explore the responsiveness of both patient-report and performance-based outcome measures to determine functional changes during the acute and long-term postoperative recovery after total knee arthroplasty (TKA). One hundred patients scheduled for unilateral TKA underwent testing preoperatively and at 1 and 12 months postoperatively using the Delaware Osteoarthritis Profile. All physical performance measures decreased initially after surgery then increased in the long term; however, the perceived function did not follow the same trend, and some showed an increase immediately after surgery. Patient-report measures were variable, with no to small response early, but had excellent long-term responsiveness that was twice as large as performance measures. Patient perception fails to capture the acute functional declines after TKA and may overstate the long-term functional improvement with surgery.

Mechanisms underlying quadriceps weakness in knee osteoarthritis.

PURPOSE To identify determinants of quadriceps weakness among persons with end-stage knee osteoarthritis (OA). METHODS One-hundred twenty-three individuals (mean age 64.9 +/- 8.5 yr) with Kellgren/Lawrence grade IV knee OA participated. Quadriceps strength (MVIC) and volitional muscle activation (CAR) were measured using a burst superimposition test. Muscle composition (lean muscle cross-sectional area (LMCSA) and fat CSA (FCSA)) were quantified using magnetic resonance imaging. Specific strength (MVIC/LMCSA) was computed. Interlimb differences were analyzed using paired-sample t-tests. Regression analysis was applied to identify determinants of MVIC. An alpha level of 0.05 was adopted. RESULTS The OA limb was significantly weaker, had lower CAR, and had smaller LMCSA than the contralateral limb. CAR explained 17% of the variance in the contralateral limbs MVIC compared with 40% in the OA limb. LMCSA explained 41% of the variance in the contralateral limbs MVIC compared with 27% in the OA limb. CONCLUSION Both reduced CAR and LMCSA contribute to muscle weakness in persons with knee OA. Similar to healthy elders, the best predictor of strength in the contralateral, nondiseased limb was largely determined by LMCSA, whereas CAR was found to be the primary determinant of strength in the OA limb. Deficits in CAR may undermine the effectiveness of volitional strengthening programs in targeting quadriceps weakness in the OA population.

Disease-specific gender differences among total knee arthroplasty candidates.

BACKGROUND Women with knee osteoarthritis are less likely to undergo joint replacement despite greater self-reported disability. The primary aim of the present study was to assess gender differences in the type and magnitude of osteoarthritis-related impairment prior to knee arthroplasty. METHODS Two hundred and twenty-one knee arthroplasty candidates (ninety-five men and 126 women) and forty-four healthy gender, age, and body mass index-matched individuals were tested. Individuals with contralateral limb injury or abnormality, cardiovascular disease, neurological impairment, and medical conditions limiting activity were excluded. Collected data included Medical Outcomes Study Short Form-36 mental and physical component scores, the Knee Outcome Survey Activities of Daily Living Scale score, knee range of motion, timed up-and-go test time, stair-climb test time, six-minute walk distance, normalized quadriceps strength, and volitional muscle activation. RESULTS Women in the arthroplasty group had lower Short Form-36 and Knee Outcome Survey scores, longer timed up-and-go test and stair-climb test times, shorter six-minute walk distances, and lower normalized quadriceps strength compared with men. Healthy women had longer stair-climb test times and shorter six-minute walk distances in comparison with healthy men. Between-group comparisons revealed that women in both the control group and the arthroplasty group had reduced normalized quadriceps strength in comparison with men, that healthy women had higher voluntary muscle activation in comparison with healthy men, and that female arthroplasty candidates had lower activation levels in comparison with male candidates. CONCLUSIONS Observed gender differences in strength and function appear to be inherent but are magnified in arthroplasty candidates. Strength and functional decline should be closely monitored in women with knee osteoarthritis to serve as an indicator of worsening condition, and preoperative interventions should reflect these gender-specific impairments.

Impact of Body Mass Index on Functional Performance After Total Knee Arthroplasty

The purpose of this investigation was to determine whether functional performance and self-report outcomes are related to body mass index (BMI) after total knee arthroplasty (TKA). We hypothesized that higher BMIs would negatively affect functional performance as assessed by the timed up-and-go test, stair climbing test, 6-minute walk test, and self-report questionnaires. A total of 140 patients with BMIs ranging from 21.2 to 40.0 kg/m2 were followed over the first 6 months after unilateral TKA. Hierarchical linear regression was used to evaluate the impact of BMI on functional performance at 1, 3, and 6 months after TKA, while taking into account preoperative functional performance. There were no meaningful relationships between BMI and functional performance in the subacute (1 and 3 months) and intermediate (6-month) stages of recovery.

Time Course of Quad Strength, Area and Activation after Knee Arthroplasty and Strength Training

INTRODUCTION changes in strength, activation, and morphology of the quadriceps femoris muscle group were assessed in 61 individuals that underwent unilateral total knee arthroplasty, with progressive postoperative strength training, for primary knee osteoarthritis. METHODS assessments of these three parameters were made at four time points (preoperatively and 4, 12, and 52 wk postoperatively). Maximal voluntary knee extension strength was recorded using an electromechanical dynamometer, and voluntary muscle activation was measured using a burst superimposition technique. Lean muscle cross-sectional area (CSA) was determined using magnetic resonance imaging. RESULTS preoperatively, the surgical limb was significantly weaker and smaller than the nonsurgical limb. Strength, voluntary muscle activation, and CSA of the quadriceps femoris significantly improved over the study period. At 52 wk, the surgical limb was still significantly smaller than the nonsurgical limb but had greater levels of voluntary muscle activation. In the nonsurgical limb, CSA was the primary determinant of strength across all time points, with voluntary muscle activation progressively contributing more from the preoperative assessment (R = 0.11) to the assessment 52 wk postoperatively (R = 0.26). In the surgical limb, voluntary muscle activation was the primary determinant of strength preoperatively and 4 wk postoperatively (R = 0.38 and 0.41, respectively), whereas CSA was the primary determinant of quadriceps strength 12 and 52 wk postoperatively (R = 0.44). CONCLUSION resolving the impairments in voluntary muscle activation after total knee arthroplasty may be necessary before visible gains in strength and muscle hypertrophy are evident.

Ratings of Pleasantness and Intensity for Beverages Served in Containers Congruent and Incongruent with Expectancy

Pleasantness and intensity ratings of beverages served in containers congruent and incongruent with expectancy were assessed. Past research has shown that the violation of food expectancies, e.g., color, taste, temperature, leads to more negative evaluations of food. Thus, it was hypothesized that beverages sampled from a container incongruent with expectancy, e.g., beer from a coffee cup, would be rated less favorably than the same beverage sampled from a container congruent with expectancy, e.g., beer from a beer bottle. 61 participants evaluated three beverages (beer, orange juice, and hot chocolate) in three containers (bottle, glass, and cup) using 11-point racing scales for pleasantness and intensity. Analysis indicated beverages were rated as significantly more pleasant in containers congruent with expectancy, as well as rated more intense when presented in bottles. These results further address the effects of violating expectations on producing negative hedonic evaluations.

STRENGTH AND FUNCTIONAL OUTCOMES IN UNILATERAL VERSUS SIMULTANEOUS BILATERAL TOTAL KNEE ARTHROPLASTY.

127 tively). Across groups, gait velocity decreased (p<.001) and variability in stride velocity increased (p=.001) in dual task walking. Additionally, in older subjects only, an increase in the number of errors in the cognitive task was associated with reduced gait velocity (r=-.487; p<.05) and increased variability in stride velocity (r=.534; p<.05) during dual task walking. Conclusions: The gait changes observed in dual task walking characterize decreased gait stability and indicate that performing cognitively demanding tasks during walking has a destabilizing effect on gait that is most apparent in older people. Performing cognitively demanding tasks during walking may place older people at greater risk of falling. Clinical Relevance: It is important to recognize that attention-demanding tasks have a destabilizing effect on gait and that attentional processes are involved in walking. Recognizing the potential role of attention-demanding tasks on fall risk, one might instruct older individuals who are at risk of falls to avoid performing cognitive tasks while they are walking. In contrast, one may also recognize the utility of dual tasking and choose to engage the individual in cognitive activities while walking in an effort to improve the person’s ability to perform dual tasks in a safe and functional manner.