Lower leg compensatory strategies during performance of a step up and over task in patient six-months after total knee arthroplasty.
Federico Pozzi, Adam R Marmon, Lynn Snyder-Mackler and 1 others
PMID 27362279WHAT IT FOUND
Six months after knee replacement, during stepping up, the operated leg relied more on the hip and less on the knee, and landing had lower overall support.
Leg muscle activity did not consistently differ from controls.
Key findings
01During the propulsive phase, the operated leg had a greater hip contribution to total support moment (10.35%, p = 0.047) and lower ankle and knee contributions (1.83% and 8.52%, p = 0.001).
02During lowering, knee contribution to total support moment was 8.31% lower after TKA (p = 0.011), and in the TKA group knee contribution correlated with quadriceps strength (r = 0.593, p = 0.010).
03During landing, total support moment was lower after TKA (1.89 vs 2.44, p = 0.019), and lateral gastrocnemius activity was greater (+6.7% of MVIC, p = 0.024).
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
Only 19 participants in each group had usable data, and one participant from each group was excluded because of data acquisition problems. The TKA group was heavier and had greater BMI than controls, so body size may have contributed to movement differences. The groups did not perform the step task at the same speed, and speed was adjusted for in the analysis, which may not fully account for how speed changes movement. This was a cross-sectional biomechanical comparison, not a treatment trial, so it cannot show that changing hip, knee, or ankle contribution or quadriceps strength causes better function. The patients were high functioning six months after TKA, so results may not apply to more impaired patients or different postoperative times. Trunk flexion differences were descriptive only because five participants had unusable trunk data, so trunk posture findings are tentative.
Declared interests
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The easy way to misread this
Do not conclude that hip or ankle retraining, or quadriceps strengthening, will improve step performance after total knee arthroplasty. This study was an observational comparison of movement patterns at six months, and it did not test an intervention or functional outcome.