Improving Function after Knee Replacement through Strength Training

By Richard Shank

Research published in the latest issue of Arthritis and Rheumatism found that exercise designed to progressively strengthen the quadriceps will significantly improve knee functioning after knee replacement surgery.

Researchers at the University of Delaware, Eastern Washington University, and the University of Colorado performed a randomized controlled trial between July 2000 and November 2005. Two hundred patients who had undergone primary, unilateral Total Knee Arthroplasty (TKA) for osteoarthritis were randomly entered into one of two post-operation interventions. After twelve months of surgery, both groups were assessed via a procedure that tested quadriceps strength.

Knee Osteoarthritis disrupts daily life by causing severe joint pain and reducing daily functioning. The prevalence of this condition is high enough that about 500,000 TKAs are performed, on the average, each year. Despite the ability of a TKA to reduce joint pain and restore the perception of knee functioning, patients experience a significant post-operative loss of quadriceps strength and perform poorly on assessments that test knee functionality. It has been reported in previous studies that 60% of quadriceps strength is lost by one month after surgery. Quadriceps strength is important for knee functioning and is thus a key target intervention for post-operative recovery.

Prior to this study, the impact that progressive rehabilitation has on quadriceps strength and knee functioning after a TKA had not been assessed. The researchers set out to test whether strength training alone, or if used in combination with Neuromuscular Electrical Stimulation (NMES), would improve quadriceps strength and knee function. NMES has been previously linked to post-TSA recovery. The researchers' primary hypothesis was that strength training would work in combination with NMES to provide the greatest improvement in strength and functioning.

The final results of this study indicate that the treatment group that performed only quadriceps strength exercises, and the group that performed these exercises in combination with NMES, experienced the same gains in muscle strength and knee functioning.

These findings suggest that attempts to overcome psychological barriers to knee recovery should emphasize the importance of strength training for knee functionality. Solely relying upon NMES will not produce an optimal benefit for recovering patients, despite what appears to be its placebo-like impact on rehabilitating patients.

Source: Petterson, S., Mizner, R., Stevens, J. et al. 2009. Improved function from progressive strengthening interventions after total knee athroplasty: A randomized clinical trial with an imbedded prospective cohort. Arthritis and Rheumatism 61(2): 174–183.

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