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Optimal Range of Motion Found After Knee Replacement

Better outcomes are associated with 128-132 degree range than with lower or higher ranges

WEDNESDAY, April 9 (HealthDay News) -- After total knee arthroplasty with a posterior cruciate-retaining prosthesis, a range of motion between 128 and 132 degrees is associated with an optimal outcome, according to research published in the April 1 issue of the Journal of Joint & Bone Surgery.

Merrill A. Ritter, M.D., of St. Francis Hospital in Mooresville, Ind., and colleagues reviewed 5,556 primary total knee arthroplasties performed with posterior cruciate-retaining prostheses between 1983 and 2003.

The researchers found that patients with a range of motion between 128 and 132 degrees had the highest scores for pain, walking and knee function and the highest Knee Society scores, and that patients with a range of motion below 118 degrees had the lowest scores. Although patients with a range of motion between 133 and 150 degrees had the highest scores for stair-climbing, the researchers found that a postoperative flexion contracture and hyperextension of 10 degrees or more was associated with poorer outcomes in other measures.

"This study is the first one, as far as we know, that has been designed to define optimal ranges of motion after total knee arthroplasty," the authors write. "Patients in [the 128 to 132 degree] group even performed better than those in the group with higher range of motion. This suggests that there may be a limit to the benefits gained from increased range of motion, at least for the parameters we measured."

One of the study authors received funds from Biomet.

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