Effect of total knee arthroplasty on maximal flexion.

The advantage of potential flexion offered by total knee arthroplasty (TKA) is limited. In this review of 724 replaced knees, only one-third flexed to 105 degrees, while nearly one-half did not flex beyond 90 degrees. Postoperative flexion depended partly on preoperative flexion and partly on the prosthesis used, but these factors could not be the only determinants of results, for flexion in individual knees could increase, decrease, or remain unchanged whatever the preoperative measurement and whatever the design of prosthesis. Little difference in flexion before or after TKA was found between rheumatoid and osteoarthritic knees. Success or failure of the implant, according to the crude definition used, was not associated with degree of flexion. Patients with the lowest levels of function tended to have TKA with the least flexion and vice versa. Nevertheless, the degree of flexion is only one of the factors influencing mobility.