Anterior knee pain with a posterior-stabilized mobile-bearing knee prosthesis: the effect of femoral component design.

Femoropatellar problems have been reported with some designs of posterior-stabilized knee prostheses with fixed bearings; we report similar findings with a posterior-stabilized mobile-bearing prosthesis. A review of 184 patients (193 knees) who underwent placement of a Rotaglide (Corin, Cirencester, UK) posterior-stabilized prosthesis with patellar resurfacing showed that only 33 knees (17%) had complete absence of femoropatellar complaints after at least 1 year of follow-up evaluation. Femoropatellar grinding was noted in the other 160 knees; 65 were asymptomatic, 78 were mildly symptomatic, and 17 were severely symptomatic. Two patients refused secondary treatment; 15 underwent arthroscopic debridement. The only abnormal finding was intra-articular fibrosis surrounding the patellar implant. After arthroscopic debridement of the fibrosis, all patients reported immediate relief of their symptoms followed by recurrence within 6 to 9 months. Inappropriate trochlear design of the femoral implant appears to be the main determinant of femoropatellar problems in these patients. Encroachment on the trochlea by a broad intercondylar box with a sharp anterior edge appears detrimental to function irrespective of the presence or absence of bearing mobility.