[Unicompartmental knee arthroplasty and patellar problems].

Impingement between the anterior border of the prosthesis and the patella is exceptionnal. The design of the prosthesis, in particular over-thickness, can be the cause of conflict with the patella during flexion.The prosthesis diminishes valgus deformity and hence femoro-patellar strains.Patellar operations, patellectomy or realignment of the extensor apparatus do not seem justified.Femoro-patellar involvement is not a contra-indication to unicompartmental arthroplasty.