Management of Patellar and Trochlear Chondral Injuries

Patellofemoral chondral injuries are noted in a significant subset of patients with anterior knee pain. These injuries occur as a result of both acute traumatic events and chronic patellofemoral malalignment. Focal grade III and IV chondral defects of the patella or trochlea present a significant management challenge. Anatomic factors, including an increased quadriceps angle, tight lateral retinaculum and weakened vastus medialis oblique muscle produce maltracking, which results in overload of the lateral patellofemoral joint. Patella alta, trochlear dysplasia and hyperlaxity can result in patellofemoral instability and subluxation. These factors play a role in the development of patellofemoral chondral injuries and must be addressed. A trial of 6 months of conservative management is indicated for most patients. Surgical options often include a realignment procedure in addition to treatment of the chondral injury. Traditional cartilage resurfacing techniques including debridement, abrasion arthroplasty and microfracture have been used but are limited by the inferior wear characteristics of the fibrocartilage tissue which forms over the defect. Newer cartilage repair techniques include autologous chondrocyte implantation and osteochondral autograft transfer (mosaicplasty) attempt to repair the chondral defect with hyaline cartilage. Osteochondral allograft transfer is an option for large chondral defects in which the surface contour of the patella or trochlea has been lost. Patellofemoral arthroplasty may be superior to total knee arthroplasty in patients with isolated patellofemoral joint collapse. Newer techniques such as arthroscopic autologous chondrocyte implantation using biologic scaffolds in place of the periosteal cover are currently being investigated.