Chondral and osteochondral injuries associated with acute patellar dislocation.

PURPOSE: The purpose of this study was to evaluate the frequency and precise pathology of articular cartilage injuries after acute patellar dislocation.

TYPE OF STUDY: Case series.

METHODS: In 39 consecutive knees with initial lateral patellar dislocation, the articular cartilage injuries were examined using arthroscopy or macroscopic observation.

RESULTS: Thirty-seven knees (95%) had articular cartilage injuries of the patellofemoral joint and 2 knees (5%) had no cartilage injury. In all 37 knees (95%), articular cartilage injuries were observed in the patella. The appearances were categorized into 3 groups: cracks alone (9 knees), cartilage defect caused by osteochondral or chondral fracture (7 knees), and cartilage defects caused by osteochondral or chondral fracture associated with cracks (21 knees). The main site of osteochondral fracture was the medial facet, and the main site of cracks was the central dome. Twelve knees (31%) had cartilage injury of the lateral femoral condyle.

CONCLUSIONS: From this study, articular cartilage injuries, especially of the patella, seem to be common occurrences after acute patellar dislocation. Chondral and osteochondral injuries of the patella were classified into 3 groups.