To investigate intraarticular lesions producing persistent postoperative pain, we arthroscopically examined 31 ankles in 31 patients (15 women and 16 men) with lateral ligament injury. The patients ranged in age from 15 to 33 years, with a mean of 20 years. Nine patients were freshly injured, and 22 patients had chronic injuries. All of the patients underwent arthroscopic examination immediately before the ligament operation. Chondral lesions were found in 89% of the freshly injured ankles and 95% of the ankles with chronic injuries. Most of these lesions were in the medial half of the ankle joint, especially in the anteromedial edge of the tibial plafond. After followup for 1 year postoperatively, persistent pain was noted in 4 patients who had chondral lesions of greater than one-half the thickness of the articular cartilage. Pain and tenderness were localized at the anteromedial joint line, corresponding to the location of the chondral lesions. Chondral lesions of greater than one-half the thickness of the articular cartilage were found in 8 ankles in the chronic injury group, but there were none in the fresh injury group. Thus, in lateral ligament injuries of the ankle, the longer the time elapsed from the initial injury, the more severe the associated chondral lesions became. These chondral lesions appear to cause persistent pain.