Relationship between arthroscopic evidence of cartilage damage and radiographic evidence of joint space narrowing in early osteoarthritis of the knee

We examined the relationship between articular cartilage degeneration, as visualized arthroscopically, and joint space narrowing (JSN) in standing anteroposterior knee radiographs of 161 patients with chronic knee pain. The majority of these patients had radiographic findings of mild osteoarthritis. Twenty-five (33%) of the 76 patients in the series whose radiographs showed tibiofemoral JSN had grossly normal articular cartilage in both tibiofemoral compartments at arthroscopy (false-positive). The specificity of medial JSN for the presence of medial compartment articular cartilage degeneration was 0.61, i.e., only 61% of patients with normal (grade 0) medial compartment cartilage had a normal medial joint space. Of 22 patients with greater than 50% medial JSN, 9 (41%) had normal articular cartilage in the medial compartment at arthroscopy. Of 6 patients with greater than 50% lateral JSN, 3 (50%) had normal lateral compartment articular cartilage at arthroscopy. Among 36 patients with greater than 25% JSN who had neither medial nor lateral compartment articular cartilage degeneration, JSN was associated with articular cartilage degeneration in the patellofemoral compartment in 8 (22%), with meniscus degeneration in 18 (50%), and with both in 8 (22%). Thus, in these patients with chronic knee pain, radiographic evidence of JSN in the tibiofemoral compartment did not permit confident prediction of the status of the articular cartilage.