Sonographic imaging of meniscal subluxation in patients with radiographic knee osteoarthritis.

Background/purpose: This study was undertaken to describe the sonographic features of meniscal subluxation in the weight-bearing position and to determine any association between meniscal subluxation and radiographic osteoarthritis.

Methods: In total, 238 knees with symptoms were examined successfully with weight-bearing anteroposterior and lateral radiographs and high resolution ultrasonography. The radiographs were examined to determine whether participants had radiographic osteoarthritis, graded using the Kellgren-Lawrence Scale. The degree of subluxation of the medial meniscus in each knee was measured using high resolution ultrasound with a 10-MHz linear transducer, at the level of the medial collateral ligament in weight-bearing condition. The degree of subluxation was compared in knees with the presence or absence of radiographic osteoarthritis using Students t test. Additional analysis between knees with early and advanced radiographic osteoarthritis was also performed.

Results: Meniscal subluxation for knees with (n = 141) and without (n = 97) radiographic signs of osteoarthritis were 4.3 1.9 mm and 0.7 0.6 mm, respectively. The difference was highly significant (p < 0.001). After age adjustment, the medial meniscal subluxation of age-matched subjects were 4.8 1.7 mm for knees with radiographic osteoarthritis (n = 43) and 1.0 0.8 mm for knees without such changes (n = 43). The difference between the two groups was still significant (p < 0.001). The greatest meniscal subluxation was seen in knees with advanced radiographic signs of osteoarthritis; no knee with osteoarthritic changes on radiographs had an undisplaced meniscus.

Conclusion: Meniscal subluxation is a prominent feature on weight-bearing sonographic imaging in patients with radiographic osteoarthritis and could be considered as a risk factor for the development of knee osteoarthritis. By using musculoskeletal ultrasonography, one can detect this occult meniscal derangement early before the appearance of radiographic signs of osteoarthritis.