Investigating meniscal symptoms in patients with knee osteoarthritis--is MRI an unnecessary investigation?

The aim of this study was to evaluate the relationship between radiographic knee osteoarthritis and the presence of a relevant meniscal tear detected on MRI in symptomatic patients over the age of 60. Seventy seven patients over the age of 60 who had been investigated with a knee MRI over a 1-year period were identified. Sixty patients had a full set of data available for analysis. Their plain radiographs were blindly graded for osteoarthritis using the Kellgren-Lawrence (K-L) scale. The indications for the MRI were subdivided into: meniscal symptoms, general knee pain and "other". These indications were correlated with the K-L grade and result of the MRI. Overall, 40% of patients with a K-L grade of 0 had a meniscal tear compared to 89% of patients with a K-L score of 3, and 88% with a K-L score of 4. The indications for an MRI were grouped into meniscal symptoms (49), general pain (6) and other (5). In the group investigated for meniscal symptoms, the incidence of meniscal tears was 92% and 100% with a K-L grade of 3 and 4 respectively. This equated to a positive predictive value of 93% for K-L grade 3 and above, and 100% for K-L grade 4 alone. Given the predictability of the MRI findings in patients with significant osteoarthritis as well as meniscal symptoms, we conclude that this is an unnecessary investigation when used for this indication.