Magnetic resonance imaging of osteoarthritis: correlation with gross pathology using an experimental model.

Conventional radiography has several limitations in the study of osteoarthritis (OA): changes occur late, they are restricted to bone, and they do not correlate well with the patient's symptoms. Magnetic resonance imaging (MRI) can visualize with great detail the soft tissue changes in and around joints. We have obtained MR images of knees using an experimental model of OA in order to study the early changes of OA, to correlate the images with the gross pathology, and to compare MR images with radiographs. The changes on MRI correlated with the gross pathological changes as assessed by Kendall's rank correlation test as follows: meniscal changes, tau = 0.58 (p less than 0.01); osteophytes, tau = 0.59 (p less than 0.05); capsular fibrosis, tau = 0.55 (p less than 0.05); and overall, tau = 0.68 (p less than 0.001). Abnormalities were evident on MRI as early as 4 weeks after the onset of the disease, which is 8 weeks before they appear on radiographs. Thus, MRI can show changes in OA earlier than radiography can, and the images correlate with the gross pathology.