High-resolution MRI detects cartilage swelling at the early stages of experimental osteoarthritis

Objective: The progressive early changes in cartilage and subchondral bone in an experimental model of osteoarthritis (OA) were investigated with high -resolution magnetic resonance imaging (MRI) and microradiography. Methods: Partial medial meniscectomy was performed in the left knee of 16 r abbits. Four normal and four sham-operated additional rabbits were used as controls. Changes in cartilage and subchondral bone were sequentially asses sed after surgery with MRI at 0, 2, 4, 6, 8 and 10 weeks, subchondral bone variations quantified postoperatively on microradiographs of sagittal secti ons at 6 and 10 weeks and the macroscopic alterations graded according to t he severity of joint changes. Results: MRI demonstrated a progressive increase in the articular cartilage thickness in the weight-bearing area of the femur at weeks 4, 6 and 8 vs b asal. Tibial cartilage thickness only showed a significant increment at wee k 6. No significant abnormalities were detected on X-rays in subchondral bo ne when compared to controls. Macroscopically, 4 weeks after the operation CA rabbits had only slight cartilage discoloration. Cartilage eburnation, p itting, superficial erosions and osteophytes were detected at week 6. These abnormalities were more evident at 8 and 10 weeks after meniscectomy. Conclusion: The focal increase in cartilage thickness is one of the earlies t measurable changes in CA and preceeds subchondral bone remodeling. The me asurement of cartilage thickness variations with MRI can be used to follow the course of CA and to evaluate the potential beneficial effect of novel t herapies. (C) 2001 OsteoArthritis Research Society International.