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Objective: This study was undertaken to analyse the diffusion characteristics of synovial fluid in degenerative and inflammatory arthropathies., Design and Patients: Ten in vitro specimens of synovial fluid from patients with both degenerative and inflammatory arthropathy were studied at body temperature with a navigator-corrected spin echo diffusion sequence (B values 0-512 s/mm2), on a Philips 1.5-T Gyroscan. Subsequently synovial fluid from knee joint effusions of 25 patients (10 patients with osteoarthritis, 10 patients with effusions following trauma and 5 patients with effusions secondary to inflammatory arthritis) was evaluated with the same navigator-corrected spin echo diffusion sequence., Results: Both in vitro and in vivo study demonstrated decreased diffusion in patients with effusions secondary to degenerative joint disease (less than 2.40 x 10(-5) cm2/s) relative to patients with effusions accompanying knee trauma (greater than 2.75 x 10(-5) cm2/s) and inflammatory arthritis (in vitro and in vivo greater than 3.00 x 10(-5) cm2/s)., Conclusion: Synovial fluid in degenerative arthritis shows less diffusion or free water movement than synovial fluid in inflammatory arthritis. Diffusion characteristics of synovial fluid may be used to predict the nature of the underlying form of arthritis in patients presenting with knee joint effusions.

Objective: This study was undertaken to determine the contribution of meniscal extrusion and cartilage loss to joint space narrowing on conventional radiographs by correlation with magnetic resonance imaging (MRI)., Subjects and Methods: Sixty-two consecutive patients, 32 patients with osteoarthritis and 30 without osteoarthritis, over the age of 60 years that were referred for both radiographic and MRI of the knee were included in the study. In each case, relative joint space narrowing on conventional AP radiographs was assessed utilizing the Kellgren-Lawrence scoring system. Subsequently, the degree of meniscal extrusion and the integrity of articular cartilage were evaluated from MR in the same patients., Results: Each of 30 patients with normal joint space (Kellgren Grade 0) were noted to have normal articular cartilage, grade 1 meniscal extrusion was identified in only three of these patients. In comparison, meniscal extrusion was identified in all 32 patients with joint space narrowing (Kellgren Grades 1-4). Definite thinning or loss of articular cartilage was identified in only 15 of the 32 cases. In 17 patients with radiographic joint space narrowing (Kellgren Grades 1-3) and meniscal extrusion, no loss of articular cartilage was observed. A statistically significant correlation (P<0.001) was observed between Kellgren Grade and degree of meniscal extrusion and cartilage thinning on MRI., Conclusion: Conventional radiographs are an unreliable method of evaluating for articular cartilage loss in patients with early osteoarthritis. Initial joint space narrowing on conventional radiographs is secondary to meniscal extrusion rather than thinning of articular cartilage in most cases.