In vitro and in vivo spin echo diffusion imaging characteristics of synovial fluid: potential non-invasive differentiation of inflammatory and degenerative arthritis

Objective. This study was undertaken to analyse the diffusion characteristi cs 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 t emperature with a navigator-corrected spin echo diffusion sequence (B value s 0-512 s/mm(2)), on a Philips 1.5-T Gyro-scan. Subsequently synovial fluid from knee joint effusions of 25 patients(l0 patients with osteoarthritis, 10 patients with effusions following trauma and 5 patients with effusions s econdary to inflammatory arthritis) was evaluated with the same navigator-c orrected spin echo diffusion sequence. Results. Both in vitro and in vivo study demonstrated decreased diffusion i n patients with effusions secondary to degenerative joint disease (less tha n 2.40x10(-5) cm(2)/s) relative to patients with effusions accompanying kne e trauma (greater than 2.75x10(-5) cm(2)/s) and inflammatory arthritis tin vitro and in vive greater than 3.00x10(-5) cm(2)/s). Conclusion. Synovial fluid in degenerative arthritis shows less diffusion o r free water movement than synovial fluid in inflammatory arthritis, Diffus ion characteristics of synovial fluid may be used to predict the nature of the underlying form of arthri tis in patients presenting with knee joint ef fusions.