Angiogenic factor from synovial fluid resembling that from tumours.

Synovial fluids from 2 of 2 patients with osteoarthritis, 2 of 8 with rheumatoid arthritis, and 2 of 2 with ankylosing spondylitis contained a low-molecular-weight angiogenesis factor apparently identical with that derived from tumours. The amount of factor present was highest in patients with osteoarthritis, 2 patients with psoriatic arthropathy gave negative results. It is suggested that angiogenesis factor is involved, directly or indirectly, in the production of synovial exudate.