Effects of intra articular corticosteroids in vivo on synovial fluid variables in rheumatoid synovitis

Synovial fluid from knee joints of twelve patients with rheumatoid arthritis were analyzed before and 4 to 30 days after an intraarticular injection of methylprednisolone. After corticoid injection, clinical improvement was moderate in five patients and mild in six; one had an exacerbation in local disease. Six of the patients showed no alteration in synovial fluid CH₅₀, C4 protein level, or rheumatoid factor titer, and the other six demonstrated a 50%, or greater change in only one of these synovial fluid values. All but one of the ten patients with paired cell counts showed a decrease in the total synovial fluid leukocyte count and the percentage of polymorphonuclear leucocytes and all but three patients had a 40%, or greater fall in synovial fluid acid phosphatase concentration following the corticoid injection. The data suggest that the transient improvement in clinical symptoms and signs which follows the intraarticular administration of corticosteroids is related to their antiinflammatory action reflected in decreases in synovial fluid leucocyte counts and lysosomal enzyme levels without any alteration of the basic immune aberrations characteristic of rheumatoid synovitis.