Biochemical and histological changes in osteoarthritic synovial membrane.

In order to investigate the relationship between the synovial inflammatory response and lysosomal enzyme activity in osteoarthritis, synovial specimens obtained from 19 osteoarthritic patients and control specimens from 10 normal joints were analysed for cathepsin D and acid phosphatase enzyme levels. In estimating enzyme activities methods previously developed for quantitative enzyme determination in cartilage were modified and applied to synovial tissues for the first time. In addition, samples of osteoarthritic synovium were histologically graded according to their degree of inflammation. It was found that in osteoarthritic synovium cathepsin D and acid phosphatase, which is a general marker for lysosomal enzyme activity, were significantly increased compared with normal control synovium. No significant relationship was found between the degree of synovial tissue inflammation and lysosomal enzyme activity.