[Nerve distribution in synovium of osteoarthritic knees].

Neural elements are widely distributed in synovium of osteoarthritic knees. In medial compartmental osteoarthritic knees, medial synovium is exposed to mechanical stimuli due to osteophytes and lateral thrust, which may accumulate neuropeptides, especially substance P, in free nerve endings. Free nerve endings containing a large amount of substance P may provoke pain sensation in synovium, and release substance P to the surrounding tissue in subsynovial tissue, which induces synovitis. Neural system may modulate synovitis as well as pain pathway in osteoarthritis of the knee.