[Extra-articular pathogenetic factors in arthritis and deformities in old age as exemplified by varus gonarthrosis]

Extraarticular, predominantly neuromuscular, factors are thought to contribute to the development of osteoarthritis. With increasing age, changed temporal dynamics of motor reflexes and reduced muscular force may affect the efficacy of neuromuscular protection of the knee joint. In three experimental studies conducted with osteoarthritis patients and healthy controls, no difference was found in monosynaptic reflex times and latencies of somatosensory evoked brain potentials. Muscular force was generally diminished in the patients, with the most prominent reduction during coxal abduction. Osteoarthritis patients had marked nociceptive hyposensitivity, but no difference was seen in fast conduction afferent systems. In an animal study with high locomotion load, interruption of articular afferent nerve fibers led to a precipitation of cartilage degeneration. It is concluded that minor extraarticular functional deficits acting over time, probably support and aggravate the development of osteoarthritic changes.