Exercise and osteoarthritis: cause and effects.

Osteoarthritis (OA) is a common chronic joint condition predominantly affecting the knee, hip, and hand joints. Exercise plays a role in the development and treatment of OA but most of the literature in this area relates to knee OA. While studies indicate that exercise and physical activity have a generally positive effect on healthy cartilage metrics, depending upon the type of the activity and its intensity, the risk of OA development does appear to be moderately increased with sporting participation. In particular, joint injury associated with sports participation may be largely responsible for this increased risk of OA with sport. Various repetitive occupational tasks are also linked to greater likelihood of OA development. There are a number of physical impairments associated with OA including pain, muscle weakness and altered muscle function, reduced proprioception and postural control, joint instability, restricted range of motion, and lower aerobic fitness. These can result directly from the OA pathological process and/or indirectly as a result of factors such as pain, effusion, and reduced activity levels. These impairments and their underlying physiology are often targeted by exercise interventions and evidence generally shows that many of these can be modified by specific exercise. There is currently little clinical trial evidence to show that exercise can alter mechanical load and structural disease progression in those with established OA, although a number of impairments, that are amenable to change with exercise, appears to be associated with increased mechanical load and/or disease progression in longitudinal studies.