The relation of exercise to osteoarthritis is one of great interest an importance. In this paper, we review two recent studies. One reported that older individuals with normal knee and hip joints who jog for recreational activities do not have an increased risk for the development of osteoarthritis in weight-bearing joints. However, in another case-control study of women with hip osteoarthritis, the risk of hip osteoarthritis increased twofold with high levels of participation in recreational activities before the age of 50 years and fourfold for women with high levels of sporting activities and occupational physical loads. Therefore, participation in certain types of sporting activities and occupations that increase loading to the hip joint before the age of 50 years may be associated with an increased risk of hip osteoarthritis. However, recreational jogging in individuals 60 or more years of age with normal knee and hip joints does not increase the risk for the development of osteoarthritis. These studies add to our knowledge base regarding lifetime and current risk factors for the development of knee and hip osteoarthritis from exercise.
The relation between exercise and health has always been one of great public interest. Millions of middle-aged individuals now participate in recreational leisure time activities on a regular basis. This raises concerns that this new social phenomenon might accelerate the development of osteoarthritis of the weight-bearing joints.
The etiology of osteoarthritis is unclear. However, damage to the articular surface can start a biological process that results in joint degeneration. Some exercise is believed to be beneficial to the joint because it increases the circulation of synovial fluid, which bathes the articular cartilage with nutrients and maintains periarticular muscle strength. However, the exact amount and types of exercise that would be beneficial and not destructive to the joint are currently not known.
The initial studies that evaluated the relationship between regular recreational weight-bearing exercise and osteoarthritis of the hip and knee generally found no effects [1–3]. However, when former elite athletes were assessed cross-sectionally, those athletes who performed their activities with high impact and high stress to the joints had an increased risk for osteoarthritis in the hips and knees compared with age-matched controls [4–6]. Next, a series of studies that assessed the longitudinal effects of aging and exercise on osteoarthritis of the hip and knee after 5 and 8 years of follow-up found no increased risk of developing osteoarthritis in the exercisers, in this case runners, compared with age-similar controls [7,8]. However, in those runners who had developed radiographic evidence of knee osteoarthritis, independent predictors for the development of knee osteoarthritis included older age and faster pace per mile . Therefore, the results from cross-sectional and longitudinal studies show that individuals who had normal joints and participated in low-impact exercises (jogging slowly—8 minutes per mile or greater) did not have an increased risk of developing osteoarthritis of the knee as they aged, but former elite athletes who performed their activities with high impact to the joints had an increased risk for development of osteoarthritis. It is important to note that these studies evaluated the effects of physical activity only from exercise and not from the individual's occupation.