Lane points out that signs of osteoporosis were evident in all the women. Despite staying relatively active, the runners lost bone mass at the same rate as the non-runners. "Age-related bone loss occurs despite continuous activities," says Lane.
The authors also cite a four-year Swedish study, in which women ages 50-70 -- some who had hip replacements because of osteoarthritis -- were interviewed about their sports activities before age 50 as well as overall health status, smoking habits, occupational history, and work at home. The study showed that sporting activities and occupational stresses -- knee-bending and lifting -- until the age of 50 appears to be a moderate risk factor in women for developing severe osteoarthritis of the hip. However, says Lane, these results must be interpreted cautiously, since women had to report from memory what they did 50 years ago.
Timothy McAlindon, MD, assistant professor of medicine at the Arthritis Center at Boston University School of Medicine, tells WebMD, "There have been case-controlled studies in Europe that -- in contrast to the studies [cited by Lane et al.] -- do show increased risk [of knee and hip osteoarthritis] from recreational activities."
The study results cited by Lane and colleagues are "generalizable to people who are similar to those participating in that [particular] study: habitual runners who are lean and appear to be in good health," says McAlindon. "Now, can you generalize that to someone who is over 40, overweight, and decides to start running? Running could do damage to the knees of someone who is very obese."
Running is relatively low-impact compared to activities like tennis and squash, which involve changing direction rapidly -- twisting -- and put more stress on the knee, says McAlindon. "Soccer and skiing are clearly very bad for knees," he says. "What you have to do is temper the message. Running seems to be relatively safe, but other sorts of activities may increase the risk of osteoarthritis, especially if there's impact involved or there's the risk of injury to ligaments."
- A high-impact, high-stress running regimen is associated with a greater risk of joint deterioration, which could lead to osteoarthritis.
- Recreational running, however -- running 2-3 times per week at an 8-minute mile pace -- does not increase the risk of developing osteoarthritis.
- Scientists do not know exactly how osteoarthritis develops, but damage to the surface of the bone can start a process that leads to joint degeneration.