Every now and then I’m asked (usually by a non-runner) about the long-term danger running presents for “wearing out your knees”. The perception of “wearing out one’s knees” relates mostly to a condition called knee osteoarthritis, a slow wearing away of the cartilage connective tissue that stabilizes our knee joints.
One of my exercise physiology research heroes, Dr. David Nieman, Ph.D., addressed this same question in an issue of the American College of Sports Medicine’s Health & Fitness Journal (Sept/Oct 2010). Dr. Nieman stated that research studies indicate the opposite, that the running knee can easily withstand years of training, given a healthy knee to start with.
Factors contributing to knee osteoarthritis include growing older, weight gain, and a previous traumatic injury to the knee. By the time we hit middle age (e.g., 45 – 64 years) about 30% of us will be diagnosed with arthritis and that figure rises to 50% once we hit 65.
The good news is that weight-bearing, vigorous exercise like running does not put you at increased risk of developing knee arthritis, given you are not over-weight and you have no pre-existing knee injuries. Running biomechanics are also a factor – if your gait cycle is reasonably efficient, your feet, ankles, knees, and hips are well-designed to handle the pounding and repetitive stress of running.
Research also indicates that weight-bearing exercise can actually strengthen our knees and reduce the likelihood of developing knee osteoarthritis. In general, a growing number of good scientific studies show that the risk of osteoarthritis decreases with the more hours we spend enjoying recreational exercise.
S0 runners – you’re at no increased risk of “wearing out your knees”. If anything, you’re at lower risk than the non-exercising population, given reasonable knee health to start with.