Orthopedic surgeons in London just published a study showing that running a marathon may strengthen the cartilage and muscles in knee joints (BMJ Open Sport & Exercise Medicine, Oct 16, 2019;5(1)). More than 80 novice runners took a four-month running/training program, and the researchers took MRIs of their knees six months before they ran their first marathon and a half month after they completed the marathon. Their ages ranged from 25 to 73, with a median age of 44. Before the marathon, most of these novice runners had MRI signs of bone or cartilage damage, even though their knees did not hurt. Incredibly, after they ran the marathon (in an average time of 5 hours and 20 minutes), their MRIs showed a remarkable reduction in the knee bone and cartilage damage and marked strengthening of the knees:
• less bone marrow edema,
• increase in cartilage of the knee cap,
• increase in the size of their knee tendons, and
• increase in the size of knee ligaments.
A few of the new marathoners did develop damage to the cartilage in the back of their knee caps, but not in the knee joint itself.
Running appears to protect your knees by decreasing knee inflammation (European Journal of Applied Physiology, December 2016;116(11–12):2305–2314), strengthening hip and knee muscles (BMC Musculoskelet Disord, 2007;8) and healing early defects in knee cartilage (J Rheumatology, January 2001, 28 (1) 156-164). However, another recent study showed that running can increase joint damage in arthritic mice by increasing inflammation (Ann Rheum Dis, 2019; 78: 787-795). Running appeared to increase inflammation with resultant joint damage in mice that had inflammatory arthritis (Annals of the Rheumatic Diseases, 2018;78:6), and researchers found the same results in human runners who had osteoarthritis (PLoS ONE, 2018; 13(10): e0205191). The new study from London excluded runners who already had a history of osteoarthritis.
Knee Osteoarthritis is Common
Eighty percent of North Americans have X-ray evidence of osteoarthritis by age 65, and 60 percent have significant knee pain. The incidence of knee osteoarthritis has risen at a frightening rate over the last 50 years, probably because of changes from an active life of farming and working in industry to a post-industrial society in which most people do not do a lot of physical labor and gain too much weight (Proc Nat Acad Sci, August 29, 2017;114(35):9332-9336). It now appears that osteoarthritis is a disease of inflammation, an overactive immune system caused mostly by lack of exercise, being overweight, eating a pro-inflammatory diet and having inadequate vitamin D levels (JAMA, November 22, 2017).
Many studies show that exercise helps to prevent and treat arthritis:
• A review of 55 studies showed that weight bearing exercise reduces pain and improves joint function in osteoarthritis (British Journal of Sports Medicine, September 24, 2015).
• Aerobic and strength training for 20 weeks markedly decreased knee pain and increased mobility (Arthritis Care & Research, 08/30/2016). No serious side effects occurred from the knee strength and conditioning program.
• A review of six studies of a total of 656 men and women with knee osteoarthritis found that exercise improves symptoms of knee pain in osteoarthritis and that it did not make much difference whether the knee exercise program was of low or high intensity (Cochrane Database Syst Rev, 2015 Oct 29;(10):CD010203).
• Aerobic and strength training for 20 weeks markedly decreased knee pain and increased mobility in 126 people with knee osteoarthritis and chronic diseases such as heart disease, heart failure, type 2 diabetes, chronic obstructive pulmonary disease (COPD) or obesity, defined as a body mass index greater than 24 (Arthritis Care & Research, August 30, 2016).
• Exercise increases cartilage quality in osteoarthritis (Med and Sci in Sprts and Ex, Mar 23, 2017).
Too Much Knee Surgery?
Surgery has not been shown to be more effective than exercise in treating knee osteoarthritis (N Engl J Med, 2013;368:1675-84). Seventeen years ago, the first of many studies showed that arthroscopic partial meniscectomy is no more effective than a placebo (N Engl J Med, 2002;347:81-8). Yet arthroscopic partial meniscectomy to trim a torn knee meniscus is one of the most common surgical procedures done in North America, with more than 750,000 knee arthroscopies done in the U.S. each year.
• Arthroscopic partial meniscectomy is not more effective than sham placebo surgery for a degenerative meniscal tear (N Engl J Med, 2013;369:2515-24).
• Removing damaged attached cartilage offers little or no benefit (Br J Sports Med, 2016;50:1473-1480).
• Exercise is more effective than surgery (arthroscopic partial meniscectomy) in treating people with knee pain and degenerative meniscal tears (BMJ, July 20, 2016). An editorial in the same issue of the journal states, “The surgery is a highly questionable practice without supporting evidence of even moderate quality . . . the latest nail into what should be a sealing coffin” (BMJ, July 20, 2016). Unfortunately, medicine is a business and the bottom line of a business is profit.
If You Have Knee Pain and Still Want to Run
Take very short steps and if that doesn’t stop your pain, you may need to try another sport. You may still be able to run if you can markedly reduce the force of your foot hitting the ground. When you run, both feet come off the ground at the same time, causing you to land with tremendous force that can injure joints, muscles and tendons. Running at a six-minute per mile pace causes your foot to hit the ground with a force equal to three times your body weight. This force is transmitted up your legs to your hips and back, and done repetitively, it can damage joints, shatter bones and tear muscles and tendons (Br J Sports Med, Apr 2016;50(8):450-7; Aug 2007; 41(8):469–480).
The force of your foot hitting the ground is determined most by the length of your stride (Scan J Med & Sci in Sports, May 30, 2018). Unnecessarily high impact can be caused by over-striding. It is not important whether you land on the front of your foot or the heel, but the more you over-stride, the more likely you are to land on your heel. A study of the 2017 IAAF World Championships showed that 54 percent of the men and 67 percent of women landed on their heels (Journal of Biomechanics, May 22, 2019). Landing on the front of your foot does not prevent injuries, it is only a marker that you are not over-striding. A study from the University of Wisconsin-La Crosse shows that as people start to feel tired during running, they shorten their strides and this decreases the force of their foot striking the ground (Med and Sci in Sp and Exer, Dec 1999;31(12):1828-33). The shorter stride lessens the force of their heel striking the ground and places it forward to the area behind the big toe. To compensate for the decreased force of their feet hitting the ground, they move their legs at a faster cadence. You can use this information to help you prevent injuries when you run. Shortening your stride will help to protect you from injuries by shifting your foot strike force forward. You can keep your speed by moving your legs at a faster cadence.
Rules for Preventing Running Injuries
1. When you are training properly, your muscles will feel sore when you get up almost every morning. If you warm up for a workout and your muscles don’t recover and feel fresh after 10 minutes, take the day off or go very slowly. It doesn’t matter what workout you have planned for that day.
2. Wear-and-tear injuries don’t just happen, they give you plenty of warning. If you are training and you feel a soreness or pain that worsens as you continue to exercise, or doesn’t go away when you slow down, stop your workout immediately. You are headed for an injury.
3. Wear-and-tear injuries are usually not symmetrical. One knee will feel far more uncomfortable than the other.
4. Stop your intense workouts immediately when your legs start to feel heavy or hurt. Worsening fatigue usually comes on suddenly during a workout.
5. You recover faster from workouts by eating food and drinking fluids immediately after you finish a workout and getting off your feet as much as possible. You recover faster by lying instead of sitting and sitting instead of standing. So eat lots of food soon after you finish intense workouts and then take a nap.
6. If you find that you cannot run, you can strengthen your knees with a variety of low-impact sports and exercise equipment, such as race walking, cycling, swimming, water aerobics, cross country skiing, and use of machines such as ellipticals or stair-steppers where your feet are supported by the equipment as you move.
Runner’s Knee (Knee Cap Pain)
Total Knee Replacement