Knee pain is inconvenient, to say the least! But, for some people, it can be debilitating to the point that it makes doing even simple activities painful. Why is knee pain so common? One of the most frequent causes of knee pain and stiffness in middle-aged and older adults is osteoarthritis of the knee. Although there are other forms of arthritis, osteo is the most prevalent type and it becomes more common with age. In fact, half of all people will experience knee pain due to osteoarthritis at some point. So, your odds are one out of two! That’s why we need to do what we can do lower the risk of knee arthritis and keep our knees healthy.
The Knee Join, Pain, and Osteoarthritis
Knee osteoarthritis is a degenerative condition that involves gradual wearing away and damage to the cartilage that covers the bones that make up your knee joint. If you’re not familiar with joint anatomy, a joint is a space between two bones. In the case of the knee, it’s the gap between the thigh bone, called the femur, and the shin bone called the tibia. In the front, is the patella or knee bone. Together these three bones make up the joints in your knees. Of course, bones are pretty sharp, and you don’t want them rubbing against one another. So, the tips of each bone are covered by a layer of cartilage. The purpose of the cartilage is to absorb friction when you walk, climb stairs, jump, or otherwise bend your knees.
All is well, as long as the cartilage is intact. But, with severe osteoarthritis of the knees, the cartilage erodes to the point that the ends of the bones become exposed. In a severe case, the bones may actually rub against each other when the knee moves. The joint becomes narrowed as functional joint space is lost and, sometimes, bone spurs form. People who have severe knee osteoarthritis may have a harder time even walking due to pain and stiffness. Although we call osteoarthritis a degenerative condition, some experts believe there’s also an inflammatory component as well.
Some people are at higher risk of developing osteoarthritis of the knees than others and these folks may develop it at an earlier age. Genetics are a factor as well. If your mom or dad had knee arthritis, you’re at higher risk too. In addition, a prior history of a knee injury increases the risk of developing osteoarthritis in the injured knee. Body weight is another factor. Being overweight or obese increases the pressure your knees are forced to bear, and this pressure and stress are magnified when you climb the stairs.
A Surprising Factor That Increases the Odds of Knee Pain and Knee Arthritis
Here’s a factor that increases the risk of knee arthritis that you may not be aware of. After perusing a database of more than 3,000 older adults who were at risk for knee arthritis or who already had the disease, researchers made an interesting observation. Those who had a significant discrepancy in the length between their two legs were more likely to have or eventually develop knee osteoarthritis.
Most of us have some small difference in leg length, but researchers found that people with leg length differences of 2 centimeters or greater were at increased odds of knee osteoarthritis. The knee of the shorter leg is most prone toward developing knee arthritis, according to some studies, but other research shows either leg can be impacted. Having a leg length discrepancy also increases the risk of back pain as well.
Ideally, you want to find out if you have a leg length discrepancy early in life, during childhood, before you place years of uneven pressure on your knees. Sometimes, length discrepancies are picked up early, yet many adults have a significant discrepancy in leg length and don’t know it. In some cases, a leg length discrepancy can develop during adulthood as well. When you have legs of unequal length, it alters your biomechanics in a way that places greater stress on your knee joints. There’s also a slightly higher risk of developing arthritis of the hips with a significant leg length discrepancy as well. What’s surprising is how common this is. According to Podiatry Today, differences in leg length affect between 60 and 90% of the population and are the third leading cause of running injuries.
What If You Have a Leg Length Discrepancy?
Ideally, you want to know that you have one as early as possible. Wearing an orthotic inside your shoe to even out the discrepancy helps correct the faulty biomechanics and take stress off the knees. You typically wear the orthotic, or a shoe lift, on the side where the leg is shorter. However, it’s not clear whether wearing an orthotic consistently lowers the risk of knee arthritis, although it makes sense that it would. However, wearing an orthotic may also lower your odds of developing back pain as well.
Other Ways to Lower Your Risk of Knee Arthritis
Leg length discrepancy is only one risk factor for knee arthritis. As mentioned, don’t let your weight climb as it places additional stress on your knees. Exercise is beneficial too. Strengthening the muscles that support your knee joint, including your quadriceps, may help prevent symptoms of knee osteoarthritis. Studies show quad strengthening improves pain and function in people who already have knee arthritis as well. In fact, a study published in the journal Osteoarthritis and Cartilage found that quadriceps weakness predicted narrowing of the joint space in the knees over a 30-month period.
The Bottom Line
Being overweight or obese or having a strong family history of osteoarthritis places your knees at higher risk of degenerative changes, but so does having a significant leg length discrepancy. If you’re experiencing knee pain, check with a sports physician and see if you have a significant difference in length between your two legs. Also, keep in mind that overly tight hamstring can create a slight leg length discrepancy that isn’t due to differences in the length of the bones. A sports physician can tell you whether that’s a contributor as well.
WebMD.com. “Having Shorter Leg Ups Arthritis Risk”
Acta Ortop Bras. 2012; 20(3): 174–179.
Practical Pain Management. “Knee Osteoarthritis Impacted By Quadricep Strength”
Osteoarthritis and Cartilage. Volume 18, Issue 6, June 2010, Pages 769-775.
Podiatry Today. “Detecting and Treating Leg Length Discrepancies”