In the physical therapy world, a large percentage of our patients suffer from some form of arthritis.  In the United States, knee osteoarthritis (OA) affects over 30% of individuals over the age of 60.  Knee OA can cause pain, inflammation, swelling, decreased motion in the knee, difficulty walking, and may eventually require surgery such as a total knee replacement.

I frequently hear patients express frustration that their knees just “wore out.”  Some blame years of physical activity, with statements like “this is what I get for running for all of those years.”  While there is certainly a link between genetics and arthritis, there are several additional risk factors that can be reduced or eliminated with the help of a physical therapist.  

Physical Activity

The big question, “Does exercise contribute to knee arthritis?”  

Currently, there is lack of agreement in the scientific community regarding if high levels of exercise contributes to knee arthritis.  Many studies have found no relationship at all between recreational running and knee OA.  One study found that long-distance running is a significant risk factor, but only at the elite level, such as lifelong marathon runners. This conflicting evidence makes it difficult to draw conclusions about whether or not physical activity contributes to the development of arthritis.  However, the multitude of other known benefits of exercise (cardiovascular, strength, mood, mental clarity, stress relief, etc) outweigh the potential risk of developing knee OA.  However, there are several other known risk factors that can be modified in order to reduce your risk of developing knee arthritis.

Obesity

People who are obese with a higher percentage of body fat have been found to have a much higher likelihood for developing OA.  The extra weight puts excessive stress on the joint surfaces, resulting in degeneration and bony changes earlier in life. For these individuals, moderate intensity aerobic exercise is indicated with the goal of weight loss in order to reduce stress on the knee joints.

Muscle strength

Several studies have found an association between muscle weakness and the development of knee OA.   Specifically, quadriceps weakness has been shown to be a significant risk factor.  A 2006 study examined the effects of a leg strengthening program on the rate of arthritis progression, where people who participated in the strength training program were found to have significantly reduced cartilage degeneration when compared to people who performed range of motion exercises only.

If you are developing arthritis, a good strength training regimen is essential in order to stabilize the knees through strengthening all of the muscles surrounding the knee, as well as those which promote ideal knee alignment (see below).  

Joint alignment

Knee joint malalignment can put increased stress on the joint surfaces of the knee.  Both genu varum (commonly called bow legs) and genu valgum (knock-knees) alignments have been associated with narrowing knee joint spaces and development of osteophytes (bone spurs) in the knee.  Given these findings, it’s no surprise that malalignment has also been identified as a risk factor for developing knee OA.

Previous injury

A known risk factor associated with the development of knee OA is a previous injury to the cartilage or ligaments surrounding the knee.  Common culprits are meniscus or ligament injuries, which result in decreased stability of the knee, increasing abnormal forces on the joint surfaces.  These increased forces can result in trauma to the joint surfaces, which can promote the formation of bone spurs and degeneration of the cartilage.

How physical therapy can reduce your risk

At your first appointment, your physical therapist will evaluate your entire musculoskeletal system in order to systematically identify areas of weakness, decreased flexibility, and malalignment/instability.  The therapist will develop and coach you through an individualized exercise plan and therapy regimen that will:

• Restore correct alignment.
• Increase muscle strength in order to stabilize potentially arthritic joints.
• Create a safe fitness regimen in order to burn calories/lose weight without increasing traumatic forces on the knee.
• Promptly rehabilitate joints from injuries to reduce risk of OA.

1. Felson DT, Naimark A, Anderson J, Kazis L, Castelli W, Meenan RF: The prevalence of knee osteoarthritis in the elderly. The Framingham Osteoarthritis Study. Arthritis Rheum 1987, 30: 914-918.
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9. Leech RD, Edwards KL, Batt ME, Does running protect against knee osteoarthritis? Or promote it? Assessing the current evidence Br J Sports Med bjsports-2015-094749Published Online First: 28 July 2015doi:10.1136/bjsports-2015-094749

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