In the United States, 25% of adults experience knee pain that impacts how they function. It's nearly impossible to estimate the percentage of people who develop knee osteoarthritis (OA) because a proportion of them do not have symptoms at all! It's important to note that there’s a very high incidence of images showing abnormalities in asymptomatic people. One study found that while 37.4% of adults over age 60 showed knee osteoarthritis (OA) on an x-ray, only 12% of these adults had knee pain (our previous blog post elaborated more on these findings). However, it is thought that the incidence of symptomatic knee OA (people who have symptoms and also demonstrate OA on imaging scans) is gradually increasing globally due to the aging population, unhealthy diets, changed lifestyles, and increased occurrence of obesity.
The knee is an extremely resilient and robust joint—it absorbs about ½ million kg of weight on a typical mildly active day. The knee is the largest joint in the body and is made up of the joints of the tibia and femur (tibiofemoral joint) and the knee cap on the femur (patellofemoral joint). There are 10 different muscles (quite large muscles might I add) that cross the knee joint and move it. The knee is made up of a strong ligamentous structure that includes the anterior and posterior cruciate ligament (ACL and PCL) and medial and lateral collateral ligament (MCL and LCL). The articular cartilage is the specialized connective tissue that covers the ends of bones where the tibia and femur articulate and form a joint, and functions to provide a smooth, lubricated surface of the joint and to facilitate the transmission of loads and lessen friction.
Osteoarthritis (also commonly called degenerative joint disease) refers to the progressive loss of articular cartilage of a joint. The longstanding notion of why or how OA occurred was considered "wear and tear", with the idea that our bodies wear out like a car. However, studies have shown that osteoarthritis is in part due to a low-grade systemic inflammation of the body. There has been a lot of extremely informative and profound evidence showing this over the last decade, however, the medical system tends to require time to catch up, and we continue to hear that osteoarthritis is due to "wear and tear" rather than a whole-body, systemic problem.
Inflammation is an important process that our body goes through for healing. Symptoms of local inflammation (inflammation in a specific area of the body) include swelling, redness, and warmth. However, when inflammation occurs in our entire body, it is considered systemic. Mild systemic inflammation often goes unnoticed. This type of inflammation can often be influenced by local inflammation or injury, diet, genes, thoughts, and body mass index (BMI). Individuals with knee OA have been found to have traits consistent with low-grade systemic inflammation, which makes us question, if this is the case then what is the best way to treat them?
When individuals hear the diagnosis of knee OA, they often jump to the concept of correcting "wear and tear" by having surgery. Other less invasive options include steroid injections and oral anti-inflammatories. Many people fear movement and exercise. However an abundance of research on individuals with knee pain and diagnoses of osteoarthritis has proven that physical therapy and exercise can be just as effective, and in some cases more effective, than other less-conservative and more passive options.
Even though more research needs to be done comparing total knee arthroplasty (TKA, also known as total knee replacement surgery) to physical therapy and exercise alone, there is a lot to say about undergoing a TKA, and in general, room for improvement. These surgeries should be considered on a case-by-case basis due to the risks and recovery periods associated with them.
What are the advantages of trying physical therapy first? Physical therapy is generally less risky than surgery and injections, as these other options both come with their own set of complications. Physical therapy is a more active approach to care, which gives patients a better sense of control over their treatment and pain, as well as self-efficacy. The goals for patients we treat with knee osteoarthritis are to reduce pain, improve function, and prolong the need for surgery because we know artificial joints have a lifespan of 10-20 years. There have been extensive studies performed to determine the efficacy of physical therapy and exercise for knee osteoarthritis.
For those who fear exercise due to ongoing knee pain or concern of further "wear and tear," rest assured that exercise will only help! Scientific research that has looked into the effects of exercise on knee joint structures has found that exercise is NOT harmful to articular cartilage, it does NOT trigger an inflammatory reaction, and it does NOT worsen tissue in x-ray studies (Young et al., 2023). We also know that loading (which refers to activities that create compressive forces through the joint) is essential for healthy joints as it stimulates bone growth and inhibits bone loss.
In summary, physical therapy has proven to be a successful way to reduce pain and improve your quality of life for patients with knee OA and should be considered the first line of treatment for patients experiencing pain and functional impairments. The mechanism of how exercise reduces pain in individuals with knee OA is largely unknown, but it may tie into exercise having anti-inflammatories effects on the body.
Although it can be difficult to predict and prevent specific injuries, we can help our knees by having a generally healthy lifestyle. Here are a few tips:
Are you experiencing knee pain? The Doctors of Physical Therapy at Aware Health can perform an evaluation with you, test your movement and strength, and offer valuable insight and treatment on how to manage and eliminate your pain, all through telehealth! OR if you need help getting onto a healthy pathway, Aware can help too by establishing a wellness program based on your goals.