Reassuring Patients with Knee Osteoarthritis: Exercise Therapy Does Not ‘Wear Down’ the Joint

A persistent concern among patients with knee osteoarthritis (OA) is the fear that exercise therapy may accelerate joint degeneration. Many believe that repetitive or high-impact activities could overload the knee and damage the cartilage further. However, this belief is outdated and not supported by current evidence. In fact, exercise therapy is not only safe but is also recommended as a first-line treatment for OA. It has been shown to alleviate pain, improve joint function, and enhance quality of life—without harming the joint structure.

Osteoarthritis is the most common joint disease, and in people aged 45 and above, it can typically be diagnosed clinically based on joint pain associated with activity, and either no morning stiffness or stiffness lasting less than 30 minutes. While imaging can detect structural changes in the joint, these changes do not always correlate with pain levels. Current guidelines, such as those from NICE, recommend against routine use of imaging unless there are signs suggesting an alternative or additional diagnosis. Importantly, pharmacological treatments should support, not replace, engagement in exercise therapy and should be used for the shortest time possible due to limited benefits and potential side effects.

The misconception that exercise therapy might “wear down” joints originates from a combination of outdated messaging and misinterpreted research. Clinicians have historically described OA as a “wear and tear” condition, reinforcing the idea of a deteriorating mechanical structure. This analogy neglects the fact that cartilage is living tissue that responds positively to appropriate loading. The fear was also fueled by animal studies in the 1970s, which showed cartilage damage following abnormally high and repetitive loading in guinea pigs and rabbits. Unfortunately, these findings were rapidly translated into clinical assumptions without considering their limited relevance to human therapeutic exercise. Moreover, confusion around terminology—what differentiates exercise therapy, general exercise, and physical activity—has contributed to misunderstandings. Exercise therapy refers specifically to professionally prescribed programs targeting impairments with safe joint loads, whereas exercise and physical activity may involve higher or more variable loading.

Extensive research now confirms that exercise therapy does not harm knee cartilage in OA patients. Randomized controlled trials using imaging and molecular biomarkers have consistently found no evidence of cartilage degeneration due to exercise therapy. On the contrary, some studies suggest improvements in cartilage quality, especially in younger individuals with a healthy weight. Trials involving middle-aged, often overweight or obese individuals undergoing 12 to 48 weeks of aerobic and strength-based programs showed no adverse effects on cartilage structure, volume, or composition. Similarly, no increase was found in inflammatory markers or cartilage breakdown indicators in response to structured exercise.

Despite this strong evidence base, exercise therapy remains underutilized in clinical practice, where pharmaceutical and surgical interventions often dominate. This reliance on less effective or more invasive treatments is not only inefficient but also ethically questionable, as it deprives patients of evidence-based care that could delay or even prevent the need for total knee replacement surgery. Exercise therapy is recognized as beneficial for at least 26 chronic conditions, many of which commonly co-occur with OA. Beyond musculoskeletal benefits, exercise improves cardiovascular health, cognitive function, and mood, with minimal risk of serious adverse effects.

To help patients overcome their fears, therapists can adopt a simple three-step approach during consultations. First, assess the patient’s beliefs by asking whether they are concerned that exercise might damage their knees. Second, address these fears with clear, evidence-based explanations, perhaps using the sponge analogy: cartilage, like a sponge, relies on gentle compression and release to absorb nutrients and expel waste. Regular movement supports the metabolic activity of chondrocytes—the repair cells in cartilage—and enhances joint health. Third, support adherence through goal setting, self-monitoring, and action planning, as these strategies are proven to increase long-term engagement with exercise and other health-promoting behaviors.

In summary, the notion that exercise therapy ‘wears down’ the knee joint is a myth. Decades of research show that well-designed, professionally guided exercise is safe and beneficial for individuals with knee OA. Therapists have a pivotal role to play in shifting this narrative and ensuring patients receive the care they deserve—care that not only addresses symptoms but also empowers them to live more active, healthier lives.