For patients with knee osteoarthritis, aerobic activities such as walking, cycling, or swimming are likely to be the best exercise for improving pain, function, gait performance, and quality of life, finds a study published in The BMJ.

While other exercises may offer complementary benefits to patients, they should not replace aerobic exercise as the main strategy, say the researchers.

Osteoarthritis occurs when the protective cartilage on the ends of bones wears away, causing pain, swelling, and impaired movement. While any joint can be affected, it’s most common in the knees, with nearly 30% of people over the age of 45 showing signs of knee osteoarthritis on X-rays, half of whom also have severe knee symptoms.

Exercise is one of the main treatments for osteoarthritis, but current guidelines provide limited information about the specific types of exercise that should be recommended for patients with knee osteoarthritis.

To fill this evidence gap, researchers set out to assess the effectiveness and safety of various types of exercise for managing knee osteoarthritis.

Their findings are based on the results of 217 randomized trials published between 1990 and 2024 involving 15,684 participants that compared common exercise therapies (aerobic, flexibility, strengthening, mind-body, neuromotor, and mixed exercise) with a control group.

The trials were of varying quality, but the researchers were able to assess the certainty of evidence using the recognized GRADE system. The main measures of interest were pain, function, gait performance, and quality of life, assessed at short-term (four weeks), mid-term (12 weeks), and long-term (24 weeks) follow-up.

Overall, aerobic exercise consistently showed the highest probability of being the best treatment across outcomes among the exercise therapies studied in clinical trials.

Moderate-certainty evidence showed that compared with controls, aerobic exercises were beneficial in relieving short and mid-term pain, improving short-term, mid-term, and long-term function, and improving short- and mid-term gait performance and quality of life.

Moderate-certainty evidence also showed that mind–body exercise probably results in a large increase in short-term function, neuromotor exercise probably results in a large increase in short-term gait performance, while strengthening and mixed exercise probably result in a large increase in function at mid-term follow-up.

None of the exercise interventions resulted in more adverse safety events than the control group, suggesting that exercise therapy is a safe treatment approach.

The authors acknowledge some limitations. For example, most results come from indirect comparisons, some outcomes lacked long-term data, and small-study effects may have influenced findings at early timepoints.

However, the researchers say this study presents a comprehensive and up-to-date analysis of the effects of exercise intervention as a treatment strategy for knee osteoarthritis, which could assist clinicians in prescribing therapy to improve treatment outcomes for patients.

Given these findings, they suggest aerobic exercise “as a first-line intervention for knee osteoarthritis management, particularly when the aim is to improve functional capacity and reduce pain,” and say that if aerobic exercise is not possible owing to individual limitations, “alternative forms of structured physical activity may still be beneficial.”