How much exercise for knee osteoarthritis, and does the benefit last?

Exercise is a recommended way to manage the symptoms of knee osteoarthritis (OA) [2, 3]. While the general benefits of exercise for knee OA are well-established, many people wonder about the specific details: what kind of exercise is most helpful, how much is needed, and do the benefits continue after an exercise program ends? This article explores these questions, drawing on recent research.

For a broader overview of how exercise helps with knee OA, you can read our article on Exercise therapy for knee osteoarthritis: what the evidence shows.

What type and amount of exercise may help with knee OA?

In 2014, a systematic review and meta-regression analysis by Juhl and colleagues looked at 48 randomized controlled trials to understand the optimal exercise program for reducing pain and disability in knee OA [1]. A meta-regression analysis combines data from many studies to identify patterns and relationships between different features of an intervention and its effects [1].

Exercise types and effectiveness

The Juhl review compared different types of exercise programs: * Single-type vs. mixed programs The study found that exercise programs focusing on a single type of exercise were more effective at reducing pain than programs that included different exercise types [1]. For example, a program focused only on aerobic exercise might be more effective than one combining aerobic, resistance, and performance exercises [1]. * Specific exercise types Aerobic exercise, resistance exercise, and performance exercise (which focuses on functional movements) all showed similar benefits in reducing pain [1]. * Quadriceps-specific exercise The review found that exercises specifically targeting the quadriceps muscles (at the front of the thigh) led to more pain reduction compared to more general lower limb exercises [1].

How often and for how long?

The Juhl review also investigated the impact of how exercise programs were delivered: * Supervised sessions For aerobic exercise, the study found that pain relief increased with a greater number of supervised sessions [1]. This suggests that having a professional guide your exercise may be beneficial. * Frequency Supervised exercise performed at least three times a week led to greater pain reduction compared to less frequent sessions [1]. * What didn't show an impact The study did not find that the intensity of exercise, the duration of individual sessions, or specific patient characteristics (like how severe their OA was or their baseline pain levels) affected the outcomes [1].

What Juhl et al. concluded about optimal programs

Based on their findings, Juhl and colleagues concluded that exercise programs for knee OA should have a clear goal [1]. These programs should focus on improving either aerobic capacity, quadriceps muscle strength, or overall lower extremity performance [1]. For the best results, these programs should be supervised and done three times a week [1]. Such programs showed similar effects regardless of a person's individual characteristics, including how severe their OA appeared on X-rays or their initial pain levels [1].

Does the benefit of exercise for knee OA last?

A 2024 Cochrane review by Lawford and colleagues looked at 139 trials involving over 12,000 participants to assess the effects of land-based exercise for knee OA [2]. Cochrane reviews are highly respected systematic reviews that aim to provide reliable evidence about healthcare interventions [2]. This review updated a previous one from 2015 [2].

It's important to understand that the benefits reported by this review are primarily "immediately post-intervention" [2]. This means the effects were measured at the end of the exercise program, not necessarily at a later time after the program had stopped. The published abstract does not detail how long the benefits lasted after the intervention period ended.

The review compared exercise in three main ways: 1. Exercise versus attention control or placebo (e.g., sham therapy or general health education) [2]. 2. Exercise versus no treatment, usual care, or limited education [2]. 3. Exercise added to another treatment versus that other treatment alone (e.g., exercise plus weight loss diet compared to weight loss diet alone) [2].

The interventions in the studies varied in length, from 2 to 104 weeks [2]. Most of the trials had some risk of bias, meaning there were potential flaws in their design or conduct that could affect the results [2]. For example, in 94% of trials, participants knew whether they were receiving exercise or a comparison treatment, which could influence their reported outcomes [2].

Short-term effects immediately after intervention

Here's what the Cochrane review found regarding effects immediately after the exercise intervention:

• Exercise versus attention control or placebo

  • Pain: Low-certainty evidence suggests exercise may slightly improve pain (an average of 8.70 points better on a 0 to 100 scale) [2].
  • Physical function: Moderate-certainty evidence indicates exercise likely improves physical function (an average of 11.27 points better on a 0 to 100 scale) [2].
  • Quality of life: Exercise likely leads to little to no improvement in quality of life (an average of 6.06 points better on a 0 to 100 scale) [2].
  • Treatment success: Moderate-certainty evidence suggests exercise likely increases participants reporting treatment success [2].
  • Withdrawals and adverse events: Exercise likely does not increase study withdrawals and may not increase adverse events [2].

• Exercise versus no treatment/usual care/limited education

  • Pain: Low-certainty evidence suggests exercise may improve pain (an average of 13.14 points better on a 0 to 100 scale) [2].
  • Physical function: Moderate-certainty evidence indicates exercise likely improves physical function (an average of 12.53 points better on a 0 to 100 scale) [2].
  • Quality of life: Moderate-certainty evidence indicates exercise likely leads to a slight improvement in quality of life (an average of 5.37 points better on a 0 to 100 scale) [2].
  • Treatment success: Low-certainty evidence suggests exercise may result in no difference in participant-reported treatment success [2].
  • Withdrawals and adverse events: Exercise likely results in no difference in study withdrawals, but may increase adverse events [2].

• Exercise added to another co-intervention versus the co-intervention alone

  • Pain: Moderate-certainty evidence indicates that adding exercise likely improves pain (an average of 10.43 points better on a 0 to 100 scale) [2].
  • Physical function: Adding exercise likely results in a slight improvement in physical function (an average of 9.66 points better on a 0 to 100 scale) [2].
  • Quality of life: Adding exercise likely leads to a slight improvement in quality of life (an average of 4.22 points better on a 0 to 100 scale) [2].
  • Treatment success: Moderate-certainty evidence suggests adding exercise likely increases participant-reported treatment success [2].
  • Withdrawals and adverse events: Adding exercise likely slightly reduces study withdrawals and slightly increases adverse events [2].

Clinical significance of findings

The Cochrane review authors compared their findings to "minimal important difference" (MID) scores [2]. These scores represent the smallest change in an outcome that a person with knee OA would consider meaningful [2]. For pain, the MID was 12 points on a 0-100 scale; for physical function, 13 points; and for quality of life, 15 points [2].

The review found that the confidence intervals for the average differences in pain, physical function, and quality of life either did not reach these MID thresholds or included both clinically important and unimportant improvements [2]. This means that while exercise showed statistical improvements, it's uncertain whether these average improvements would be considered clinically meaningful by individuals with knee OA [2].

The authors noted that since participants in most trials were aware of their treatment, this lack of blinding may have contributed to the reported improvements [2].

What the Cochrane review did not find

In contrast to the Juhl review, the Cochrane review did not find differences in effects between different types of exercise [2]. It also found no relationship between changes in pain or physical function and the total number of exercise sessions prescribed, or the amount of real-time consultation with a healthcare provider [2].

Maintaining exercise benefits for knee OA

The Osteoarthritis Research Society International (OARSI) provides guidelines for the non-surgical management of knee OA [3]. These guidelines are developed through expert consensus and a review of high-quality meta-analytic data [3].

OARSI identifies "structured land-based exercise programs" as a "Core Treatment" for knee OA [3]. This means that exercise is considered a fundamental and essential part of managing the condition [3]. For knee OA, these core treatments also include arthritis education and may involve dietary weight management [3].

While the OARSI guidelines recommend exercise as a core treatment, they do not explicitly detail how long an individual should continue exercising to maintain benefits. However, classifying it as a "core treatment" suggests it is an ongoing strategy for managing symptoms rather than a temporary intervention. Continuing to engage in regular, appropriate exercise is generally understood to be important for long-term management of chronic conditions like OA.

What this means for you

Understanding the specifics of exercise for knee OA can help you make informed decisions about your care. Research suggests that focusing on a single type of exercise, such as aerobic, resistance, or performance-based movements, may be more effective than combining many types [1]. Quadriceps-strengthening exercises appear particularly beneficial for pain reduction [1]. If you are engaging in supervised exercise, aiming for at least three sessions per week may offer greater pain relief [1].

The benefits of exercise for knee OA, in terms of pain and physical function, are evident immediately after an exercise program [2]. However, the current research, as summarized in the Cochrane review, primarily focuses on these short-term effects and does not provide extensive data on how long these benefits last after the program stops [2]. This means that continued, regular physical activity is generally important for ongoing management of knee OA symptoms.

The improvements seen with exercise are often statistically significant, but whether these average improvements are "clinically meaningful" (i.e., a noticeable difference in your daily life) can vary for each individual [2]. It's important to remember that research findings represent averages across many people, and your personal experience may be different.

To determine the most suitable exercise program for your specific situation, including the type, intensity, and frequency of exercise, it is best to consult a regulated healthcare professional. A physiotherapist, for example, can assess your condition, consider your individual needs and abilities, and help you develop a safe and effective exercise plan. You can find physiotherapy clinics in Calgary through our directory. In Alberta, you can verify the registration of a physiotherapist by contacting the College of Physiotherapists of Alberta [4].