Strength Training for Knee OA: Muscle Gains Don’t Always Reduce Joint Load | Healio Rheumatology News

The conventional wisdom that building leg strength can alleviate pain and improve function in knee osteoarthritis may be incomplete, according to recent research. Whereas strength training demonstrably improves muscle strength, a follow-up analysis of a significant trial indicates it doesn’t necessarily translate to reduced stress on the knee joint itself during walking. The findings, stemming from work at Wake Forest University and published in Arthritis Care & Research, add nuance to the long-held belief that strengthening muscles around the knee will directly lessen the biomechanical forces contributing to osteoarthritis pain.

The Evolution of Exercise Recommendations for Knee Osteoarthritis

For decades, the approach to managing knee osteoarthritis has shifted from advocating rest to encouraging movement. Initial studies in the late 1990s, led by Stephen P. Messier, PhD, demonstrated that both walking and strength training were more effective than no exercise at all in improving disability related to knee pain. This spurred a broader acceptance of exercise as a core component of osteoarthritis management. Later research began to focus on the potential benefits of combining exercise with weight loss, and then specifically on strength training, particularly targeting the hip muscles to address abnormal knee alignment.

The underlying theory was that strengthening hip abductors would counteract the inward pull on the knee – the internal knee adduction moment – which places increased stress on the medial compartment of the knee, a common site of pain in osteoarthritis. However, as Dr. Messier explains, data supporting this specific mechanism remained limited.

What the Recent Studies Showed

The current research builds on an 18-month strength training program involving 377 patients with knee varus alignment (bow-leggedness) and medial tibiofemoral osteoarthritis. Participants were assigned to either a high-intensity strength training protocol, a low-intensity protocol, or a control group receiving general wellness advice. The initial 2021 study, published in JAMA, revealed that while strength training significantly improved muscle strength, it didn’t result in noticeable differences in pain levels between the intervention and control groups.

This unexpected finding prompted a deeper dive. Researchers then conducted a post-hoc analysis of 88 patients from the original trial who exhibited the most substantial gains in leg muscle strength. This analysis, published in February 2026, aimed to determine if increased strength correlated with improvements in key biomechanical measures: the internal knee abduction moment and knee compressive force.

The results were striking. Participants in the strength training group demonstrated significant improvements in quadriceps, hamstring, and hip abductor strength – gains of 45%, 68%, and 42% respectively, compared to less than 5% in the control group. Despite these substantial strength gains, there were no significant differences between the groups in terms of peak internal knee abduction moment or peak knee compressive force. Interestingly, the intervention group did reveal a 27% reduction in internal knee extension moment, though the clinical significance of this finding requires further investigation.

Understanding Knee Joint Loading and Osteoarthritis

Dr. Messier emphasizes that osteoarthritis progression is driven by two primary pathways: mechanical load and inflammation. While weight loss addresses both – reducing load and lowering inflammatory markers – the impact of exercise on these pathways is more complex. The research suggests that while strength training can improve muscle strength and potentially reduce inflammation through increased fitness, it doesn’t necessarily alter the fundamental biomechanics of knee loading in a way that directly alleviates stress on the joint.

The concept of knee alignment is also crucial. Many individuals with knee osteoarthritis exhibit varus alignment, meaning their knees angle inward. The prevailing thought was that strengthening hip muscles would correct this alignment and reduce the internal adduction moment. However, the study’s findings challenge this assumption, suggesting that muscle strength alone may not be sufficient to alter knee alignment and reduce stress on the medial compartment.

What Does This Mean for Patients and Clinicians?

These findings don’t negate the benefits of strength training for individuals with knee osteoarthritis. Improved muscle strength can enhance overall function, mobility, and quality of life. However, they do suggest that focusing solely on strengthening muscles may not be enough to address the underlying biomechanical issues driving pain and progression of the disease.

Dr. Messier and his team are now exploring the role of muscle power – the ability to exert force quickly – in mitigating knee stress. A recent systematic review suggests that faster repetitions during strength training may be more beneficial. Current research, led by Dr. Messier and Paige E. Rice, PhD, MSc, is investigating whether increasing muscle power can prevent the onset of osteoarthritis. This builds on growing concerns about transparency in clinical trials for osteoarthritis treatments.

The Path Forward: A Multifaceted Approach

The key takeaway from this research is the need for a more comprehensive approach to managing knee osteoarthritis. While strength training remains a valuable component, it should be integrated with other strategies, such as weight management, low-impact aerobic exercise, and potentially interventions aimed at correcting knee alignment.

As Dr. Messier concludes, the most significant message for older adults with osteoarthritis is to remain active. Maintaining mobility is crucial for preserving independence and overall health. The specific type of exercise is less important than simply finding an activity that is enjoyable and sustainable over the long term.

For more information:

Stephen P. Messier, PhD, can be reached at [email protected].