Introduction

“I can’t lift weights anymore – my knees just won’t let me.” This is something physiotherapists often hear from patients with knee osteoarthritis (OA). Pain, stiffness, and reduced mobility make daily life difficult for millions worldwide. While exercise is a proven treatment, many patients struggle to find a form of training that is both effective and sustainable.

Knee osteoarthritis is the most common joint disease and the leading cause of knee pain in adults. The most significant risk factors include obesity, aging, genetic predisposition, knee injuries, and long-term heavy joint loading, such as physically demanding work. The condition affects the entire joint, with changes in cartilage, bone, joint capsule and surrounding muscles, which cause pain, stiffness, and reduced function. As populations age and obesity becomes more common, the burden of knee osteoarthritis is expected to increase further (Pohjolainen 2024.)

Physiotherapy and exercise are central in treatment. Movement, muscle strength and stretching exercises are important for self-management, and in many cases, patients need guidance from a physiotherapist. (Pohjolainen 2024.) The key question for rehabilitation is therefore what kind of exercise provides the best outcomes for these patients.

Our group conducted a mini literature review as part of the physiotherapy curriculum at Savonia University of Applied Sciences. This article is part of a series produced within the course Professional in Physiotherapy, which is included in the physiotherapy degree programme. The article was created as part of the evidence-based physiotherapy section of the course. In small groups, students practice elements of a systematic literature review, including systematic information retrieval, critical appraisal using the PEDro Scale tool, and writing up the results in the form of a scientific article.

The aim of our mini literature review was to examine recent randomized controlled trials that investigated strength training interventions for knee osteoarthritis and to explore their effects on pain, muscle strength, functional ability and quality of life.

Methods

The literature search was carried out in the PubMed database using the keywords “knee osteoarthritis” AND “strength training” AND “randomized controlled trial”. The search was limited to articles published within the last ten years (2015–2025). The inclusion criteria were adult participants with clinically diagnosed knee osteoarthritis, randomized controlled trial (RCT) design, and an intervention that included strength training. The exclusion criteria were studies not designed as RCTs, populations without knee osteoarthritis (e.g. hip OA, rheumatoid arthritis), and interventions not including strength training (e.g. aerobic exercise only, yoga without resistance component).

The methodological quality of the included studies was assessed with the PEDro scale (Physiotherapy Evidence Database), which is widely used in physiotherapy to evaluate the internal validity and reporting of randomized controlled trials. (PEDro, 2025.) The Physiotherapy Evidence Database (PEDro) is an online, freely accessible resource that provides information about the quality and content of physiotherapy-related research. It includes randomized controlled trials, systematic reviews, and clinical practice guidelines relevant to physiotherapy. Each RCT indexed in PEDro is independently rated for methodological quality using the PEDro scale, which assesses criteria such as random allocation, blinding, and adequacy of follow-up. This allows clinicians and researchers to quickly identify high-quality evidence to support evidence-based practice in physiotherapy.

Results

The review included three studies published between 2020 and 2023. One trial compared strength training, aerobic exercise and usual care (Øiestad et al., 2023). Another investigated concentric versus eccentric resistance training (Vincent & Vincent, 2020). A third study added strength training to neuromuscular exercise and education (Holm et al., 2020). Across these studies, participants were adults with clinically diagnosed knee osteoarthritis, most of them middle-aged or older. The interventions ranged from traditional resistance programs to combination approaches that included education and neuromuscular training. The studies may be found in the references section.

The study by Øiestad et al. (2023), which compared strength and aerobic exercise interventions versus usual care in patients with knee osteoarthritis, received a PEDro score of 7 out of 10. This score reflects strengths such as random allocation, concealed group allocation, blinded assessors, and adequate follow-up, while recognizing that blinding of subjects and therapists was not feasible in this exercise trial.

Vincent and Vincent (2020) examined the effects of concentric and eccentric resistance training on physical function and pain outcomes in older adults with knee osteoarthritis. Their trial also achieved a PEDro score of 7 out of 10, benefiting from assessor blinding, concealed allocation, and randomized design, but lacking intent-to-treat analysis and blinding of participants and therapists.

Holm et al. (2020) tested low-dose strength training combined with neuromuscular exercise and education compared to neuromuscular exercise and education alone. This study had a slightly higher PEDro score of 8 out of 10 due to additional strengths such as participant and assessor blinding and intention-to-treat analysis.

The evidence showed that strength training consistently improved muscle strength and often reduced pain. Eccentric training (Vincent & Vincent, 2020) demonstrated strong effects on specific outcomes. Short-term improvements were also seen in physical function, for example in sit-to-stand and stair-climb performance. However, long-term benefits in mobility were less consistent, and sustaining improvements in quality of life beyond the intervention period proved difficult. The short-term physiological benefits were also positive when comparing strength exercise and aerobic exercise versus usual care but in the long-term the benefits in quality of life were not significant (Øiestad et al., 2023). At the same time, the research highlighted that strength training interventions were safe. Adverse events were rare, supporting the use of strength training as a suitable rehabilitation strategy for patients with knee osteoarthritis.

Summary and Conclusions

Based on our review, strength training should remain a core component of rehabilitation for people with knee osteoarthritis. Exercise can safely reduce pain and increase muscle strength, but the approach must be tailored to each individual. The main findings of the reviewed studies are as follows:

• Eccentric-focused training may reduce pain during everyday tasks such as climbing stairs (Vincent & Vincent, 2020).
• Combination programs that include neuromuscular exercise, patient education, and strength training may offer more comprehensive benefits for function and self-management (Holm et al. 2020).
• Efficacy of strength or aerobic exercise on quality of life and knee function didn’t have significant improvement in knee-related quality of life at 1 year; however, the study supports that exercise interventions improved physiological outcomes in the short term but may need longer or more intensive approaches or personalized strategies to achieve lasting quality of life benefits (Øiestad et al. 2023).

The reviewed studies highlight the potential of strength training but also underline existing gaps in knowledge. The protocols varied widely, which makes it difficult to directly compare results. Most interventions lasted only 8–12 weeks, leaving the long-term effects uncertain. Future research is needed to identify the optimal exercise intensity, frequency and duration to achieve lasting improvements in function and quality of life.

The main challenge lies in maintaining the benefits over time. Physiotherapists play a crucial role in encouraging adherence, supporting motivation, and helping patients integrate exercise into daily life after supervised rehabilitation ends.

Future studies should explore optimal exercise intensity, frequency, and duration to achieve lasting improvements in function and quality of life. For now, the message is clear: exercise is medicine for knee osteoarthritis, but it must be prescribed and practiced in the right way.

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Authors:

Eetu Korpinen, physiotherapy student, Savonia University of Applied Sciences

Tino Kulmala, physiotherapy student, Savonia University of Applied Sciences

Aleksi Koistinen, physiotherapy student, Savonia University of Applied Sciences

Eero Kilpeläinen, physiotherapy student, Savonia University of Applied Sciences

Marja Äijö PT, PhD, principal lecturer of gerontology and rehabilitation, Savonia University of Applied Sciences

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References:

Holm, P. M., Schrøder, H. M., Wernbom, M., & Skou, S. T. (2020). Low-dose strength training in addition to neuromuscular exercise and education in patients with knee osteoarthritis in secondary care – a randomized controlled trial. Osteoarthritis and Cartilage, 28(6), 744–754. https://doi.org/10.1016/j.joca.2020.02.839

PEDro 2025. PEDro scale. Physiotherapy Evidence Database. Centre for Evidence-Based Physiotherapy. Saatavilla: https://pedro.org.au/english/resources/pedro-scale/. Viitattu 3.10.2025.

Pohjolainen, T. 2024. Polven nivelrikko. Lääkärikirja Duodecim. Helsinki. Kustannus Oy Duodecim. Saatavilla: https://www.terveyskirjasto.fi/dlk01081. Viitattu 2.10.2025

Øiestad, B. E., Årøen, A., Røtterud, J. H., Østerås, N., Jarstad, E., Grotle, M., & Risberg, M. A. (2023). The efficacy of strength or aerobic exercise on quality of life and knee function in patients with knee osteoarthritis. A multi-arm randomized controlled trial with 1-year follow-up. BMC Musculoskeletal Disorders, 24(1), 714. https://doi.org/10.1186/s12891-023-06831-x

Vincent, K. R., & Vincent, H. K. (2020). Concentric and eccentric resistance training comparison on physical function and functional pain outcomes in knee osteoarthritis: A randomized controlled trial. American Journal of Physical Medicine & Rehabilitation, 99(10), 932–940. https://doi.org/10.1097/PHM.0000000000001450