Most physical therapists maintain that resistance training is beneficial to patients with knee osteoarthritis, but evidence from trials that have been designed with consistency is lacking. Experts discuss how to create an effective regimen given this information vacuum.
By Jill R. Dorson
Osteoarthritis (OA) affects nearly 27 million people in the United States; it is more common in those ≥65 years.1 The disease causes progressive erosion of the surface layer of the cartilage and, eventually, underlying bone, resulting in pain, swelling, and stiffness that limit mobility, cause disability, and impair quality of life.2 OA of the knee is the most common form.2
According to the American College of Rheumatology 2012 update to its guidelines for treating OA of the hand, hip, and knee,3 symptomatic pain relief in patients without contraindication can be managed medically with acetaminophen (to a maximum dosage of 4000 mg/d); oral and topical nonsteroidal anti-inflammatory drugs (topicals are preferred for patients ≥75 years); tramadol; opioids; and intra-articular corticosteroid injection; these can be prescribed in conjunction with nonpharmaceutical modalities, such as thermal therapy, joint-protection techniques, and assistive devices. Moreover, the College strongly recommends that patients with OA of the knee participate in aerobic, aquatic, or resistance exercises according to their physical capabilities and preferences.
What research demonstrates
Resistance training is one of the most widely used nonpharmacotherapeutic methods for treating OA, although there is debate over what form it should take.4 A 2017 systematic review of 34 studies of OA of the knee found that, because principles of resistance training were inconsistently applied within the studies, it was difficult to say definitively that resistance training had a positive effect on OA of the knee.4 The authors found that <10% of the studies reviewed were properly designed to develop gains in strength.
Although that review recommended that future studies should follow a stricter, more uniform protocol, lead author Claire Minshull, PhD, a researcher at the Carnegie School of Sport, Leeds Beckett University, Leeds, United Kingdom, and a specialist in rehabilitation and conditioning, believes that proper strength training is effective.
“For me, resistance training, when done correctly, can have a significant and positive effect on symptoms of knee osteoarthritis,” she said. “However, the problem that we have, which we highlighted in our systematic review, is that so many of the randomized controlled trials have been poorly designed.”
Keep on moving
Anecdotally, physical therapists do see a clear benefit from resistance training for OA of the knee. Resistance training can take any of several forms: Patients can use their own body weight, gravity, free weights, exercise machines, and resistance bands—essentially, any technique that gives the targeted muscle group something to work against. The goal is to improve muscle strength and exercise endurance. For physical therapists treating patients with OA of the knee, the first order of business is to get the affected joint moving so the patient can participate in therapy.
“The emphasis here is about getting [patients] functional again,” said Aaron Robles, PT, MPT, CFMT, president and owner of John Goetze Physical Therapy, Jacksonville Beach, Florida. “Early on, [OA] causes pain and keeps you from moving: ‘I have to do the exercises to protect my knee,’ patients tell me, ‘but it hurts.’ So then we have to loosen [the knee joint] up.”
Physical therapists accomplish this by manually moving the patella up and down and side to side; they can train patients to do this themselves and show them how to test to see if the joint is tight before beginning exercise. Exercising the knee without proper preparation is like asking someone to paint a room blue with red paint, said Taylor Miksell, PT, DPT, also at John Goetze. “The room is never going to be painted blue if you don’t give them the right tools.”
Open-chain and closed-chain exercises
Once the joint is loosened up, Robles and his team work with patients on exercises ranging from simple to complex. He and Miksell said they use both open-chain and closed-chain exercises, depending on patients’ needs and capabilities:
- Open-chain exercises. The foot is not fixed in place, unlike its position when using a weight machine; this allows isolation of specific muscle groups. The seated leg extension is an example of an open-chain exercise: The seated patient lifts his (her) leg from a 90o angle to straight in front and then lowers it to the original position.
- Closed-chain exercises. The foot is stationary—set on the floor, for example, or attached to a piece of exercise equipment. An example of a closed-chain exercise is a squat, in which the feet are placed firmly on the floor.
Physical therapists and researchers agree that resistance training is most effective when there is a clear plan of action, which includes progression in both repetitions and weight load. Minshull said that some physical therapists increase repetitions first; in her experience, however, adding weight before increasing repetitions is more effective.
Bo Bregenhof, MD, a PhD candidate in the Orthopaedic Research Unit, Faculty of Health Sciences, University of Southern Denmark, Odense, is also a proponent of increasing weight before repetition. He is lead researcher for a clinical trial5 that studied the effect of combined, progressive-resistance, and neuromuscular exercises on knee-flexor and extensor strength. The study focused on prevention of OA as well as strengthening the hamstring following anterior cruciate ligament (ACL) reconstruction.
As mentioned, many patients with OA are ≥65 years,1 and working with an older population can present challenges that require medical professionals and physical therapists to be flexible in developing a treatment plan. Older patients might not be motivated to join the local health club, Bregenhof said, or they might not live near one. Resistance bands can provide a good alternative.
“The main strategy should focus on progression,” Bregenhof added. “In terms of resistance training for the OA population, there are as many views as there are health professionals. Still, heavy resistance and progression are the main ideas.”
Best practices in treating OA
Best practices for resistance training vary from professional to professional, as Bregenhof pointed out but, Minshull said, by definition, strength training involves lifting weights, with a target of 3 to a maximum of 5 repetitions, because after 5 repetitions the weight load becomes too heavy to complete another repetition.
In the opinion of many physical therapists, including Minshull, weight should increase before the number of repetitions to gain strength. Once the patient can do more than 6 reps at a certain weight, the number of reps can be increased. Leg extensions, leg presses, and mini-squats are effective and straightforward gym-based exercises, Minshull said. She added that, for older patients with more OA progression, lighter, body weight–focused exercises, such as sit-to-stands, step-ups, and mini-squats, possibly with a weighted backpack, are good options.
Robles and Miksell follow the patterns that Minshull and Bregenhof describe, first trying exercises that use body weight. Miksell said, “We’re not going to add resistance to someone who can’t [lift] their own body weight.” They will strive to increase endurance next, eventually adding ankle weights or resistance bands.
Robles works along the same lines, increasing repetitions at a given weight and adding more weight with fewer repetitions before building back up the maximum number of reps.
Keeping patients motivated
Motivating patients to stick to the program is among the major challenges in training, according to researchers and physical therapists.
“You can have the best intervention in the world; however, if you don’t get the buy-in from your patients, then it’s useless,” Minshull said. “I work closely with a consultant psychologist for this reason. Each person has his or her own personal barriers and motivations that will determine whether … they adhere to their rehabilitation.… There will be a section of the population, who, despite your best efforts, will not adhere.”
Despite not having consistent protocols for the management of OA of the knee, physical therapists can still create a clear plan for treatment, recognizing that each patient is unique.
“We’re either challenging patients to do more or pulling them back from doing too much,” Robles said. “It depends on personality.… We have to understand the patient’s goal and keep them motivated to keep the goal in sight.”
Besides consulting with a psychologist, Minshull builds individualized programs for each patient and then measures even the smallest gain—such as level of pain while descending stairs—twice a month to provide motivation.
Studies have shown that, over time, building strength is the cornerstone of treating OA of the knee. Two 12-week studies measured the relationship between increased strength and improved physical function:
- In a 2015 study,6 the authors concluded that increasing strength in the upper leg significantly reduced pain in patients with OA of the knee.
- A 2017 study7 found that, although increased knee-extensor strength did not result in improvement in function for patients with mild-to-moderate knee OA, patients with severe dysfunction at the start of the trial did see improvement.
These studies mirror what medical professionals and physical therapists see daily. Bregenhof is hopeful that the results of his trial will, ultimately, help prevent OA of the knee in patients who have had ACL surgery.
Although it seems clear that resistance training is an accepted and effective treatment for managing symptoms of osteoarthritis of the knee, there is no standard for research, making it difficult, and often frustrating, to interpret the results of studies.
“Despite having 34 ‘high-quality’ papers included in our review stating that their intervention was ‘strength training’ in nature, fewer than 10% of investigations designed their intervention properly to elicit strength gains,” Minshull said.4 “As such, you can see why it’s unclear whether … resistance training truly help[s] with osteoarthritis of the knee.”
Jill R. Dorson is a freelance writer based in San Diego, CA.
- NIH Research Portfolio Online Reporting Tools (RePORT): Osteoarthritis. Bethesda, MD: US Department of Health & Human Services, National Institutes of Health; 2010 Oct. https://report.nih.gov/nihfactsheets/ViewFactSheet.aspx?csid=55&key=O#O. Accessed April 15, 2018.
- Wallace IJ, Worthington S, Felson DT, et al. Knee osteoarthritis has doubled in prevalence since the mid-20th century. Proc Natl Acad Sci U S A. 2017;114(35):9332–9336.
- Hochberg MC, Altman RD, April KT, et al. American College of Rheumatology 2012 recommendations for the use of nonpharmacologic and pharmacologic therapies in osteoarthritis of the hand, hip, and knee. Arthritis Care Res (Hoboken). 2012;64:465-474.
- Minshull C, Gleeson N. Considerations of the principles of resistance training in exercise studies for the management of knee osteoarthritis: a systematic review. Arch Phys Med Rehabil. 2017;98:1842-1851.
- Bregenhof B, Jørgensen U, Aagaard P, et al. The effect of targeted exercise on knee-muscle function in patients with persistent hamstring deficiency following ACL reconstruction – study protocol for randomized trial. Trials. 2018;19:75.
- Knoop J, Steultjens MP, Roorda LD, et al. Improvement in upper leg muscle strength underlies beneficial effects of exercise therapy in knee osteoarthritis: secondary analysis from a randomised controlled trial. Physiotherapy. 2015;101(2):171-177.
- Hall M, Hinman RS, van der Esch M, et al. Is the relationship between increased knee muscle strength and improved physical function following exercise dependent on baseline physical function status? Arthritis Res Ther. 2017;19:271.