Predictors of Physiotherapy Success in Knee Osteoarthritis

Osteoarthritis of the knee (KOA) is a primary contributor to this situation. Due to an aging population and increasing obesity, KOA’s prevalence has more than doubled in the past ten years, pointing to an impending endemic state.1,2 As the world’s tenth largest contributor to years lived with disabilities, KOA surgeries and hospitalisations cost world healthcare systems billions of dollars yearly.3,4

This scenario heightens the importance of focusing on the most effective treatments. The research showing the efficacy of exercise therapy for KOA is definitive. Physiotherapy ameliorates KOA progression while quickly reducing pain and improving function with effects comparable to surgery.5-7 Additionally, adults with KOA and a body mass index higher than 25kg/m2, report improved pain, ability, and quality of life from weight reductions as modest as 5% to 10%.8

Diet-only treatments do not seem to relieve pain.9 However, diet strategies with nutritional education, exercise, and behavioural therapy can help patients with osteoarthritis achieve clinically effective weight loss.8 Exercise physiologists have training in these approaches, making the combination of physiotherapy and exercise physiology an ideal referral for KOA. The combination of exercise therapy and weight loss proves more effective than either approach alone.10

Despite the general effectiveness of exercise therapy for KOA, some patients achieve clinically significant improvements in knee function while others do not. Dalerie Lieberz and colleagues set out to find predictors of clinical success. They performed an analysis of health records from 34 outpatient physiotherapy clinics. Their study includes 706 patients with KOA who received a physiotherapy assessment and at least one physiotherapy visit. They measured treatment success as a clinically important improvement in the Lower Extremity Functional Scale (> 8 points). The study expresses likelihood of success in odds ratios (OR). An OR lower than 1.0 means less likelihood of success. Likewise, ORs greater than one signify increasingly greater likelihood of success. 

By far, the strongest predictor of success was the number of physiotherapy visits. Patients with only two visits had an OR of 0.36, while patients with 18 visits enjoyed a 6.21 OR. For each visit over 2, the OR increased by 0.39, up to 18 visits. Beyond 18 visits, the OR did not improve. Younger patients had improved odds. Patients with opioid prescriptions scored better results in physiotherapy if they were older than age 65 (OR 3.46) but worse results if they were younger (OR 0.85). Interestingly, exercise therapy that was adherent to the treatment guidelines from the American Academy of Orthopaedic Surgeons correlated with worse outcomes (OR 0.72). This may suggest deficits with the guidelines. Alternatively, this observation may indicate that physiotherapists who customise treatment plans with evidencedbased care for multiple diagnoses and patient motivations outperform care plans based on a single-diagnosis approach.

References

1. Englund M, Turkiewicz A. Osteoarthritis increasingly common public disease. Lakartidningen. 2014;111(21):930.

2. Kyu HH, Abate D, Abate KH, Abay SM, Abbafati C, Abbasi N, Abbastabar H, Abd-Allah F, Abdela J, Abdelalim A, Abdollahpour I. Global, regional, and national disability-adjusted life-years (DALYs) for 359 diseases and injuries and healthy life expectancy (HALE) for 195 countries and territories, 1990–2017: a systematic analysis for the Global Burden of Disease Study 2017. The Lancet. 2018 Nov 10;392(10159):1859-922.

3. Hawker GA. Osteoarthritis is a serious disease. Clin Exp Rheumatol. 2019 Sep 1;37(Suppl 120):3-6.

4. Palazzo C, Nguyen C, Lefevre-Colau MM, Rannou F, Poiraudeau S. Risk factors and burden of osteoarthritis. Annals of Physical and Rehabilitation Medicine. 2016 Jun 1;59(3):134-8.

5. Katz J, Brophy R, Chaisson C, et al. Surgery versus physical therapy for a meniscal tear and osteoarthritis. NEJM. Mar 19 2013; DOI: 10.1056/NEJMoa1301408.

6. Pinto D, Robertson M, Abbott J, et al. Manual therapy, exercise therapy, or both, in addition to usual care, for osteoarthritis of the hip or knee. 2: economic evaluation alongside a randomized controlled trial. Osteoarthritis and Cartilage. 2013; joca.2013.06.014.

7. Fransen M, McConnell S, Harmer A, et al. Exercise for osteoarthritis of the knee. Br J Sports Med. 2015; 49 (24): 1554-1557.

8. Chu IJ, Lim AY, Ng CL. Effects of meaningful weight loss beyond symptomatic relief in adults with knee osteoarthritis and obesity: a systematic review and meta‐analysis. Obesity Reviews. 2018 Nov;19(11):1597-607.

9. Hall M, Castelein B, Wittoek R, Calders P, Van Ginckel A. Diet-induced weight loss alone or combined with exercise in overweight or obese people with knee osteoarthritis: a systematic review and meta-analysis. In Seminars in Arthritis and Rheumatism 2019 Apr 1 (Vol. 48, No. 5, pp. 765-777). WB Saunders.

10. Brosseau L, Taki J, Desjardins B, Thevenot O, Fransen M, Wells GA, Imoto AM, Toupin-April K, Westby M, Gallardo IC, Gifford W. The Ottawa panel clinical practice guidelines for the management of knee osteoarthritis. Part one: introduction, and mind-body exercise programs. Clinical Rehabilitation. 2017 May;31(5):582-95.

11. Lieberz D, Regal R, Conway P. Observational study: predictors of a successful functional outcome in persons who receive physical therapy for knee osteoarthritis. Evaluation & the Health Professions. 2022 Jun;45(2):137-46.