By Jessica Orner, MD

Family Medicine Physician, Special Interest: Integrative Medicine, LGHP Family Medicine Quentin, Lebanon, PA

Dr. Orner reports no financial relationships relevant to this field of study.

SYNOPSIS: Tailored exercise therapy can improve physical functioning in patients with knee osteoarthritis and comorbid conditions.

SOURCE: de Rooij M, et al. Efficacy of tailored exercise therapy on physical functioning in patients with knee osteoarthritis and comorbidity: A randomized controlled trial. Arthritis Care Res (Hoboken) 2017;69:807-816.

Osteoarthritis is recognized as a major cause of disability. It is estimated that knee osteoarthritis affects 20-30% of American adults and is a leading cause of lower extremity impairment in older adults.1 Interventions for knee osteoarthritis include pharmaceuticals, physical therapy, and surgical and nonsurgical procedures. Although exercise therapy is recommended as an option in the management of knee osteoarthritis, patients with comorbidities often are excluded from pertinent clinical trials.2 This may lead to a reluctance to prescribe exercise therapy for those with comorbidities. There may be a concern about the therapy aggravating a condition or patients unable to tolerate the exercises. About 68-85% of patients with osteoarthritis have a comorbid condition.3

De Rooij et al evaluated tailored exercise therapy for physical functioning in patients with knee osteoarthritis and some of the most common comorbidities, including cardiovascular disease, heart failure, chronic obstructive pulmonary disease (COPD), obesity, and type 2 diabetes mellitus.3 In this single-blind, randomized, controlled trial, 126 study participants were enrolled from December 2011 to January 2014. Participants were randomized to either 20 weeks of an individualized comorbidity-adapted exercise program or to a wait list with current medical care and then comorbidity-adapted exercise after 32 weeks. Randomization was conducted with the MagMin, a web-based program that balances comorbid diseases and pain severity between the treatment and control groups.3 Inclusion criteria were diagnosis of knee osteoarthritis; at least one of the following comorbidities: coronary disease, heart failure, diabetes mellitus type 2, COPD, or a body mass index ≥ 30 kg/m2 and Cumulative Illness Rating Scale (CIRS) score > 2.3 The CIRS is an assessment of 14 organ systems in which the severity of comorbidity in that system is graded from 0 (no problems) to 4 (extremely severe). A score > 2 indicates that the comorbidity affects daily activities and that the patient is receiving treatment for the disease. The CIRS score, which has been shown to be a reliable, valid instrument in primary care, can be performed by trained nurses.4 Exclusion criteria included absolute contraindication for exercise therapy, total knee replacement or plan for one in the near future, participation in exercise therapy for knee OA in the preceding three months, dementia, significant physical limitations, expectation of being lost to follow-up, insufficient understanding of the Dutch language, psychological distress necessitating treatment, and refusal to sign informed consent. The authors did not indicate whether enrollees had received a diagnosis of bilateral or unilateral knee osteoarthritis. Also, they did not detail all the items that would qualify for an expectation of being lost to follow-up. However, one example was a planned change of residency. Regarding the psychological distress, it was not clear if the authors excluded those requiring cognitive or pharmaceutical treatment vs. those with more severe distress requiring hospitalization. The rehabilitation physician made the final determination on inclusion or exclusion. The intervention group received individualized 30- to 60-minute exercise therapy sessions twice weekly for 20 weeks. A physical therapist supervised the therapy sessions, which included muscle strength training, aerobic training, training on activities of daily living, and additional flexibility/stability exercises if needed. Comorbidity-related symptoms were monitored at each session, and any adaptations made to the therapy were dependent on the comorbidity.3 The primary outcome the authors assessed was physical functioning, which was determined using the physical function subscale of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC-pf) and the 6-minute walk test (6MWT). The secondary outcomes were serious adverse events, knee-pain severity, and perceived effect. The perceived effect was split into improved or not improved.3

The WOMAC is a 24-item health status questionnaire specifically developed for use among patients with hip and/or knee osteoarthritis. It is divided into three subscales: pain, stiffness, and physical function. The physical function subscale (WOMAC-pf) includes 17 items and assesses elements such as stair use, household duties, shopping, and ability to transfer in and out of the bath. Higher scores indicate worse pain, stiffness, and functional limitations.5 The 6MWT measures the distance a patient can walk in six minutes. According to the American Thoracic Society guidelines, patients should walk alone and the test should not be administered on a treadmill where the patient can adjust speed or slope nor on an oval or circular track.6 WOMAC-pf, 6MWT, and pain scales were assessed at baseline, week 10, week 20, and week 32 (12 weeks post-therapy). There was a statistically significant improvement in physical functioning for the intervention group. Three months after the intervention ended, mean improvement in the intervention group was 11.6 points (33%) on the WOMAC-pf scale and 59 meters (15%) on the 6MWT.3 Unfortunately, P values and 95% confidence intervals (CI) were not provided for these data. However, the differences over time between groups favored the intervention group, with a decrease in the WOMAC-pf score and an increase in the walking distance on the 6MWT. WOMAC-pf change by -7.43 (95% CI, -9.99 to -4.87; P < 0.001) and the 6MWT increased by 34.16 meters (95% CI, 17.68-50.64; P < 0.001). There were no serious adverse events reported that could be ascribed to the exercise therapy.


Based on this trial, clinicians should consider exercise therapy for patients with knee arthritis and comorbidities. However, additional clinical trials including patients with comorbid diseases are needed.

It is important for clinicians to ensure that the physical therapy group to which their patient is referred includes tailored therapy and monitors patients for signs of exacerbation of any comorbid condition, such as COPD or heart failure. This may help ensure the patient receives adequate therapy and that the intensity is not reduced to the point of ineffectiveness. It is unclear if physical therapists are familiar with the exercise protocol developed in this study. Both this and the limited diversity of the Dutch population may reduce generalizability of the results.


  1. Neogi T, Zhang Y. Epidemiology of osteoarthritis. Rheum Dis Clin North Am 2013;39:1-19.
  2. Boyd CM, et al. Informing evidence-based decision-making for patients with comorbidity: Availability of necessary information in clinical trials for chronic diseases. PLoS One 2012;7:e41601.
  3. de Rooij M, et al. Efficacy of tailored exercise therapy on physical functioning in patients with knee osteoarthritis and comorbidity: A randomized controlled trial. Arthritis Care Res (Hoboken) 2017;69:807-816.
  4. Hudon C, et al. Cumulative Illness Rating Scale was a reliable and valid index in a family practice context. J Clin Epidemiol 2005;58:603-608.
  5. Western Ontario and McMaster Universities Osteoarthritis Index (WOMUOI). Available at: Accessed Dec. 6, 2018.
  6. Enright PL. The six-minute walk test. Respir Care 2003;48:783-785.