Stratified exercise therapy compared with usual care by physical therapists in patients with knee osteoarthritis: A randomized controlled trial protocol (OCTOPuS study)

Abstract

Objectives Knee osteoarthritis (OA) is characterized by its heterogeneity, with large differences in clinical characteristics between patients. Therefore, a stratified approach to exercise therapy, whereby patients are allocated to homogeneous subgroups and receive a stratified, subgroup‐specific intervention, can be expected to optimize current clinical effects. Recently, we developed and pilot tested a model of stratified exercise therapy based on clinically relevant subgroups of knee OA patients that we previously identified. Based on the promising results, it is timely to evaluate the (cost‐)effectiveness of stratified exercise therapy compared with usual, “nonstratified” exercise therapy. Methods A pragmatic cluster randomized controlled trial including economic and process evaluation, comparing stratified exercise therapy with usual care by physical therapists (PTs) in primary care, in a total of 408 patients with clinically diagnosed knee OA. Eligible physical therapy practices are randomized in a 1:2 ratio to provide the experimental (in 204 patients) or control intervention (in 204 patients), respectively. The experimental intervention is a model of stratified exercise therapy consisting of (a) a stratification algorithm that allocates patients to a “high muscle strength subgroup,” “low muscle strength subgroup,” or “obesity subgroup” and (b) subgroup‐specific, protocolized exercise therapy (with an additional dietary intervention from a dietician for the obesity subgroup only). The control intervention will be usual best practice by PTs (i.e., nonstratified exercise therapy). Our primary outcome measures are knee pain severity (Numeric Rating Scale) and physical functioning (Knee Injury and Osteoarthritis Outcome Score subscale daily living). Measurements will be performed at baseline, 3‐month (primary endpoint), 6‐month (questionnaires only), and 12‐month follow‐up, with an additional cost questionnaire at 9 months. Intention‐to‐treat, multilevel, regression analysis comparing stratified versus usual care will be performed. Conclusion This study will demonstrate whether stratified care provided by primary care PTs is effective and cost‐effective compared with usual best practice from PTs.

Construct validity of the OCTOPuS stratification algorithm for allocating patients with knee osteoarthritis into subgroups

“…Moreover, weight losswith or without exerciseis expected to play a role in delaying structural progression of knee OA, next to improving clinical outcomes [32]. So far, only limited evidence is available on the effect of such a combined intervention in obese persons with knee OA [33][34][35], but is currently being tested in multiple trials, including our OCTOPuS-trial [15]. A few limitations in our study design should be noted.…”

“…On the other hand, in contrast to our hypotheses, these subgroups did not differ substantially in effects of usual exercise therapy. An ongoing RCT (OCTOPuS-study [ 15 ]) will demonstrate whether our stratification algorithm together with subgroup-specific exercise therapy improves clinical and economic outcomes, thereby having added value for clinical practice.…”

“…Second, a ‘high muscle strength subgroup’ that is comparable to the proposed ‘post-traumatic phenotype’ [ 1 ] and expected not to benefit from exercise therapy, as no clinical effects can be expected from further muscle strengthening [ 14 ]. Therefore, this subgroup should only receive a minimal intervention of education and advice [ 15 ]. Third, an ‘obesity subgroup’ that is comparable to the proposed ‘metabolic phenotype’ and expected to benefit most from exercise therapy targeting both muscle strengthening and aerobic capacity, supplemented with a weight loss intervention [ 15 , 16 ].…”

“…Therefore, this subgroup should only receive a minimal intervention of education and advice [ 15 ]. Third, an ‘obesity subgroup’ that is comparable to the proposed ‘metabolic phenotype’ and expected to benefit most from exercise therapy targeting both muscle strengthening and aerobic capacity, supplemented with a weight loss intervention [ 15 , 16 ]. In contrast to our proposed, subgroup-specific interventions, previous studies as well as current practice usually offers a standardized muscle strengthening program based on a ‘one size fits all’ approach [ 15 ].…”

“…Third, an ‘obesity subgroup’ that is comparable to the proposed ‘metabolic phenotype’ and expected to benefit most from exercise therapy targeting both muscle strengthening and aerobic capacity, supplemented with a weight loss intervention [ 15 , 16 ]. In contrast to our proposed, subgroup-specific interventions, previous studies as well as current practice usually offers a standardized muscle strengthening program based on a ‘one size fits all’ approach [ 15 ]. We hypothesize that the three subgroups substantially differ in effects on pain and physical function of such a treatment, with large effects expected in the ‘low muscle strength subgroup’, medium effects in the ‘obesity subgroup’ and only small effects in the ‘high muscle strength subgroup’.…”