2022, Article / Letter to editor (Osteoarthritis and Cartilage, vol. 30, iss. 1, (2022), pp. 32-41)Hip and knee osteoarthritis (OA) are leading causes of global disability. Most research to date has focused on the knee, with results often extrapolated to the hip, and this extends to treatment recommendations in clinical guidelines. Extrapolating results from research on knee OA may limit our understanding of disease characteristics specific to hip OA, thereby constraining development and implementation of effective treatments. This review highlights differences between hip and knee OA with respect to prevalence, prognosis, epigenetics, pathophysiology, anatomical and biomechanical factors, clinical presentation, pain and non-surgical treatment recommendations and management.
2022, Article / Letter to editor (Journal of Physiotherapy, vol. 68, iss. 3, (2022), pp. 182-190)QUESTION: In people with knee osteoarthritis, how much more effective is stratified exercise therapy that distinguishes three subgroups (high muscle strength subgroup, low muscle strength subgroup, obesity subgroup) in reducing knee pain and improving physical function than usual exercise therapy? DESIGN: Pragmatic cluster randomised controlled trial in a primary care setting. PARTICIPANTS: A total of 335 people with knee osteoarthritis: 153 in an experimental arm and 182 in a control arm. INTERVENTION: Physiotherapy practices were randomised into an experimental arm providing stratified exercise therapy (supplemented by a dietary intervention from a dietician for the obesity subgroup) or a control arm providing usual, non-stratified exercise therapy. OUTCOME MEASURES: Primary outcomes were knee pain severity (numerical rating scale for pain, 0 to 10) and physical function (Knee Injury and Osteoarthritis Outcome Score subscale activities of daily living, 0 to 100). Measurements were performed at baseline, 3 months (primary endpoint) and 6 and 12 months (follow-up). Intention-to-treat, multilevel, regression analysis was performed. RESULTS: Negligible differences were found between the experimental and control groups in knee pain (mean adjusted difference 0.2, 95% CI -0.4 to 0.7) and physical function (-0.8, 95% CI -4.3 to 2.6) at 3 months. Similar effects between groups were also found for each subgroup separately, as well as at other time points and for nearly all secondary outcome measures. CONCLUSION: This pragmatic trial demonstrated no added value regarding clinical outcomes of the model of stratified exercise therapy compared with usual exercise therapy. This could be attributed to the experimental arm therapists facing difficulty in effectively applying the model (especially in the obesity subgroup) and to elements of stratified exercise therapy possibly being applied in the control arm. REGISTRATION: Netherlands National Trial Register NL7463.
2021, Article / Letter to editor (BMC Musculoskeletal Disorders, vol. 22, iss. 1, (2021), pp. 633)BACKGROUND: We recently developed a model of stratified exercise therapy, consisting of (i) a stratification algorithm allocating patients with knee osteoarthritis (OA) into one of the three subgroups ('high muscle strength subgroup' representing a post-traumatic phenotype, 'low muscle strength subgroup' representing an age-induced phenotype, and 'obesity subgroup' representing a metabolic phenotype) and (ii) subgroup-specific exercise therapy. In the present study, we aimed to test the construct validity of this algorithm. METHODS: Data from five studies (four exercise therapy trial cohorts and one cross-sectional cohort) were used to test the construct validity of our algorithm by 63 a priori formulated hypotheses regarding three research questions: (i) are the proportions of patients in each subgroup similar across cohorts? (15 hypotheses); (ii) are the characteristics of each of the subgroups in line with their proposed underlying phenotypes? (30 hypotheses); (iii) are the effects of usual exercise therapy in the 3 subgroups in line with the proposed effect sizes? (18 hypotheses). RESULTS: Baseline data from a total of 1211 patients with knee OA were analyzed for the first and second research question, and follow-up data from 584 patients who were part of an exercise therapy arm within a trial for the third research question. In total, the vast majority (73%) of the hypotheses were confirmed. Regarding our first research question, we found similar proportions in each of the three subgroups across cohorts, especially for three cohorts. Regarding our second research question, subgroup characteristics were almost completely in line with the proposed underlying phenotypes. Regarding our third research question, usual exercise therapy resulted in similar, medium to large effect sizes for knee pain and physical function for all three subgroups. CONCLUSION: We found mixed results regarding the construct validity of our stratification algorithm. On the one hand, it is a valid instrument to consistently allocate patients into subgroups that aligned our hypotheses. On the other hand, in contrast to our hypotheses, subgroups did not differ substantially in effects of usual exercise therapy. An ongoing trial will assess whether this algorithm accompanied by subgroup-specific exercise therapy improves clinical and economic outcomes.
2020, Article / Letter to editor (Arthritis Research & Therapy, vol. 22, iss. 1, (2020), pp. 54)BACKGROUND: The concept of osteoarthritis (OA) heterogeneity is evolving and gaining renewed interest. According to this concept, distinct subtypes of OA need to be defined that will likely require recognition in research design and different approaches to clinical management. Although seemingly plausible, a wide range of views exist on how best to operationalize this concept. The current project aimed to provide consensus-based definitions and recommendations that together create a framework for conducting and reporting OA phenotype research. METHODS: A panel of 25 members with expertise in OA phenotype research was composed. First, panel members participated in an online Delphi exercise to provide a number of basic definitions and statements relating to OA phenotypes and OA phenotype research. Second, panel members provided input on a set of recommendations for reporting on OA phenotype studies. RESULTS: Four Delphi rounds were required to achieve sufficient agreement on 11 definitions and statements. OA phenotypes were defined as subtypes of OA that share distinct underlying pathobiological and pain mechanisms and their structural and functional consequences. Reporting recommendations pertaining to the study characteristics, study population, data collection, statistical analysis, and appraisal of OA phenotype studies were provided. CONCLUSIONS: This study provides a number of consensus-based definitions and recommendations relating to OA phenotypes. The resulting framework is intended to facilitate research on OA phenotypes and increase combined efforts to develop effective OA phenotype classification. Success in this endeavor will hopefully translate into more effective, differentiated OA management that will benefit a multitude of OA patients.
2020, Article / Letter to editor (Physiotherapy, vol. 106, (2020), pp. 101-110)OBJECTIVES: To explore the feasibility of a newly developed model of stratified exercise therapy in primary care for patients with knee osteoarthritis (OA). DESIGN: Mixed method design (process, outcome and qualitative evaluation). SETTING: Six physical therapy practices in primary care around Amsterdam. PARTICIPANTS: Fifty eligible patients with knee OA, visiting one of the participating physical therapists (PTs). INTERVENTION: Patients were allocated to a subgroup based on a simple stratification tool and received subgroup-specific, protocolized, 4-month, exercise therapy. MAIN OUTCOME MEASURES: Feasibility of this model of stratified exercise therapy was explored by multiple process parameters, outcome measures (physical functioning and knee pain; at baseline and 4-months follow-up) and experiences from patients and PTs. RESULTS: From 97 potentially eligible patients, fifty patients were included and allocated to the 'high muscle strength subgroup' (n=17), 'depression subgroup' (n=4), 'obesity subgroup' (n=6) or 'low muscle strength subgroup' (n=23). Three patients dropped out during the study period. PTs provided relatively low numbers of sessions (on average 10 sessions), although exceedance of the recommended maximum number of sessions did occur frequently. We found clinically relevant improvements on physical functioning and knee pain (P<0.001 for both) for the total group. In general, the model of stratified exercise therapy was considered to be easily applicable and of added value for daily practice. CONCLUSIONS: Our model of stratified exercise therapy seems to be feasible in primary care, although a number of limitations were reported. Future research should determine the (cost-)effectiveness of an adapted model, compared to usual, non-stratified exercise therapy.
2020, Article / Letter to editor (Physiotherapy Research International, vol. 25, iss. 2, (2020), pp. e1819)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.