Effect of High-Intensity Strength Training on Knee Pain and Knee Joint Compressive Forces Among Adults With Knee Osteoarthritis: The START Randomized Clinical Trial

Key PointsQuestionIs high-intensity strength training more effective than low-intensity strength training and attention control for the outcomes of knee pain and knee joint compressive forces in participants with knee osteoarthritis? FindingsIn this randomized clinical trial involving 377 participants with knee osteoarthritis, high-intensity strength training, compared with low-intensity strength training and an attention control, did not significantly improve knee pain or knee joint compressive forces at 18 months. MeaningThese findings do not support the use of high-intensity strength training over low-intensity strength training or attention control in adults with knee osteoarthritis. ImportanceThigh muscle weakness is associated with knee discomfort and osteoarthritis disease progression. Little is known about the efficacy of high-intensity strength training in patients with knee osteoarthritis or whether it may worsen knee symptoms. ObjectiveTo determine whether high-intensity strength training reduces knee pain and knee joint compressive forces more than low-intensity strength training and more than attention control in patients with knee osteoarthritis. Design, Setting, and ParticipantsAssessor-blinded randomized clinical trial conducted at a university research center in North Carolina that included 377 community-dwelling adults (>= 50 years) with body mass index (BMI) ranging from 20 to 45 and with knee pain and radiographic knee osteoarthritis. Enrollment occurred between July 2012 and February 2016, and follow-up was completed September 2017. InterventionsParticipants were randomized to high-intensity strength training (n=127), low-intensity strength training (n=126), or attention control (n=124). Main Outcomes and MeasuresPrimary outcomes at the 18-month follow-up were Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) knee pain (0 best-20 worst; minimally clinically important difference [MCID, 2]) and knee joint compressive force, defined as the maximal tibiofemoral contact force exerted along the long axis of the tibia during walking (MCID, unknown). ResultsAmong 377 randomized participants (mean age, 65 years; 151 women [40%]), 320 (85%) completed the trial. Mean adjusted (sex, baseline BMI, baseline outcome values) WOMAC pain scores at the 18-month follow-up were not statistically significantly different between the high-intensity group and the control group (5.1 vs 4.9; adjusted difference, 0.2; 95% CI, -0.6 to 1.1; P=.61) or between the high-intensity and low-intensity groups (5.1 vs 4.4; adjusted difference, 0.7; 95% CI, -0.1 to 1.6; P=.08). Mean knee joint compressive forces were not statistically significantly different between the high-intensity group and the control group (2453 N vs 2512 N; adjusted difference, -58; 95% CI, -282 to 165 N; P=.61), or between the high-intensity and low-intensity groups (2453 N vs 2475 N; adjusted difference, -21; 95% CI, -235 to 193 N; P=.85). There were 87 nonserious adverse events (high-intensity, 53; low-intensity, 30; control, 4) and 13 serious adverse events unrelated to the study (high-intensity, 5; low-intensity, 3; control, 5). Conclusions and RelevanceAmong patients with knee osteoarthritis, high-intensity strength training compared with low-intensity strength training or an attention control did not significantly reduce knee pain or knee joint compressive forces at 18 months. The findings do not support the use of high-intensity strength training over low-intensity strength training or an attention control in adults with knee osteoarthritis. Trial RegistrationClinicalTrials.gov Identifier: NCT01489462 This randomized trial compares the effects of high- vs low-intensity strength training vs control on 18-mo knee pain and knee joint compressive force among adults with knee pain and radiographic evidence of osteoarthritis.