QUESTION:In adults following primary total knee arthroplasty, does the incorporation of hip abductor strengthening exercises into a 6-week rehabilitation program improve muscle strength, functional performance and patient-reported outcomes at the end of rehabilitation and at 26 weeks? DESIGN:Randomised controlled trial with concealed allocation, blinded assessors and intention-to-treat analysis. PARTICIPANTS:One hundred and five adults admitted to an inpatient rehabilitation facility immediately following total knee arthroplasty. INTERVENTION:Participants in both groups attended 12 days of inpatient physiotherapy followed by 6 weeks of outpatient physiotherapy, which aimed to improve knee range of movement, strength and mobility. The experimental group completed a standard rehabilitation protocol with the addition of hip abductor strengthening. The control group completed the same standard rehabilitation protocol, with the addition of 15 minutes of general functional exercises. OUTCOME MEASURES:Primary outcomes were the Knee Injury and Osteoarthritis Outcome Score (KOOS) and isometric hip abductor muscle strength normalised to body mass index. Secondary outcome measures included the stair climb test, 6-minute walk test, Timed Up and Go test, 40-m fast-paced walk test, 30-second chair stand test, step test, isometric quadriceps muscle strength, Lower Extremity Functional Scale, and Short Form-12. RESULTS:The experimental intervention did not result in significantly greater improvements in hip strength, KOOS or any of the secondary outcome measures than the control intervention at 6 weeks or 26 weeks. CONCLUSION:Similar improvements in muscle strength, functional performance and patient-reported outcomes were observed whether specific hip-strengthening exercises were incorporated or general functional exercises were continued instead as part of a postoperative rehabilitation program for participants after total knee arthroplasty. REGISTRATION:ANZCTR 12615000863538.