Objectives This study aimed to address the effects of three modes of aerobic exercise (lower limbs with and without weight bearing and upper limb) combined with resistance training in patients with knee OA.

Methods In a randomised clinical trial, 78 patients older than 40 years, who had knee OA according to the criteria of the American College of Rheumatology (ACR) and an OA grade of 2 or 3 on the Kellgren/Lawrence classification based on plain radiographs, were randomly assigned to participate in 12 supervised sessions of strength training combined with one of three treadmill, cycle, or arm ergometer aerobic training. All groups completed visual analogue scale (VAS) and knee injury and osteoarthritis outcome score (KOOS) questionnaire to assess pain and function before and after the intervention. The 6 minute walk test (6MWT), timed up and go (TUG) and 30 second chair stand tests were also done to evaluate the performance.

Results Comparing the three interventional groups in terms of baseline characteristics showed no significant difference across the groups. Before and after the intervention, there was no significant difference between groups in terms of VAS and functional tests. However, all three groups had a significant improvement in the VAS, functional tests and KOOS score, after the intervention. After adjusting for baseline characteristics, the change in VAS was significantly higher in arm ergometer than in treadmill group (p = 0.03). Contrarily, the change in TUG was significantly higher in treadmill than arm ergometer group (p = 0.02). Also, the change of function in sport was significantly higher in Arm compared to treadmill group (p = 0.04).

Conclusions Our trial showed that 12 sessions of supervised exercise program, including aerobic and strength training may be efficacious to improve the pain and function of patients with mild to moderate knee osteoarthritis immediately after the program, regardless of the mode of aerobic exercise. In total, all three modes of aerobic exercise combined with strength training reduce pain severity and improve physical function. Nevertheless, the effect of Arm ergometry in pain relief and sport performance, and treadmill in TUG, is substantially more.

Acknowledgment The authors would like to express appreciation for the support of the Deputy of Research, Tehran University of Medical Sciences (Project number:93.04.30.27160)