Thirty-six patients with rheumatoid arthritis (RA), 30 patients with cox- or gonarthrosis (OA), and a control group of 40 patients with diabetes mellitus (DM) were studied with the aim of analyzing and comparing patient experienced muscular problems of muscle-strength analyzing and comparing patient experienced muscular problems of muscle-strength, endurance and balance/coordination with muscle function as assessed by standardized tests. The results indicated that patient-experienced problems of muscle function of the lower extremities were frequent in both the RA and the OA groups (about 80%) compared to the DM group (10%). Multivariate analyses of variance (MANOVAs) on experienced and tested muscle strength, endurance and balance/coordination, revealed a significant RA-OA difference (p less than 0.05). Separate analyses of variance (ANOVAs) indicated OA patients to show decreased tested endurance compared with the RA group. There was no significant RA-OA difference as to pain. Results provide evidence for considering muscle function of the lower extremities in therapeutic programs for RA and OA within primary health care.