PURPOSE: The present study investigates behavioral conformity regarding physical activity (PA) and sedentary behavior (SB) in older couples where one partner suffers from osteoarthritis (OA). Hereby the question is addressed whether and to what extent the typical physical limitations of OA patients have negative effects on their partners. PATIENTS AND METHODS: The habitual PA and SB of end-stage osteoarthritis patients (n = 32, 52– 81 years | n = 14 gonarthrosis, n = 18 coxarthrosis), their spouses (n = 32, 50– 83 years) and control couples (n = 26 subjects, 52– 78 years) were assessed by accelerometry. Besides individual results of accelerometry hourly couple-specific performance ratios were calculated for four parameters of PA (number of steps, vector magnitude (VM), metabolic rate (MET), and total time in moderate-to-vigorous PA (MVPA)) and two parameters of SB (number of sedentary bouts and total time of sedentary bouts per hour). Analyses of covariance were used to explore differences in hourly couple-specific performance ratios between couples affected by osteoarthritis and control couples. RESULTS: Significant differences in PA were observed between the three groups, whereby the patients showed the lowest PA and the subjects of the control group the highest PA. In contrast to this, SB did not differ between the three groups. The hourly analyses of couple-specific performance ratios revealed significant differences between the target couples (patients and spouses) and the control couples for all parameters of PA. Thereby, the deviance in PA between the patients and their spouses was always smaller than in control couples and also decreased with age. The investigation of SB, on the other hand, revealed larger deviations between the patients and their spouses as compared to control couples and no changes with age. CONCLUSION: This study confirmed the known negative impact of osteoarthritis on the PA and SB of elderly patients. More important, however, was the finding that the patients’ spouses adapt to this poor health behavior and show reduced PA as well. Consequentially, spouses of OA patients should be considered as a risk group for inactivity-related diseases in old age. This should be considered in interventions that aim to use the individual support of spouses to increase the PA of OA patients.