<p>Mental rotation can be performed more efficiently for objects that resemble the human body than for abstract objects. This human-body advantage is thought to reflect the involvement of body representations and motor processes. The present study investigated whether this advantage is reduced in older adults with knee osteoarthritis (OA), a condition associated with motor degeneration and altered body representation. Fifty-nine women with knee OA and thirty-six age-matched healthy controls completed a chronometric mental rotation task involving cube-shaped stimuli with or without a face. Results showed a significant human-body advantage in the control group but not in the knee OA group. This group difference remained even after controlling for body mass index and functional mobility, suggesting that the reduced advantage in the knee OA group may be associated with OA-related impairments such as disruptions in body schema or motor imagery. An exploratory analysis found no significant associations between the magnitude of the human-body advantage and clinical measures of knee OA severity (radiographic grade, symptom scores, gait-related self-efficacy, and functional mobility). These findings suggest that intact body representations may play a role in supporting the human-body advantage in mental rotation. They may also inform assessment of body representation in OA.</p>