Spatially defined disruption of motor imagery performance in people with osteoarthritis.

OBJECTIVES: To determine whether motor imagery performance is disrupted in patients with painful knee OA and if this disruption is specific to the location of the pain.

METHODS: Twenty patients with painful knee OA, 20 patients with arm pain and 20 healthy pain-free controls undertook a motor imagery task in which they made left/right judgements of pictured hands and feet. Accuracy and reaction time of judgements were compared between groups and pain locations (side: left vs right; site: upper vs lower).

RESULTS: Patients with knee pain were less accurate (P < 0.01) than healthy controls, but not different from people with arm pain (all P > 0.11). There were no differences in reaction time between groups (P = 0.64). Further, there was no effect of side or site of pain on reaction time (P = 0.43, 0.54, respectively) and no effect of site of pain on accuracy of left/right judgements (P = 0.12). However, there was an interaction effect of side of pain on accuracy of left vs right images (P = 0.03). If left-sided pain was present, accuracy was lower when images showed left hands/feet than when images showed right hands/feet.

CONCLUSION: Motor imagery performance is disrupted in patients with knee OA, but is also disrupted in patients with arm pain. Accuracy of left/right judgements is disrupted in a spatially defined manner, raising the important possibility that brain-grounded maps of peripersonal space contribute to the cortical proprioceptive representation.