Left/right limb judgement task performance following total knee replacement

Purpose: Working body schema (WBS) of the limbs may be indirectly assessed using left/right limb judgement (LRLJ) task performance. This study aimed to investigate if: 1) Total Knee Replacement (TKR) patients perform LRLJ tasks using implicit motor imagery 2) patients have a disrupted WBS following a TKR for the replaced knee compared to the contralateral knee 3) LRLJ task performance changes following post-surgical rehabilitation using change in upper limb LRLJ task performance as a control. Methods: In a convenience sample (n=18, age 69±7yrs, 12F 6M) of TKR patients <1month post-surgery, WBS was assessed using LRLJ task performance for the upper (pictures of the hand) and lower limb (pictures of the foot) before and after rehabilitation. Accuracy and response time (RT) were analysed using a series of 2x2x2 ANOVAs. Results: LRLJ task performance for images corresponding with the operated and non-operated side were comparable for accuracy (p=0.83) and RT (0.28). Accuracy for hand images was comparable from baseline to post-rehabilitation (p=0.54) whereas accuracy for feet images increased significantly (p=0.03). Responses for awkward posture images were significantly slower than for more natural postures (p=0.001). Conclusions: LRLJ task performance data reflected biomechanical constraints that were indicative of implicit motor imagery being performed by patients. There was no evidence of a disrupted LRLJ task performance for the replaced knee compared to the contralateral knee. Following post-surgical rehabilitation patients’ lower limb LRLJ task performance improved whilst hand LRLJ task performance remained unchanged. These findings are the first to show that working body schema improves with rehabilitation following TKR, this may explain some of the clinical improvements seen. Implicit motor imagery could theoretically be a useful adjunct to current post-TKR rehabilitation.