Poor functional task performance and compensatory trunk movements remain two years after total knee arthroplasty

Lower limb kinematics are still impaired during functional activities one year after total knee arthroplasty (TKA) [1], yet recent studies highlighted a significant knowledge gap concerning trunk movements during such activities [2,3]. Trunk movements are often used as a compensatory strategy to unload the impaired or painful lower limb. As lower limb kinematics during these activities have the potential to improve even after seven years post-TKA [4], a better understanding about these compensatory mechanisms could optimize long-term rehabilitation. Is functional task performance impaired two years post-TKA and are truncal compensations observed? Thirty subjects (68 ± 7.6 years, 45% male, 22 months post-op, 36 operated knees) and 20 aged-matched controls (68 ± 8.2 years, 63% male, 40 knees) underwent a full-body gait analysis (Full Body Plug-In Gait) in an instrumented 3D-movement laboratory equipped with 14 Vicon cameras and 2 AMTI force plates. Primary outcome measures were the temporal characteristics of six functional activities: lunge, squat, stand up, sit down, stair climbing with a regular step and a high step. Secondary outcomes measures were range of motion (RoM) and maximal amplitudes of the lower limb (sagittal) and trunk (sagittal, frontal and transversal). Student’s t-test was performed to analyze differences in performance between cases and controls. Cases performed less flexed lunges (knee: -26°, hip: -8°, p<.006) in a same amount of time compared to controls, by shortening the loading phase (-7%, p=.020) to compensate for a longer push-back phase (+6%, p=.02) requiring increased ML trunk excursions (+3°, p=.04). Squats post-TKA were performed faster (+0.55 s, p=.038) but less deep (knee: -16°, hip: -13°, p<.017) without compensatory strategies. Cases took longer to stand up and sit down (+.59 s, p=.014), due to the longer sit down phase (+2.04%, p=.006) accompanied with an increased anterior pelvic tilt (+6°, p≤.003). As seen in Fig. 1, time to step up and down was similar between cases and controls when the step was low, but not when it was high (+1.70 s, p=.036) due to a longer preparatory parallel phase on the step (+8%, p=.028). Decreased knee flexion (-10°, p≤.0.01) and increased hip flexion (5-15°, p<0.03) was seen when stepping down, while truncal compensations were present in all three planes while stepping up and down.Download : Download high-res image (152KB)Download : Download full-size image Although cases performed some functional tasks as fast as controls, compensatory truncal strategies during unilateral loading (i.e., lunges, stairs climbing) of the prosthesis was observed two years post-TKA. In contrast, bilateral activities (i.e., squatting and sit to stand to sit) took longer but could be performed with minimal lower limb deficits and compensations. Poor performance during functional activities could lead to harmful loads on the prosthesis [5], which could not only endanger quality of life of the individual but also increase revision rates after TKA.