Relationship between biomechanical asymmetries during a step up and over task and stair climbing after total knee arthroplasty

• Patients after TKA reduce the demand on the operated knee during a stepping task.
• Compensations include increased effort of contralateral knee and ipsilateral hip.
• Stronger quadriceps strength is related to faster stair climbing after TKA.
• Stronger knee extensor muscles may be needed for more sagittal plane mechanics.

BackgroundPatients six months after total knee arthroplasty (TKA) demonstrate movement asymmetries and functional deficits, which may be related to poor functional performance. The aims of this study were to 1) compare biomechanical variables between subjects 6 months after TKA and an age-matched healthy control group during a step up and over task and 2) determine the relationship between quadriceps strength, movement patterns and stair climbing performance.MethodsTwenty patients 6 months following unilateral TKA and twenty healthy controls were enrolled. Participants completed questionnaires, isometric quadriceps strength testing and performance based tests to quantify functional performance. Motion analysis was performed during a step up and over task. Functional and biomechanical variables were analyzed using a 2× 2 ANOVA. The symmetry ratios (operated/non-operated limb * 100) for biomechanical variables were analyzed using independent t-tests. Pearson correlations were performed to determine the relationships between biomechanical variables, strength and stair climbing performance.FindingsIn the TKA group, subjects had lower peak moments, power and sagittal plane excursion in the operated knee compared to the contralateral knee (P < 0.05), while the hip on the operated side had greater power generation (P = 0.014). Compared to the control group, all symmetry ratios were significantly lower in the surgical group (P < 0.05). Stair climbing time was correlated with quadriceps strength of the operated limb (R = − 0.762, P < 0.001).InterpretationIndividuals 6 months after TKA had worse performance with respect to biomechanics, quadriceps strength, and performance-based tests. Biomechanical asymmetries after TKA reduce the demand on the operated knee and increase reliance on the contralateral limb and ipsilateral hip.