title: Lower leg compensatory strategies during performance of a step up and over task in patient six-months after total knee arthroplasty.
abstract: The purpose of this study was to assess the ankle, knee, and hip joint contributions to the total support moment (TSM) and the activation patterns of muscles in the lower leg in patients after total knee arthroplasty (TKA) and healthy older adults during the step up and over task. Moreover, the relationship between quadriceps strength and knee contribution to TSM was measured. Twenty patients six-months after TKA and twenty healthy controls were recruited for this study. Motion and surface electromyographic (EMG) analyses were performed during a step up and over task. Biomechanics and EMG variables were compared between groups using ANCOVA models with movement speed as covariate. Patients after TKA had reduced contribution to the TSM from the knee joint, and greater contribution from the hip and ankle joints, possibly to compensate for the reduced contribution at the knee. No consistent differences of EMG activation or co-contraction were found between groups. Patients with stronger quadriceps had significantly higher knee contribution to TSM during the lowering phase of the task. The results of this study suggest that patients after TKA may use compensatory strategies at the hip and ankle joints to safely perform the step up and over task. Patients may rely on the force generating ability of the quadriceps during the lowering phase as they are not able to compensate with other joints of the lower extremity during this phase of the task.
authors.affiliation: Division of Biokinesiology and Physical Therapy, University of Southern California, 1540 Alcazar St., CPH 155, Los Angeles, CA 90266, United States. Electronic address: pozzi@usc.edu.
authors.forename: Federico
authors.initials: F
authors.lastname: Pozzi
authors.affiliation: Department of Physical Therapy, University of Delaware, United States; Department of Orthopaedics and Rehabilitation Services, Christiana Health Care System, United States.
authors.forename: Adam R
authors.initials: AR
authors.lastname: Marmon
authors.affiliation: Department of Physical Therapy, University of Delaware, United States.
authors.forename: Lynn
authors.initials: L
authors.lastname: Snyder-Mackler
authors.affiliation: Department of Physical Therapy, University of Delaware, United States.
authors.forename: Joseph
authors.initials: J
authors.lastname: Zeni
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000534:rehabilitation*; D004576:Electromyography; D005260:Female; D005500:Follow-Up Studies; D006621:Hip Joint / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D007866:Leg / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D052097:Quadriceps Muscle / Q000502:physiology*; D013997:Time Factors
keywords: Electromyography; Quadriceps strength; Total support moment; Trunk