Abstract
Background Investigating modifiable factors that contribute to functional limitations in patients with total knee arthroplasty (TKA) may guide changes in rehabilitation protocols and improve functional outcomes. Whereas quadriceps muscle weakness has been demonstrated to contribute to functional limitations in TKA, the role of hip abductor weakness has not received attention.
Objective The purpose of this study was to determine whether hip abductor strength (force-generating capacity) contributes to physical function beyond what can be explained by quadriceps muscle strength in patients after a TKA.
Design A cross-sectional design was used in the study.
Setting The study was conducted in a clinical laboratory at an academic center.
Patients Thirty-one people with TKA (74% female; mean age=68 years, SD=8; mean body mass index=31 kg/m2, SD=5) participated in the study.
Measurements Strength of quadriceps muscles and hip abductors was measured using an isokinetic dynamometer. Performance-based physical function was assessed with 4 measures: self-selected walking speed, the Figure-of-8 Walk Test, the Stair Ascend/Descend Test, and the 5-Chair Rise Test. Self-reported physical function was assessed with the Western Ontario and McMaster Universities Osteoarthritis Index Physical Function Subscale.
Results In hierarchical regression models, after accounting for demographic and anthropometric factors, quadriceps muscle strength was associated with performance on the Stair Ascend/Descend Test. After accounting for demographic, anthropometric, and quadriceps strength, hip abductor strength was associated with performance on the Stair Ascend/Descend Test, the Figure-of-8 Walk Test, and the 5-Chair Rise Test.
Limitations The study design precluded ascertainment of causal relationships.
Conclusions After TKA, hip abductor strength influenced physical function in participants more than did demographic or anthropometric measures or quadriceps strength. Longitudinal studies with larger samples are warranted. If findings are replicated, they will justify targeting the hip abductors during rehabilitation after TKA.
Footnotes
Dr Piva, Mr Teixeira, Mr Almeida, Dr DiGioia, Mr Levison, and Dr Fitzgerald provided concept/idea/research design. Dr Piva, Mr Teixeira, Mr Almeida, Dr Gil, Mr Levison, and Dr Fitzgerald provided writing. Mr Teixeira, Mr Almeida, and Dr Gil provided data collection. Dr Piva and Mr Teixeira provided data analysis. Dr Gil provided project management. Dr Piva and Dr Fitzgerald provided fund procurement. Dr DiGioia and Mr Levison provided participants and institutional liaisons. Mr Almeida and Dr Gil provided clerical support. Dr DiGioia, Mr Levison, and Dr Fitzgerald provided consultation (including review of manuscript before submission).
This study was approved by the University of Pittsburgh Institutional Review Board.
This study was supported, in part, by the Claude D. Pepper Older American Independence Center (P30-AG024827); the Central Research Development Fund, University of Pittsburgh; the University of Pittsburgh Medical Center Health System Competitive Medical Research Fund; the National Center for Research Resources, a component of the National Institutes of Health (NIH), and NIH Roadmap for Medical Research (KL2 RR024154–02); and the American College of Rheumatology Research Education Foundation New Investigator Award.
- Received April 6, 2010.
- Accepted October 7, 2010.
