T Mark Campbell1, Guy Trudel2, Philip G Conaghan3, Katherine Reilly4, Robert J Feibel5, Dennis McGonagle6. 1. Department of Physical Medicine and Rehabilitation, Elisabeth Bruyère Hospital, Ottawa; Bone and Joint Research Laboratory, Faculty of Medicine, Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, and Division of Physical and Rehabilitation Medicine, Department of Medicine, Ottawa Hospital Research Institute, Ottawa, Canada. tcampbell@bruyere.org. 2. Bone and Joint Research Laboratory, Faculty of Medicine, University of Ottawa; Division of Physical and Rehabilitation Medicine, Department of Medicine, Ottawa Hospital Research Institute; and Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Canada. 3. Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, and NIHR Leeds Musculoskeletal Biomedical Research Centre, Leeds, UK. 4. Bone and Joint Research Laboratory, Faculty of Medicine, University of Ottawa, Canada. 5. Division of Orthopaedic Surgery, Department of Surgery, The Ottawa Hospital, Ottawa, Canada. 6. Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, Leeds, and NIHR Leeds Musculoskeletal Biomedical Research Centre, Leeds, UK.
Abstract
OBJECTIVES: Knee osteoarthritis (OA) is often accompanied by a flexion contracture (FC), resulting in worse clinical outcomes. Our objective was to determine associations between knee FC and specific regional and/or structural alterations on magnetic resonance imaging (MRI) using the Osteoarthritis Initiative (OAI). METHODS: 600 knees from the Foundation for the National Institutes of Health sub-study of the OAI were included. Knee extension was measured with a goniometer and FC was defined as inability to extend the knee to 0°. Structural alterations within the MRI Osteoarthritis Knee Score (MOAKS)-assessed regions that could potentially obstruct knee extension were primarily analysed. Multivariable linear regression models evaluated the effect size of MRI outcomes on knee extension. RESULTS: One-third (33.4%) of all participants had knee FC: 155 mild (1-5°, 26.0%), 44 moderate-severe (≥6°, 7.4%). Mean knee alignment was 0.3±3.7° valgus. Cartilage morphology and bone marrow lesion (BML) scores on the femoral side of the lateral patellofemoral joint were associated with lost knee extension (β=0.709, p<0.001, and β=0.666, p<0.001, respectively) as were higher osteophyte scores in multiple regions, worse meniscal score in the medial meniscal body (β=0.164, p<0.040) and posterior horn (β=0.400, p<0.001), and a worse effusion score (β=0.711, p<0.001). CONCLUSIONS: Knee flexion contractures were associated with non-specific, widespread MRI degenerative changes including cartilage loss and BMLs in the lateral patellofemoral joint, osteophytes, meniscal alterations and whole-joint effusion. Loss of knee extension in OA is likely a structurally-multifactorial outcome.
OBJECTIVES: Knee osteoarthritis (OA) is often accompanied by a flexion contracture (FC), resulting in worse clinical outcomes. Our objective was to determine associations between knee FC and specific regional and/or structural alterations on magnetic resonance imaging (MRI) using the Osteoarthritis Initiative (OAI). METHODS: 600 knees from the Foundation for the National Institutes of Health sub-study of the OAI were included. Knee extension was measured with a goniometer and FC was defined as inability to extend the knee to 0°. Structural alterations within the MRI Osteoarthritis Knee Score (MOAKS)-assessed regions that could potentially obstruct knee extension were primarily analysed. Multivariable linear regression models evaluated the effect size of MRI outcomes on knee extension. RESULTS: One-third (33.4%) of all participants had knee FC: 155 mild (1-5°, 26.0%), 44 moderate-severe (≥6°, 7.4%). Mean knee alignment was 0.3±3.7° valgus. Cartilage morphology and bone marrow lesion (BML) scores on the femoral side of the lateral patellofemoral joint were associated with lost knee extension (β=0.709, p<0.001, and β=0.666, p<0.001, respectively) as were higher osteophyte scores in multiple regions, worse meniscal score in the medial meniscal body (β=0.164, p<0.040) and posterior horn (β=0.400, p<0.001), and a worse effusion score (β=0.711, p<0.001). CONCLUSIONS: Knee flexion contractures were associated with non-specific, widespread MRI degenerative changes including cartilage loss and BMLs in the lateral patellofemoral joint, osteophytes, meniscal alterations and whole-joint effusion. Loss of knee extension in OA is likely a structurally-multifactorial outcome.