MRI-Based Assessment of Lower Extremity Muscle Volumes in Patients with Meniscal Pathology and Knee Osteoarthritis

Abstract

Meniscal pathology has been identified as a predisposing source of joint degeneration and catalyst for disease progression. Muscle weakness and atrophy are hallmark clinical manifestations of joint injury; however, study of skeletal muscle function is largely limited to the thigh musculature in knee-injured populations. Volumetric measurements of skeletal muscle can provide information about individual muscle function that is challenging when using force-based or electromyographic techniques. PURPOSE: To describe lower extremity muscle volumes in patients with a history of meniscal injury and radiographic evidence of knee osteoarthritis (RKOA). METHODS: A lower extremity MRI was obtained for seven patients (6M/1F, 47.1 ± 9.2 years, 182.5 ± 4.7 cm, 99.1 ± 20.5 kg) with a history of meniscal injury and radiographic evidence (Kellgren-Lawrence ≥ 1) of unilateral knee joint osteoarthritis. Axial images were acquired from the ankle to the thoracic vertebrae, and thirty-four lower extremity muscles were manually segmented using a semi-automated program written in Matlab. Normalized muscle volumes (cm3/kg*m) were converted to Z-scores relative to a database of volumes collected from healthy volunteers. Z-scores were averaged, and means with 95% confidence intervals were calculated for each muscle. Z-scores were calculated for muscle groupings as a secondary analysis. RESULTS: On average, the vastus lateralis was the only muscle to exceed 2 SD below the corresponding muscle volume means of the healthy cohort (Z = -3.4 [-6.0, -0.9]), whereas, the vastus intermedius exceeded 2 SD above healthy (Z = 2.6 [0.7, 4.6]). Muscle groupings revealed reduced muscle volumes of the anterior (Z = -1.1) and medial hip (Z = -1.1), and anterior (Z = -1.3), lateral (Z = -1.1), and deep posterior (Z = -1.1) compartments in patients with knee pathology. CONCLUSION: Patterns of lower extremity muscle deficits were observed about the knee, hip, and ankle in patients with knee pathology. Muscle volumetric adaptations may occur in regions proximal and distal to the knee in patients with meniscal pathology and RKOA. Assessment of post-traumatic lower extremity muscles may provide a targeted rehabilitation approach for health care professionals.