Acute Effects of Walking on The Deformation of Femoral Articular Cartilage

Abstract

Background and Purpose: Knee osteoarthritis (OA) is characterized by a progressive loss of the articular cartilage, increasing the amount of friction in the joint, resulting in pain and decreases in mobility and function. Additionally, it has been demonstrated that frontal plane lower extremity (LE) malalignment (e.g., varus, valgus) is associated with onset and progression of OA. Previous studies showed that static loading of 50% body weight at the knee results in more cartilage deformation in those with knee OA compared to healthy controls. As walking produces forces in the knee that are 2-3 times body weight, it may result in greater cartilage deformation. The purpose of our study was to compare the acute effects of walking on the femoral cartilage deformation between individuals with and without knee OA and determine whether LE alignment is associated with greater cartilage deformation. Subjects: 10 subjects without OA (5 females and 5 males; 55.0 ± 1.8 yrs; 78.8 ± 14.0 kg; 1.8 ± 0.2 m) and 9 subjects with OA were recruited (4 females and 5 males; 55.6 ± 4.5 yrs; 97.4 ± 15.0 kg; 1.7 ± 0.1 m). Methods: Each subject underwent X-ray and MRI assessment. For X-ray assessment, persons with Kellgren/Lawrence grades 2-3 were assigned to the OA group whereas subjects with grades 0-1 were assigned to the control group. During MRI assessment, 3T, frontal-plane MRI was obtained before and immediately after 30 minutes of treadmill walking at 3-4 mph. LE alignment was obtained by measuring the angle between the long axes of femur and tibia using a goniometer. To obtain cartilage deformation post-walking, the medial and lateral femoral cartilage of the weight-bearing areas were segmented on subjects’ MRI. Cartilage thickness was quantified by computing the perpendicular distance between opposing voxels defining the edges of the femoral cartilage. Cartilage volume was quantified by multiplying the segmented area by slice thickness. Independent t-tests were used to compare cartilage deformation (i.e., percent changes in medial and lateral cartilage thickness/volume) in response to walking between the 2 groups. Pearson correlation coefficients were used to assess the association between cartilage deformation and LE alignment of all subjects. Results: Independent t-tests revealed no significant difference in percent change of cartilage thickness between OA group and control group in medial (p=0.873) or lateral (p=0.688) femur. Additionally, there was no difference in percent change of cartilage volume between the two groups in medial (p=0.159) or lateral (p=0.327) femur. Pearson correlation coefficient analyses revealed a significant correlation between reductions in lateral femoral cartilage thickness and increased knee valgus alignment (p=0.030).