The Effects of Locomotion-Induced Shock Loading on Tibiofemoral Bone Stress Response

Abstract

Purpose/Hypothesis: Knee osteoarthritis (Coats, Zioupos, & Aspden) is a degenerative joint disease that negatively impacts the quality of life. About 9.3 million people in the U.S. population are affected. It has been suggested via magnetic resonance imaging (MRI) studies that bone marrow edema (i.e., indicative of bone stress response) and joint structure changes may be the main contributing factors of pain in OA. Frontal plane lower extremity (LE) alignment has been a topic of much interest regarding development of OA in the knee joint. It is hypothesized that varus alignment increases forces through the medial compartment of the knee, thereby leading to bone stress response and initiation of OA. The purpose was to investigate the effects of locomotion-induced shock loading and LE alignment on tibiofemoral bone stress response in older adults without knee OA. Number of Subjects: Five male and five female subjects with no medical diagnosis of knee OA (57.9 ± 3.9 years; 84.2 ± 12.7 kg; 1.7 ± 0.1 m) participated. Materials/Methods: Each subject underwent a clinical biomechanical testing session and an MRI assessment session. During the clinical biomechanical testing, static LE alignment was obtained by measuring the angle between the long axes of femur and tibia. Dynamic LE alignment, in particular the peak frontal plane LE angle during loading response of fast walking, was obtained using a 3-dimensional motion capturing system. During the MRI assessment session, a chemical-shift-encoded water-fat MRI protocol was applied to the dominant knee. MRI data was obtained before fast walking and immediately following a 30-minute fast walking session. Bone stress response was determined by quantifying the bone water content within the weight-bearing regions of iii the medial and lateral compartments. Paired t-tests were used to compare bone water content before and after fast walking. Pearson correlation coefficient analyses were used to determine the associations between LE alignment and changes in water content after fast walking. Results: The paired t-tests revealed no change in water content after fast walking within medial femur (p = 0.671), lateral femur (p =0.174), medial tibia (p = 0.461), and lateral tibia (p = 0.190). Pearson correlation coefficient analyses revealed a significant moderate correlation between increased bone water content of the medial femur and increased static varus alignment (R = 0.688, p =0.027). Additionally, a trend with moderate correlation was observed between increased bone water content of the medial tibia and increased static varus alignment (R = 0.437, p = 0.206). No association was found between changes in bone water content and dynamic alignment (p Conclusions: This is the first study assessing the acute effects of locomotion on bone stress response in older adults without knee OA. Although there was no significant change in bone water content post locomotion, a greater varus alignment was associated with increased water content in the medial…