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Medial Compartment Gap Is Decreased During Forced Marching And Running Load Carriage Tasks

Medial compartment cartilage thickness can provide an indication of early stage osteoarthritis (OA), so determining tibiofemoral joint space during dynamic loading tasks is an important step in investigating potential long-term joint degeneration. Women experience higher rates of knee OA than men and military personnel are at an even greater risk, so understanding how militaryrelevant load carriage tasks will affect tibiofemoral arthrokinematics in a female population is of great importance in order to inform training strategies and prevent injury. PURPOSE: The purpose of the study was to determine the effects of load carriage and locomotion pattern on tibiofemoral dynamic joint space. METHODS: Twelve physically active females (age: 24.5±2.4 years) walked (WK), ran (RN), and force marched (FM, or walking at a high velocity) on a treadmill while unloaded (bodyweight, or BW) and while loaded with an additional +25%BW or +45%BW (14.3±2.0 kg, 25.6±3.5 kg). Synchronized biplane radiographs of the right knee were collected at 150 images/second for 1 second during each movement trial. A validated model-based tracking system determined femur and tibia motion (accuracy: 0.9°, 0.7 mm). Subchondral bone distances were calculated. Two-way RMANOVA with post-hoc Bonferroni correction were used to analyze the interactions and within-subjects effect of load (BW, +25BW, +45%BW) and percent of right leg support (0%, 10%, 20%, 30%) on minimum medial and lateral compartment gap during WK, RN, and FM, independently (α=0.05). RESULTS: No significant interactions were observed between load and percent support. Medial and lateral gap was lower at initial contact vs. 10% and 20% support for FM (Medial: 38%, 33% decrease, Lateral: 26%, 23% decrease). Medial gap was 23% lower at 30% vs. 20% support for FM. For RN, medial gap was lower at 30% support vs. 10% and 20% (35%, 19% decrease). No significant changes in joint space were observed for lateral RN or medial/lateral WK. No significant differences due to load were observed. CONCLUSION: Changes in knee dynamic joint space appear to be more sensitive to differences in knee kinematics rather than additional load magnitude and suggest kinematics plays a vital role in knee cartilage loading and potentially the development of OA. Supported by the Freddie Fu Student Research Grant.