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 military-relevant 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.