Abnormal tibiofemoral contact kinematics are related to superficial cartilage damage

s / Osteoarthritis and Cartilage 24 (2016) S63eS534 S115 177 ABNORMAL TIBIOFEMORAL CONTACT KINEMATICS ARE RELATED TO SUPERFICIAL CARTILAGE DAMAGE D. Kumar y, S. Segev z, N. Calixton z, L. Nardo z, X. Li z, T. Link z, S. Majumdar z, R. Souza z. yMed. Univ. of South Carolina, Charleston, SC, USA; zUniv. of California, San Francisco, San Francisco, CA, USA Purpose: To investigate the association of tibiofemoral contact kinematics with superficial and deep cartilage damage as assessed with T1rho and T2 MRI relaxation times in people with and without medial compartment cartilage lesions. Methods: Subjects (n1⁄4 94, age1⁄4 54.1± 10.5 years; BMI 1⁄4: 24.4± 3.4 kg/m2; Men:Women1⁄4 35:59) with (Kellgren-Lawrence Grade > 1) and without (Kellgren-Lawrence Grade 1, n1⁄4 28) and without lesions (grade 1, n1⁄4 66) in the medial tibiofemoral compartment. Groups were compared for differences in medial femur (MF) andmedial tibia (MT) superficial and deep T1rho and T2, and medial tibiofemoral compartment centroid translation in the medial-lateral (ML) and anterior-posterior (AP) directions. Analyses were adjusted for age, gender, knee alignment, and BMI. Correlations were evaluated separately in the two groups between kinematic and T1rho and T2 measures. Results: Subjects with cartilage lesions were older (P1⁄4 0.005), had greater BMI (P1⁄4 0.023), and had knees in more varus (P1⁄4 0.043). They had greater AP translation of centroid extension to flexion (P1⁄4 0.047), and worse KOOS scores on all subscales (P from 0.004-0.018). Superficial layer MF T1rho (P1⁄4 0.014) and T2 (P1⁄4 0.025) were higher in the lesion group. Superficial cartilage MT T2 (P1⁄4 .017) was also higher with the difference in superficial layer MF T1rho (0.066) being close to significance. The differences in deep layer MF and MT T1rho and T2 were not significant. There were no significant correlations between centroid translation and T1rho and T2 in the no-lesion group. In the lesion group, higher AP translation was associated with higher superficial MF T2 (r1⁄4 0.44, P1⁄4 0.023), superficial MT T2 (r1⁄4 0.62, P1⁄4 0.001), higher deep MF T2 (r1⁄4 0.45, P1⁄4 0.023), and trend for higher superficial MT T1rho (r1⁄4 0.38, P1⁄4 0.052). Across all subjects, higher AP translation was associated with higher total medial compartment cartilage lesion score (Spearman’s r1⁄4 0.38, P1⁄4 0.049). Conclusions: These novel cross-sectional data show that abnormal AP contact kinematics are related to medial compartment cartilage damage, especially in the superficial layer, in people with medial cartilage lesions. Modifiable factors that may be related to abnormal AP contact kinematics like neuromuscular control should be investigated to develop interventions that can improve these abnormal kinematic patterns, in an attempt to slow cartilage damage. In our cohort, we are further exploring the longitudinal effects of these abnormal contact kinematics on progression of cartilage damage over 2-years. 178 THE RELATIONSHIP OF ANKLE/FOOT ALIGNMENT WITH KNEE LOADING AND FOOT CENTER OF PRESSURE RESPONSES TO A FLEXIBLE FOOTWEAR INTERVENTION S. Weinberg, R.H. Lidtke, C. Ferrigno, M.A. Wimmer, J.A. Block, N. Shakoor. Rush Univ. Med. Ctr., Chicago, IL, USA Purpose: The use of flexible footwear results in reduced dynamic medial knee loading, however, the mechanisms underlying these reductions are unclear. Also, medial shifts in the foot center of pressure (COP) have been associated with medial knee load reduction (knee adduction moment, KAM). Ankle and foot anatomy likely affect the response to footwear-mediated interventions. We hypothesized that ankle/foot alignment would be associated with reduction in medial knee loading andmedialization of foot COPwith use of flexible footwear over 24 weeks. Methods: Participants with symptomatic medial compartment knee OA(KL 2 and 3) were evaluated at baseline using simultaneous barefoot COP and 3-D gait analyses. To test the hypothesis that a kinetic response to the flexible shoes is related to the foot’s ability to pronate and evert during walking, x-ray images at a baseline visit were performed while subjects stood statically on an inclined board set at 10 degrees eversion (Fig). A second radiograph was taken while subjects performed maximal foot pronation. The mechanical axis was defined as the angle of inclination of the fibula relative to a line parallel with the floor (Fig). All participants were provided flexible shoes (Dr. Comfort Flex-OA, Mequon, WI) at the baseline visit and instructed to wear them at least 6 hours/day, 6 days/week. Gait and COP analyses were repeated after 12 and 24 weeks of wearing the shoes. Gait analyses at all visits consisted of five trials each while barefoot, in subjects “own shoe”, and in the flexible shoe. During barefoot trials, plantar pressure distribution was acquired simultaneously by mounting a pressure platform onto a force plate and leveling the stacked assembly with the walkway. COP was quantified by determining the Medial to Lateral Pressure Index (MLPI) and normalizing to foot width. Paired samples t-tests were used to evaluate changes in KAM and foot COP during the first half of stance. Spearman correlations were used to evaluate the association between KAM reduction and medialization of foot COP with foot mechanical axis measurements. Results: 28 participants were evaluated (mean age 59± 7 years, 21 women). At 24 weeks, the KAM in the flexible shoe was reduced compared with their own shoes (2.88± 0.99 vs 2.73± 0.81%BW*Ht, p1⁄4 0.030). Overall there did not appear to be significant medialization in foot COP and medialization was not related to KAM reduction. At 24 weeks of wearing flexible shoes, greater reduction in the KAM was associated with a less varus mechanical axis at the ankle on the eversion boards (rho1⁄4 0.573, p1⁄4 0.004) while medialization of foot COP was associated with a greater varus mechanical axis of the ankle on the eversion boards (rho1⁄4 0.476,p1⁄4 0.022) and during maximal pronation (rho1⁄4 0.458, p1⁄4 0.028). Conclusions: The mechanical axis of the ankle is associated with both a reduction in medial knee loading and a medialization in foot center of pressure after 24 weeks of a flexible footwear intervention, however in opposite directions. While a less varus axis was associated with greater medial knee load reduction, a greater varus axis was associated with medialization in foot COP. The reasons for these relationships are not clear but may explain the lack of association between medial knee load reduction and change in foot COP in this study. Similar to the knee mechanical axis, ankle and foot mechanical axis may be a useful parameter to consider when evaluating foot-mediated biomechanical interventions. Figure. Participant on eversion boards. Angle between one line bisecting the fibula and one line parallel to the floor defined the mechanical axis. 179 MUSCLE ACTIVATION RESPONSES TO MEDIAL AND LATERAL WALKWAY PERTURBATIONS DURING GAIT IN INDIVIDUALS WITH MODERATE KNEE OSTEOARTHRITIS D.J. Rutherford, M. Baker, B. Stanish. Dalhousie Univ., Halifax, NS, Canada Purpose: Knee osteoarthritis (OA) muscle activation levels have been investigated to understand the mechanisms utilized to maintain joint function during walking. These studies typically focus on safe, level and controlled walking surfaces, devoid of challenges to the knee that may