Principal Investigator: Thomas P. Andriacchi, PhD Objective: This study is to identify specific characteristics of the motion and loading at the knee during locomotion that influences progression of osteoarthritis (OA) at the knee. Specific Aims Aim 1: To evaluate the relationship between loading at the knee during locomotion and regional variations in cartilage thickness Aim 2: To evaluate the relationship between a positional offset at the knee during locomotion and regional variations in cartilage thickness. Aim 3: To evaluate the relationship between motion at the knee during locomotion and regional variations in cartilage thickness Progress during 2006 Study 1: The effects of body mass index (BMI, weight/height2), knee adduction moment during walking and time past injury on cartilage thickness change were tested for anterior cruciate ligament (ACL) ruptured subjects. Seventeen unilateral ACL deficient subjects (41.1±12.1 years, 11 males and 6 females, BMI 24.2±4.8 kg/m2) who do not have knee osteoarthritis (OA) based on clinical examinations underwent bilateral knee MRI and gait test after IRB approval and informed consent were obtained. BMI and peak knee adduction moment were not significantly associated with overall cartilage thinning in the injured knee relative to the contralateral knee in the early stage group but they were significantly associated in the late stage group with R2=0.81 and p<0.01 based on the multiple linear regression test. In the late stage group, the thinning increased with an increase of the peak knee adduction moment in the ACL deficient knee and BMI. Study 2: The movement of contact points in the medial and lateral compartments of the knee were examined for healthy subjects as an antecedent study to understand the spatial cartilage thickness distribution in the knee. Twenty-six healthy subjects (39.3±13.6 years, 17 males and 9 females, BMI 23.8±2.3 kg/m2) without any previous knee injuries underwent gait test after IRB approval and informed consent were obtained. The anteriorposterior range of movement (AP-ROM) of the tibiofemoral contact points were significantly larger in the medial than lateral compartments during the stance phase of normal ambulation according to the linear mixed-effects model. The results suggest that the pivoting point in the knee is in the lateral side of the knee during normal ambulation. It is expected that the spatial cartilage thickness distribution might be affected by this lateral pivoting pattern in the knee, which will be explored as an ensuing study. Plan for Subsequent Years The association between knee joint kinematics and cartilage thickness distribution will be tested to explore specific Aims 2 and 3. Publications Andriacchi T, Muendermann A: The role of ambulatory mechanics in the initiation and progression of knee osteoarthritis. Current Opinion in Rheumatology, Sep; 18(5): 514- 518, 2006. Koo S, Giori N, Gold G, Dyrby C, Andriacchi T: Accuracy of cartilage thickness in MRI changes with cartilage thickness: laser scanner based validation of in vivo osteoarthritis cartilage. Journal of Biomechanics, submitted for publication, October 2006. Funding Source: NIH
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