KNEE MECHANICS OF HEALTHY AND OSTEOARTHRITIC JOINTS
Objective: Knee Osteoarthritis (OA) can be the result of both mechanical and biological events that interfere with normal joint function. The aims of this thesis were to (1) quantify the biomechanical factors that differentiated structural OA progression, (2) determine if knee biomechanics changed over time in response to structural changes, (3) identify sex and puberty specific differences that may mechanically predispose females to OA, and (4) determine the response of healthy knee joints to a high dose of sport to assess the contribution of knee mechanics to tissue damage. Methods: A three-year prospective study of knee OA progression addressed Aim 1 by measuring principal components (PCs) of knee moments and muscle activation patterns that differentiated the progression group, and for Aim 2, identified PC scores that changed with and without knee OA diagnosis and progression. A cross-sectional comparison of PCs between sex and puberty cohorts addressed Aim 3. A five-month prospective study of female varsity athletes addressed aim 4, where the knee joint response to one season of sport was measured with MRI. Results: (1) The peak KAM was higher prior to structural progression confirming previous findings however greater lateral muscle activity with progression was contradictory. (2) Knee joint moment and muscle activation patterns changed over the three years, with the greatest magnitude of difference occurring in the progression group. (3) Later puberty stages had higher frontal and transverse plane moments when walking and altered patterns of frontal and transverse plane moments when running. (4) The athletes that had worsening of MRI features had different features of knee joint moments characterizing lower magnitude joint loading. Conclusions: Higher frontal and altered transverse plane knee moments in the OA progression group highlights the sensitivity of the osteoarthritic knee joint to altered mechanical load. The change in mechanics over time reinforces the dynamic mechanical environment with OA and the sensitivity of gait to this changing structure. The lack of congruence of MRI changes of asymptomatic knees with mechanical features related to knee OA suggests that longer prospective studies are needed to trace mechanical factors in young adulthood to knee OA initiation.