Study hypotheses: 1) Participants in the stability training group will demonstrate less pain and higher levels of physical function, based on self-report measures of pain and function (WOMAC, Lower Extremity Function Scale), and less time to complete the Get Up and Go test, a physical performance measure of function. 2) During walking and the step down task, participants in the stability training group will demonstrate greater knee motion during weight bearing, greater vertical ground reaction forces and loading rates, and reduced ratios of co-contraction between quadriceps/hamsting and tibialis anterior/gastrocnemius muscle pairs compared to the standard group. Participants in the stability group will also demonstrate greater step lengths, single limb support times, and average walking velocity compared to the standard group.