Altered patellofemoral (PF) kinematics, associated with joint malalignment, muscle imbalances, or ligament injury, is speculated to be a potential cause of abnormal stresses, possibly leading to cartilage degeneration. The relation between kinematics and joint mechanics has not been well established. The purpose of this research was to investigate relations between kinematics, joint congruence, and cartilage stresses in a cat PF joint. Firstly, the congruence was quantified as a function of flexion angle, for a range of medial to lateral patellar tracking positions. Secondly, the effect of lateral versus central tracking on cartilage stresses and strains was quantified using a finite element model. Congruence and cartilage stresses were sensitive to patellar position. Lateral tracking decreased contact area by approximately 40%, and increased cartilage stresses and strains between 100% and 200%. This preliminary work suggests that patellar alignment may have important implications in terms of joint function and cartilage health.