Matrix-induced autologous chondrocyte implantation (MACI ®) is a cartilage repair technique that uses cells seeded in a type I/type III collagen membrane to assist in tissue formation within a defect site. There is minimal research on the long-term mechanical performance of these grafts in a large animal model. Two defects (15 mm) were placed in the lateral trochlear ridge of the right or left joint of 27 horses (1.5-6 years, 300-400 kg). The defects were filled with the following treatment options: 1) MACI and membrane alone (n=12); 2) empty and MACI (n=12); 3) 2 empty (n=3). The contralateral joint was left untouched for control. At 1 year post-implantation, two 3 mm plugs were removed from the defect and control tissue to be used for confined compression testing (to determine aggregate modulus and hydraulic permeability) and confocal strain mapping (to determine global and local shear modulus). In compression, MACI grafts had modulus and permeability values that were not statistically different than control and performed better than the other repair groups (p<0.05). In shear, all repair groups were significantly lower than the control shear modulus and showed little variation with depth from the articular surface. Mechanical testing suggests that MACI grafts are able to retain native compressive properties but not native shear properties. This study further characterizes the mechanisms of cartilage repair and performance of MACI grafts.