This study investigated the biomechanical strategy adopted by older adults with medial compartment knee osteoarthritis for successful obstacle crossing. Fifteen older adults with bilateral medial compartment knee OA and 15 healthy controls were recruited to walk and cross obstacles of heights of 10%, 20% and 30% of their leg lengths. Kinematic and kinetic data were obtained using a three-dimensional (3D) motion analysis system and forceplates. The groups had comparable walking speeds, toe clearances and horizontal foot-obstacle distances (p>0.05). When the swing toe was above the obstacle, the OA group showed smaller swing knee flexion (p=0.01) and stance hip adduction (p=0.003) and internal rotation (p=0.04). They showed greater swing ankle dorsiflexion (p=0.04) as well as swing-side pelvic listing (p=0.006) and backward rotation (p=0.02). They also exhibited greater peak knee abductor moments (p=0.02) during early stance while adopting similar knee abductor moments (p=0.04) and greater hip abductor moments (p=0.04) when the leading toe was above the obstacle and thereafter. Smaller knee extensor (p<0.004), yet greater hip extensor moments (p<0.04), were found in the OA group throughout the stance phase. People with medial compartment knee OA had acquired different biomechanical strategies to compensate for the compromised function of the diseased knee.