Biomechanical testing of cadaver stifles in 13 Rottweilers and 15 Racing Greyhounds, at the flexion angles determined from the gait analysis, examined the stability of the joints and the material and structural properties of the cranial cruciate ligaments and their bony attachments when loaded in tension. The geometry of the tibial plateau was also investigated. The stifle joints became less stable with increasing joint flexion, the Rottweiler joint being consistently more lax than the Racing Greyhound. This may explain the tendency of the Rottweiler stifle joint to extend more fully than the Racing Greyhound, which is recognised as one mechanism of cranial cruciate ligament rupture. In extension, the tensile strength of the Racing Greyhound cranial cruciate ligament was greater than the Rottweiler, although the strength of the latter increased with increasing joint flexion. The contact angle between the femoral condyles and the tibial plateau changed as the joint was flexed, more so in the Rottweiler where there was a greater backward slope of the plateau. The conformation and gait of the Rottweiler hind limb do appear to influence cranial cruciate ligament damage. The normal Rottweiler stifle joint is more extended than the Racing Greyhound at foot placement when the cranial cruciate ligament is weaker. As the joint flexes, the ligament appears stronger but the greater backward slope of the tibial plateau contact point results in a greater force tending to move the tibia forward relative to the femur which must be counteracted by the cranial cruciate ligament. Therefore it appears that as the Rottweiler stifle joint flexes from full extension, the ligament and its attachments become biomechanically stronger but the load on the cranial cruciate ligament becomes greater.