Gait alterations in dogs after transection of the anterior cruciate ligament.

We calculated mean peak vertical forces (MFz) of each limb of 9 adult mongrel dogs before and 2 weeks, 6 weeks, and 12 weeks after left anterior cruciate ligament transection (ACLT). Five additional dogs were studied before and 2 weeks and 6 weeks after sham ACLT. The gaits of 3 dogs that had undergone ACLT 2.5 years previously were also analyzed. Preoperatively, there were no differences in the MFz of the right and left hind limbs of the 9 dogs; we found that each limb exerted approximately 70% of the dog's static body weight on the force plate. Two weeks following ACLT, the MFz of the operated limbs decreased to 25% of the static body weight, while at 6 weeks and 12 weeks after surgery, the MFz generated by the operated limbs rose to about 32% and 37% of static body weight, respectively. No change was noted in the MFz of the contralateral hind limbs. In the 3 dogs that had undergone ACLT 2.5 years earlier, the MFz in the unstable stifle joint was 50% of static body weight. At both 2 weeks and 6 weeks after surgery, the MFz values for all 4 limbs of the animals subjected to sham ACLT were comparable with baseline values. These observations indicate that the osteoarthritic changes seen in the unstable limb are associated with decreased loading of that limb, without increased (compensatory) loading of the contralateral hind limb.