• ground reaction forces;
  • gait analysis;
  • force platform;
  • peak vertical force (PVF);
  • vertical impulse (VI);
  • cranial cruciate ligament rupture;
  • Labrador Retriever;
  • dog

Objective— To determine the combination of ground reaction forces (GRFs) that best discriminates between lame and non-lame dogs. To compare the sensitivity of force platform gait analysis and visual observation at detecting gait abnormalities in Labradors after surgery for rupture of the cranial cruciate ligament (CCL).

Animals— All dogs were adult Labrador Retrievers: 17 free of orthopedic and neurologic abnormalities, 100 with unilateral CCL rupture, and 131 studied 6 months after surgery for unilateral CCL injury, 15 with observable lameness.

Procedure— Dogs were walked over a force platform with GRF recorded during the stance phase. Analytic properties of force platform gait analysis were calculated for several combinations of forces. The probability of visual observation detecting a gait abnormality was compared with that of force platform gait analysis.

Results— We determined that a combination of peak vertical force (PVF) and falling slope were optimal for discriminating sound and lame Labradors. After surgery, many dogs (75%) with no observable lameness failed to achieve GRFs consistent with sound Labradors.

Conclusion— A force platform is an accurate method of assessing lameness in Labradors with CCL rupture and is more sensitive than visual observation. Assessing lameness with a combination of GRFs is better than using univariate GRFs.

Clinical Relevance— Therapies for stifle lameness can be accurately and objectively evaluated using 2 vertical ground reaction forces obtained from a force platform.