Walking kinematics of growing pigs associated with differences in musculoskeletal conformation, subjective gait score and osteochondrosis

Despite orthopaedic problems being a major concern for the pig industry, there is a lack of biomechanical, hence quantitative, investigation of locomotor pathology in pigs. The objective of this study was to determine whether there are detectable changes in joint and stride kinematics of clinically sound and unsound pigs, with or without post mortem joint lesions of osteochondrosis. A cohort of 24 pigs underwent five camera-based motion captures, 7-10 d apart and between 63 kg and 90 kg average liveweight, during which 3D coordinate data of reflective skin markers attached to leg anatomical landmarks were collected. Pigs walked on the same solid concrete walkway during captures. Statistical analysis was performed within captures across pigs which were categorised based on a series of deficiency characteristics. Results showed that pigs with clinical deficiencies and degenerative joint lesions had altered kinematics, although there were capture-related fluctuations in the findings. For pigs with conformational and perceived gait abnormalities there were significant differences in joint flexion values and left and right flexion symmetry, mainly reflected in the swing ranges of motion, compared to sound animals. Buck-kneed front legs were found to cause flexion deficiencies during the stance phase of stride cycles (P≤0.05; −9 degrees). Pigs with osteochondral joint lesions had mainly stance-related angular changes (P≤0.05) and asymmetry. Irregularity in the step-to-stride length relationship was elevated in both clinically and subclinically deficient pigs (respectively P=0.06, 1.5 times greater; P≤0.05; 1.5 times greater), but not the healthy pigs. These data provide basic kinematic values for clinically sound and affected pigs which could be used for further research into early and automated detection of leg disorders as well as for improved selection of breeding animals for longevity characteristics.