Context-aware machine learning for lameness side and severity prediction in trotting horses: A proof-of-concept study

In clinical practice, lameness evaluation often relies on visual assessment under different examination conditions, including ground and figures, and remains subjective. Although objective symmetry indices provide quantitative measures of gait asymmetry, their interpretation across multiple conditions remains challenging because several complementary indices are required and their thresholds vary with context.

To assess the ability of a context-aware machine learning approach to predict lameness side and severity at the trot using trunk-mounted IMUs.

Retrospective observational study.

A neural network incorporating contextual parameters (ground, figure) via feature-wise linear modulation (FiLM) was trained on symmetry indices derived from head, withers and pelvis motion in 625 horses examined during routine clinical evaluations, after exclusion of bilateral lameness. Reference lameness grades were extracted from clinical examination reports for each recording and aggregated into four ordinal severity levels. The model generated a predicted lameness class and an associated confidence score.

Exact accuracy reached 46% (43%-53% across contexts) for forelimbs and 47% (45%-52%) for hindlimbs. Most errors occurred between neighbouring ordinal categories, while left-right limb inversion remained below 3%. A limited subset of high-confidence predictions showed improved accuracy.

Reference labels were based on subjective clinical grading, without systematic confirmation by diagnostic analgesia or repeated objective measurements. Additional limitations include the single-clinic dataset, limited number of evaluators, and separate forelimb and hindlimb models.

This proof-of-concept study shows that a context-aware approach can integrate multiple IMU-derived indices across examination conditions to predict lameness side and severity. Agreement with subjective clinical grades was moderate, and most errors occurred between adjacent severity categories, whereas left-right limb inversion was uncommon. Further validation using stronger reference standards and independent datasets is required before clinical relevance can be assessed.