Myofascial trigger points as a primary cause of equine lameness: a biomechanical, neurophysiological, and fascial review.

Equine lameness diagnosis is dominated by a joint- and tendon-centric paradigm. The standard diagnostic algorithm relies on gait observation, perineural and intrasynovial anesthesia, and cross-sectional imaging. It is directed almost exclusively at skeletal and articular structures. Myofascial trigger points (MTrPs) are hypersensitive, hyperirritable loci within taut bands of skeletal muscle. They produce local and referred pain on compression or contraction. In horses, MTrPs are a clinically relevant but systematically overlooked source of primary lameness. This review synthesises evidence from equine and comparative research. We argue that MTrPs can act as the primary-not merely secondary-cause of gait asymmetry, performance deficits, and pain behavior in horses. Key mechanisms include the energy crisis model of MTrP formation, peripheral and central sensitization, referred pain projection mimicking distal limb pathology, and the biomechanical consequences of MTrP-induced muscle inhibition on gait. Electrophysiological studies confirm that equine MTrPs show the same spontaneous electrical activity as human and animal MTrPs. Prevalence studies indicate that MTrPs are present in many sport horses. Dressage horses show particularly high prevalence in the cervical and thoracolumbar musculature. Of clinical importance is the referred pain phenomenon: MTrPs in proximal muscles such as the gluteus medius, longissimus lumborum, and biceps femoris may produce apparent distal limb pain. Such pain can be clinically indistinguishable from joint or tendon pathology. This has direct and underappreciated implications for diagnostic accuracy. We propose that systematic myofascial palpation should be integrated into the routine equine lameness workup as a first-tier diagnostic step. Rapid resolution of gait asymmetry following targeted MTrP treatment should be interpreted as supportive evidence of myofascial origin. We further delineate the clinically relevant trigger point activity spectrum from active to latent states, address differential diagnoses such as Lyme-associated diffuse myalgia and primary myopathies (PSSM2, MIM, IMM), summarise the principal therapeutic modalities used in equine MTrP management, and examine biotensegrity as a mechanobiological framework explaining the multisegmental fascial effects of myofascial dysfunction.