Equine Lameness for the Layman. G. Robert Grisel, DVM
Forms of Lameness
There are many terms used to describe and characterize lameness in the horse (fig. III.1). Gaining familiarity with both the literal and conceptual meaning of each (as it pertains to one’s visual interpretation) is vital to becoming a competent observer. The outward expression of various forms of lameness will be discussed in section VI (p. 157).
III.1 Common Forms of Lameness
| Limb Lameness | Associated with one or more of the horse’s limbs. Example: Foot abscessation usually causes severe limb lameness. |
| Axial Lameness | Affects the median anatomy of the horse, which comprises the head, neck, chest, back, pelvis, and tail. Concurrent limb lameness may or may not be present. Example: Horses with lower back pain will often display axial lameness when trotting in a tight circle. |
| Primary Lameness | Occurs as a result of injury, trauma, or an event outside of the horse’s body or control. Example: A chip fracture in the horse’s knee would result in primary forelimb lameness. |
| Secondary Lameness | Occurs as a result of an issue or lameness that coexists elsewhere in the horse’s body. Example: A horse suffering from a chip fracture in the knee might develop secondary suspensory desmitis in the other forelimb due to excessive overloading of the latter. |
| Simple Lameness | Only one limb or region of the horse is affected. Example: The recent loss of a shoe might produce a simple lameness associated only with the affected limb. |
| Complicated Lameness | Multiple limbs or areas are affected. Complicated lameness can be interpreted as a conglomerate of simple components, since each is assessed separately during the evaluation process. Each complicated lameness comprises at least one primary component; other components might be secondary or tertiary. Example: Laminitis often results in complicated lameness involving both front or all four limbs. |
| Multifactorial Lameness | Refers to complicated lameness with two or more primary components, each of which will require exclusive attention during the diagnostic and treatment processes. Example: A horse with lower hock pain and forelimb coffin joint disease might be suffering from multifactorial lameness in all four limbs. |
| Unilateral Lameness | Affects the right or left side of the horse, but not both. Example: A loss of a single shoe often produces a simple, unilateral lameness. |
| Bilateral Lameness | Affects both sides of the horse. Example: Navicular syndrome is often considered a bilateral disease, affecting both front feet. |
| Quadrilateral Lameness | Affects both sides and both ends (i.e. all four limbs) of the horse. Example: Grass founder can make all four feet sore, producing quadrilateral lameness. |
| Pain-Mediated Lameness | Lameness resulting from something that produces pain (i.e. something that “hurts”). Example: Foot abscessation results in pain-mediated lameness. |
| Biomechanical Lameness | Lameness resulting from something that physically prohibits or restricts normal movement, in the presence or absence of pain. Example: Fibrotic myopathy of the horse’s hamstring musculature can generate biomechanical lameness in the affected limb. |
| Neurologic Lameness | Lameness resulting from neuropathy and usually due to a lack of motor innervation and/or reduced proprioception. Example: Horses diagnosed with wobbler’s syndrome often exhibit neurologic lameness. |
| Weight-bearing Lameness | Gait abnormalities will be most obvious during the stance phase of the stride, when the foot is in contact with the ground surface. Example: Due to severe pain, foot abscessation often results in obvious weight-bearing lameness in the affected limb. |
| Non Weight-bearing Lameness | Gait abnormalities are most evident during the flight phase of the stride, when the foot is airborne. Example: Fibrotic myopathy of the hamstring musculature often produces a biomechanical, non weight-bearing asymmetry by prohibiting full extension of the affected hind limb. |
| Combination Lameness | Lameness displaying both weight-bearing and non weight-bearing characteristics. Example: A recent chip fracture in the horse’s knee often produces simple, unilateral, combination lameness of the affected limb |
| Associated Lameness | A secondary lameness that occurs in the same locality and as a direct consequence of a primary issue. Example: Altered loading of the lower limb due to fetlock joint pain could precipitate associated bruising of the foot. |
| Compensatory Lameness | A secondary issue that occurs in a different locale or limb and as an indirect consequence of a primary lameness. Example: Moderate hock pain might produce compensatory forelimb lameness as a result of chronic overloading and excessive challenge to the suspensory ligaments. |
| Referred Lameness | An artificial precipitation of gait deficit(s) occurring in one limb as a product of gait deficit(s) in one or more of the other limbs. Referred gait deficits are not genuine and disappear pursuant to successful treatment of the primary lameness. Example: A horse might exhibit a primary left hind weight-bearing lameness with a referred left front weight-bearing component. |
| Intermittent Lameness | A lameness that appears to come and go from one day to the next. Issues that occasionally provoke biomechanical interference can generate intermittent lameness, as can sporatic bouts of muscle cramping or inflammation. Example: Equine Hyperkalemic Periodic Paralysis (HYPP), a muscular disease caused by an inherited genetic mutation, can produce symptoms of intermittent lameness in Quarter Horses and related breeds. |
| Shifting Lameness | A lameness that appears to move from one limb or region of the horse to another, depending on the day or time of evaluation. Example: Some horses with bilateral forelimb navicular pain will exhibit shifting-limb lameness; one minute they’ll be worse in the left front and the next minute they’ll be worse in the right front. |
| Metabolic Lameness |
Lameness that occurs as a result of something not directly |