Manual of Equine Lameness
Manual of Equine Lameness
Fundamentals of Lameness Diagnosis
DEFINITION OF LAMENESS
Lameness is an indication of a structural or functional disorder in one or more limbs or the axial skeleton that is evident while the horse is standing or at movement. Usually lameness is most evident visually at a trot or jog. Significant lameness often is seen at a walk, whereas more subtle lameness may not become apparent until the horse is worked.
Lameness can be caused by trauma (single event or repetitive work), congenital or acquired anomalies, developmental defects, infection, metabolic disturbances, circulatory and nervous disorders, or any combination of these. It is important to differentiate between lameness resulting from pain and nonpainful alterations in gait, often referred to as "mechanical lameness," and lameness resulting from neurologic (nervous system) dysfunction. Lameness due to pain originating from the musculoskeletal system is most common in the horse. A complete lameness examination is used to help differentiate among the many types of lameness problems that can occur in horses. The objectives of a lameness examination are to determine:
1. If the horse is lame
2. Which limb or limbs are involved
3. The site or sites of the problem
4. The specific cause of the problem
5. The appropriate treatment
6. The prognosis for recovery
The steps to perform a routine or traditional lameness examination include:
1. Complete history, including signalment and use
2. Visual exam of the horse at rest
3. Palpation of the musculoskeletal system, including hoof tester examination of the feet
4. Observation of the horse in motion (usually at a straight walk and trot/lope followed by circling)
5. Manipulative tests such as flexion tests
6. Diagnostic anesthesia if necessary
7. Diagnostic imaging
Palpation of the limbs and axial skeleton, and hoof tester examination of the feet, are usually performed prior to exercising the horse. However, some clinicians prefer to observe the horse at exercise prior to palpation of the musculoskeletal system. Diagnostic anesthesia and imaging often follow to document the location of the pain, the specific cause of the problem, the extent of injury, and the prognosis for recovery.
CLASSIFICATION OF LAMENESS
There are a variety of ways to classify lameness in the horse. In most cases, a primary or baseline lameness contributes to the most obvious gait abnormalities. Compensatory, secondary, or complementary lameness results from overloading of the other limbs as a result of the primary lameness. Lameness also may be classified according to when it occurs (or is best observed) within the stride. The different classifications of lameness are defined below.
Supporting limb lameness is apparent when the foot first contacts the ground or when the limb is supporting weight (stance phase). Injury to bones, joints, soft tissue support structures (e.g., ligaments and flexor tendons), and the foot are considered causes of this type of lameness. This is by far the most common type of lameness identified in the horse.
Swinging limb lameness is evident when the limb is in motion. A variety of pathologic changes may be the cause, and the majority of these problems are thought to involve the upper limbs or axial skeleton.
Mixed lameness is evident both when the limb is moving (swing phase) and when it is supporting weight (stance phase). Mixed lameness can involve any combination of structures affected in swinging or supporting limb lameness.
Primary or baseline lameness is the most obvious lamene