Definitions:

LAMENESS: Horse is limping	SOUNDNESS: Horse is not limping
THORACIC LIMB: Front leg	PELVIC LIMB: Back leg
CRANIAL: Towards the front of the horse	CAUDAL: Towards the back of the horse
ACUTE: Just happened	CHRONIC: Has been going on for a while
DISTAL: Towards the lower limb (ground)	PROXIMAL: Towards the upper limb (body)
MEDIAL: Towards the inside of the limb	LATERAL: Towards the outside of the limb
AXIAL: Towards the center of the limb	ABAXIAL: Towards the edge of the limb
UNIAXIAL: One side of the limb	BIAXIAL: Both sides of the limb
UNILATERAL: One limb (either right or left)	BILATERAL: Both limbs
CONTRALATERAL: On the other side of the body	IPSILATERAL: On the same side of the body
ABDUCTION: Moving the limb away from the body	ADDUCTION: Moving the limb towards the body
HYPERMETRIC: Picking up the leg higher than usual	HYPOMETRIC: Not picking the leg up as high as usual
MYOPATHY: Muscle problem	ITIS: Inflammation
ARTHRITIS: Inflammation of a joint	SYNOVITIS: Inflammation of a joint membrane
DESMITIS: Inflammation of a ligament	MYOSITIS: Inflammation of muscle
PATHOPNEUMONIC: Specific for a certain problem. For example, "goose stepping" is pathopneumonic for fibrotic myopathy of the medial branch of the semitendinosis muscle.	EXCURSION: Tilting of the pelvis

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Grades of Lameness
Grade 1:	Horse is sound at a walk and trot in a straight line. Lameness is exhibited only in special circumstances (e.g. in a circle, down hills, when collected, etc.).
Grade 2:	Lameness is detectable at a trot in a straight line.
Grade 3:	Lameness is detectable at a walk.
Grade 4:	Lameness is detectable during standing; horse is non-weightbearing on the affected limb.
Grade 5:	Horse is recumbent.

Types of Lameness

Weightbearing
The horse experiences pain during the caudal phase of the stride: when the limb is on the ground and bearing weight. A horse with a weightbearing lameness will "drop into" or "fall into" the more comfortable limb. Lameness will usually be more obvious when the horse is circled toward the affected limb (since they are bearing more weight on the inside limb).

• Thoracic limb: The shoulders, withers, and or head will drop on the comfortable limb
• Pelvic limb: The pelvic will tilt on the comfortable limb; the uncomfortable hip will drop

Non-weightbearing
The horse experiences pain during the cranial phase of the stride: when the limb is airborne and not bearing weight. A horse with a non-weightbearing lameness will throw the uncomfortable limb and body upward. Lameness will usually be more obvious when the horse is circled away from the affected limb (since the stride is longer on the outside limb).

• Thoracic limb: The shoulders, withers, and or head will raise up during the cranial phase of the stride of the affected limb and/or the horse will drag the affected limb
• Pelvic limb: The horse will drag the affected limb
  
  

Abnormal Gait Characteristics for Specific Problems:

NAVICULAR INFLAMMATION
Horse will exhibit weightbearing thoracic lameness. Worse toward the more affected limb. Since navicular inflammation is usually bilateral, the horse may limp on the right thoracic limb when moving to the right and the left thoracic limb when moving to the left (i.e be lame in both thoracic limbs). May have difficulty making sharp turns (even at a walk) on hard surfaces. Worse on hard surfaces; better on soft surfaces. May come out of the stall very stiff/lame and slowly improve with exercise.

FOOT ABSCESS
Similar to gait characteristics observed in horses with navicular inflammation, but lameness has a more rapid onset, tends to be more severe, and is only in one limb. Horse may exhibit grade 4/5 lameness in severe cases. Increased pulse to the foot variable. Increased heat in foot variable. Pulse and heat may be uniaxial.

LAMINITIS
Horse will appear to be walking on egg shells. If thoracic limbs are more affected, thoracic limbs will be parked out in front and pelvic limbs will be up under the body. Back is generally tense and stiff: horse is attempting to reduce thoracic limb weight. If all four limbs are affected, the horse will place all four limbs up and underneath the body. Steps will be very short and cautious. Horse will have difficulty making sharp turns, especially on hard surfaces. Worse on hard surfaces; better on soft surfaces. Extremely sore on gravel surfaces. Increased pulse to the foot variable. Increased heat in foot variable.

SHOULDER, BICIPITAL BURSA, ELBOW, SUPRACARPAL INFLAMMATION
These are the most common things that will result in a non-weightbearing thoracic lameness. Lameness is worse when the affected limb is on the outside of a circle.

PROXIMOLATERAL SUSPENSORY DESMITIS, LATERAL COLLATERAL DESMITIS OF THE FETLOCK JOINT, LATERAL CARPAL PAIN, AND MEDIAL FOOT PAIN
These are about the only things that will result in a weightbearing lameness that is worse with the affected limb on the outside of a circle.

DISTAL TARSITIS
Lameness is weightbearing. Pelvic limb gait will be hypermetric and often abductive (stabby). Horse will jab the lateral toe quarter into the ground. The lateral toe quarter of the shoe will tend to wear most rapidly. Pelvic limb flexion usually increases both hypermetricity and lameness.

STIFLE SYNOVITIS
Lameness is both weightbearing and non-weightbearing. Pelvic limb gait will be hypometric. Horse often drags the pelvic toes (which may be excessively worn). Pelvic limb flexion usually increases both hypometricity and lameness.

INTERMITTENT UPWARD PATELLAR FIXATION
Horse will have a "hitch" in the pelvic limb gait. Because IUPF involves the stifle area, pelvic limb gait is usually hypometric and toe-dragging is common. The point of the hock will have a characteristic "shake" or "shimmy" at the moment the horse picks up the pelvic limb to advance it forward. May be mild or severe; may or may not interfere with performance. In severe cases, horse's back end may "drop out" from underneath the rider. In mild cases, horse may exhibit generalized resistance. This problem is not inflammatory-mediated and is therefore non-painful.

EBAXIAL MYOSITIS (BACK PAIN)
Horse will be unwilling to come through or maintain collection. Tend to be inverted or "hollowed" out in the back. Horse will resist dropping the head. These horses may frequently stick their tongues out during exercise. Horse may react to digital pressure over the thoracolumbar back area and/or to placement of a saddle. Ebaxial myositis is almost always secondary to pelvic limb asymmetry/lameness.

FIBROTIC MYOPATHY
Represents fibrosis or scarring of muscle. Consequently, the structure loses pliability ("stretchability") and a restriction in the stride is observed. These problems are generally non-painful. Depending on the muscle(s) involved, the horse may have a pathopneumonic gait abnormality (e.g. "goose-stepping").