Lameness is a general term that refers to a horse with an abnormal gait or stance. This is a common issue that requires assessment by a veterinarian to determine the cause and best course of action.
Common causes of lameness include strain or injury, acute or chronic laminitis, genetic traits, infection, metabolic issues, or neural disorders.
A timely lameness exam can identify the underlying cause and how to manage it to relieve pain and support longevity.
A lameness exam typically involves discussing the horse’s history, observing the horse at rest and in motion, performing flexion tests and using hoof testers to identify sources of pain. Further diagnostic tests may be needed if these assessments are not sufficient.
Lameness evaluations are also a crucial part of pre-purchase exams. Identifying possible lameness in a horse you are interested in purchasing allows you to determine if you would like to proceed with the purchase. If you purchase the horse, lameness exams can indicate what may become an issue in the future.
Types of Lameness
According to the American College of Veterinary Surgeons, lameness is defined as an abnormality of a horse’s gait or stance. Lameness is not a disease itself but is a clinical sign that can be caused by pain, restrained movement or neuromuscular dysfunction.
Lameness is usually caused by pain in the muscles, tendons, bones, ligaments, or joints. Less commonly, non-painful lameness can also occur from neurological dysfunction. 
Most lameness can be separated into the following categories:
- Front end lameness
- Hind end lameness
- Pain in the back and sacroiliac
- Compensatory lameness
- Neurological lameness
Front End Lameness
Front leg lameness is the easiest to see with even the untrained eye. Front end lameness produces the classic “limp” one would expect to see with a painful limb.
When looking to see if a horse is lame in front, look for two features of the gait:
- Head bobbing
- Differences in range of motion
When stepping on a painful limb, most horses will use the placement of their head to try to alleviate pressure on that limb. Horses will raise their head when they step on a sore limb to reduce pressure on that limb and lower it when they step with the non-painful limb.
When trotting your horse on a circle or straight line, pay attention to when they lift and lower their head. If you are only able to trot your horse on a circle, make sure you are looking at their gait in both directions, as they could be lame on both limbs. 
If a horse has a sore muscle or painful joint, it will likely exhibit a reduced range of motion, referring to how far a limb can move with little pain in a gait cycle. 
Horses should move their limbs evenly and smoothly during a gait cycle. Any hitching or unevenness can indicate pain. 
Hind End Lameness
Hind end lameness can be subtle, with most horse owners noticing that something is “off” without being able to put their finger on the source. Horses lame in behind may exhibit:
- An uneven rise and fall of the hips and buttock
- Differences in range of motion
Horses that are lame in behind will drop the hip on the sore side slightly more than the non-painful side and may produce odd-looking movement patterns in their hind limb joints to compensate for painful areas.
Like front-end lameness, horses will often show differences in their range of motion when lame in the hind legs. The lame leg may not come forward underneath the horse’s body or extend out as far behind the body as much as the non-painful leg. 
Back and Sacroiliac Pain
- Discomfort during grooming or pressure on the back
- Abnormally short strides
- Resistance to saddling or girthiness
- Behavioural issues during performance such as refusing fences, bucking, rearing, etc.
When a horse experiences pain or discomfort in one area of the body they often develop compensatory movements to alleviate pain in the affected area. For example, if the horse is lame in one forelimb it may alter its gait and weight-bearing to shift more weight onto the other forelimb.
Unfortunately, this can lead to compensatory lameness in the previously healthy limb. Compensatory lameness can be difficult to distinguish from the original source of lameness.
Asymmetry in the vertical movement of the withers can help distinguish primary and compensatory lameness when both front limbs are affected. 
Lameness due to a neurological disease can be subtle, extremely obvious or somewhere in between. It may begin in early life or following an infection.
Early in the disease progression, your horse may exhibit:
- Subtle abnormalities in their range of motion, which come and go
- Minor stumbling or tripping
- Issues retaining balance when turning in small circles
- Reluctance when transitioning from one ground surface to another
- Weakness and inability to balance when a leg is held up
Late in the disease progression, your horse may exhibit: 
- A wide stance when standing or walking
- Swaying back and forth
- Low muscle tone in the tail and anus
- Frequent falling
Lameness due to a neurological disease or injury is always very serious and needs a thorough work-up by your vet. Examples of neurological diseases that can cause incoordination include equine protozoal myeloencephalitis (EPM) and equine herpesvirus type 1 myeloencephalopathy.
Genetic conditions can also cause incoordination and lameness. One example is neuroaxonal dystrophy found in Morgan horses. Signs of these typically appear within the first 2 years of life and have a variable prognosis.
When performing a lameness exam, your veterinarian will follow a protocol that maximizes the likelihood of identifying the location of pain while minimizing the need for major diagnostic tests.
The American Association of Equine Practitioners uses the following scale to help owners and veterinarians identify the severity of lameness. On this scale, a grade of 0 means no lameness and 5 means extreme lameness.
- Grade 0: Lameness is not perceptible under any circumstances; manipulating the limbs does not produce gait abnormalities.
- Grade 1: Lameness is difficult to observe and is not consistently apparent regardless of circumstances.
- Grade 2: Lameness is difficult to observe at a walk or trot in a straight line but consistently apparent in certain circumstances.
- Grade 3: Lameness is observable at a trot under all circumstances.
- Grade 4: Lameness is obvious at a walk.
- Grade 5: Lameness produces a complete inability to bear weight or a complete inability to move.
The first thing your veterinarian will do is evaluate your horse’s medical history. They will want to know if your horse has any past lameness issues and what signs you have observed during the current episode.
This exam will include questions such as: 
- What type of exercise does your horse do? Did lameness first appear during exercise?
- How long has the horse been lame? Has it been stable or gotten worse/better?
- Have they been rested or exercised since lameness first appeared?
- Does lameness improve as they warm up to exercise?
- When is the lameness most consistently evident?
- Have you given any treatments? What were the effects?
- When was the horse last shod or trimmed? What is their typical farrier care?
- What abnormalities do you notice when riding or watching the horse?
Additional information such as your horse’s age, pedigree and past use can also be valuable to determine underlying contributing factors.
Depending on the type of work the horse does they may be more prone to certain lameness conditions. For example, racehorses are more prone to lameness associated with repetitive overuse such as foot bruising, fractures and suspensory injuries.
Knowing the type of work, intensity and training history will help your veterinarian understand your horse’s likelihood of certain injuries or conditions.
Observing Your Horse at Rest
Your veterinarian will want to study your horse while they are standing still on flat ground. They will evaluate your horse’s conformation, how they are weight-bearing at rest, and whether there are any obvious signs of strain. 
Observations will be made from a distance and up close. From farther away your vet can evaluate stance, frequency of weight shifting, unusual limb positioning, body conformation and body condition.
From up close, your vet can assess the feet for conformation and balance, hoof cracks, hoof size and abnormal wear. Joints and tendons can be inspected for swelling, and muscles can be inspected for swelling and/or atrophy.
Your veterinarian will emphasize comparing one side of the body to the other to identify the source of lameness.
Observing Your Horse in Motion
As part of diagnosing lameness, your vet will want to see your horse walk and trot in a straight line. They will observe your horse from the front, back, and sides as they walk and jog in hand.
They may want to watch your horse walk, trot, and canter in a circle to see how they move in the gait and how they transition between gaits.
Your vet will look for any gait deviations such as plating or winging, altered range of motion and abnormal placement of the feet.
This will help identify abnormal movement asymmetries in the body that can indicate the source and severity of lameness. Slight asymmetries in head and pelvic movements are a normal part of biologica