Lameness in horses and other equidae is a term used to refer to any number of conditions where the animal fails to travel in a regular and sound manner on all four feet. There are many causes of lameness, which can be broadly grouped into the following categories:
- Laminitis or other inflammatory diseases of the hoof
- Injury to bone, muscle, tendons or ligaments, ranging from pulled muscles to broken bones.
- Complications of inflammation or stocking up related to overwork
- Injury induced by compensation for strain or pain in other parts of the body, particularly the back
- Neurological disorders, such as Wobbler's syndrome
- Diseases affecting connective tissue, such as Equine Exertional Rhabdomyolysis and HYPP
Diagnosing and treating lameness
Lameness severity is typically evaluated on a scale of 1 to 5, with higher numbers indicating a more significant degree of impairment. A 1 rating suggests a horse with a minor gait deficit, a 5 is "broken-legged" lame, indicating that the horse will not put weight on the affected leg. Initial assessment may include a visual check for outward injuries such as cuts or swelling, observation of a horse as it travels at different gaits, particularly the walk and trot. Flexion tests may also be performed, and hooves will be checked for signs of injury.
After the initial assessment, a typical procedure is to perform regional limb anesthesia (nerve blocks) to help to pinpoint the area affected. Once the causative area is determined, then radiographs or ultrasound are performed to determine which particular structures are involved. More advanced imaging techniques include scintigraphy, computed tomography, and MRI.
Treatment varies depending on the condition diagnosed, but at a minimum includes rest, appropriate medication and other supportive therapies. Consultation with a veterinarian is generally recommended, even for mild cases, as some types of mild lameness may worsen if not properly diagnosed and treated.
An important component of an equine prepurchase exam is a thorough lameness examination to rule out existing unsoundness.
Types of lameness
There are dozens of different types of lameness in horses. In addition, many conditions sometimes, though not always, have lameness as a symptom. Finally, there are a number of permanent blemishes that indicate that a horse has been lame in the past or has been subjected to strain that may lead to lameness in the future. These assorted conditions include:
- Bone spavin - A bone spavin is the inflammation of bones that are between the inside of the hock joint and is extremely painful. It is caused by pounding on hard surfaces, sliding, roping, reining, and poor conformation. A jack spavin is a bony growth that irritates tendons under the inside of the hock. When the hock is flexed or bent there is much pain. The causes are from a hit to the joint, stress, trauma, and poor conformation. A knee spavin is a bony growth at the back of the inner side of the knee and is not very common. Joint stress and trauma are the causes of this.
- Bowed tendon - Bowed tendons are the inflammation or the rupture of the sheath of the tendon from the knee to the fetlock. The tendon can be the deep flexor tendon or the superficial flexor tendon and occurs in front legs. Severe trauma and over extension, a short warm up, fatigue, or a hit are the causes of a bowed tendon.
- Capped joint - A capped hock is the swelling of the point of the hock and is caused by a hit to the area, the kicking of the wall, and lying on hard surfaces. A capped knee is the swelling and bruising of the knee and the tendons on the knee. This can be caused by a fall, banning, over work, and poor conformation. When the capsule of the knee is involved, fluid can leak into the area.
- Curb - Curbs are the inflammation of the upper rear of the cannon bone, below the point of the hock. Curbs can be caused by a hit to the area, kicking of a wall, or a violent extension of the plantar ligament.
- Laminitis - Laminitis is the vascular disease, causing ischemia or homeostasis. It affects the inside of the lamina where it becomes inflamed and obstructs with the bone bond. Symptoms of this are lameness, elevated temperature, breathing, and plus rate, pain in the toe, and depression in the skin near the wall of the hoof. The causes could be from a pre-existing illness, like Cushing's syndrome, excess cards and weight, stress, long transportation, excess work on a hard surface, black walnut bedding, drinking when overheated, and insulin resistance. Laminitis can spread to all four legs and can be seen twenty four to seventy two hours after the incident. When Laminitis is chronic there is the displacement of the distal phalanx with no activity in the laminar necrosis. The growth of the dorsal lamina in the hoof becomes abnormal. The treatment is to be off the feet as much as possible, dietary restrictions, administering fluids and medicine, and soft bedding. Magnetic hoof pads can be used to increase circulation and relieve pain. Foundering, which can result from laminitis, is when the coffin bone become detached, rotates, or sinks. The horse usually shifts its weight to the back legs with the front extended.
- Osselets - Green osselets is the inflammation of the joint capsule in the front of the fetlock. It is caused by too much racing at a young age. True osselets is a bony growth at the front of the fetlock joint and is the late stage of green osselets, which was not allowed to heal.
- Sesamoiditis - Sesamoiditis is the inflammation of the bone above and the back of the fetlock joint. A hit or trauma to the joint causes this ailment.
- Shoe boil, usually a blemish after the acute period
- Speedy cut - A speedy cut is from the striking of the inner lower side of the knee with the hoof of the opposite leg. The causes can be from poor conformation or an accident in the fields.
- Splints - Splints are a bony enlargement commonly on the inside of the front leg by the knee. The causes are poor conformation, rapid growth, trauma, or being struck by the other leg. Shin splints also known as bucked shins are the inflammation of the membrane that covers the cannon bone. They are caused by a hit to the area. They are usually a blemish after the acute period.
- Sprain - A sprain can be of the ankle or the suspensory ligament. An ankle sprain affects the ligaments that support the fetlock joint and a sprain of the suspensory causes inflammation and strain of the ligament.
- Stocking up - Stocking up is fluid retention in the lower back legs. The causes can be from poor circulation from lack in exercise, being confined to a stall that is too small, or the over feeding of grain. Stocking up can cause kidney problems in some cases.
- Thoroughpin - Thoroughpin is the swelling of the deep digital flexor tendon sheath. Stress to the tendon from over work or over extension, trauma to the tendon and joint, or poor conformation of the hock joint can cause thoroughpin.
- Windpuffs - Wind puffs also called wind galls is the spongy swelling around the back, front, or side of the fetlock joint. If the joint becomes inflamed the capsule swells up with more fluid. Hitting of the joint, excessive work when young, stress, and fatigue can cause wind puffs.
- Giffen, James M. and Tom Gore. Horse Owner’s Veterinary Handbook., 2nd ed. New York:Howell Book House, 1989, 1998. ISBN 0876056060
- King, Christine, BVSc, MACVSc, and Mansmann, Richard, VDM, PhD. Equine Lameness. Equine Research, Inc. 1997.