Usually all feet are affected at once, and is one of the most painful conditions to afflict horses since the swelling is constrained within the hoof walls. Chronic laminitis where the pedal bone has rotated is called founder. Treatment is with hoof trimming and special shoeing. Sudden changes of food may also cause this condition. For more go to our Laminitis Feature Article

Laryngeal Hemiplegia (roaring) a condition involving larynx dysfunction that can severely compromise a horse?s ability to breathe, especially during exercise. The problem is usually first discovered in growing, tall male horses but the condition is permanent (they don't grow out of it). The majority of horses which develop laryngeal hemiplegia will be 16 hands or more when mature. The Thoroughbred seems to be the breed most often afflicted. However, other breeds that have the genetic tendency to be tall also are affected. Young horses often are first diagnosed when they begin undertaking serious exercise for an athletic career and make a noise, or they are exercise intolerant when training or performing over a distance.

laryngoplasty. A surgical procedure for roaring that involves the placement of prosthetic sutures between the cricoid and arytenoid cartilages, which, when tied, permanently abduct the affected arytenoid cartilage.

Lesion internal, visible change of the structure,colour, size or shape of an organ or part of the body;area of damaged tissue; any abnormal change in the structure of a part due to injury or disease.

Lice Lice infestations can occur usually reaching a peak in late winter and spring. Horses with long heavy winter coats are more prone to heavy infestation. Biting lice are usually found on the back of the body and head. Sucking lice are generally found under the mane, tail and fetlocks. Horses with heavy infestations of sucking lice can become anaemic. Lice cause intense itching and irritation of the skin as well as loss of condition. Horses bite and rub the skin, causing the hair to fall out leaving red, weeping areas. Your vet can advise you on suitable sprays or powder insecticides which can be used to treat horses. Rugs and harness should also be sprayed and left unused for 14 days. A second treatment 17 days after the first treatment is advisable. As well as lice, horses are susceptible to a wide range of other skin conditions. Due to their variety a correct diagnosis is essential to their proper treatment. Early veterinary advice can reduce the likelihood of incorrect treatment.

Ligate tie off a blood vessel or body part with a suture.

lobe Well defined portion of any organ. e.g. right lobe of lung

lymph Transparent yellowish-liquid containing mostly white blood cells and derived from tissue fluids. Forms the basis of the lymphatic system which fights disease in the body.

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Myositis Inflammation of muscle, specifically it refers to conditions where muscle fibres are damaged and their contents released into the tissues and circulation. Further damage may then occur.

Offset Knees Conformational defect where the cannon bone is set towards the outside of the knee, instead of forming a straight line with the forearm through the knee.

Oedema Fluid accumulation in tissues esp. lungs, under the skin, within the cornea etc. Depending on the cause, treatment may include anti-inflammatory or diuretic drugs. Factors: trauma, poor blood circulation, lack of exercise.

Oestrus Period of time during the mare's productive cycle when she is receptive to the stallion and is fertile. Also known as being in heat or in season. Lasts approx 5 days in every 21 day cycle.

Osteophyte A break or outgrowth of new bone as a result of arthiritis or local trauma. Common in osteoarthritis. In some cases can be removed surgically.

Osteoarthritis Inflammation of a joint involving the bone ends, resulting in bone damage around the joint. May not necessarily cause lameness but is a common cause of joint pain, lameness and loss of performance, esp in older horses. Treatments include rest, joint medication and anti-inflammatory therapy

Osteomyelitis Infection of the bone including the marrow tissues. If not detected early or if close to a joint, can result in irreparable damage. Commonly affects foals in association with septic arthritis (joint ill) or following an injury which penetrates the skin and damages the underlying bone. Surgical treatment may be combined with vigorous antibacterial therapy.

Osteopathy Similar to chiropratic, osteopathy relieves tension in the body by encouraging the spine and pelvis into a correct position. Osteopaths use long slow movements and may exert pressure on a body part far removed from the one they are actually treating.

Overreach Injury to the heel of one of the front hooves being struck by one of other of the hind feet. Can cause bruising, cuts or damage to the hoof wall at the heel. Boots and protectors can help.

Over at the Knee Conformation where knee is constantly slightly bent forward. Relatively common in foals, which may remedy itself in time.

Parrot Mouth Condition where the horse's upper teeth overhang the lower jaw. Affected horses are still able to eat but require regular tooth care to reduce hooks on molars. Refer to our dental feature article

Pedal Bone Coffin bone or lowermost bine of the leg, which is fully contained within the hoof.

Physitis Damage to the physis (the growth plate responsible for elongation of long bones) can result in inflammation which in turn can result in limb deformity. 

Periosteum Very thin membrane covering the surface of the bone providing nutrients and materials for new bine production. If the membrane is bruised or damaged , it can result in the production of a bony lump.

Phenylbutazone ( 'BUTE' ) One of the main anti-inflammatory and pain killing druges in use for horses. Effective for low to moderate pain and usually safe. Administered by mouth or injection.

Pleuropneumonia Bacterial infection of the lungs and lining of the chest. Symptoms include high temperature, reluctance to move, depression, lack of apetite. Can be life threatening and requires urgent treatment. Factors: Previous viral infection, commonly occurs in animals during or after transportation over long distances.

Pituitary Gland Small gland at the base of the brain which is responsible for production of several important hormones.

Proprioception the sense of position.i.e. the ability to know where ones own limbs are.

Papilloma Correct term for a wart. All warts are the result of the papilloma virus and resolve spontaneously (no treatment is required and claims of wart cures are usually coincidental)