It shouldn’t happen to a dog – but it does. Hind limb lameness is a real pain and not something that should be ignored.
For convenience, let’s divide the causes of lameness into two categories: the first where lameness occurs suddenly, and the second where it occurs slowly or progressively worsens.
Immediate lameness
Immediate lameness is usually due to some form of traumatic injury. This can range from simple and usually obvious causes such as a cut, wound or foreign body (e.g. a splinter) occurring in the pad or pads of the foot or to more devious conditions such as ruptured ligaments, fractures or joint diseases or infections.
If a dog is licking its paws excessively and is lame, this could suggest a cut or foreign body affecting the pads or skin of the foot, but it can also suggest an infection called Interdigital Dermatitis that often occurs between the pads on a dog’s paws. This dermatitis is, itself, sometimes caused by an injury or allergy that the dog has being licking excessively. The more it licks, the more it itches so the more it licks. This ‘lick/itch’ cycle establishes quickly and veterinary treatment is often necessary to resolve the problem though sometimes, bathing the wound in salt water and applying a soothing cream may help.
One common cause of immediate limping occurs when a dog ruptures its cruciate ligament in the knee joint. This is often seen in active, energetic dogs. The typical history is that the dog was racing around the garden playing with the owner, often chasing balls, when it suddenly slipped and was then lame.
The cruciate ligaments cross through the middle of the knee joint and stabilise the joint. When ruptured, the tibia (the shank or shin bone) and the femur (the thigh bone) which meet at the knee joint, slip and slide over each other in a most unhappy fashion. The joint loses its strength and stability and the dog experiences pain and discomfort. The best cure for this condition is surgery to repair or replace the ligament.
Fractures are a common cause of lameness and usually follow some significant accident like being struck by a car. When fractures cause lameness, they can be almost anywhere in the leg or hip. They can range from mild (but painful) greenstick fractures where the bone is only cracked to major compound fractures where the bone is shattered into pieces, sometimes with fragments of bone poking out through the skin.
Some owners report an unusual form of lameness in their dogs. Characteristically, they will say their dog was suddenly very lame in one back leg, dragging the leg behind them with the leg stiff and straight. They will then say with wonder that suddenly the dog became normal again. Often they ask if the dog had a fit.
While fitting does sometimes causes this problem, dislocating kneecaps (luxating patellas) are a much more common reason. This can occur in any breed, but seems to be most common in small breeds such as Chihuahuas and Poodles. It is caused by the sideways movement of the kneecap. When the kneecap moves out of position, it acts like a wedge and tightens the ligaments around the knee so that the animal cannot bend its leg. Suddenly the kneecap slides back into position and the dog can walk normally again.
Another condition of small dogs, especially young ones, that will cause lameness is a condition known as Legg-Calve-Perthes Disease or Femoral Head Necrosis. This is often a condition these small dogs inherit from their parents. Due to a failure of the blood supply to the neck of the femur (the ‘ball’ part of the hip) the neck decays and a fracture occurs. Severe lameness then results.
Occasionally, lameness in the hind limbs has nothing to do with the legs at all. It is often caused by decay of the discs in the spine and the protrusion of those discs into the spinal cord (a slipped disc). This often occurs around the neck or in the spine in the middle of the back. By pressing on the spinal cord, the disc affects the transmission of signals down the nerves and if the nerve affected goes to the legs, lameness can occur.
When chatting about lameness, we should not forget ticks and their associated problems.
In a ‘textbook’ tick paralysis case, the dogs initially develop a weakness in the hind limbs that can look like lameness. Usually this quickly progresses to the stage that the dog cannot bear weight on its hind limbs and is unable to walk. At the same time, paralysis of the front legs is usually developing, as well as a moist cough that sounds as if the dog is trying to vomit or choke.
Gradual lameness
When lameness occurs gradually, it is usually due to some progressive condition. The commonest condition by far that causes lameness in the hindquarters is arthritis in all its forms.
Arthritis is often an ‘old age’ condition and is caused by a number of changes in the structure and function of the bones, joints and ligaments. It can occur in almost any joint but is common in the hips, along the spine, and in the knee joints. A very common cause of arthritis is the condition Hip Dysplasia where there is a deformity of the ball and socket joint of the hip. Instead of the joint being a silky smooth ‘ball and socket’, it is more like a ‘square peg in a round hole’ that grinds and grinds away as the dog walks.
Arthritis can cause its effect through the formation of bony bridges and spikes in and around joints or the bony protrusions can push against nerves along the spine. Typically, a dog with arthritis will have trouble rising after lying down for a while and when first walking will be very stiff, slow and sore. Usually, they get better as they ‘warm up’ and the joint fluid starts to mobilise.
Thankfully, there are many new anti-arthritic medications on the market that give arthritic dogs a zest for life again.
One of the more serious conditions causing a gradual onset of lameness is tumour development. Tumours in the central nervous system and in the bones often cause lameness. The nastiest are bone tumours or osteosarcomas for which chemotherapy and usually amputation of the effected limb is needed.
Lameness and limping can certainly be serious problems for dogs and cats. If your animal is showing any of the signs above, see your veterinarian as soon as you can to prevent your pet experiencing unnecessary pain.
More information
By Dr Cam Day BVSC
Last updated on 15 November 2019
