What causes limping?
Essentially limping, or irregularity in the gait, is caused by pain or a problem with conformation.
If a pet is born with one leg shorter, or crookeder, than its counterpart on the same side or end, the gait will be unusual.
Injuries can also cause abnormal shapes. A growth plate is the area from which parts of bones grow in youngsters. Growth plates at the ends of bones determine their length. If a growth plate suffers compressive damage, slippage or is invaded by an orthopaedic device to repair a fracture, it may stop growing. The result is a shortened or crooked bone.
Sometimes trauma shatters long bones into so many pieces that the original length cannot be reproduced in the surgical repair process, resulting in one short and three normal-length legs.
Just as a chair with one short leg wobbles, a pet with one short leg is not going to walk the same as a pet with four correct-length legs.
When pain causes a limp, it can come from many sources.
The most common is temporary pain from an injury, such as a blow, bruise, twist or sprain. “The leg bone is connected to the thigh bone,” so, when animals walk every connected part has some degree of movement, and every injured part that moves, hurts.
The most extreme pain results in a carrying-leg-lameness, one in which the patient refuses to put the foot on the ground when moving, even though he may use it to keep his balance when standing still. Carrying-leg lameness may occur with a thorn in the foot because the pain is so acute, or from bone cancer, in which case the pain is less acute, but still extreme.
Less-painful conditions cause the gait irregularities we call a limp. With low-level pain or very stoic individuals, limping can be so subtle that the pet must be walked, run and trotted for long periods before your pet’s doctor can even determine which leg is affected. With intermediate levels of pain a pet may “give” to the pain when the affected limb bears weight, making the source of pain more obvious.
The second most-common source of pain is arthritis. The combination of two Latin words, arth- refers to joints and -itis means inflammation. Thus, arthritis is inflammation of a joint.
As with people, there are a number of types of arthritis in animals, with the two most common being osteoarthritis, which is most simply explained as wearing out of the cartilage of a joint, and infectious arthritis, in which a joint’s cartilage is damaged by an infectious agent. In either case the joint hurts because it is no longer has smooth, well-lubricated surfaces working together. Instead the joint has heat, pain, swelling and loss of function.
Regardless of the cause of the limp, the veterinarian’s job is to find the source and begin specific treatment.
When a definitive cause cannot be found we may begin symptomatic treatment in an effort to relieve pain and gain return to function without ever knowing the cause.
See you tomorrow, Dr. Randolph.