If your rabbit suddenly goes weak in his hind legs, you know something's wrong. However, hind end weakness in rabbits can happen gradually, the result of the aging process. If your rabbit displays signs of hind leg weakness, take him to the vet as soon as possible. Causes of hind leg weakness in rabbits include trauma, heart disease, neurological issues, arthritis, bacterial or parasitic infection and intervertebral disc disease.
Trauma in Rabbits
If your rabbit's hind legs are weak or paralyzed, it's possible he suffered a spinal fracture from jumping suddenly and landing hard. Of course, trauma can result from more obvious occurrences, such as an attack by another animal. Your rabbit's prognosis depends on the extent of his injuries. Your vet will tell you whether surgery is an option.
As with other species, aging rabbits experience degenerative diseases. Larger, older rabbits -- especially females -- are vulnerable to spondylosis in the lower back. This progressive condition occurs when the lower back vertebrae develop bone spurs, eventually coming into contact and fusing with nearby vertebrae. While your vet might prescribe pain medication to ease your bunny's woes, ask if you can help her gain relief with massage and acupuncture. Intervertebral disc disease occurs when the shock-absorbing discs in the spinal vertebrae bulge out or tear, affecting spinal cord nerves. Depending on radiograph or magnetic resonance imaging results, your vet might recommend pain medication and anti-inflammatories along with strict rest for your rabbit. Severely affected rabbits might require surgery.
Parasitic and Bacterial Infections
The parasite Encephalitozoon cuniculi infects many rabbits, but most show no ill effects. Certain rabbits exhibit neurological problems, including hind leg weakness or paralysis. Your veterinarian might prescribe long-term daily use of a dewormer to rid your pet of this parasite. Baylisascaris procyonis, a type of ascarid, also can cause hind leg weakness; your vet likely will recommend a dewormer for treatment. If the hind leg weakness results from a bacterial infection, your vet might prescribe a course of antibiotics. Your bunny might have to stay in the veterinary hospital and receive the medication intravenously.
Rabbits also might suffer a stroke, resulting in hind leg weakness or paralysis. Cardiac issues can cause hind leg weakness, because muscle tissues don't receive sufficient oxygen. The same holds true for respiratory disease, because the bunny doesn't take in enough oxygen. If your rabbit lives on wire most of the time, he could develop pododermatitis, or foot ulceration. Kidney or liver disease can cause toxins to build up in the bunny's body, causing muscle problems. Your vet will test blood and urine samples and perform X-rays, among other diagnostic procedures, to get to the bottom of your bunny's hind leg weakness.