Spondylolisthesis (Kinky Back) in Chickens

Spondylolisthesis, often called kinky back, is a developmental disorder of the spine in chickens. In affected birds, a thoracic vertebra becomes rotated and displaced, which can narrow the spinal canal and press on the spinal cord. That pressure can lead to weakness, poor balance, or even paralysis of the back legs.

This problem is reported most often in young, fast-growing broiler-type chickens, usually when they are only a few weeks old. Merck Veterinary Manual describes it as the most common vertebral column deformity in poultry, although the overall incidence is still considered low. Females may be affected more often than males, and both growth rate and genetic background appear to matter.

For backyard flocks, the condition can look dramatic. A chick or young chicken may seem normal one day and then suddenly start sitting back on the hocks or tail, pushing the legs out, or struggling to stand. Because several other serious conditions can look similar, your vet should evaluate any bird with sudden weakness or paralysis as soon as possible.

Spondylolisthesis in chickens is considered a developmental spinal deformity, not a simple sprain or routine leg injury. Merck Veterinary Manual notes that the free thoracic vertebra is rotated and displaced, leading to spinal cord compression. In practical terms, the bones of the back do not line up the way they should as the bird grows.

The condition is seen most often in broilers and other fast-growing meat-type birds, especially between about 2 and 8 weeks of age. Research and veterinary references suggest that rapid growth rate and genetic background both play important roles. Older literature and poultry extension materials also describe a hereditary component in some lines.

That said, not every bird with rear-leg weakness has kinky back. Your vet may also consider vertebral osteomyelitis or spondylitis, trauma, Marek disease, nutritional problems, or other causes of lameness and paralysis. This is one reason a home diagnosis can be misleading. The outward posture may look similar, but the underlying problem and treatment options can be very different.

Your vet usually starts with a hands-on exam and a careful history. Helpful details include the bird's age, breed type, growth rate, when the weakness started, whether one or both legs are affected, and whether other flockmates are showing similar signs. A neurologic and orthopedic exam can help your vet decide whether the problem is more likely to be spinal, muscular, infectious, or traumatic.

Radiographs can be useful, especially when your vet is trying to confirm vertebral deformity or rule out fracture and other spinal disease. Older avian pathology studies specifically used radiology to diagnose affected broilers. In some cases, the diagnosis is strongly suspected based on age, posture, and exam findings, but imaging helps with confidence and planning.

If the bird dies or humane euthanasia is chosen, necropsy can provide the clearest answer and may be the most practical way to confirm the diagnosis in flock situations. This can also help rule out infectious conditions such as vertebral osteomyelitis, which can mimic kinky back but has a different cause and flock-health significance.

Prevention focuses on risk reduction, not guarantees. Because kinky back is strongly linked to broiler-type genetics and rapid growth, the biggest preventive step is thoughtful flock planning. If you are choosing birds for a backyard setting, talk with your hatchery, breeder, or your vet about whether a slower-growing strain may be a better fit for your goals.

Good general management still matters. Provide secure footing, dry bedding, enough space to move, and a complete, balanced poultry diet appropriate for the bird's age and purpose. Nutritional mistakes do not appear to be the main cause of spondylolisthesis, but poor overall management can worsen mobility problems and make it harder for a weak bird to cope.

For broiler-type chicks, close observation during the first 2 to 8 weeks is especially important. Watch for birds that start sitting back, lagging behind, or struggling to rise. Early veterinary evaluation may not reverse the deformity, but it can help your vet separate developmental kinky back from infectious or traumatic problems and guide humane next steps.

If you are breeding chickens, do not breed birds that have shown signs consistent with this disorder unless your vet and breeding advisor have ruled out the condition. Older studies support a hereditary influence, so selective breeding away from affected lines is part of long-term prevention.