Arthrogryposis in Lambs: Congenital Joint Contracture in Sheep

Arthrogryposis means a lamb is born with one or more joints that are fixed, stiff, or severely contracted. In practical terms, the legs may look bent and unable to straighten, and the joints may feel rigid rather than flexible. It is a congenital problem, which means it is present at birth rather than something the lamb develops later.

In lambs, the front limbs are often most obviously affected, especially the carpal and fetlock regions, but the hind limbs, neck, or spine can also be involved. Severity varies. Some lambs have mild contracture and can stand with help, while others cannot rise, nurse, or survive. Merck notes that prognosis depends heavily on how severe the contracture is and whether the joints can be manually straightened.

Arthrogryposis is not one single disease with one single cause. Instead, it is a visible birth defect pattern that can happen when the fetus does not move normally in the uterus or when the developing nerves, muscles, or skeleton are damaged. That is why your vet may look beyond the joints themselves and consider genetics, infectious disease, and pregnancy exposures when working up a case.

Arthrogryposis develops when normal fetal joint movement is reduced or absent during pregnancy. If a fetus cannot move normally, the surrounding soft tissues tighten and the joints may become fixed in abnormal positions before birth. The underlying reason for that reduced movement can differ from flock to flock.

One important category is genetic disease. A published report in pedigree Suffolk lambs described congenital arthrogryposis as an inherited limb deformity, with 30 of 52 lambs affected in one flock after introduction of a new ram. That does not mean every case is inherited, but it does mean breeding history matters and should be reviewed carefully.

Another category is fetal infection during pregnancy. Merck describes arthrogryposis as part of congenital deformity syndromes linked to certain viruses in ruminants, and Cornell has reported Cache Valley virus in sheep flocks where malformed fetuses showed arthrogryposis along with scoliosis, mandibular brachygnathism, and hydranencephaly. Timing of infection during gestation matters because the fetus is most vulnerable during key stages of nervous system development.

A third category is teratogenic exposure, meaning toxins or plants that interfere with fetal development. Some congenital deformity syndromes in sheep and cattle have been linked to toxic plant exposure during pregnancy. In individual cases, your vet may also consider whether the contracture is part of a broader syndrome involving the brain, spinal cord, muscles, or other organs.

Diagnosis starts with a hands-on exam of the newborn lamb and a careful pregnancy and flock history. Your vet will look at which joints are affected, whether they can be gently extended, whether the lamb is otherwise bright and able to nurse, and whether there are other defects such as spinal curvature, jaw abnormalities, or neurologic signs. The lambing history also matters, because congenital deformities can contribute to dystocia.

If the lamb is alive, your vet may recommend radiographs to look for bone and joint abnormalities and to help separate true congenital contracture from fractures, tendon problems, or incomplete ossification. Merck specifically notes that radiographic examination is indicated in neonates with marked carpal or tarsal hyperflexion because abnormal bone development can be part of the picture.

When a lamb is stillborn, nonviable, or one of several affected fetuses, flock-level diagnostics become especially important. These may include necropsy, histopathology, and submission of fetal tissues and fluids for infectious disease testing. Cornell advises keeping suspect fetuses cold and arranging sample collection through your veterinarian when congenital viral disease such as Cache Valley virus is a concern.

Your vet may also review breeding records and consider inherited disease if there is a pattern within a family line or after use of a particular ram. In many cases, the diagnosis is really two parts: confirming that the lamb has arthrogryposis, and then trying to identify the most likely underlying cause so future pregnancies can be managed more safely.

Prevention depends on the cause, so the most useful first step is to work with your vet after any affected birth rather than assuming it was random. If possible, save stillborn or nonviable lambs for veterinary examination and laboratory testing. A diagnosis can guide breeding decisions, pasture management, and pregnancy planning for the next season.

For genetic risk, keep detailed breeding records and review whether affected lambs trace back to a specific ram or family line. If an inherited defect is suspected, your vet may recommend removing certain animals from the breeding program. This is especially important when multiple affected lambs appear after introducing a new sire.

For infectious risk, ask your vet about regional vector-borne disease concerns and the best timing of breeding relative to insect season. Cornell notes there is no vaccine for Cache Valley virus, so prevention focuses on reducing exposure risk and investigating outbreaks promptly. Good flock biosecurity and diagnostic follow-up matter when congenital defects appear in clusters.

For toxin risk, review pasture, hay, and browse sources for plants known or suspected to cause fetal deformities in pregnant small ruminants. Also look at feed changes, chemical exposures, and any unusual grazing conditions during early to mid-gestation. Not every case can be prevented, but a careful flock review after one abnormal lamb can lower the chance of repeat losses.