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Viral Arthritis

Other Names: Reovirus Infection, Tenosynovitis, Ruptured Gastrocnemius Tendon

Viral arthritis/tenosynovitis is caused by different serotypes and pathotypes of avian reovirus. The disease occurs predominately in commercial "meat-type" chickens, where it is controlled by vaccination of breeder flocks, and provides protection to progeny via maternal antibodies. Avian reoviruses are found worldwide in chickens, turkeys, and other species of birds.

Clinical Signs of Viral Arthritis

Chickens are more susceptible to infection with the avian reovirus when they're young, between 6 to 16 weeks of age. There is an increased resistance with age. When older chickens are infected, the clinical signs are less severe.

During the early stages of the disease, chickens may display varying degrees of lameness and abnormalities in the feet which gradually spread up the legs to the hocks. There will be marked swelling of the digital flexor and metatarsal extensor tendons, which are located just above the hock joint. The area of the swelling usually feels warm to the touch.

Once the disease is advanced, the articular cartilage of the joint can completely erode, resulting in chronic tendinitis and rupture of the gastrocnemius tendon. When this occurs, there is usually green discoloration of the skin and subcutaneous tissues at the site of rupture (from internal bleeding), and the bird is unable to extend the affected foot or put weight on the leg.

Diagnosis of Viral Arthritis

Diagnosis is based on the detection of avian reovirus in the chicken’s joint fluid. The gross lesions of viral arthritis often resemble those caused by Staphylococcus aureus and Mycoplasma synoviae.

Clinical Signs

Swollen foot pad
Swollen hock joint
Enlarged hock joints
Reluctance to move
Greenish skin discoloration near the joint
Joint stiffness
Reduced range of motion in joint
Painful on palpation


  • History
  • Clinical signs
  • Physical exam
  • Necropsy


Supportive care: Isolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress.:



  • Vaccination
  • Biosecurity



Scientific References

Age Range

Chickens between 6 to 16 weeks of age.

Risk Factors

  • History of recent trauma to the foot or leg
  • Cornish and meat-type chicken breeds