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Slipped Tendon

Perosis, Slipped Hock, Luxation Of The Achilles (gastrocnemius) Tendon

Slipped tendon, also known as perosis, occurs when the duck's Achilles (gastrocnemius) tendon pops off the side of the bone, resulting in pain and reluctance to put weight on the leg. Affected ducks may be seen having a difficult time walking, and will have a limp to their walk--or they may continuously land with one foot on top of the other. There is often a variable amount of swelling around the hock joint. If the duck's tendon is completely ruptured, they may even walk "flat-footed" or "dropped", with their toes in that leg curled downward in a crab claw stance, like they are trying to grip the floor or perch on a roosting bar.

If identified early enough when ducks are still growing, and action is swiftly taken, sometimes the condition can be reversed, or at least improved through providing support and stabilization of the hock through splinting. It may easily be confused with splay leg, however with splay leg, the whole leg deviates rather than just at the hock. Rickets may also be mistaken for slipped tendon in ducklings, however with rickets, it is caused by the long bone deformity, not tendon displacement.


Sudden onset of lameness
Leg rotation
Swelling over the back point of the hock
Difficulty walking
Increased time spent laying down
Intermittent severe lameness with interposed periods of mild lameness
An intermittent popping sound may be heard each time the tendon dislocates


  • History
  • Clinical signs
  • Physical exam
  • Radiographs


MethodMethod Summary
Supplemental manganeseAdded to the diet, while ensuring not to provide excess calcium (calcium binds manganese)
SplintingMay be beneficial for early cases. A figure-of-eight bandage is applied around the hock, providing the duckling support and stabilization.
SurgeryPerformed by an Avian veterinarian, may be indicated if identified during the early stages of the condition
Anti-inflammatory medications
ManagementProtect the duck or duckling from other flock members by providing a separate area for them to not be bullied by others, but can still see and interact with them.


  • Provide feed specifically formulated for waterfowl
  • Don't feed excessive calcium, as it can cause manganese deficiency
  • Ensure adult ducks that are intended to be used for breeding purposes are receiving enough manganese in their diet, and not excessive calcium.



Risk Factors

  • Manganese deficiency - the condition will occur within 2-10 weeks of being fed a manganese-deficient diet.
  • Too much calcium in diet - Note that high calcium levels in a diet reduces manganese absorption
  • Breeder parents had a manganese-deficient diet
  • Choline deficiency
  • Excess protein
  • Trauma

Case Stories

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