06/22/2026
🐴 Peroneus Tertius Rupture in Horses: Understanding a Unique Injury
The peroneus tertius is a key component of the horse’s reciprocal apparatus, a specialized system that mechanically links the stifle and hock. In a normal horse, when the stifle flexes, the hock flexes as well. The peroneus tertius runs down the front of the hind limb and helps coordinate this movement.
🚨 What happens when it ruptures?
A rupture of the peroneus tertius breaks this connection, allowing the horse to do something it normally cannot:
➡️ Flex the stifle while extending the hock.
Common clinical signs include:
• Hind limb lameness
• Swelling along the front of the hock or tibia
• Difficulty coordinating hind limb movement
• Ability to extend the hock while the stifle remains flexed (a classic diagnostic finding)
• Reduced athletic performance
🔍 Diagnosis
Diagnosis is often made through physical examination and observation of abnormal limb motion. Ultrasound can help identify the location and severity of the tear and evaluate associated soft tissue injuries.
💉 Treatment
Most cases are treated conservatively with:
• Stall rest and controlled exercise
• Anti-inflammatory medications
• Supportive bandaging when indicated
• A structured rehabilitation program
More severe injuries or those involving additional structures may require prolonged rehabilitation and close monitoring with repeat ultrasound examinations.
⏳ Prognosis
Many horses can return to athletic function following appropriate rehabilitation, although recovery time often ranges from several months to longer depending on the severity of the injury and the horse’s intended use.