Musculus flexor digitorum superficialis
The superficial digital flexor muscle originates from the medial epicondyle of the humerus in the forelimb and from the supracondylar fossa of the distal femur in the hindlimb. The tendon runs down the palmar (forelimb) or plantar (hindlimb) aspect of the limb, superficial to the deep digital flexor tendon, and inserts primarily on the proximal and middle phalanges (P1 and P2). In the forelimb it receives an accessory ligament (superior check ligament) from the radius and forms a sleeve around the deep flexor tendon at the fetlock joint. Its actions are to flex the fetlock and pastern joints, provide primary fetlock support during stance, and act as part of the stay apparatus. In the hindlimb it is more tendinous, forms part of the common calcanean tendon, passes over the calcaneus, and functions as part of the reciprocal apparatus. It is innervated by the median and ulnar nerves in the forelimb and the tibial nerve in the hindlimb. Injuries are less common in the hindlimb than in the forelimb.
Origin: Supracondylar fossa of the distal femur
Insertion: Proximal and middle phalanges (P1 and P2) of the hind limb
Action: Flexes the digit and fetlock; extends the hock; part of the reciprocal apparatus
Innervation: Tibial nerve (L5-S2)
Superficial digital flexor tendon (SDFT) injuries are common in performance horses, especially in the mid-cannon region. Diagnosis uses clinical examination and ultrasound. Management is usually medical with rest and controlled rehabilitation. Injuries can alter limb biomechanics and indirectly affect loading of the foot. The accessory ligament can also be injured.
## Overview Tendinitis of the superficial digital flexor tendon (SDFT) in the hind limb produces swelling, heat, and pain on the plantar cannon. Lameness may be subtle at first. It is less common tha
## Overview Calcanean tendon disruption refers to partial or complete rupture or severe strain of the common calcaneal tendon (primarily the gastrocnemius component) or its insertion on the tuber cal
Sudden swelling or heat along the back of the cannon bone after work should be evaluated. Early diagnosis and appropriate rest improve outcomes. Protective boots can help reduce risk in some disciplines.
## Overview Tendinitis of the superficial digital flexor tendon (SDFT) in the hind limb produces swelling, heat, and pain on the plantar cannon. Lameness may be subtle at first. It is less common than forelimb SDFT injury but follows the same principles. ## Causes Overload or hyperextension injury. ## Diagnosis Palpation and ultrasound measuring cross-sectional area and fiber pattern. ## Treatment Prolonged rest, controlled rehabilitation, anti-inflammatories, and sometimes regenerative therapies. Return to work is gradual. ## Recovery and Prognosis Fair to good with adequate time. Re-injury risk exists. ## Prevention Conditioning and appropriate surfaces. Signs include: swelling on the plantar cannon of the hind limb; heat and pain; hind-limb lameness; confirmed on ultrasound
## Overview Calcanean tendon disruption refers to partial or complete rupture or severe strain of the common calcaneal tendon (primarily the gastrocnemius component) or its insertion on the tuber calcanei. The injury produces a dropped hock appearance and severe hind-limb lameness because the horse can no longer extend the hock effectively. It is uncommon but career-threatening. ## Causes Acute overload during slipping, jumping, or traumatic hyperextension of the hock is the usual mechanism. Degenerative change may predispose older horses. ## Diagnosis Characteristic dropped hock, inability to bear weight normally, swelling, and pain at the point of the hock or along the tendon are diagnostic. Ultrasound confirms fiber disruption and the degree of rupture. Radiographs rule out avulsion fractures. ## Treatment Complete ruptures generally require surgical repair or tenorrhaphy when feasible, followed by prolonged immobilization. Partial tears may be managed with extended rest and controlled rehabilitation. Supportive bandaging or casting protects the repair. ## Recovery and Prognosis Prognosis is guarded to poor for return to athletic use after complete disruption. Partial injuries have a better outlook with lengthy rehabilitation. Many horses are retired to pasture. ## Prevention No specific prevention beyond minimizing traumatic incidents and maintaining good conditioning. Signs include: severe hindlimb lameness; dropped hock appearance; swelling at the point of the hock or along the Achilles tendon; inability to extend the hock
Superficial digital flexor tendon (SDFT) injuries are common in performance horses, especially in the mid-cannon region. Diagnosis uses clinical examination and ultrasound. Management is usually medical with rest and controlled rehabilitation. Injuries can alter limb biomechanics and indirectly affect loading of the foot. The accessory ligament can also be injured.
Sudden swelling or heat along the back of the cannon bone after work should be evaluated. Early diagnosis and appropriate rest improve outcomes. Protective boots can help reduce risk in some disciplines.
See the Superficial Digital Flexor (Hind) on our interactive 3D horse model. Open 3D Model