The superficial digital flexor tendon (SDFT) is one of the major tendons in the equine distal limb (i.e. lower leg). Due to its location and heavy use, the SDFT is prone to injury. This blog article outlines the anatomy of the superficial digital flexor tendon and highlights common causes of injury, diagnosis and treatment options.
The role of the SDFT is to flex and stabilise the fetlock. The superficial digital flexor tendon works with the superficial digital flexor muscle to make the lower leg move.
The SDFT emerges from its parent muscle, the superficial digital flexor muscle, which is located above the carpus (knee) or hock. The SDFT runs down the back of the leg to the short pastern, where it splits into two and connects to both the inside and outside of the short pastern.
In the thoracic (front) limb, the accessory ligament to the SDFT (also known as the superior check ligament) meets the SDFT just below the carpus. There is no superior check ligament in the pelvic (hind) limb. The check ligaments form part of the stay apparatus, a network of muscles, tendons and ligaments that allows the horse to stand.
The SDFT is protected by a series of tendon sheaths as it passes over the joints in the lower leg. The digital sheath is located at the fetlock, the tarsal sheath at the hock and carpal sheath at the knee.
The location of the SDFT at the back of the leg makes it especially vulnerable to injury. SDFT injuries are common and can have a range of causes. For example, horses can injure themselves by overreaching with their hind hooves and striking their own front legs, or by brushing a hoof against the opposite leg.
Furthermore, leaving a leg behind over a jump or working on uneven ground can also contribute to an injury to the superficial digital flexor tendon.
Overextension of the fetlock can occur as a result of sudden acceleration or braking, and this can strain the SDFT.
Failing to warm the horse up before exercise can make a tendon injury more likely as cold tendons are less able to stretch. Furthermore, cooling the horse down after exercise aids recovery and repair of micro trauma. Not cooling your horse down effectively after exercise can cause minor injuries to accumulate and eventually lead to more serious injury.
The type and severity of injury to the superficial digital flexor tendon can vary from minor trauma to total laceration of the tendon. Any injury that involves the tendon sheath can lead to a fatal infection if it is not dealt with promptly.
The symptoms of an injury to the SDFT are similar to those of other tendon injuries. Heat, swelling and lameness are all telltale signs of a tendon injury. However, lameness is not always obvious and it can be difficult to spot if it is very subtle. Read our guide on the signs of lameness in horses for more information.
It is always a good idea to call your vet if you suspect an injury to the SDFT, even if the symptoms are mild. Sudden, severe lameness and open wounds may require an emergency equine vet visit.
Often, horses will present with lameness or poor performance without an obvious injury to a specific area. In these cases, your vet is likely to carry out a range of investigations, including trot-ups, palpation and nerve blocks, in order to identify where the issue lies before diagnosing a specific injury.
Diagnosing an injury to the superficial digital flexor tendon is similar to diagnosing other tendon injuries. Clinical examination, including checking for heat or pain on palpation, as well as ultrasound scans are likely to be used to assess the type and extent of the injury.
Once an injury to the SDFT is confirmed, treatment will usually consist of icing or cold hosing, box rest, anti-inflammatory medication and a gradual re-introduction to work. There are a number of regenerative therapies that may improve the quality of healing and reduce the likelihood of re-injury. These include stem cells, platelet rich plasma and shockwave therapy.
The horse’s progress will be monitored using regular assessments and scans as required. Whilst the prognosis for an injury to the superficial digital flexor tendon is usually good, this will depend on the severity of the injury and the type and level of work the horse is used for.
Here at Avonvale Equine Vets, we are highly qualified and well-equipped to diagnose and treat tendon and soft tissue injuries. Whether you require lameness investigation or poor performance investigation, our team of equine vets take a methodical, holistic approach. The facilities at our independent equine vet practice near Banbury, Oxfordshire, allow us to carry out a range of orthopedic treatments including stem cells, shockwave therapy and platelet rich plasma. Register your horse or pony with our equine vet practice today.
