Superficial digital flexor (SDF) tendinitis

Veterinary advice should be sought before applying any treatment or vaccine.

Superficial Digital Flexor (SDF) Tendinitis

Bowed Tendon

Superficial digital flexor tendon (SDFT) injuries are among the most common type of tendon injuries in performance horses, especially racehorses and top-level event horses. The most common site of SDFT injury is the middle of the tendon, which has the smallest cross-sectional area. The SDFT is found in the horse's fore and hind limbs; running along the back of the cannon bone and connecting the short pastern to the coffin bone.
Superficial digital flexor (SDF) tendinitis
The SDFT's primary functions are stabilization and energy storage. Along with the suspensory ligament, the SDFT has a major role in supporting the fetlock joint.

SDFT injuries occur in horses as a result of sudden overloading or progressive weakening of the tendon. However, most tendon injuries are the result of cumulative damage as opposed to a single event, unless its associated with a fall or a strike from another limb. Horses with SDFT injuries often show pain, swelling and lameness 2-3 days following the injury. Lameness is commonly mild to moderate, transient or intermittent.

Initial treatment goals for SDFT injuries in horses are aimed at reducing inflammation and limiting lesion expansion. Therapy should begin immediately and includes stall rest combined with no longer than 30 minutes of cold therapy (cold hosing, Game Ready, ice boots) applied several times a day, administration of nonsteroidal anti-inflammatory drugs (NSAIDs), and support bandaging to help reduce swelling. Once swelling subsides, gradual return to exercise can usually start, with a rehabilitation exercise program constructed by your veterinarian; each program is customized for each individual horse, and differ according to the extent and location of damage, use and current exercise level of the horse, affordability on behalf of the owner, and other factors may apply. Many exercise programs include the use of aqua therapy, complimented with various new regenerative therapies such as stem cell, plasma rich platelets, shockwave therapy, and therapeutic laser.

Symptoms

Presence of heat
Sensitivity to palpation
Lameness, moderate to severe
Thickening
Swelling
Abnormal tendon profile
Lameness improves w/ stall rest
Bow-like palmar swelling

Diagnosis

  • History
  • Clinical signs
  • Physical exam
  • Ultrasonography

While waiting for your veterinarian

  • Keep in stall until your veterinarian arrives to conduct a lameness exam.

Treatment


TreatmentDetails
Reduce inflammationStall rest
Cold therapy (cold hosing, Game Ready, ice boots)
Poultices
Support bandages
Regenerative laser
Promote healing tissue generation through medical therapiesShockwave therapy
Stem cell therapy
PSGAG
Plasma rich platelets (PRP)
SurgeryTendon splitting
Annular desmotomy
Transection of the accessory ligament of the SDFT
Rest and RehabilitationLong-term stall rest (amount depends on the severity of the injury)
Hand-grazing/walking
Controlled, gradual return to exercise
Aquatread sessions
Periodic ultrasound checks to monitor healing

Prevention

  • Increase work load gradually as opposed to abruptly.
  • Keeping up with regular farrier appointments to avoid horse from developing a long toe, low heel hoof configuration
  • Properly warm up and cool down prior to and after exercise training
  • Early recognition and treatment of lameness
  • Avoid purchasing a horse with a 'back at the knee' conformation
  • Don't work horse on footing that is deeper than the horse is use to or uneven

Prognosis

Depends on the location of the injury, severity of the injury, and the expected athletic career of the horse. Reinjury is common.

Scientific Research References

Good Overviews

  • tendonitis icon
  • tendonitis icon
  • bowed tendon icon
  • bowed tendon icon

Risk Factors

  • Poor bandaging technique
  • Deep or inconsistent ground surface: SDFT loading is significantly affected by the ground surface horses are worked on. Deep, soft footing such as sand, puts horses more at risk of injury to the SDFT if they are usually worked on surfaces composed of different materials.
  • Existing lameness in the opposite limb
  • High heel angles
  • Unfit horse
  • Poor conformation