Tendon Injuries

By Laura Werner, DVM, ACVS, MS

Tendon and ligament injuries are common in performance and racing horses. These injuries usually occur as a horse becomes fatigued during exercise leading to incoordination and an increase in stress and strain on the tendon. Poor shoeing or poor footing may also contribute to the injuries. Often these injuries go undetected or may be subclinical before the clinical signs of tendonitis/desmitis (inflammation of the tendon/ligament) are observed. Clinical signs of tendon and ligament injuries include lameness, swelling, thickening or enlargement, heat, pain on palpation, excess fluid in the tendon sheath, and/or the typical "bow" profile of the tendon area. There sometimes is an increase in these clinical signs several days after the initial injury as the inflammation in the area increases. Diagnosis is based on clinical signs, lameness examination, thermography, and ultrasound examination of the area.

Superficial digital flexor tendon (SDFT) injuries are the most frequent injuries among race and event horses due to the high speed involved. This injury is often referred to as a "bowed tendon" because of the appearance of the injury. They most commonly occur in the middle of the tendon region of the limb and often occur in the front limbs. Deep digital flexor tendon (DDFT) injuries are atypical and seen in the fetlock region of the leg. Small tears in the DDFT can also occur on the edges of the tendon. These injuries are often associated with effusion (excess fluid) in the flexor tendon sheath. Accessory ligament of the deep digital flexor tendon (Check ligament) injuries are also less common. They are observed in jumping and dressage horses and are associated with swelling in the upper third of the cannon bone area.

Suspensory ligament injuries are also common and may be overlooked as the source of lameness. Nuclear scintigraphy (bone scan) or diagnostic nerve blocks are sometimes necessary to diagnose this problem since outward swelling is often less evident or non-existent with this injury. These injuries occur in racehorses as well as many types of performance horses and can be seen in the front and hind limbs. Suspensory injuries can often be associated with splint bone injuries or "splints" due to the relationship between these structures.

Treatment depends on the stage of the injury. Initial therapy includes icing, bandaging, and sweating the limb to decrease inflammation, as well as non-steroidal anti-inflammatory therapy (Bute and/or Banamine). Advanced recovery systems such as Game Ready that use intermittent compression and cold therapy aid in decreasing inflammation. Acute tendon injuries can also be treated with tendon splitting surgery. This procedure helps decrease swelling associated with core tendon lesions and may introduce some growth factors into the area of injury to promote healing. Injuries in the tendon sheath area can also be surgically treated with tenoscopy (scoping the tendon sheath) or splitting of the annular ligament surgically. Initial injuries are treated with approximately 4-6 weeks of stall rest with a gradual return to careful, controlled exercise thereafter. The tendon and /or ligament injury is monitored with serial ultrasound and lameness examinations to determine the progress of healing, especially as the horse returns to work. These injuries can sometimes take 9-18 months to fully heal before the horse returns to normal activity.

A huge area of research in veterinary medicine is devoted to developing new methods to get these injuries to heal faster and better. New treatment options include extracorporeal shock wave therapy, which can help increase blood flow and healing of the affected tendon and/or ligament. Other new therapies such as platelet rich plasma, bone marrow, stem cells, and IRAP (Interleukin-1 Receptor Antagonist Protein) are hot topics of veterinary research currently, since the injured area has less elasticity than before, making it prone to re-injury. These new treatment modalities help the injury heal more like the original tissue, decrease inflammation, and have been shown to promote better healing with a faster return to work. Please call The Equine Center if you think your horse may have this type of injury or if you have more questions about this topic.