Tendon Injuries

A tendon is the cordlike tissue at the end of each muscle bundle that connects it to bone. The tendons that travel over bony structures are enclosed within a sheath that lubricates the tendon, allowing it to slide easily over the bones. Although tendons are very strong, tendon injuries do occur, mostly in cases of over-use or misuse. The following are the most common tendon injuries seen in horses.

Bowed Tendons

Example of high, middle and low bowed tendons.A bowed tendon is the result of a case of tendonitis that has been undiagnosed or untreated. The horse has swelling and inflammation on the rear side of the metacarpus. Depending on its location, the bowed tendon is called “high,” “middle,” or “low” (see graphic). In a low bowed tendon, the deep digital flexor tendon may be involved. Damaged fibers result in hemorrhage and swelling, weakening both damaged and healthy fibers. Prolonged disruption of blood flow to the area can result in irreversible tissue damage. Scar tissue that develops during the healing process may result in limited motion and elasticity to the tendon.

Treatment for Bowed Tendons: During the first 48 hours, inflammation should be controlled through immediate application of ice/cold therapy, cold water pressure bandages, removal of the shoes, administration of non-steroidal anti-inflammatories (NSAIDs) and sodium hyaluronate, topical application of DMSO and capsaicin, low level light therapy, massage, and passive range of motion exercises with stretching. The next step is to encourage repair of the tissues by application of warm moist heat to increase blood flow, cold therapy after exercise, therapeutic ultrasound, low level light therapy, controlled exercise and, when effective, the use of systemic and topical anti-inflammatories. The healing process may take twelve months or more.

Tendon Rupture

Example of tendon rupture with laceraton of the sheath (top) and within the sheath (bottom).Tendon rupture is the most severe of the tendon strains. A rupture can occur within the sheath or through a laceration in the sheath. Initially the fetlock will drop due to excessive stretching of the tendon. Inflammation, swelling and increased temperature at the site of injury, accompanied by lameness, usually occur within the first 24 hours after the injury. Damaged fibers result in hemorrhage and swelling, weakening both damaged and healthy fibers. Prolonged disruption of blood flow to the area can result in irreversible tissue damage. Scar tissue that develops during the healing process may result in limited motion and reduced elasticity of the tendon.

Treatment for Tendon Rupture: Treatment includes immediate physical therapy and rehabilitation to minimize inflammation and the development of scar tissue while maintaining blood flow to the tendon. Physical therapy techniques for tendon rupture include warm moist heat, cold therapy, therapeutic ultrasound, low light therapy, massage, and passive exercise with stretching. Systemic and topical anti-inflammatories can be used to facilitate healing. As healing progresses, warm moist heat is alternated with ice/cold therapy. Low-level light therapy and systemic and topical anti-inflammatories are continued. Hydromassage is used to combine the benefits of massage and temperature effects. Passive exercise can be replaced with light walking. Next, to encourage repair of the tendinous tissues apply warm moist heat to increase blood flow and follow exercise with cold therapy. Also encourage healing with therapeutic ultrasound, low-level light therapy, controlled exercise and, when effective, the use of systemic and topical anti-inflammatories.

Tendonitis

Tendonitis example.Tendonitis is inflammation within the tendon and its corresponding paratendon. Initially a slight swelling of the tissue and heat in the area are noted. When tendonitis occurs in a sheathed tendon, it is called tendosynovitis. If left untreated, additional inflammation can cause gait changes due to lameness, and can lead to bowed tendons. Damaged fibers result in hemorrhage and swelling, weakening both healthy and injured fibers. Prolonged disruption of blood flow to the area can result in irreversible tissue damage. In the future, scar tissue at the site of the injury may limit motion and elasticity in the tendon.

Treatment for Equine Tendonitis: Treatment includes immediate physical therapy and rehabilitation to minimize inflammation and the development of scar tissue while maintaining blood flow to the tendon. Physical therapy techniques for tendon rupture include the following: warm moist heat, cold therapy, therapeutic ultrasound, low light therapy, massage, and passive exercise with stretching. Systemic and topical anti-inflammatories can be used to further promote healing. As healing progresses, alternating warm moist heat with ice/cold therapy is beneficial. Low-level light therapy and systemic and topical anti-inflammatories should continue. Another treatment option, Hydromassage, combines massage and temperature for additional positive effects. Passive exercise can be replaced with light walking.

Tendosynovitis

Tendosynovitis example.Tendosynovitis is inflammation within the tendon sheath that irritates the tendon. The first sign of this condition is a slight swelling of the tissue and increased temperature at the site of injury. If left untreated, additional inflammation can cause slight lameness, affecting the horse”s gait or, untreated tendosynovitis can lead to bowed tendons. Damaged fibers in the tendon can hemorrhage and result in swelling, weakening both damaged and healthy fibers. Prolonged disruption of blood flow to the area can result in irreversible tissue damage, which may result in limited motion and reduced elasticity of the tendon.

Treatment for Tendosynovitis: Treatment includes immediate physical therapy and rehabilitation to minimize inflammation and the development of scar tissue while maintaining blood flow to the tendon. Treatment for tendosynovitis will include one or more of the following: warm moist heat, cold therapy, therapeutic ultrasound, low light therapy, massage, systemic and/or topical anti-inflammatories and passive exercise with stretching. Eventually, alternating warm moist heat with ice/cold therapy will be added to the physical therapy routine. Hydromassage may be employed in treating tendosynovitis, as it combines the benefits of both temperature (hot or cold) and massage. When the horse is ready, passive exercise can be replaced with light walking. Cold therapy should follow after the horse exercises. Therapeutic ultrasound, low level light therapy, controlled exercise and the use of anti-inflammatories round out the healing process.

Superficial and Deep Digital Flexor Tendon Injuries

Digital Flexor Tendon example.Injury to these tendons is the most common soft tissue injury in horses. Overloading and overstretching of the tendon commonly lead to injuries. Some common causes include:

  • toed-in or toed-out conformation
  • long toe and low heel
  • muscle fatigue
  • working on uneven surfaces or in mud
  • improper tack
  • unbalanced trimming and shoeing.

Treatment for Digital Flexor Tendon Injuries: Each case of injury to the digital flexor tendon requires evaluation for the appropriate method of treatment. Some methods commonly used are:

  • warm moist heat alternated with ice/cold therapy
  • therapeutic ultrasound
  • therapeutic shoes with pads
  • hydrotherapy coupled with massage
  • passive exercise with stretching
  • magnetic therapy
  • walking.