Equine Tendon and Ligament Injuries
In this diagram you can see the structures from the side
The primary site of soft tissue injuries in the horse is the back of the cannon bone. The structures starting from the skin going forward to the cannon bone are the Superficial Flexor Tendon, the Deep Flexor Tendon, the Check Ligament and the Suspensory Ligament. Injuries to any of the structures threaten an equine athletic career and can take the better part of a year to heal before returning to their prior work. Recovery depends on a combination of veterinary treatment and a dedication by owners and trainers to a rehabilitation program that returns your horse to work while at the same time not over stressing the injury. Re-injury rates are high. Veterinary treatment and rehabilitation is crucial to maximize the quality of the healed injury and reduce rates of re-injury.
After lifting up your horse's leg and holding it by at the fetlock with one hand, you should be able to use your other hand to identify the different structures by applying your thumb and forefinger on either side of the leg. It can be difficult to identify separately the Deep Digital Flexor Tendon from the Check ligament as the Check Ligament sort of cradles the Deep Digital Flexor Tendon.
On a cross sectional ultrasound image of these same structures you can see an image as if you were looking down from on top of the leg.
Here is an ultrasound image without the structures marked.
Here is the same image with the structures marked and labeled.
The densely packed tendon fibers show up as the white dots on the ultrasound images.
When one of the tendons or ligaments suffers an injury, the ultrasound appearance changes. Swelling of the tendon or ligament will enlarge its appearance and that enlargement can be measured. A tear will appear as a black hole in the middle of tendon or ligament. By recording these changes on ultrasound and doing follow-up ultrasound examinations over the course of the recovery process, you can follow the progress of the injury and adjust treatment based on what is observed.
The big risk with tendon and ligament injuries is re-injury. As many as 56% of Superficial Flexor Tendon injuries will suffer a re-injury within two months of cantering when rehabilitation alone is used as the only treatment. Other structures also have significant re-injury risk. The injury often comes at the junction between the normal and healed tissue which is the weakest point of a healed tendon or ligament. To maximize the chance of the best structural healing, therapy aims to promote healed fibers to align along the original vertical path of the tendon or ligament. You want the fibers to be lined up like guitar strings on along the neck of the guitar. If not properly treated and rehabilitated you end up with a healed tendon or ligament with fiber strands are a jumbled woven mess. That kind of healing is much more likely to suffer a re-injury.
Versus rest and rehabilitation alone, various veterinary treatments have demonstrated success is improving both the quality and speed of recovery from these soft tissue injuries.
The choice of veterinary treatment can vary depending on the severity the injury. Where there is a clear tear Stem cell treatment is now the recommended approach. Stem cells are undifferentiated cells that can grow into a variety of cell types. They generally are harvested from fat or bone marrow. After being harvested, cells are cultured in a lab to expand the population. The Stem cells are then injected into the injured tissue or locally into the blood supply of the injured tissue in a procedure known as regional limb perfusion. For fat cells used as a source of Stem cells there is now a procedure where collection can be done via a long needle with a very tiny incision vs. what once was a 6 to 8 inch incision along the rump of horse.
For injuries where there is not a tear but defined area of injury a local injection of PRP, Platelet Rich Plasma, can be appropriate. Platelets are cells that are part of a horse's own blood. Concentrating platelets and injecting them directly into the injured tissue or into inflamed joints has been shown to stimulate healing. PRP has become very popular among elite human athletes as a treatment for tendon and joint disease. PRP can be harvested from your horse's own blood and there is some work on using PRP from donor horses as well.
For small minor injuries where enlargement or tissue damage is minimal, cold treatment initially followed by controlled rehabilitation may be all that is warranted.
Additional treatments include shockwave therapy which uses the same sound pulsing technology used in lithotripsy to break up kidney stones. With shockwave treatment sound waves are focused on the injured area. This provides pain relief and stimulates healing as well. There is Novobrace, a bioadhesive that helps to halt growth of lesions and allows cells to repopulate the lesion and speed healing. For superficial flexor tendon injuries there is a surgery to consider where the other check ligament located above the horse's knee is cut. This surgery has been shown to decrease re-injury in racehorses.
In contributing to healing an injury, various veterinary treatments might be considered 25% of the treatment approach, 75% is controlled rehabilitation. This requires time and patience. In the initial stages hand walking and cold therapy is important. Overtime exercise is increased in small increments starting with tack walking. Next small periods of trot are added to tack walking. The load of work progresses from there. The time for horse with a significantly "bowed tendon" to return to competition can be close to a year. Those with minor injuries can be back to full work in 3-6 months. I cannot stress enough how important regular and increasing but controlled exercise is for stimulating fiber alignment and healing. It is a classic case where, like Goldilocks, you don't want to do either too much or too little. If you can find and work in the middle range you maximize your horse's chance to return to their prior level of activity.