Last Updated on February 22, 2022 by Allison Price
Tendons are elastic strap-like structures that connect muscles to the bones they serve. Tendons are usually short and rarely broken. The tendons that run along the limbs can be damaged by exercise or trauma. We will be discussing the most important structures, the flexor tendon.
These tendons are located
The flexor tendons, which are the deep digital flexor tendon and the superficial digital flexor tendency (SDFT), run down the back side of the limb starting at the knee/hock.
The DDFT and SDFT terminate at the back of your pedal bone. A fluid-filled sheath surrounds the tendons at the level of the knee, hock, and the pastern region. The digital sheath covering the fetlock/pastern area is the most well-known, with the sheath covering the hock (the tarsal sheath) and the knee carpal sheath. In high-movement areas like joints, there are several strong and short annular ligaments that help keep the tendons in their place.
Tendons are made up of bundles of fibres that run along the length of the tendons. The blood supply to ligaments and tendons is less than that to muscles or other tissues.
Different types of tendon injuries
Exercise can often cause injury to these tendons. Even unfit horses can be injured by strenuous exercise, which can cause fibres to tear. Even horses that are fit can cause damage to these structures by jumping fast, on uneven ground, or over-extending tendon tendons. You can get minor damage with very little fibre damage or severe tendon rupture.
A zone is a region within the tendon where a portion of the fibres are most often damaged. The tendon may become a distinct hole that extends for a variable length.
A slight knock to the tendon can cause mild bruising, or even rupture. Sharp trauma that cuts through the skin may cause minor tendon damage or complete laceration. These can cause serious infection if the tendon sheath is not removed promptly.
First symptoms of tendon injury
Tendon damage can cause inflammation, which is commonly felt as heat or swelling. Mild fibre damage can cause a slight swelling of the affected tendon, which is warmer than the area in the opposite limb. Most often, mild sprains don’t cause lameness. The limb may become painful if there is severe injury. In this case, the toes might be tipped up or the fetlock may fall during walking. Horses that have tendon sheath sepsis will also be severely lame.
Diagnose tendon injuries
For advice and to make an appointment, call the clinic if you think your horse may have a tendon injury. The clinic will conduct a clinical examination to determine if there are any concerns. This will include looking for heat and pain on palpation. It is difficult to accurately assess the extent of damage through palpation and look. If the injured structure is above the hoof capsule, an ultrasound scan will allow us to visualize it.
There are many treatment options
Tendon injuries can be treated in a variety of ways, but none guarantee a permanent return to normal. The tendon is less flexible than its original structure and can heal with poorly arranged fibres. The tendon that has been damaged is less resilient and more susceptible to re-injury.
The following are the most common initial treatments for injuries within 10-14 days.
- Box rest.
- Ice application, cold hosing 2 to 3 times per day and/or application kaolin poultice
- Bandaging is used to immobilise the limb.
Bute is an anti-inflammatory medication that can reduce swelling and provide pain relief.
These steps will help reduce inflammation and pain, as well as prevent further injury. After the initial inflammation has stabilized and the severity of the injury is confirmed, a controlled exercise program may be initiated.
Exercises that are controlled
This is an important part of recovery and treatment. Your vet will tell you what is best for your injury. Generally, this will be hand walking with box rest for one to two weeks. Then gradually increase the amount every other week for three months. In some cases, a period of complete box rest may be recommended. These injuries can often keep horses out of work for 6-12 months. Exercise can be controlled to align the tendon fibers longitudinally, resulting in greater strength and flexibility.
As an aid to the healing process, repeat ultrasound scans can be invaluable. They also help in the adjustment of the exercise program such as when to add trot work or steady-canter exercise. Sometimes horses are unable to compete in full and may need to be trained to do less stressful work to minimize the chance of injury.
There are other options
All treatments can reduce the horse’s time off. However, the goal is to improve the horse’s ability to recover and to reduce the chance of injury upon return to exercise.
- Tendon splitting and fenestration. To remove the blood clots from the core lesion, a scalpel can be used or many needle holes may be made. This will allow new blood vessels to grow in the area. This procedure must be completed within one to two week of the initial injury.
- Tendon injections. PSGAG’s are a group of drugs that can be used to successfully inject tendon injuries. They also aid in short-term healing. We now commonly inject stem cells or platelet rich Plasma directly into tendon after injury.
Platelet rich plasma
The platelets are small blood cells that are responsible for clotting blood. Many growth factors are contained in them. The growth factors stimulate new blood vessels to form at the site of injury, allowing for normal tendon fibers to develop. You can take the horse’s blood and extract the platelet fraction. This can then be injected directly into the tendon. To desensitise the limb, this is done under light sedation and a nerve block
The bone marrow is home to stem cells, which can grow into different types of tissue depending on where they are located. Many growth factors are also found in bone marrow, similar to platelets. To culture more stem cells, bone marrow can also be taken from the horse’s sternum or pelvis. They are then injected into injured tendon using local anaesthesia and sedation. These stem cells are then transformed into new tendon cells, a process that is very inefficient normally. This results in a higher quality tendon repair.
- Tendon lacerations can be performed to protect the tendon edges. Tendon sheath sepsis is used to treat infection. Both of these procedures can be done under general anaesthesia.
The SDFT accessory ligament can be cut in certain circumstances to allow the muscle or tendon to stretch further. This reduces the chance of SDFT re-injury. This procedure should be done under general anaesthesia, but it is not routinely performed. It can also increase the chance of sustaining a suspensory injury.
- Tendon Firing. Tendon Firing has been performed since the Middle Ages. After blistering or firing, it is important to rest. This is usually enforced by the inflammation.
Ligaments are elastic soft tissue structures which connect bone ends at joints. They attach to the bone via a tendon in certain cases, ie the inferior checking ligament. They support a joint and keep bones aligned. They can be found on either side or the top of a joint. Because of their location, the name collateral is often found in their names. Some joints have one ligament per side, while others, such as the stifle, have two.
What causes ligament injuries?
They can be caused by direct trauma, abnormal forces or excessive forces on a joint (eg speeding). You can experience mild to severe lameness. In severe cases of rupture, instability can occur in the affected joint. The area of injury can often experience heat, pain, and swelling.
Common Ligament injuries in horses include:
- Suspensory ligament desmitis.
- Collateral ligaments are found in the coffin, fetlock and hock joints.
- The fetlock’s palmar annular ligament.
- Check the accessory (check) ligament for deep flexor tendon.
- The stifle has meniscal and cruciate ligaments.
Diagnose of ligament injuries
To aid in the diagnosis of severe ligament injuries, heat, swelling, and pain may be present. Ultrasound will confirm this. A full lameness examination may be necessary for cases that are more subtle or involve the hoof. To diagnose, this would include radiography, ultrasonography, and nerve blocks.
Treatment for ligament injuries
These injuries can often be treated in a similar manner to tendon injuries. It may involve a combination of initial treatment within the first 10-14 days following an injury.
- Box rest.
- Ice application, cold hosing 2 to 3 times per day, and/or application kaolin poultice.
- Bandaging is used to immobilise the limb.
- Bute is an anti-inflammatory that can reduce swelling and provide pain relief.
A slow rehabilitation plan is usually followed by this. This can take up to nine months and allow you to resume your normal exercise program if you are successful. Initial rehabilitation may include a period of box rest, followed by controlled walking for up to three months.
There are other treatment options
These options are similar to tendon injuries.
- Surgery – Used to assess further the extent or debride lesions. To relieve lameness symptoms, proximal supensory desmitis may include lateral nerve neurectomy or fasciotomy.
- Platelet derived plasma.
- Stem cells
- Extracorporal shockwave treatment – This involves the application of short, high-impact, and brief duration shock waves to damaged or inflamed tissues. The machine delivers a series (physical rather than electrical) of shocks to the area of tissue damage. This is typically repeated for up to four times at intervals of seven to ten days. Although the exact mechanism of this machine’s action at the cellular level is unclear, there are evidence to suggest that it can increase blood flow, decrease pain, suppress nerve ending activity, and increase tendon and ligament generation.