Understanding Equine Ligament and Tendon Injuries

Horses are commonly used for athletic purposes because of their speed and endurance. A horse’s limbs are adapted for fast running, the downside of which is the commonness of limb injuries.

 

Introduction to Tendons and Ligaments.

Ligaments and tendons are vital parts of the musculoskeletal system of a horse. Ligaments are short flexible fibrous bands that connect bones and hold joints and organs in place.

A tendon is a flexible inelastic fibrous band that attaches bone to muscle. It transmits force from muscle to bone.

Both ligaments and tendons are made up of fibrous connective tissue mainly composed of type I collagen fibres. As well as collagen fibres, ligaments also contain spindle shaped fibrocytes, which synthesize collagen and ground substance.        

          A tendon contains proteoglycan, elastin, glycosaminoglycans, inorganic components, and a few tenocytes, which are rod or spindle shaped fibroblast-like cells which synthesise collagen.

Morphologically, both ligaments and tendons are similar. As mentioned earlier, these are mainly composed of type I collagen that is arranged in a triple helix. The dry matter of tendons and ligaments is made up of approximately 80% type I collagen, with some type III collagen also present. Collagen fibrils are arranged in bundles and appear as a crimped pattern when viewed under a light microscope.  

Normally, tendons are surrounded by a tendon sheath.

Bones have roughened areas where ligaments and tendons attach to the bone.  This area is known as the enthesis. Ligaments and tendons attach to this site through osteotendinous or osteoligamentous junctions.

The horse’s forelimbs and hind limbs contain several tendons and ligaments. There are two main types of tendons in the horse’s limbs, named according to their function. Flexor tendons are located on the backside of the limb and help to flex the limb. The superficial digital flexor tendon(SDFT) and deep digital flexor tendon (DDFT) are present in both the forelimb and the hind limb of a horse, allowing the lower part of the limb to be flexed.

Extensor tendons are located on the front side of the limb and help with limb extension. Lateral digital extensor tendons found in both fore and hind limbs; common digital extensor tendons found in the hind limbs; and long digital extensor tendons in the forelimbs are all important tendons that allow the limb to be extended.

Ligaments located on either side of a joint are called collateral ligaments, and can be divided into medial and lateral collateral ligaments. Annular ligaments and suspensory ligaments also help stabilise the joints by wrapping around them or connecting two bones together.

 

What causes tendon and ligament injuries?

Injuries to tendons and ligaments can result in the disruption of the internal organisation of these structures. Injuries can be divided into acute injuries and overuse injuries.

An acute injury occurs via a sudden trauma to the horse, for instance a fall, twist or blow, sprains, strains, contusions, jumping at high speed, and sudden accidents.

Overuse injuries occur gradually over time. These occur when an athletic (or other) activity is repeat often, not allowing the body sufficient time to heal any injury sites.

Most tendons are short and strong, so rarely get damaged. Longer tendons, however, are more frequently damaged during races and exercise.

Enthesis, where the ligaments or tendons attach to the bone, are vulnerable to both acute and overuse injuries.

 

Different types of injuries.

Strenuous exercise can result in the tearing of collagen fibres in the tendons and ligaments of horses. Over-stretching of tendons, work on un-level ground, high speed jumping or sudden accidents can damage these structures.

The degree of damage can vary from minor to severe with total tendon rupture being the worst outcome.

Mild injuries may result in bruises caused by the rupturing of blood vessels in the injured site. In fortunate cases, these mild injuries may not lead to lameness.

Severe damage leading to tendon rupture can ultimately result in lameness. If a tendon sheath incurs damage, this may even result in the animal’s death.

Injuries can affect any tendon or ligament in a horse’s body. SDFT and DDFT injuries are the most common injuries in horses. Both tendons run down the back of the limb from the knee/hock joint level to the lower limb. SDFT occurs on the pastern bone, one of the middle phalanxes of the horse, whilst DDFT ends on the back of the pedal bone, a distal phalanx. SDFT injuries commonly occur in the forelimb of the horse but can also affect the horse’s hindlimb. DDFT injuries can occur in both the forelimbs and the hind limbs of a horse.

Ligaments provide support to joints. Direct trauma or excessive force to a joint can cause ligament injuries to occur.

Ligament injuries commonly occur in suspensory ligaments, collateral ligaments of the coffin, fetlock and hock joints, and the palmar annular ligament of the fetlock joint.

The most commonly injured tendons and ligaments are those on the plantar or palmar aspect of the distal limb.

 

How to diagnose tendon and ligament injuries?

To diagnose a tendon or ligament injury of the equine distal limb, a clinician will consider the history of the animal including exercise time and types of exercises carried out. Inflammatory signs such as swelling, heat, pain, and lameness can be diagnosed via a physical examination.

The repair of tendons and ligaments occurs in three phases:

  1. Inflammation
  2. Cell and matrix proliferation (healing)
  3. Remodelling and maturation

The inflammatory phase is short. A haemorrhage occurs in the injured site of the tendon or ligament. A hematoma is usually formed at this stage. Consequently, there is increased blood flow to the area and cardinal signs of inflammation such as swelling, redness, and increased temperature can be observed in the injured site. This can result in severe pain to the animal, and the horse will usually become lame.

During the 2nd phase, the healing of the ligament or tendon occurs. The scarred tendon is not as strong as a healthy tendon. During healing, the usually predominant type I collagen is replaced by type III collagen. In the remodelling phase levels of type I collagen do increase, however this does not return to previous levels.

During the inflammatory phase, lameness can be observed. This can usually be resolved, but in some tendon and ligament injuries such as DDFT overstrain injuries, persistent and marked lameness can be observed.

The location of the injury can be found thanks to inflammatory cardinal signs such as swelling of the injured site. Swelling of SDFT is most apparent when assessing the palmar contour of the limb. In severe SDFT tendinopathy, the affected limb shows greater than normal overextension of the metacarpal joint when the animal is walking. A clinical examination will confirm the ligament and tendon injury, but the extent of the damage is difficult to assess by external observation and palpation alone.

Therefore, an ultrasound scan is carried out for further diagnosis. An ultrasonographic evaluation allows the damaged structures to be visualised if the injuries occur above the hoof capsule of the horse.

Additionally, radiography and gamma scintigraphy can be used for diagnosis. The advent of magnetic resonance imaging (MRI) and computed tomography (CT) for horses has enabled us to identify injured ligament and tendon areas where ultrasonography is limited.

 

How to Treat Tendon and Ligament Injuries?

There are several treatments for tendon and ligament injuries.

Physical therapies like cold pressure treatments can be carried out in the acute inflammatory phase of tendon and ligament injury. To carry out this treatment, apply ice 2 or 3 times per day. Because ice packs numb pain and cause vasoconstriction, they reduce the swelling of the injured site.

As well as cold hosing, we can also administer anti-inflammatory drugs like phenylbutazone to help reduce inflammation. This helps to reduce the inflammatory signs and the pain of the horse. Bandaging the affected area controls the mobilisation of the joint. This helps to improve the healing process.

       Even after the healing process is complete, injured ligaments and tendons are weaker than normal uninjured ones. Therefore re-injury is common in damaged sites. We must therefore look after an injured horse carefully. Box rest can be a helpful method to ensure this. During box rest, the horse requires mild exercise to prevent the injured sites from accumulating with adhesives, which could otherwise lead to immobility of the injured joints.

                       Tendon injections such as polysulfated glycosaminoglycan (PSGAG) can also be administered to help speed up the healing process. Nowadays, however, it is more common to inject stem cells or platelet-rich plasma directly into the injured site soon after the injury occurs. Extracorporeal shock wave therapy is also used as a treatment for tendon and ligament injuries in horses.

 

Conclusion.

Healthy tendons and ligaments are vital to maintaining a horse’s wellbeing and athleticism. 
       Tendons attach muscle to bone, while ligaments connect bones to other bones. Both ligaments and tendons are bands of connective tissue that can be injured through sudden traumatic accidents and overwork. The injury of these structures is a common cause of lameness in horses. Understanding these conditions will help you to prevent these injuries from occurring and to treat them properly if necessary.  Remember, early identification can save the animal from undergoing severe pain. If you miss the early signs, conditions can worsen, making it difficult to restore your horse to its normal fitness. If you do not feel confident in your knowledge of these conditions it is always advisable to seek help from a professional. 

Halting and Collection

Halting 

‘Halting’ is a term used to describe bringing a horse to a stop.  Learning to stop a horse is the first step in becoming a great rider! This technique will help you to develop a bond with your horse and is reasonably easy for beginners to learn. This does rely, however, on your relationship with your horse having a strong basis of confidence and understanding. 

 Stopping occurs in three phases which involve interacting with the horse through the use of your body, riding equipment, and even voice commands.

In a dressage test, a halt must be carried out at least once. Asking a horse to stand still will disturb its innate instinct of flight. When you command the horse to stop, the horse must think ahead and must come to feel comfortable and balanced.  It is essential to gain the horse’s complete confidence by showing it that nothing bad will happen if it halts.

 

What is a good halt?

In an ideal halt, the horse should be straight and square. Each leg should bear the same weight equally so that the horse can stand up straight.

If the stop is unbalanced, the horse can tip on its forehand and drop its poll when it stops, or it may throw its head back against the touch and fail to stop square. The horse should remain calm and comfortable while waiting for the next orders from its trainer. When asked to move away, it should then step forward. 

Halting is usually the very first technique taught when learning to ride.

 

How to practice halts

Gaining trust is an important part of halting. There are many goals to fulfil when perfecting halts, such as making them square, straight, and still. It is important not to confuse horses with multiple, conflicting exercises. Concentrate on one goal at a time and wait for a lesson to be understood by your horse before introducing anything new.

Patience is also very important. Perfecting a halt is a slow process that can take years of preparation. Balance, straightness, squareness, and self-carriage develop over time as a result of proper dressage training.

The whip should never be used as a punishment.  Instead, it should be used to improve the sensitivity of forward driving aids. Using the whip during a halt will cause stress to your horse and result in a loss of trust.

It is also important not to halt a horse when it is feeling afraid, as doing so can result in the horse developing a fear of stopping.

Good timing is the key to achieving a successful stop, and practice is the only way to perfect this. If you overdo this, however, your horse may grow to hate halting! Practice a few times a week, including 10 or fewer interruptions in each session.

Avoid stopping at high speeds as this is rough on the horse’s legs, and can also trigger a change in the horse’s attitude towards the technique. Instead of this, “downshift” in phases. If you are in an extended canter, for instance, transition to a medium canter, then collect the canter before stopping.

 

Stages of halt

When your horse feels balanced, comfortable, and attentive, this is a great time to start practising halts! If, however, your horse does not seem prepared, try an easier transition. For example, instead of halting from a canter, try a transition from canter-trot or canter-walk. This will strengthen the horse’s equilibrium and reactivity to your instructions and will prepare it for halting in the future.

Regardless of speed, it is important to integrate a transition so that the horse is ready to stop. If you close the reins and fail to control your legs, the horse will lose engagement when it stops. The stop will then become unbalanced, and the horse will not be square.

Step 1

Support your horse by performing two or three shorter, more collected trots or walking steps before you halt. This will force the horse’s hind legs underneath it, helping it keep its balance. Give your horse a simple half-halt and halt. Be careful not to ride to a halt too abruptly, as this will unbalance your horse.

Maximise the quality of your horse’s gait by riding it from back to front, using your legs and the reins. Teaching the horse to be more responsive to rein aids is essential; in order to do so, practice trot work transitions and half halts. It will take several exercise sessions before the horse learns to move forward in response to pressure from your leg. It is also important throughout your work to think about increasing the “RPMS” of your horse rather than “MPH”. After working on all of these things, you can then teach the horse to halt.

Step 2

As a second step, practice half halts. These help to rebalance the horse by teaching it to carry its weight on its hindquarters. These also improve the horse’s self-carriage power. To begin, you must sit straight on the horse. Use your rein aid to signal to the horse. Lengthen your legs slightly then tighten your back muscles to create resistance. When the horse shows signs of stopping, signal to it to keep moving forward. In order to do this, you can use verbal commands until the horse becomes more used to this technique.

Step 3

Next, try to carry out a full halt. In a good halt, your horse should stop immediately from a trot without taking any further steps. In the early stages of training, your horse may not be able to do this but as training progresses, you will be able to direct the horse to take fewer steps before eventually completing the transition from trot to stop without walking.

      If the horse executes a stop correctly, sit still and let the horse relax and rest. Loosen the reins and relax your shoulders. After a few moments, you can resume putting a little pressure on the horse via your legs and the reins.

Step 4

When the horse has made a fine, square, straight stop and is obediently waiting for your next order, it is very important to reward it with a treat or with verbal praise. This will help the horse to remember this moment in a positive light and to strive to repeat it. When you are satisfied that you have rewarded your horse sufficiently, ask the horse to walk on.

If all this has been carried out properly, you should now be able to make a smooth transition from halt to walk. Not every halt you make will be perfect, but if you focus on making your aids consistent, your horse will continue trying to do the best it can. 

 

What is collection? 

Collection is a technique where the horse’s centre of gravity is moved backwards. Energy is guided in a more horizontal direction with less forward movement. This is a way to reinforce the top line of the horse, to add brilliance to its gait, and to boost its physical resilience.

Collection itself is a mixture of engaged hindquarters, a light forehand, raised withers, a shortened, rounded back, an arched jaw, and a gentle bridle.

Since horses naturally bear about 60 percent of their weight on the front of their legs, when we ask a horse to collect, this often means moving its centre of gravity backwards, raising its shoulders and lightening its front end.

A lifted, engaged back creates a lightened forehand, making it easier for the horse to spring into action and for its joints to withstand shock.

Achieving a successful collection takes a lot of work and it is important to practice in the correct manner. This can initially be physically exhausting for a horse as the technique differs from its usual way of moving. The horse must therefore build muscles which help support the required posture and action.

 

Why is collection important?

Collection is an important element of riding. If a rider wants to make more advanced movements or to jump, collection is essential. This helps the horse to walk athletically and comfortably. Not only this, but it helps avoid wear and tear to the horse’s legs. Through training, the horse learns to collect himself when asked to do so by the rider. If performed well, an observer will get the impression of a horse with great strength under perfect control.

In dressage assessments, collected gaits consist of walks, halts and trots. Collection is also an important aspect of jumping. Most horses will find it difficult to leap exceptionally high fences.  Without the aid of collection, the horse cannot gather enough strength to jump over a high fence. Increased speed is not a replacement for a good collection. The horse must lift his forehand upwards on takeoff and gain adequate height to jump over the fence. Without performing a collection, the horse is likely to jump flat, without a tilt, and will be much more likely to pull a rail. 

Collection provides many benefits, enhancing the balance of the horse, as well as improving its athleticism, responsiveness, and grace, making it a pleasure to watch and ride.

 

Loss of collection

Collection is an important gait, helping with riding and activities such as jumping. A horse who cannot collect may find it very difficult to smoothly shorten its stride and may be forced to reach too close or too far away from a hurdle.

To perform this correctly, strong engagement of the hindquarters and upward rounding of the back is required. Muscular-skeletal problems resulting in pain can often interfere with this functionality. In such cases, soreness to the back and lameness are major contributing factors to this problem. 

The synchronisation of activities can be difficult for horses with neurological disorders and horses suffering from such problems may find collection difficult. A horse with low-grade abdominal pain (most often caused by gastric ulcers), or a horse whose general fitness is poor may also have difficulty with this technique.

Effective practice is essential. Without practice, it is impossible to achieve a perfect halt or good collection, but as with so many aspects of horse riding, you will usually find that your hard work pays off!