What are sesamoids in horses?
Sesamoids are two little bones positioned at the back of a horses fetlock joint.
Every horse has two proximal sesamoid bones on each limb, meaning each horse has eight sesamoid bones. Their purpose is to anchor the suspensory ligaments, allowing the horses fetlocks to operate and move properly and provide weight-bearing support to the fetlock joint.
The navicular bone that is positioned within the foot or patella in the horses stifle is also a sesamoid bone.
Due to their location and the amount of movement and pressure subjected to that area of a horses foot, sesamoids are extremely vulnerable to injury which can lead to pain and discomfort for the horse and be extremely complicated to treat.
In many cases where a horse has injured a sesamoid, it is often an injury experienced through high-speed movement. Because of this it is more commonly found with horses leading an active lifestyle.
The injury can be a strain resulting in inflammation of the sesamoid bone and surrounding ligaments, or even a fracture of the sesamoid bone itself.
As sesamoids are surrounded by an intricate design of ligaments, any injury to the sesamoid bone will naturally increase the likelihood of an injury to one or more of these supportive ligaments. On the other hand, if an injury occurs to one of the surrounding ligaments first this can then lead to a fracture within the sesamoid bone.
Put simply, it’s an extremely important area of a horses anatomy to understand and particularly if caring for the wellbeing of an active or competing horse.
How to determine a sesamoid injury?
Depending on the extent of the injury, degrees of lameness in a horse with a sesamoid injury varies.
In more serious cases pain is visible with any degree of movement in the fetlock area. The horses ligaments will likely be operating at less than 50% of their normal flex, so mobility levels will be greatly reduced. In some cases the horses fetlocks will be hot to touch, often a sign of an internal injury, along with swelling of the fetlock itself.
In milder cases the horse will show signs of discomfort but it can be frustrating to self-diagnose milder sesamoid injuries due to the location and inability to see inflammation, heat or swelling in the bone.
It’s also worth remembering; if a ligament surrounding the sesamoid has been damaged and caught early then further trauma to the sesamoid can potentially be avoided.
It is a medical emergency and thus vital to seek professional advice.
Technologies used for diagnosis of sesamoid injuries
Veterinary diagnosis is traditionally carried out using local nerve blocks alongside detailed lameness examinations.
Ultrasounds, Radiographs, X-rays and MRI scans can be used to help diagnose the exact issue.
X-rays will determine the precise location and configuration of the fractured bone whilst ultrasounds can be used to determine the extent of any soft tissue damage, especially to the suspensory ligaments.
MRI scans, if affordable, offer a valuable insight into both the bone and soft tissues of the horse and importantly without the need for anaesthesia. With ‘standing-MRI technology’ now widely available it provides a compelling reason for horse owners to use it’s non-invasive approach.
Treating sesamoid injuries
How to best treat a sesamoid injury entirely depends on the severity of the individual case. In many cases they are fully treatable with little to no lasting effects. Rest and rehabilitation are key, with a period of time on box rest required.
No matter the severity of the injury it is important to reduce the inflammation within the fetlock area.
Vets will likely prescribe an anti-inflammatory medication (NSAID) and advise the horse is rested and confined to their stall for up to 30 days. Many will not be ridden for several months and certainly not competing for many months to come.
Some vets will suggest intra-articular treatments of the fetlock joint often with hyaluronic acid used to reduce inflammation in the actual joint.
In severe cases an operation may be required to repair/remove the sesamoid bone or repair the ligaments. Some horses will require bars in their shoes to provide further support to the joint and ligaments.
Tack developed to reduce inflammation is now commonly used as a complementary form of support. From Ice-boots which reduce heat within the leg by creating a cooler effect (check out the Horseware Ice Boots) to the latest advanced magnetic technology which create no heat and can be worn 24/7 (Check out EQU StreamZ horse bands) - devices such as these provide a valuable tool in an equestrians armoury.
Sesamoid injuries in sports horses
It is common for professional-level sports horses to experience sesamoid injuries.
It is widely thought to be the most common fracture within racehorses and is common in many high-paced disciplines such as barrel racing, showjumping, polo, cross country and eventing.
Top-level racehorse trainers are known to have regular MRI scans carried out on their horses legs to prevent poor performance and avoid the risk of further injury. Prevention is as important as cure and having the ability to see first-hand any potential issues are of high importance to many sports horse trainers. Regular MRI scans are not as available to the majority of trainers however due to the price prohibitive nature of MRI technologies.
As with any athlete, the ongoing wellbeing and management of a sports horse is of great importance. For this reason many competing horses are kitted out with the latest and greatest products aimed at supporting the horse.
The most common sesamoid fractures in Standardbreds and Thoroughbreds are caused by overextension and often are associated with suspensory ligament damage. Many injuries occur towards the end of a race when fatigues has set in and hyperextension of the fetlock joints is greatest. This is seen across many disciplines all over the world.
Many trainers will try and reduce training on hard surfaces and provide the horse with plenty of time to rehabilitate after any active exercise.
What is Sesamoiditis?
As opposed to a result of an injury, Sesamoiditis is a complex condition related to the sesamoid bones where the bone and its surrounding tissues become inflamed and are thus unable to work efficiently.
Sesamoiditis is common in athletic and sports horses, and is age and breed related. Sesamoiditis is also reported in overweight horses and young horses who have developed quickly.
There are two widely described forms of sesamoiditis found in horses: Periostitis form and Osteitis form.
Periostitis sesamoids are a type of sesamoid inquiry which occur as a result of damage to the bone-ligaments surrounding the sesamoid bones. This can result from injuries to the palmar/plantar annular ligaments within the horses fetlock joint or the suspensory ligament branches.
Osteitis sesamoids occur as a secondary result of horses with arteriosclerosis, thrombosis, and local ischaemic necrosis where the bone itself dies.
Preventative measures for sesamoid injuries
Applying the approach of ‘prevention is better than cure’ is widely regarded as the best way to manage any potential sesamoid issues, particularly in an active horse.
As sesamoid injuries are common in horses moving and turning at speed, ensuring rest and recuperation between exercising is advised. Holistic therapies such as massage and reflexology are widely used to boost this recovery process.
Many injuries occur whilst the horse is fatigued so keeping the horse fit and healthy is important to helping prevent an injury. Carrying out good shoeing and regular balancing of the feet can also play an important role.
In some cases owners carry out ‘preventive-measure MRI scans’ with a view to looking at the horses bone density and reviewing any potential area of concern and addressing it before any fracture or injury occurs.
Nothing can guarantee the prevention of sesamoid injuries, but continuous care and monitoring of the horses fetlock are essential in detecting any early signs.