The deep digital flexor tendon (DDFT) is one of the most important structures in a horse’s leg, allowing for smooth movement and shock absorption. Understanding deep digital flexor tendon injuries is important to maintaining a horse’s soundness and performance.
A deep digital flexor tendon injury can be debilitating and significantly impact a horse’s quality of life. We look at the anatomy of the deep digital flexor tendon, causes and symptoms of injury, diagnosis, treatment and management options, and long term care for horses with a deep digital flexor tendon injury.
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Anatomy of the Digital Flexor Tendons in Horses
The deep digital flexor tendon (DDFT) is attached to the deep digital flexor muscle and runs through the digital flexor tendon sheath down to the navicular bone, where it attaches to the coffin bone. The palmar annular ligament is responsible for maintaining the health of the digital flexor tendon sheath, allowing the tendon to withstand stress and strain while remaining strong and agile.
The superficial digital flexor tendon (SDFT) lies above the DDFT. The accessory ligament, also known as Lisfranc’s ligament, helps to stabilize the DDFT. The distal digital annular ligament and surrounding synovial structures, such as the distal interosseous and sagittal sesamoid bursae, protect the tendon and allow it to move freely through the hoof and leg.
Causes and Risk Factors for Deep Digital Flexor Tendon Injuries
Deep digital flexor tendon injuries can be caused by a variety of factors, including:
- Overuse: This is a very common cause of deep digital flexor tendon injuries in performance horses. Repeated stress and strain on the tendon over time can cause micro-tearing and damage.
- Acute Trauma: Slipping, falling, or being pulled or jerked on the leg can cause an immediate deep digital flexor tendon injury.
- Supporting Structures: Problems with the navicular bone, hoof capsule, or fetlock joint can cause compensatory stress on the deep digital flexor tendon, making it more prone to injury. Injuries to the ligaments, such as the palmar annular ligament, can also cause secondary stress on the deep digital flexor tendon.
Symptoms of Deep Digital Flexor Tendon Injuries
Deep digital flexor tendon injuries can cause a range of symptoms, from mild to severe. The location and severity of the lesion will help determine the symptoms exhibited by the horse. Horses with a deep digital flexor tendon injury may display:
- Lameness: Lameness can be mild and intermittent or severe and chronic.
- Pain and Swelling: Pain and swelling in the pastern area or fetlock is common.
- Performance Problems: Difficulty with high-impact or high-speed activities.
Diagnosis
Clinical Examination
The first step in diagnosing a deep digital flexor tendon injury is a thorough clinical examination. The veterinarian will evaluate the overall structure of the leg and palpate the tendon sheath for pain or swelling. Flexion testing can also be done to assess range of motion.
Imaging Studies
- Ultrasonography: Ultrasonography is good at evaluating the core of the tendon and any superficial damage to the tendon or sheath.
- Magnetic Resonance Imaging (MRI): MRI is the gold standard for evaluating the type of lesion, dorsal border lesions, and tendon sheath pathology. MRI is very good at evaluating the synovial structures, accessory ligament, and surrounding anatomy, which helps the veterinarian determine clinical relevance and treatment options.
Treatment for Deep Digital Flexor Tendon Injuries
The type of treatment a horse receives for a deep digital flexor tendon injury will depend on the severity of the injury and the horse’s purpose. Treatment options for deep digital flexor tendon injuries are often similar to those for other soft tissue injuries, and may include:
Conservative Therapy
- Rest and Hand Walking: Gradually walking the horse on a leash (hand walking) helps to prevent stiffness while allowing the injured tissue to heal without putting excessive stress on it.
Advanced Therapy Options
- Platelet-Rich Plasma (PRP Therapy): PRP therapy helps to promote repair and healing in core lesions or mild deep digital flexor tendon injuries.
- Stem Cell Therapy: Stem cell therapy can help to repair damaged tendon fibers and promote healing in chronic or severe deep digital flexor tendon injuries.
- Red Light Therapy: Increasingly used as a choice for treatment. See our Activo-Med Therapy Products.
Surgical Therapy
Surgery is typically only considered in cases of severe damage to the digital sheath or distal annular ligament, or for horses with structural problems that are not responding to other therapies.
Rehabilitation for Deep Digital Flexor Tendon Injuries
Rehabilitation is an important component of therapy for deep digital flexor tendon injuries. Once healing has occurred, as evident on follow-up MRI, a gradual exercise program can be initiated. Lead walking is usually the first step, and progression to trotting or other activities will depend on the severity of the injury and location of the lesion.
Recovery Time
Recovery time for deep digital flexor tendon injuries can take several months to over a year. Regular follow-up exams and MRI evaluations help to ensure the tendon is healing properly and reduces the risk of re-injury. Horses that are returned to too quickly can cause further injury to the tendon and compromise their ability to perform at their previous level.
Preventing Tendon Injuries in Horses
Preventing tendon injuries in horses requires a multi-faceted approach that involves proper care, training, and monitoring. Here are some great ways to keep your horse’s tendons healthy:
- Regular Exercise and Training: Consistent exercise and training helps to condition the tendons and surrounding muscles, making them more resilient to stress and strain. Be sure to incorporate a variety of activities to help balance development.
- Proper Hoof Care: It is critical that the hooves are balanced and aligned properly. A good farrier or shoer can help to prevent uneven stress on the tendons by keeping the hooves in proper alignment.
- A Healthy Weight: Extra weight puts additional stress on the joints and tendons. Be sure your horse is at a healthy body weight by monitoring his diet and exercise regimen.
- Regular Veterinary Care: Regular check-ups and maintenance care by your veterinarian can help to prevent problems before they arise. Many tendon injuries can be prevented with early detection and treatment of underlying problems.
- Proper Tack Fitting and Use: When riding or training, use well-fitting equipment and gentle training techniques that do not strain the tendons. Saddle fit and your riding position are important.
- Adequate Rest and Down Time: Be sure your horse has plenty of time to rest and recover, especially after intense exercise or shows. Overuse is a common cause of tendon injuries, and horses need time to recover and rebuild.
- Gradually Increasing Workloads: Help your horse’s tendons adapt and become stronger by gradually increasing his workload. Avoid sudden changes in his routine or workload.
- Safe Pastures and Living Quarters: Be sure your horse’s living space is safe and free of hazards that could cause him to slip, fall, or be injured. Pasture and arena footing is also critical.
- Monitoring Your Horse’s Overall Health: Evaluate your horse’s overall health and well-being on a regular basis. Address any signs of discomfort or lameness early to prevent further injury.
By following these guidelines, you can help to prevent tendon injuries and keep your horse healthy and sound.
Prognosis and Outcome
The outcome for horses with deep digital flexor tendon injuries depends on factors such as the type of lesion, response to therapy, and presence of additional injuries. Research, including studies by the UC Davis veterinary medicine team, has shown that 50-70% of horses returned to their previous activity level.
Proper hoof care, balanced nutrition, and training are all critical to preventing re-injury and promoting a successful long-term outcome.
Final Notes
Deep digital flexor tendon injuries can be challenging, but they are treatable. Early detection and diagnosis, along with a combination of conservative and advanced therapies, can help to promote healing and alleviate symptoms.
Technologies like equine MRI and therapies such as PRP and stem cell therapy can help to improve outcomes for horses with deep digital flexor tendon injuries. Understanding the clinical significance of these injuries and following a recommended rehabilitation program can help to ensure your horse is given every opportunity to recover and thrive.
Popular Questions
Below are common questions we get asked.
What are the consequences of a Deep Digital Flexor Tendon (DDFT) injury on a horse’s ability to perform?
The consequences of a Deep Digital Flexor Tendon injury are far-reaching and impact a horse’s ability to perform at all. Even after a horse has fully recovered from an injury, the tendon is often significantly compromised, making re-injury much more likely.
The research is stark: only 23% of horses with severe DDFT injuries are able to go back to their previous level of performance after rehab. This statistic is especially concerning for riders who hope to do more with their horses.
How can horse owners prevent DDFT injuries?
Preventing DDFT injuries requires a multi-faceted approach. Horse owners should work with their farriers or shoers to minimize stress on the tendon, set a fitness regimen that’s appropriate for their horse, and not push their horses during training or competition.
Regular veterinary exams are also very important. Many strains and injuries are caught early by our experienced veterinarians before they become serious.
Are there new and different treatments for horses with DDFT injuries?
There are new and different treatments available. Regenerative therapies like stem cell therapy and platelet-rich plasma (PRP) injections are very effective at helping horses with DDFT injuries.
These treatments stimulate the body’s natural healing ability by applying growth factors and stem cells to the injured tendon. While they won’t reduce recovery time, they can improve the quality of the healing, which is very important for horses.
