Tendon Injury in Horses: Treatment, Recovery and Rehab

By Dr Duncan Houston

Tendon injuries are one of the most frustrating causes of lameness in horses because they rarely heal quickly and they love testing everyone’s patience. A horse can look mildly lame one week, then develop obvious heat, swelling, and a bowed tendon the next if the injury is worked through.

The big challenge is not just getting the horse comfortable. It is helping the tendon heal with strong, organised tissue that can tolerate work again. That usually takes months of controlled rehabilitation, repeat assessment, and painfully boring consistency.

This article explains how tendon injuries happen, how vets diagnose them, which treatments actually matter, where regenerative therapies fit, and how to reduce the risk of reinjury.

Quick Answer

Tendon injuries in horses usually involve damage to the superficial digital flexor tendon, although the deep digital flexor tendon and other soft tissue structures can also be affected. Treatment usually includes stopping exercise, controlling early inflammation, ultrasound diagnosis, compression or support where appropriate, corrective farriery, and a progressive controlled exercise program. Regenerative treatments such as stem cells and platelet-rich plasma may help selected cases, but they do not replace careful rehabilitation. (Merck Veterinary Manual)

What Is a Tendon Injury in Horses?

A tendon connects muscle to bone and helps transfer force during movement. In horses, tendons in the lower limb are under enormous load, especially during fast work, jumping, galloping, tight turns, and repeated collected movement.

The most commonly discussed tendon injury is superficial digital flexor tendonitis, often shortened to SDFT tendonitis. This tendon runs down the back of the cannon region and helps support the limb during weight-bearing.

Tendonitis refers to acute inflammation and injury of a tendon. Chronic or recurring tendon injury is often more accurately called tendinopathy. Merck Veterinary Manual notes that acute tendon injury is usually associated with microdamage to collagen fibres and varying degrees of tendon fibre disruption. (Merck Veterinary Manual)

Which Tendons Are Most Commonly Injured?

The main tendons and related structures involved in equine lower limb injuries include:

SDFT injuries are classically associated with overstrain, especially in Thoroughbred racehorses, and Merck notes that these injuries commonly occur in the forelimb and often involve a central core lesion. (Merck Veterinary Manual)

What Causes Tendon Injuries in Horses?

Tendon injuries usually happen when the load placed on the tendon exceeds what the tissue can safely tolerate. This may occur suddenly, but many cases involve accumulated microdamage before the obvious injury appears.

Common risk factors include:

• Fast work

• Fatigue

• Poor conditioning

• Sudden increase in workload

• Working on poor or inconsistent footing

• Persistent training when early tendon inflammation is already present

• Improper shoeing

• Poor conformation

• Poor hoof balance

• Previous tendon injury

• Returning to work too quickly after time off

Merck lists poor conditioning, fatigue, poor track conditions, persistent training despite tendon inflammation, improper shoeing, poor conformation, and poor training as predisposing factors for SDFT tendonitis. (Merck Veterinary Manual)

In practice, the horses that worry me most are not always the dramatic ones. It is the horse that has a little filling after work, a slight short stride, or a tendon that feels warmer than the opposite leg. That is the stage where good decisions can stop a small injury becoming a season-ending one.

What Are the Signs of a Tendon Injury?

Common signs include:

• Heat along the back of the limb

• Swelling or thickening of the tendon

• Pain when the tendon is palpated

• Lameness

• Shortened stride

• Reluctance to work

• Filling that worsens after exercise

• A bowed appearance to the tendon

• Fetlock dropping in severe injuries

Acute tendon injuries are often associated with heat, swelling, pain, and variable lameness, while chronic injuries may show fibrosis, thickening, and lameness that returns during harder work. Severe SDFT injuries may cause fetlock hyperextension. (Merck Veterinary Manual)

The key comparison is always the opposite limb. A tendon that feels hotter, thicker, more painful, or more defined on one side deserves attention.

Why Tendons Heal Poorly

Tendons heal slowly because they have limited regenerative capacity. After injury, the body often repairs the damaged area with scar tissue. Scar tissue can fill the defect, but it is not the same as healthy tendon.

Healthy tendon fibres are organised and aligned to tolerate load. Scar tissue is usually less elastic, less organised, and more prone to reinjury.

A large racehorse SDFT study explains that tendon tissue has poor regenerative capacity and that injured tendon is often replaced by mechanically inferior scar tissue, contributing to poor functional recovery and reinjury risk. That same paper reported reinjury rates across disciplines ranging from 16% to 53%, with the highest rates in flat racehorses.

This is why tendon rehab is slow. The swelling may settle before the tissue is strong. That is the trap. The tendon can look calm while still being very much in the “please do not gallop me yet” phase.

The Three Main Phases of Tendon Healing

Tendon healing is not one simple process. It moves through overlapping phases.

Inflammatory Phase

This is the early stage after injury. The tendon may be hot, swollen, painful, and lame.

The goal is to reduce further damage, control inflammation, and stop the horse from loading the tendon aggressively.

Repair Phase

Fibroblasts begin producing new collagen. This tissue is immature and vulnerable.

The goal is to protect the tendon while gradually encouraging organised healing.

Remodelling Phase

The new collagen slowly becomes stronger and more aligned. This phase can take months.

The goal is progressive loading so fibres remodel in the direction of useful force.

A Frontiers study describes tendon and ligament healing as moving through inflammatory, reparative, collagen, and chronic remodelling phases, with weaker scar tissue increasing reinjury risk. (Frontiers)

How Worried Should You Be?

Mild

A mild tendon injury may show slight heat, subtle swelling, mild sensitivity, or a small performance change.

What to do: stop hard work and arrange a veterinary assessment. Mild tendon injuries are where early action helps most.

Moderate

A moderate tendon injury may show obvious swelling, lameness, tendon thickening, or ultrasound changes such as a core lesion.

What to do: stop ridden work, organise ultrasound, and begin a structured treatment and rehab plan.

Severe

A severe tendon injury may cause marked lameness, major swelling, obvious bowing, significant fibre disruption, or fetlock dropping.

What to do: treat this as urgent. The horse may need support, imaging, specialist advice, and a long rehabilitation plan.

Chronic or Recurrent

Chronic tendon injury may show thickened tendon tissue, recurring swelling, intermittent lameness, or failure when workload increases.

What to do: investigate why it keeps happening. Recurrence often involves scar tissue, workload, hoof balance, surface, conformation, or an incomplete previous rehab plan.

When Is a Tendon Injury an Emergency?

Call a vet urgently if your horse has:

• Sudden severe lameness

• Rapid swelling along the back of the limb

• A dropped fetlock

• Refusal to bear weight

• Severe pain

• A wound over or near a tendon

• Suspected tendon laceration

• Heat and swelling after fast work, jumping, slipping, or a fall

• Swelling that worsens over a few hours

• Fever, discharge, or signs of infection

A dropped fetlock is a major red flag because it can suggest severe failure of the limb’s support structures. That is not a “wait and see after breakfast” situation.

What Else Can Look Like Tendonitis?

Not every swollen leg is a tendon injury.

Important differentials include:

• Suspensory ligament injury

• Deep digital flexor tendon injury

• Check ligament injury

• Digital flexor tendon sheath inflammation

• Tendon sheath infection

• Annular ligament restriction

• Splint bone injury

• Cellulitis

• Abscess or wound infection

• Fetlock joint injury

• Fracture

• Hoof pain causing altered loading

• Lymphatic swelling

• Old tendon scarring without active injury

This is why ultrasound matters. Guessing from the outside of the leg is not enough.

How Do Vets Diagnose Tendon Injuries?

Diagnosis usually involves a lameness exam, palpation, comparison with the opposite limb, and imaging.

Your vet may assess:

• Heat

• Swelling

• Pain on palpation

• Tendon thickness

• Lameness at walk and trot

• Digital pulses

• Hoof balance

• Limb conformation

• Response to flexion tests

• Whether the horse worsens on soft ground, hard ground, or turns

Ultrasound

Ultrasound is the main diagnostic tool for most tendon injuries. It helps evaluate tendon enlargement, fibre disruption, hypoechoic lesions, lesion length, lesion size, and healing progression. Merck describes ultrasonography as the most commonly used and available diagnostic tool for documenting tendon injury in horses. (Merck Veterinary Manual)

Repeat ultrasound is often more useful than one scan. Tendon healing changes over time, and the rehab plan should change with it.

MRI

MRI may be recommended when the injury is deep, difficult to define, located within the hoof capsule, or when ultrasound does not explain the lameness. Merck notes MRI can be useful for deep digital flexor tendon lesions within the hoof capsule and in proximal metacarpal or metatarsal regions. (Merck Veterinary Manual)

Early Treatment: What To Do in the First Few Days

The first goal is to prevent a small lesion becoming a larger one.

Early treatment may include:

• Stop exercise immediately

• Stall rest or controlled confinement

• Cold therapy

• Compression bandaging if appropriate

• Anti-inflammatory medication under veterinary direction

• Support or immobilisation in selected severe cases

• Early veterinary assessment

• Ultrasound once suitable

Merck lists cold hydrotherapy, compression bandaging, corrective shoeing, and controlled exercise as key treatments, and states that acute tendonitis is best treated early with stall rest and aggressive control of swelling and inflammation. (Merck Veterinary Manual)

Do not keep riding to see if the horse “warms out.” Tendons are not coffee machines. If they warm out, that does not mean they are fine.

Controlled Exercise: The Most Important Part of Rehab

After the acute inflammatory phase, controlled loading becomes essential. The aim is not to rest the horse forever. The aim is to load the tendon in a careful, staged way so the healing fibres align and strengthen.

A 2024 review notes that tendon and ligament fibre maturation depends on mechanical loading, that controlled stretching after the inflammatory phase can improve collagen synthesis and fibre alignment, and that prolonged immobilisation can leave collagen weaker and more randomly organised. (MDPI)

That is the boring but powerful truth: controlled exercise is not just “something to do while waiting.” It is part of treatment.

Example Tendon Rehab Timeline

This is a general framework only. The exact plan should be based on the tendon involved, ultrasound findings, pain, swelling, discipline, and veterinary advice.

One published controlled exercise protocol suggests early hand walking during weeks 0 to 4, gradual walking increases over the following weeks, ridden walking around weeks 13 to 16 if sound and improving, and cautious introduction of trot and canter later in recovery. (MDPI)

This does not mean every horse follows that exact timeline. Tendon rehab should be customised. The calendar is a guide. The tendon gets the final vote.

Where Do Stem Cells Fit?

Stem cell therapy is used in selected tendon injuries to try to improve tissue repair quality. The most common approach involves injecting stem cells into the tendon lesion under ultrasound guidance.

Stem cells may be:

• Bone marrow-derived

• Adipose-derived

• Autologous, from the same horse

• Allogeneic, from a donor source

The evidence is promising but not equal across every stem cell type, tendon type, and case.

A 2023 Equine Veterinary Journal study of 213 Thoroughbred racehorses with SDFT injury found that all horses were prescribed the same 12-month controlled exercise rehabilitation program. Horses treated with bone marrow-derived mesenchymal stem cells had higher odds of returning to racing and completing five or more races after injury compared with controlled exercise rehabilitation alone, while adipose-derived mesenchymal stem cells did not show the same association in that study.

That is useful, but it does not mean “stem cells fix every tendon.” Case selection, lesion type, timing, product type, rehab compliance, and follow-up all matter.

Where Does PRP Fit?

Platelet-rich plasma, or PRP, uses concentrated platelets from the horse’s blood. Platelets release growth factors that may influence healing.

A recent PRISMA-guided review of PRP studies in equine tendon and ligament injury reported improvements in lameness, tissue healing, and return-to-competition outcomes, but PRP studies vary in preparation methods, injury types, and protocols. (PMC)

In plain English: PRP can be useful in selected cases, but it is not a magic injection. It still needs accurate diagnosis, ultrasound guidance where appropriate, and a proper rehab plan.

What About Shockwave, Laser and Other Therapies?

Shockwave therapy and other physical therapies may be used as adjuncts in some tendon injuries. Their role depends on the case, the stage of healing, the structure involved, and the goal of treatment.

Merck notes that shockwave and intralesional treatments such as stem cells or platelet-rich plasma are now common forms of treatment, while also stating that the amount of evidence varies between treatment modalities. (Merck Veterinary Manual)

That sentence is important. “Common” does not always mean “equally proven.”

What About Eccentric Loading Exercises?

Eccentric loading gets discussed a lot in human tendon rehab, but horses are not humans with gym memberships and questionable squatting form.

For horses, the most evidence-based version of tendon loading is progressive, controlled, straight-line exercise guided by clinical signs and ultrasound. Weight-shifting, core work, raised poles, hill walking, and water treadmill work may have roles in some rehab programs, but they should be introduced only when appropriate.

A withers pull or weight-shifting exercise may help body control or gentle loading, but it should not be sold as the main tendon-healing tool. The main event is still controlled, staged exercise.

What Treatments Should Be Avoided?

Some approaches can make tendon injuries worse.

Avoid:

• Continuing work through heat and swelling

• Lunging a horse with an acute tendon injury

• Turning out a fresh horse in a large paddock too early

• Aggressive massage over an acute swollen tendon

• Injecting random products without a diagnosis

• Using pain relief to keep the horse working

• Returning to jumping, galloping, or deep footing too soon

• Skipping ultrasound rechecks

• Injecting corticosteroids directly into tendon tissue

Merck specifically states that intratendinous corticosteroid injections are contraindicated because they inhibit repair mechanisms. (Merck Veterinary Manual)

What Should You Do Right Now?

If you suspect a tendon injury:

1. Stop exercise immediately.

2. Move the horse to a safe, controlled area.

3. Check both limbs for heat, swelling, and pain.

4. Do not lunge or ride to test it.

5. Cold therapy may be useful early if your vet agrees.

6. Contact your vet for an examination.

7. Arrange ultrasound if tendon injury is suspected.

8. Follow a written rehab plan.

9. Monitor the tendon daily for heat, swelling, pain, and filling.

10. Do not increase work unless the horse remains sound and the tendon is improving.

If the horse is severely lame, has a dropped fetlock, has a wound near the tendon, or swelling worsens quickly, treat it as urgent.

Common Mistakes Owners Make

Waiting Too Long

A mild tendon injury can become a major lesion if the horse keeps working.

Assuming Swelling Means the Same Thing Every Time

Tendonitis, suspensory injury, cellulitis, tendon sheath inflammation, and trauma can all cause swelling.

Resting for Months, Then Restarting Too Fast

Rest alone does not rebuild a functional tendon. Controlled loading is needed.

Skipping Repeat Ultrasound

You cannot judge tendon fibre organisation from the outside of the leg.

Chasing Expensive Therapies Without a Rehab Plan

Stem cells, PRP, shockwave, and other therapies are only useful if the diagnosis, timing, and rehab plan make sense.

Turning Out Too Early

A healing tendon does not appreciate galloping, bucking, spinning, and general paddock nonsense.

Ignoring Hoof Balance

Long toes, poor support, poor breakover, and conformation issues can increase tendon strain.

Can Tendon Injuries Be Prevented?

Not every tendon injury can be prevented, but risk can be reduced.

Practical prevention includes:

• Build fitness gradually

• Avoid sudden workload spikes

• Avoid repeated hard work on deep, slippery, or uneven ground

• Maintain regular farrier care

• Avoid long toes

• Warm up properly

• Cool down properly

• Monitor tendons after work

• Investigate heat, swelling, or filling early

• Allow recovery after hard sessions

• Avoid pushing through subtle lameness

• Use discipline-appropriate conditioning

• Bring horses back slowly after time off

The best prevention is often boring management done consistently. Tendons love boring. Sadly, they were not designed for drama.

Will My Horse Return to Work?

Many horses do return to work after tendon injury, but the outcome depends on:

• Tendon involved

• Lesion size

• Lesion length

• Fibre disruption

• Whether this is a first injury or reinjury

• Discipline

• Speed and jumping demands

• Hoof balance

• Surface

• Rehab compliance

• Follow-up ultrasound findings

Merck describes the prognosis for flat-racing Thoroughbreds returning to racing after SDFT injury as guarded, regardless of treatment, while sport horses and horses that do not jump or compete at high speed generally have a better prognosis. (Merck Veterinary Manual)

A 2-year follow-up study using tenogenically induced mesenchymal stem cells with PRP reported that 79.2% of SDFT horses returned to previous performance at 12 months and 85.7% at 24 months, with reported SDFT reinjury rates of 12.5% at 12 months and 14.3% at 24 months. The authors also noted limitations, including the need for more objective assessment and the lower certainty of non-blinded case series compared with controlled trials. (Frontiers)

So the honest answer is this: some horses return fully, some return at a lower level, and some need a different job. Early diagnosis and disciplined rehab give the horse the best chance.

FAQs

How long does a tendon injury take to heal in horses?

Most tendon injuries take months, not weeks. Mild injuries may improve in a few months, but moderate to severe SDFT injuries often require 6 to 12 months or longer before full work is considered.

Should I ice a tendon injury?

Cold therapy is commonly used in the early acute phase to help control inflammation and swelling. It should be part of a broader plan that includes rest, assessment, and veterinary guidance.

Are stem cells worth it for horse tendon injuries?

Stem cells may help selected tendon injuries, especially some SDFT lesions, but results depend on the type of injury, the stem cell product, timing, and rehab compliance. They are not a replacement for controlled exercise.

Can a horse recover from a bowed tendon?

Yes, some horses recover from bowed tendon injuries and return to work. The prognosis depends on lesion severity, ultrasound findings, the horse’s discipline, and how carefully rehabilitation is managed.

When can my horse start trotting again after a tendon injury?

Trotting should only be introduced when the horse is sound, swelling is controlled, and ultrasound findings support progression. Many plans do not introduce trot until several months into rehab, but timing must be case-specific.

Final Thoughts

Tendon injuries need patience, structure, and good decision-making. The goal is not just to make the leg look less swollen. The goal is to rebuild enough organised tendon tissue for the horse’s future workload.

The best outcomes usually come from early diagnosis, inflammation control, ultrasound monitoring, farriery review, controlled exercise, and carefully selected regenerative therapy where appropriate.

The worst outcomes usually come from guessing, rushing, and letting optimism write the rehab plan.

A tendon injury is not automatically career-ending, but it is a serious warning. Slow down, scan it, plan it, and respect the tissue.

If your horse has a suspected tendon injury, confusing ultrasound findings, or you are unsure how quickly to progress rehab, ASK A VET™ can help you understand what signs to monitor and what questions to ask your treating vet before the next step.