Tendon damage in horses: symptoms, healing & feeding

Anyone who has ever received this diagnosis from the vet knows the feeling: first the shock, then the long months of uncertainty. Tendon damage in a horse is one of the most feared injuries – and at the same time one of the most misunderstood. This article answers the three questions you probably have in your head all at once right now: How severe is it? How long does it take? And what can you actively do yourself to ensure your horse truly recovers?

We will go through the symptoms, realistic healing times and the rehab structure step by step – backed by studies from equine medicine, a concrete weekly plan, and our own journey through a tendon rehab. You won't get any miracle cure promises. You will get what you need right now: guidance, facts and figures, and a plan.

What is tendon damage in horses?

Tendon damage in a horse is an injury to the tendon fibres, usually the superficial digital flexor tendon (SDFT) of the foreleg, triggered by overstrain or acute trauma. Individual fibres can tear (micro-lesions), fibre bundles can be damaged, or in the most severe cases, the entire tendon can be severed.

Structure of a healthy tendon

A tendon consists of densely packed, parallel collagen fibres – primarily type I collagen. In the horse's leg, we distinguish between four functionally central structures: the superficial digital flexor tendon (SDFT, the most common site of injury), the deep digital flexor tendon (DDFT), the suspensory ligament and the extensor tendon. Tendons connect muscle and bone, transfer force and cushion movement. With every canter stride, they carry a multiple of the body weight.

Why tendons heal so poorly – the problem of poor blood circulation

Tendon tissue has a very low metabolic rate. It has poorer blood circulation than muscle tissue, and this is exactly what makes healing so protracted (Dowling et al., 2000). Newly formed tissue also often consists of type III collagen instead of type I – it is mechanically less resilient than the original tendon tissue. This inferior repair is the main reason why so many horses get injured again later on.

Symptoms: How do I recognise tendon damage?

The classic symptoms of tendon damage in a horse are swelling, heat, tenderness to pressure on the tendon, and sudden or gradual lameness. The earlier you notice them, the better the prognosis.

Acute signs

With an acute tendon injury, you will see a clear, often bow-shaped swelling at the back of the cannon bone ('bowed tendon') within a few hours. The area is warm, and sometimes the artery is noticeably pulsating. Your horse will react to pressure by clearly pulling the leg back. Lameness can range from a slight loss of rhythm to severe, three-legged lameness.

Gradual / chronic signs

With chronic overstrain, the signs are more subtle: a slight thickening of the tendon over weeks, occasional heat after training, a gait that doesn't seem 'quite fresh', and reluctance towards hard ground or tight turns. These horses are exactly the risk group for a complete injury that suddenly appears 'out of nowhere'.

Severity levels at a glance

Causes – how does tendon damage occur?

In most cases, tendon damage does not arise from a single moment, but from the sum of many small micro-traumas that add up over months and then suddenly lead to a visible injury under normal strain.

Acute trauma vs chronic overstrain

Acute traumas – stepping into a hole, stumbling out hacking, a fall – lead to classic complete injuries. However, chronic overstrain is more common: tiny micro-tears during training that are not given enough time to heal. Clinically inconspicuous, but the tissue becomes increasingly unstable.

Risk factors

The most important risk factors include deep, heavy or uneven ground, incorrect hoof balance (especially underrun or overly long heels), building up training too intensely without sufficient breaks, being overweight, inadequate warming up and age – from around 15 years, the tendon structure changes and its ability to regenerate decreases.

Diagnosis by the vet

A reliable diagnosis of tendon damage in a horse is made through a clinical examination in combination with imaging techniques – above all, ultrasound. Avoid self-diagnosis: accurately assessing a tendon injury is the vet's job.

Palpation, ultrasound, MRI – when to use what?

Palpation – feeling the tendon – is the first step and reveals heat, swelling and tenderness. Ultrasound is the gold standard for structural diagnosis: fibre tears, haematomas and the healing process can be made visible. An MRI is used when ultrasound does not provide a clear result, especially for injuries in the hoof area (navicular bursa, DDFT insertion). Regular ultrasound checks every 8–12 weeks during rehab are mandatory, not optional – they determine when you can safely increase the workload again.

Healing & healing time – what you can realistically expect

Healing of tendon damage in a horse usually takes 3 to 12 months, depending on the severity, the age of the horse and rehab discipline. In the case of severe injuries, it can take 12 to 18 months before the horse can carry a full workload again.

The 3 phases of tendon healing

Tendon healing takes place in three phases (Smith, 2008; Dowling et al., 2000):

Inflammatory phase (days 1–7): The tissue is warm, swollen and painful. Inflammatory mediators are released and repair cells migrate into the area.

Repair phase (week 2 to month 3): Fibroblasts produce collagen – however, predominantly type III, which is mechanically weaker. The tendon appears 'filled' on the ultrasound, but is still very prone to injury.

Remodelling phase (month 3 to 12+): Type III collagen is gradually converted into more resilient type I collagen, and the fibres align themselves along the line of tension. This phase is crucial – and it needs controlled movement as a stimulus.

Realistic timeline

Prognosis & relapse rate

The uncomfortable truth: in thoroughbred racehorses, the relapse rate after a tendon injury lies between 50 and 80 per cent (Dowling et al., 2000). In leisure and sport horses with moderate workloads, the figures are significantly better, but the risk remains. The decisive factor for the prognosis is not the severity of the initial injury, but discipline during rehab.

Treatment & therapy

Treating tendon damage in a horse always combines acute care, potentially modern therapy methods and, above all, a consistent rehab phase. There is no single procedure that 'repairs' the tendon.

Acute care

In the first 48 to 72 hours, the following count: cooling (ice water, cooling boots, 15–20 minutes several times a day), resting (box, support bandage) and, if required, non-steroidal anti-inflammatory drugs (NSAIDs) prescribed by the vet. Important: do not move the horse – every step in this phase can worsen the injury.

Modern procedures

Depending on the severity and the vet's assessment, platelet-rich plasma (PRP), stem cell therapy, shockwave therapy, Tildren infusions or laser therapy may be used. The available studies are heterogeneous, but some procedures – especially intratendinous stem cell therapy – show promising results regarding the quality of the healing tissue (Smith, 2008). Let your vet advise you on what makes sense for the specific injury.

Bandages, compression & physical therapy

Support and compression bandages reduce swelling and take the strain off the injured tendon, but they must be applied correctly – incorrectly wrapped, they do more harm than good. Magnetic fields, solariums and controlled water training (water treadmill, swimming) can support the building-up process in the later phases.

Rehab & building up – the controlled way back

Rehab for tendon damage in a horse follows a clear principle: controlled, gradually increasing workload instead of total rest. Box rest alone does not heal a tendon – it only keeps acute damage to a minimum.

Box rest vs controlled walking – what the research says

Complete immobilisation leads to poorer fibre alignment and weaker healing tissue. As soon as the acute phase is over (typically after 4–8 weeks, depending on the severity), controlled walking in-hand begins – initially for 5 to 10 minutes a day, then gradually increasing. This moderate mechanical stimulation helps to align the collagen along the axis of strain.

Box rest and the horse's psyche

We receive the most messages on exactly this point: 'My horse is going crazy in the stable.' From our work with horse behaviour, we know how closely stress and healing are linked. A chronically stressed horse produces more cortisol – and cortisol slows down tissue regeneration. Look out for signs of stress: constant weaving, crib-biting, loss of appetite, frantic eating, aggression when being groomed.

What helps: visual contact with at least one neighbour, mental stimulation via hay nets with small holes, slow feeders, branches to nibble on, and dedicated grooming and massage times. It's important not to present the stable as a 'punishment' – horses read our moods very accurately. Many rehab horses also benefit from having a calm stable neighbour as a social anchor. The first two weeks are the hardest; after that, most horses adapt, provided stimulation and social contact are right.

Week-by-week build-up training plan

Phase | Workload | Timeframe Week 1–4 | Box rest, possibly 5–10 mins walking in-hand from week 3 | strictly in-hand Week 5–8 | Walking 15–25 mins, firm paths, no soft ground | daily, in-hand Week 9–16 | Walking under saddle 20–40 mins, possibly first short trots | after ultrasound check Week 17–24+ | Increase trot in a controlled way, first canters from month 6–7 | with vet's approval From month 9–12 | Gradually rebuild full workload | depending on severity

Feeding with tendon damage – what the studies really show

Feeding a horse with tendon damage should specifically provide collagen peptides, MSM, glucosamine, hyaluronic acid as well as copper, zinc and vitamin E to support tendon healing at a cellular level. Feeding does not replace rehab – but without the right building blocks, the body simply lacks the material for high-quality repair tissue.

Which nutrients does healing tendon tissue need?

Collagen peptides are the direct building blocks of new tendon fibres. They are broken down into short-chain amino acids and peptides, which are available for tissue regeneration. MSM (methylsulfonylmethane) is a source of organic sulphur – sulphur is a component of the disulphide bridges that stabilise collagen fibres, and it has an inflammation-modulating effect. Glucosamine and hyaluronic acid are classic building blocks of the extracellular matrix and support the connective tissue's water balance. Trace elements such as copper (collagen cross-linking via the lysyl oxidase enzyme family), zinc and manganese are indispensable cofactors. Vitamin E protects the newly formed tissue from oxidative stress – particularly relevant with increasing workload in the build-up phase.

What studies show

MSM in sport horses: In a placebo-controlled study on showjumpers, Marañón et al. (2008) showed a significant reduction in markers of oxidative stress after exercise when given MSM (8 g/day over six weeks).

Glucosamine/chondroitin: Forsyth et al. (2006) examined older horses with joint problems and found improvements in their gait pattern compared to a placebo when given oral glucosamine/chondroitin.

Oral hyaluronic acid: In a study on thoroughbred yearlings, Bergin et al. (2006) were able to show that orally administered hyaluronic acid significantly reduces post-operative joint effusion in the hock – proof of the bioavailability of oral HA, which had long been disputed.

Collagen peptides: Direct studies on horses are still scarce, but in human and veterinary sports medicine there is growing evidence that specific collagen peptides can positively influence tendon and ligament regeneration. In practice, collagen is increasingly being used in rehab concepts for horses.

Dosing practice – course or maintenance?

In the acute and repair phase, a course dose over at least 8 to 12 weeks makes sense. Typical daily rations for a 600 kg horse are 1,500–3,000 mg glucosamine, 2,000–10,000 mg MSM, 100–200 mg hyaluronic acid and 2,000–5,000 mg collagen peptides – the exact amount depends on the product and the severity. After the repair phase, you lower it to a maintenance dose. Important: nutrients don't work 'acutely after three days'. Plan in weeks, not in days.

Acceptance at the feed trough – why the form of administration matters

We receive this exact question every day: 'My horse won't eat the powder – what should I do?' From our background in behavioural research, we know that feed acceptance in horses is a highly sensitive system. Horses are neophobic – they are sensitive to new smells, tastes and consistencies, especially during stressful phases of life like rehab. On top of this, many rehab horses eat less and are fussier anyway while on box rest. Powder lying on top of their hard feed is often deliberately sorted out. What is supposedly 'convenient' ends up in the manger – but not in the horse.

Snack or pellet forms have two advantages from a behavioural psychology perspective: as a 'reward' they hold positive emotional associations, and they cannot be selectively spat out. In everyday yard life, this simply means: what is eaten, works. What is left in the trough does not.

We – Katja and Andrés – developed nuvallo move Snacks precisely to fill this gap: a functional joint snack with 1,500 mg glucosamine, 2,550 mg collagen, 2,250 mg MSM and 150 mg hyaluronic acid per daily ration. In a snack format, because we know from experience that horses often refuse powders during the rehab phase.

Supplements are not miracle cures – they replace neither box rest nor veterinary treatment.

Preventing tendon damage

Prevention doesn't start at the moment of exertion, but in the weeks before. The most important adjustments are more mundane than most people think – and that is exactly why they are underestimated.

Warming up: At least 15 to 20 minutes of walking before any intensive session, and longer on competition or jumping days. Cold tendons are tendons prone to injury.

Hoof care: Hoof trimming by an experienced farrier or barefoot trimmer every six to eight weeks. Underrun or overly long heels shift the axis of tension of the flexor tendons and significantly increase the risk of injury.

Ground quality: Deep, heavy or uneven ground is the most common external risk factor. If you have no influence over the arena surface, adapt the training intensity to the conditions – not the other way around.

Training build-up: Increase gradually, schedule breaks, and do not have two intensive days in a row. Fitness is built in weeks, tendons need months.

Observation: Run your hand over the tendon after every training session. Heat, thickening or tenderness to the touch the day after are early warning signs – they are not 'normal after jumping'.

Frequently asked questions (FAQ)

How long does tendon damage in horses take to heal?

Healing tendon damage in a horse takes 3 to 12 months depending on the severity, and up to 18 months for severe injuries. The decisive factor is not the acute phase, but the months-long remodelling phase. Without consistent rehab, the healing tissue remains inferior and the risk of relapse stays high.

Can a horse with tendon damage be ridden again?

Yes, the majority of horses can be ridden again after tendon damage. With severity grades 1 and 2, many horses regain their original performance level. With grade 3, an adjustment to their workload is often necessary. The prerequisite is always a complete rehab over several months, accompanied by a vet.

What helps with tendon damage in a horse?

What helps with tendon damage is acute cooling, resting, a structured rehab plan with controlled walking, and targeted feeding with collagen, MSM, glucosamine and hyaluronic acid. Modern procedures such as PRP or stem cell therapy can make sense depending on the diagnosis. There is no single 'miracle solution'.

How long should box rest last for tendon damage?

Box rest for tendon damage lasts 4 to 8 weeks depending on the severity, and up to 12 weeks in severe cases. The transition to controlled walking in-hand is important – complete immobilisation leads to poorer healing tissue quality. The exact timing is determined by ultrasound checks.

What should I feed a horse with tendon damage?

For tendon damage, you should provide the building blocks for tissue regeneration: collagen peptides, MSM, glucosamine, hyaluronic acid as well as copper, zinc and vitamin E. A course lasting 8 to 12 weeks throughout the repair phase makes sense, after which you can reduce to a maintenance dose. Pay attention to acceptance – powder that isn't eaten doesn't work.

What does tendon damage in a horse feel like?

When palpated, a damaged tendon feels warm, thickened and often firm or swollen in a bow shape. The horse will react to pressure by clearly pulling the leg back. Always compare it with the healthy leg on the opposite side – a difference in heat or swelling between sides is one of the most reliable early signs.

Sources

Bergin, B.J., Pierce, S.W., Bramlage, L.R., Stromberg, A. (2006): Oral hyaluronan gel reduces post operative tarsocrural effusion in the yearling Thoroughbred. Equine Veterinary Journal 38(4):375–378.

Dowling, B.A., Dart, A.J., Hodgson, D.R., Smith, R.K. (2000): Superficial digital flexor tendonitis in the horse. Equine Veterinary Journal 32(5):369–378.

Dyson, S.J. (2004): Medical management of superficial digital flexor tendonitis: a comparative study in 219 horses (1992–2000). Equine Veterinary Journal 36(5):415–419.

Forsyth, R.K., Brigden, C.V., Northrop, A.J. (2006): Double blind investigation of the effects of oral supplementation of combined glucosamine hydrochloride (GHCL) and chondroitin sulphate (CS) on stride characteristics of veteran horses. Equine Veterinary Journal Supplement 36:622–625.

Higler, M.H., Brommer, H., L'Ami, J.J., de Grauw, J.C., Nielen, M., van Weeren, P.R., Laverty, S., Barneveld, A., Back, W. (2014): The effects of three-month oral supplementation with a nutraceutical and exercise on the locomotor pattern of aged horses. Equine Veterinary Journal 46(5):611–617.

Marañón, G., Muñoz-Escassi, B., Manley, W., García, C., Cayado, P., de la Muela, M.S., Olábarri, B., León, R., Vara, E. (2008): The effect of methyl sulphonyl methane supplementation on biomarkers of oxidative stress in sport horses following jumping exercise. Acta Veterinaria Scandinavica 50:45.

Smith, R.K.W. (2008): Mesenchymal stem cell therapy for equine tendinopathy. Disability and Rehabilitation 30(20–22):1752–1758.

About the authors

Katja and Andrés are the founders of nuvallo. They combine over 15 years of practical experience with horses – from horse care and equestrian sports to rehab support – with a background in psychology. Their particular research and practical focus is on the feeding behaviour of horses and the question of why supplements are often not accepted in the yard. nuvallo move Snacks was born out of this combination.