Stagnation edema, also known as stocking up, is a common cause of leg swelling in stabled horses. It occurs due to impaired circulation from periods of reduced activity.

This short-lasting form of edema typically affects both hind limbs and causes swelling from the coronary band up to the hock. Occasionally, it occurs in the forelegs as well. Stocking up is also called distal limb edema because it affects to lower portion of the limbs.

Another term for stocking up is pitting edema. This is because when pressure is applied to the area, a pit or indentation will remain temporarily.

Stocking up results from the pooling of lymph, a clear fluid that circulates in the lymphatic vessels. Sometimes this circulation is compromised allowing fluid to accumulate. This typically occurs if blood flow and lymphatic drainage are impaired.

Though stocking up may look alarming, it is typically not serious and resolves quickly once the horse begins moving again. However, in some cases of chronic stocking up, the swelling could be a symptom of a larger problem.

Many other causes of lower leg swelling may appear similar to stocking up but indicate a more serious condition. Being able to differentiate between stocking up and other conditions is important for horse owners.

Understanding the Horse’s Lymphatic System

To understand why horses stock up, it’s important first to learn how their lymphatic system functions.

When blood flows from the arteries to the capillary beds in tissues, some of the fluid escapes the blood vessels. Most of this is resorbed into the veins, however some remains outside the blood vessels. This remaining fluid enters the lymphatic vessels that run alongside blood vessels.

The main role of the lymphatic system is to maintain fluid balance and bring the fluid back to the general circulation. It also is
part of the immune system, helping to protect against disease and infection.

Lymph fluid passes through lymph nodes which can detect pathogens and release white blood cells (lymphocytes).

Lymph flows along the lymphatic vessels due to contraction of the vessels or from external compression via muscular contractions. [1]

Impaired Lymph Clearance Leads to Swelling

Normally, movement of the horse’s legs assists in pushing lymph up out of the lower limbs. However, if the horse is stationary or circulation is impaired due to other causes, the movement of lymph is reduced. [2]

Because the horse’s heart and body mass are higher than the limbs, gravity causes the fluid leaking from the bloodstream and lymphatic vessels to fill spaces in the tissues of the leg, resulting in swelling or edema.

Lower leg swelling can occur with increased lymph production, slower lymph clearance, or both. [1]

Horses have no muscles below their knees to help push lymph back into the body, making them more prone to stocking up. [3]

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Causes of Stocking Up in Horses

Horses in the wild travel vast distances daily, but many domesticated horses have long periods of inactivity. Stocking up is most common in horses that are stalled overnight or after a period of exercise. [1]

While inactivity and gravity naturally contribute to stocking up, there are other factors that make some horses more susceptible to this condition than others.

For example, horses with inflammation of the legs are more likely to stock up. This is because inflammation contributes to fluid leaking from the blood vessels into the leg tissues.

Examples of inflammatory conditions include allergies, local mild dermatitis, and some skin conditions. Excessive exercise or even hoof care changes can also promote inflammation.

Dietary imbalances can cause horses to retain fluid in the legs as well. These could include: [3]

  • Low protein diets
  • Diets with excessive protein
  • Starvation
  • Overfeeding/obesity

Dehydration is another factor that can lead to stocking up. A dehydrated horse may have lower than normal blood pressure, which can reduce the lymphatic system’s ability to push blood back up the leg. [4]

Sodium balance and electrolyte intake also affect how easily fluids move across cells. A horse with low sodium in their diet may be more susceptible to stocking up. [4]

Stocking up may also be a side effect of some medications that cause an increase in blood pressure. It can also be triggered by hot weather in some cases. [1]

Chronic Stocking Up

Chronic stocking up may be a sign of something more serious going on. Chronic stagnation edema may be diagnosed by your veterinarian if your horse persistently experiences limb swelling over a long period of time or if the condition recurs constantly.

Horses can experience chronic stocking up due to the following conditions: [1]

  • Kidney disease
  • Heart failure
  • Chronic lung disease
  • Thyroid disease
  • Liver disease
  • Severe parasite infection
  • Damaged blood vessels
  • Damage or blockage of lymphatic vessels

If your horse experiences chronic stocking up, it’s best to have him evaluated by your veterinarian.

Signs Your Horse is Stocking Up

It’s important to know the signs of stocking up so you can determine whether your horse is experiencing this condition or if it is something more serious.

One thing to note about stocking up is that it is usually not painful. The horse may have mild stiffness and a reluctance to move, but there should be no other signs of illness or injury. The horse should have a normal attitude and appetite. [2]

Stocking up may look similar to other forms of leg swelling, but it is a temporary condition that is easily resolved in most cases.

To determine if your horse is experiencing stocking up, apply pressure with your fingers over the swollen area to see if it leaves an indentation. This should not be painful to the horse, and the pits will slowly refill within 30-60 seconds. [5]

Other inflammatory limb conditions will typically feel harder to the touch and be more painful for the horse.

How To Treat Stocking Up

Stocking up usually resolves after 10-15 minutes of gentle exercise. Movement helps to raise the horse’s heart rate, increasing the return of blood and fluid back to the heart. [3]

With movement, the feet also help force blood and fluid back up the leg and toward the heart. [3]

The horse’s digital cushion – the wedge-shaped structure at the back of the hoof — acts as a pump, which pushes blood and fluid back up the legs. [4] This is why the hooves are sometimes referred to as additional hearts.

If the horse is reluctant to move or if the swelling appears to cause any discomfort at all, you may want to use additional therapies to help resolve the edema.

Cold Water Hosing

Cold water hosing is helpful if the horse appears to be experiencing any pain or if the swelling does not resolve after light exercise.

Applying cold water will reduce any heat in the leg and push fluid back into circulation. [3] Alternating between cold water and heat can be helpful for horses with mild to moderate stocking up.

Ice Compresses or Boots

Another option to reduce swelling in the lower legs is using ice boots, especially if your horse is experiencing any discomfort. [1]

These can be purchased from equine supply catalogues or specialized websites. You can also make your own ice compress using conjoined frozen popsicles (ice pops) and polo wraps.

Compression/pressure pumps may also be effective for some horses, but not all horses will tolerate this. [6]

Bandaging

Bandaging affected legs with pressure wraps can help to force fluid in the soft tissue space back into the lymphatic system and general circulation.

The pressure provided by the bandage can also reduce fluid loss from the lymphatics and blood vessels. [3]

Make sure not to wrap bandages too tightly or leave them on for too long as this can actually cut off the circulation of the lower limb and hoof. Leaving a pressure wrap on for 10-12 hours and then removing it for 10-12 hours is sufficient. [3]

Massage

Massaging the lower legs can also promote lymph flow and reduce swelling. [1] Studies show that massage increases skin temperature and enhances blood flow in local regions. [7]

Topical Therapies

Using topical dimethyl sulfoxide (DMSO) alone or combined with a topical steroid can also help horses that stock up. DMSO is a natural organosulfur compound with anti-inflammatory and antioxidant properties.

DMSO is sometimes applied under a breathable leg wrap. Apply for 10-12 hours then remove for 10-12 hours and use cold or warm water therapy. [3]

Applying liniment, oils, or poultices to the affected area can also be helpful in some cases.

How to Prevent Stocking Up

The best way to prevent stocking up is to avoid stall confinement if possible and ensure your horse gets adequate turnout. Movement facilitates blood and lymph flow, reducing the likelihood of your horse stocking up.

After strenuous exercise, take time to properly cool your horse down and hose their legs with water. If you must stall your horse, use supportive standing leg wraps to help prevent fluid from pooling in the lower legs. [2]

Since dehydration can also play a role in stocking up, ensure that your horse always has clean, fresh water and access to salt. [4] Salt is an important electrolyte and promotes thirst to encourage water intake.

If your horse seems prone to stocking up, have a qualified farrier evaluate his shoeing and hoof care.

Some horses improve with sole/frog support, which increases the contact of these structures with the ground surface (helping to pump blood and lymph back up the leg). Avoid bar shoes if possible to prevent sole and frog contact with the ground.

If you or your veterinarian suspect allergies are contributing to chronic stocking up, work to reduce your horse’s allergen exposure from feed, stall bedding, and the environment. Ensure your barn is well-ventilated and consider steaming or soaking your horse’s hay to remove dust and other irritants.

Nutritional Strategies

The best nutritional strategy to support a horse that is stocking up is to ensure they are being fed a balanced, forage-based diet.

This means ensuring that all vitamin and mineral requirements are met and feeding adequate protein and fibre. Avoid grain-based feeds with high sugar or starch content, as these feeds can contribute to inflammation.

Nutritional supplements may help to support your horse’s circulatory system and maintain healthy inflammatory regulation, but supplements shouldn’t be added until your horse’s underlying diet is balanced.

You can submit your horse’s information online for a free diet balancing by our qualified equine nutritionists.

Some supplements that can help to support a healthy inflammatory response and cardiovascular health include:

Other Causes of Lower Leg Swelling in Horses

If your horse’s legs remain swollen after turnout and trying the additional therapies listed above, it is likely that your horse is affected by another condition.

Furthermore, if your horse has swelling in only one leg or in all four legs, this indicates something other than stocking up.

Consult with your veterinarian if lameness, a digital pulse, heat in the hooves, and/or other signs of illness or injury are present. [2]

Some other conditions that cause leg swelling and may appear similar to stocking up include: [1][3][5]

  • Insect or snake bites
  • Blood clots
  • Severe infection
  • Endotoxemia
  • Wind puff
  • Joint swelling
  • Purpura haemorrhagica (complication of strangles)
  • Trauma to the leg
  • Tendon or ligament injuries
  • Inflammation of blood vessels

Three serious conditions that might at first be mistaken for stocking up include:

Lymphangitis

This condition is characterized by inflammation within the lymphatic system, which can lead to compromised lymph flow.

Lymphangitis impacts normal fluid circulation and causes fluid to leak into surrounding tissues. The result is extreme swelling in one hind leg, extreme pain, and an elevated temperature. [3][8]

Horses with lymphangitis usually have reduced appetite, are depressed and may tremble, breathe rapidly, and sweat. [8] This condition is usually associated with a bacterial infection such as an advanced case of Strangles or other types of bacterial infections. [3]

Cellulitis

Cellulitis is inflammation and infection within the subcutaneous tissue that lies beneath the skin of the leg. It typically only affects one leg and is often secondary to a wound or the spread of a bacterial infection from another part of the body.

The swelling in the soft tissues of the leg can impair blood and lymphatic circulation, leading to increased pressure and poor blood and fluid flow. [3][9]

Cellulitis usually involves prominent swelling and severe lameness. It often develops rapidly. The affected limb may be warm and painful to the touch, and the horse may have a fever and be lethargic. [9]

Chronic Progressive Lymphedema (CPL)

Chronic Progressive Lymphedema is a disabling disorder that affects many draft horse breeds. Affected horses will have progressive swelling of the lower leg, often associated with scaling, dermal fibrosis, as well as skin folds and nodules.

CPL starts when the horse is young and often leads to disfigurement and disability of the legs. Secondary bacterial and parasitic infections can complicate these lesions and worsen symptoms. CPL appears to be a multifactorial process with an underlying genetic component. [10][11]

Summary

Stocking up or stagnation edema may appear worrisome, but it is generally not a serious condition. It is most often caused by limited movement, usually when a horse is stalled overnight or after a period of exercise.

The lack of movement slows blood and lymph fluid circulation, causing fluid to pool in the legs.

Stocking up is easily resolved with gentle exercise or with therapies such as cold water hosing, ice wraps, topical treatments, or massage.

If the swelling doesn’t resolve, if one or all four legs are affected, or if the horse is experiencing other symptoms, consult with your veterinarian to determine whether your horse is affected by another medical condition.

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References

  1. Martin, D. Why do horses suffer from stocking up? Haygain. 2022.
  2. Thal, D. Stocking Up, Stagnation Edema. Horse Side Vet Guide. 2018.
  3. Schell, T. Stocking Up; A Pain in the Leg. Curost. 2022.
  4. Paulick Report Staff. Taking Stock: Do Salt And Water Play A Role In Equine Leg Swelling? Paulick Report. 2019.
  5. Stewart, J. Swollen Legs. Hoofbeats. 2020.
  6. Ramey, D.W. Use of a linear compression pump to control distal limb edema in horses. J Equine Vet Sci. 1988.
  7. Hidetoshi, M. et al. Effect of massage on blood flow and muscle fatigue following isometric lumbar exercise. Med Sci Monit. 2004.
  8. Keckler, K. Lymphangitis: A Frustrating Condition. AAEP. 2022.
  9. Hughes, L. Understanding Equine Cellulitis. New England Equine Medical and Surgical Center.
  10. Affolter, V.K. Chronic Progressive Lymphedema in Draft Horses. Vet Clin North Am Equine Pract. 2013.
  11. Powell, H. Therapy for horses with chronic progressive lymphoedema. Vet Record. 2009.