Last Updated on February 25, 2022 by Allison Price
5 causes of swelling, from benign triggers and major concerns
Your horse’s strong, sleek legs have been unaffected by his athletic endeavors. One day, as you are about to give him breakfast, you notice that he has a “fat” leg. It is a sign of something more serious than a simple problem. Let’s take a look at all the possible causes of limb swelling.
Initial Assessment Steps
Consider that leg swelling can be treated quickly and easily, so don’t assume the worst. Instead of waiting and seeing, get on top of the situation immediately and call your veterinarian.
Before you call, gather information that you can share with your vet. Rosemary Cuming (BVSc MS), MANZCVS and Dipl. ACVIM of Scone Equine Hospital in New South Wales, Australia advises owners to take notes about the horse as a whole, not just his legs.
She says to pay attention to the horse’s behavior, appetite, water intake and fecal output. “Has the horse been showing signs of illness in recent times, or have any changes been made regarding diet, medication, blanketing, bandaging or bedding?
Matt Randall, DVM of Collier Equine in Waller (Texas), urges horse owners not to forget to check the horse’s rectal temperature.
Cuming suggests creating a list of questions to be addressed. Pay attention to the horse when he stands still, then move around and ask yourself these questions:
- Is the horse comfortable or does he seem stiff?
- Is he deaf? Is he lame?
- Are multiple legs swelling?
- Are you able to see drainage?
Note any abnormalities and feel the affected limbs.
- Is there heat in the limbs?
- Is the horse unable to hold the pain after a gentle touch or firm touch on the swollen area?
- Are there any unusual sensations in your skin or hair such as scabs or crusts, moist, oozing or dry discharge or lumps?
- Are the swellings localized (confined to a small area) or generalized pitting (the fluid swelling spreads over a large area and the tissue remains depressed when you press on it with your finger).
- Is the swelling located near or within a synovial structure, such as a joint?
Randall states that fever, lameness and wounds involving the synovial structures increase the need for immediate veterinary attention in cases of limb swelling.
Cuming adds that limb swelling may be harmless or can indicate a more serious disease process in one or more of the legs or other systems. Your veterinarian can assess whether the horse’s limb swelling needs immediate attention. If it is not, they will be able to treat the horse symptomatically.
Here are five common diagnoses your veterinarian might make.
1. Stock up
Cuming explains that stocking up refers to swelling in the lower limbs of horses (below the knees, hocks) due to fluid pooling in the tissues.
She says that horses are often stockpiled when they have restricted movement, such as when they are kept in stalls. The lower limbs swell when there is a decrease in the normal physiologic pumping fluid. It’s like swelling in your ankles after a long flight.
The horse’s lymphatic system moves fluid, proteins, nutrients and other substances around the body. Cuming says that fluids, proteins, and nutrients often leak from blood vessels in horses to provide nutrients for the cells. Cuming says that fluids, including cellular debris, dead cells, bacteria and other pathogens (disease or damage-causing organisms), toxins and protein molecules, are then removed from the legs via lymphatic vessels. These thin-walled, valved structures can hold large amounts of fluid. The lymph fluid is then filtered through the lymph nodes, and then returned to bloodstream via the veins.
She continues, “The lymphatic system does not have an active pump (like a heart), and pressure and movement within the tissues and organs surrounding lymph vessels can influence flow.” “The movements of the hoof’s digital cushion, the soft tissue under the sole that separates tendons and bones from the frog and heel bulb, play an important part in horses’ lower legs helping to ‘pump up’ lymph fluid.
Although stocking up is possible in all horses, Cuming states that veterinarians are more likely to see it in older horses, those with lymphangitis, cellulitis or previous leg injuries (see next section). This is due to poor circulation. She recommends that the horse be moved. Some swelling can be reduced by active exercise, such as hand-walking or longeing. The fastest way to reduce swelling is with support bandaging. Bandaging for too long can lead to further lymphatic and blood loss and may even prolong the condition.
2. Cellulitis and Lymphangitis
Lymphangitis and cellulitis can often cause severe and serious limb swelling. Limb cellulitis is usually an acute condition. The horse may appear fine and then suddenly become lame, according to Cuming. Cellulitis, a bacterial infection that spreads quickly and extensively through the tissue planes, is a form of diffuse bacterial infection. Staphylococcal and streptococcal bacteria enter the skin through a cut. Sometimes you can see the wound, other times the entry point is not obvious. She says that leg boots might cause microabrasions.
Randall says that swelling can cause significant lameness or fever, and it is often in one limb. Randall says that he has seen multiple limbs involved in cases when horses were stuck for days in floodwater following Hurricane Harvey.
Cuming says that the affected limb will be hot and swollen to the touch. There may also be mild to severe lameness. A few horses will go lame, but only a small percentage of them will. You can feel the heat or mild pitting edema on the affected leg, and this is when you suspect that you have cellulitis. Cellulitis can cause pain and swelling as well as lethargy and fever.
To avoid serious complications such as supporting leg laminitis (founder on the opposite or supporting foot), dermal necrosis, (skin tissue death), persistent lameness, recurrent cellulitis, and vascularthrombosis (clotting the vessels), early diagnosis and treatment are crucial. Cuming says that any of these advanced conditions can lead to chronic debilitation and even death.
The clinical signs of ulcerative lymphangitis include fever, lameness and lethargy. However, infection and inflammation can cause the lymphatic vessels to become engorged with hard nodules, which then lead to abscesses. This can be caused by bacterial infection such as Corynebacterium fauxtuberculosis (which causes Pigeon fever). It is transmitted via biting flies or deeper penetration by streptococcal or staphylococcal species. However, lymphangitis can be caused by bacterial infection. Cuming states that this is not always the case. It can also be caused by genetic anomalies in draft horses.
Randall and Cuming warn that chronic lymphangitis can lead to persistent thickening of lymphatic tissue, which may cause swelling and stocking up. This could result in the limb becoming thicker and wider than usual.
3. Infectious Disease
Multiple limbs are more likely to be affected by limb swelling and edema. Randall says that horses often have a fever, limb swelling and lameness.
Cuming adds, “Look out for swelling in all four legs and edema elsewhere on the body like under the jaw or in the sheath. Also, monitor for any other signs that may indicate your horse is sick and not injured.”
Fever, nausea, vomiting, diarrhea, and decreased appetite are all signs of illness.
Strangles is an infectious disease that can be caused by Straptococcus equi. This can lead to a potentially fatal secondary immune disorder called purpura hemorrhagica. Randall says that horses suffering from edema can often have severe limb swellings in their chests, abdomens, and legs. Petechiation, which is a reddening of small hemorhages, can also develop in the mucous membranes or the sclera (white) of their eyes.
Vasculitis (leaky veins) can cause leg swelling as well as systemic viral infections. Cuming says that these diseases can be either mild and manageable (resolving by themselves) or life-threatening. “Examples of viral infection include equine flu and equine viral arthritis. equine herpesvirus is also present (currently, only in Australia).
Multiple limb swelling can be caused by low blood protein or circulatory compromise due to congestive heart disease or inflammatory bowel diseases.
Cryotherapy: The Magic of Cryotherapy
Rosemary Cuming, BVSc MS., MANZCVS., Dipl., suggests that cryotherapy (cold therapy), for short periods (20-30 minutes) can be used to treat cellulitis and other leg injuries. It also reduces swelling, pain and inflammation. ACVIM, Scone Equine Hospital in New South Wales. There are many forms of cold therapy, such as cold water hosing, placing the legs in a tub of water and using ice boots multiple days per day.
Matt Randall, DVM of Collier Equine in Waller Texas, says that cooling down a limb is almost impossible. Submersion of the entire limb in ice water is the best way to cool an area. Salt can be added to the ice water to reduce swelling and change the osmotic gradient. Bags of frozen vegetables and commercial ice boots are good options. These options are better to use if there is a cut in the skin. Submersion further softens or weakens already damaged tissue.
Cuming advises that you wash your skin with clean water after cryotherapy in order to prevent secondary bacterial skin infection. Exercise can be combined with cryotherapy to treat chronic, older injuries.
— Nancy Loving DVM
4. Injury
A single limb swelling is often caused by a problem that affects the skin, subcutaneous tissues, tendons, ligaments and tendon sheaths. It can also be associated with pain in the joints or bones. There are many reasons why a single limb may swell.
- Ligament or tendon injury
- After sustaining a severe injury to the leg, bone sequestrum formation occurs. This is when a bone fragment dies and separates with healthy bone.
- Pastern Dermatitis (greasy heels/mud fever/scratches);
- A foot abscess
- Sepsis of the tendon or joint sheath;
- Ringbone.
Randall says that the most obvious sign that swelling is caused by injury is the fact that the swelling appears to be localized around a tendon, ligament or other structure rather than spreading throughout the whole leg. “Usually there is no fever but lameness can vary depending on the injury and the person. Horses with ruptured superficial digitalflexor tendon tendons can walk normally, but have a higher fetlock drop. Although chronic suspensory branch injuries can cause more extensive and diffuse swelling, it is usually less fibrous with less hemorhage.
According to him, swelling due to a foot abscess rarely progresses beyond the upper pastern. Sometimes, however, edema can reach the carpus (knee), due to constrictions in the blood vessels and low-grade ascending cellsulitis.
Similar to wounds, localized swelling can develop that may become more severe due to infection.
Your veterinarian will conduct a thorough physical exam to determine the severity of injuries that horses can sustain. Then, he or she will do a lameness examination and other diagnostic tests based upon clinical findings. Radiography (X rays), radiography (ultrasound), advanced diagnostic imaging (MRI CT, nuclear scintigraphy), tissue biopsy, and bacterial culture are all possible testing options.
5. Windpuffs
Windpuff refers to swelling in a digital structure such as a tendon, bursa or joint capsule. Randall states that many of these are cosmetic and innocuous, particularly if they occur in the same place on both the front or back legs.
Randall says, “I don’t get excited if a horses is doing its job without complaining, showing no lameness or flexion of the leg, especially if the effusion, (fluid buildup), improves with exercise.” “Windpuffs are usually secondary to an inflammation response in the joint or tendon skin that increases synovial fluid, distends and stretches synovial structure.”
Similar to the loss in elasticity when you stretch a rubberband, the sheath or capsule often remains stretched but retains enough fluid to form a “puff”.
Randall recommends further diagnostic testing if the effusion is only in one limb, or if the horse is sensitive or flexed at the joint. Cuming agrees that these swellings may be indicative of an acute injury if they are asymmetrical (just one or both legs), or if they appear suddenly, become larger, feel hot or painless on palpation, or are related to a known injury, lameness, or other symptoms.
She cites two examples: a tendon tear or a torn ligament, or an acute flare up of a chronic injury. Both require prompt veterinarian attention.
Take-Home Message
Although limb swelling can be quite innocuous, it could indicate a serious problem. Your veterinarian should be consulted to determine if the swelling needs to be addressed.
