Danny was found by his owner in his stall one morning to be non-weight bearing on his left hind leg. His stall looked disheveled as if he might have been cast in his stall overnight. However, since he was standing when he was found, it was unknown exactly what had happened. Danny was so painful that he was trembling and would not put the leg down at all. His owner called SSEC, worried that Danny may have broken his leg.

Upon initial examination at the farm Danny’s left hind leg was swollen diffusely from the distal (lower) hock through the pastern. He was painful to palpation of the leg, but no localized area of exquisite pain was present. All of the long bones appeared stable upon palpation, indicating no unstable fractures were present. The leg was warmer than normal to the touch throughout the lower limb. He would not bear any weight on the limb and would often appear as if he was going to fall down rather than put the leg down.

The leg was swollen from the lower hock through the pastern. Danny was not able to bear any weight on the leg and was unable to walk out of his stall.

Any time lameness this severe is present we are concerned about a fractured bone. Fractures can range from the obvious that create instability of the limb to a subtle hairline fracture that can only be seen on radiographs. To rule out a fracture of Danny’s hind leg, radiographs were taken of the swollen area.

Radiographs of the distal (lower) cannon bone (upper row of images) and the pastern (lower row of images) appeared normal.

Several views of the swollen area were taken to ensure any subtle fractures would be seen, but no fractures were observed. Confident that no fractures were present, we looked for other potential causes of Danny’s lameness.

Due to the leg being diffusely warmer than normal to the touch and swollen, we were concerned about cellulitis, which can be defined as inflammation of subcutaneous tissues. Inflammation is trapped under the skin and is clinically expressed as heat and swelling of the affected tissues. This results in a swollen, painful leg and often the horse will be severely lame and may even have a fever. Cellulitis may be associated with a bacterial infection, but can also occur without an associated bacterial infection. The most common bacteria recovered are Staphylococcus spp., though many other bacteria have been implicated as well. Possible initial causes of cellulitis include trauma, lacerations, small puncture wounds, or pastern dermatitis; although often no definite cause is ever determined.
Treatment of cellulitis often includes hydrotherapy (cold hosing), poultice or pressure bandaging, anti-inflammatories and antibiotics. Due to the many various causes of cellulitis, treatment time varies depending on each individual case, but early treatment is essential. In Danny’s case, he was started on an aggressive treatment regimen of intramuscular penicillin, oral phenylbutazone, Naquasone, and 20 minutes of hydrotherapy 4 times daily. A poultice wrap was placed on his left leg overnight and his right leg was bandaged with a support wrap.

Upon recheck examination the following day, the swelling in the leg was more extensive, beginning at his stifle the entire limb was markedly swollen and hot. Overall Danny appeared more comfortable, eating well, and placing some weight on the leg. When taken out of his stall to walk, he was nearly non-weight bearing for the first few steps, but became more comfortable the longer he walked. He was still very lame, but was able to place full weight on the limb.

Day 2: The left leg appears almost twice the size of the right leg when viewed from behind. The swelling also extends higher up on the leg than at initial examination.

The owner had also noticed that where the poultice had been placed overnight that the skin was very wet and thought he had a reaction to the poultice. Actually, the skin was being stretched so much by the subcutaneous swelling that serum, a yellow, watery substance that composes the liquid part of blood, was beginning to ooze out of the skin. If swelling continues to increase at this point, the skin can actually split from the pressure. To get the swelling under control Danny was continued on aggressive hydrotherapy with high pressure water, hand walking, and massaging the leg multiple times daily to stimulate blood flow.

The yellow discoloration of the back of the distal cannon bone is serum. Serum could actually be seen dripping off the back of the hairs on the fetlock.

Danny was examined again the following day and the swelling appeared to have decreased slightly throughout his upper leg and he appeared to be walking more comfortably. Over the next few days Danny was turned out to encourage him to walk on his own to stimulate blood flow. Aspirin powder was also added to his treatment regimen. Due to the anti-platelet activity of Aspirin, it allows blood to enter into areas that may otherwise be too swollen or small to allow blood flow. It therefore helps retain the health of the swollen tissue and improves removal of excess fluid and edema from the limb.

At his recheck examination a few days later (approximately 1 week after the initial examination), the leg was still thickened with mild swelling throughout the distal cannon bone and pastern, but overall the swelling appeared greatly decreased throughout the leg. The previously noted increased warmth had returned to normal and he was walking much more comfortably as well. Over the next few weeks, the swelling continued to decrease and now Danny has made a full recovery!

Two months after the initial examination, Danny’s leg has returned to normal size and he has returned to his normal level of work!

While Danny is an example of the best case scenario for a cellulitis case, many cases develop complications which can be potentially life-threatening. Due to the horse not bearing weight on the affected limb for the course of the disease, the opposite limb is overloaded and becomes susceptible to laminitis. Cellulitis may also develop into a more serious case if the lymphatic vessels are involved, which would be termed lymphangitis. Lymphangitis cases are often more difficult to treat, with more complications, and may take months to resolve. A less serious complication can occur if the subcutaneous swelling impinges on lymphatic vessels enough to create permanent scar tissue, which can lead to decreased lymph drainage of the limb and results in a chronically enlarged limb. This can be a serious complication in that the horse may not be able to return to his previous level of performance and recurrences of cellulitis or lymphangitis are more frequent in these cases, but these are usually not life-threatening.

If not for the quick initial treatment and the owner’s dedication to aggressive hydrotherapy throughout each day, Danny could have had a much different outcome!

Take home message: Any non-weight bearing lameness should be considered an emergency. There are only a few potential causes of a lameness this severe, which can range from a fracture to a simple abscess, but can also include potentially serious conditions such as lymphangitis or cellulitis. Accurate diagnosis and aggressive initial treatment where appropriate are essential to a good outcome. It is always best to get any lameness checked by your vet!