A common issue that many a horse will develop at some stage in their lifetime is lower limb swelling. There are a number of different possible causes with varying degrees of severity. Sometimes there is no medical cause for the swelling and there is less cause for concern. However there are a number of important structures within the lower limb of the horse, which when damaged can contribute to swelling. A thorough physical exam is therefore important to determine the significance of swelling and the need for any treatment.
Horse can develop swellings of the lower limb due to inactivity, such as standing in the stable overnight. This is otherwise known as sporadic lymphangitis and is the less sinister form of the disease. These cases are often not painful so are not normally associated with any lameness. The swelling tends to be diffusely spread out and can affect different legs to varying degrees. The circulation back from the lower limb will increase with movement so the degree of swelling will often decrease with riding. This is one way in which it can be differentiated from ulcerative lymphangitis, as this will not decrease with exercise. Sporadic cases are normally of no medical significance so do not require any further treatment.
It is important to tell the difference between the different forms of lymphangitis as some require a much more intensive form of treatment than others. Ulcerative lymphangitis normally will affect one limb and the associated swelling can be severe. Clinical signs can include poor appetite, high temperature, sweating and even sometimes some mild colic symptoms. Discharge can often be seen coming from the affected limb. It is caused by infection with bacteria usually through an existing wound or in a limb affected by mud rash and the swelling is caused by a combination of inflammation and blocked drainage of the left by small clots wedged in the vessels that would normally carry the fluid away. Treatment should be rapid and aggressive as these cases are difficult and challenging to treat successfully and unfortunately often results in a permanently swollen leg. A combination of antibiotics, anti-inflammatories, steroids and sometimes diuretics are used to treat this disease. From an owner’s point of view this disease is very time consuming as cold hosing and exercise, when the horse is comfortable enough, are also important management aspects. It should always be noted that the horse may be predisposed to this occurring again in the future.
Trauma such as kick injuries can also lead to inflammation and swelling of the lower limb. These are commonly associated with wounds on the skin surface and can be painful to touch. The swelling can be quite substantial and diffuse even if only associated with a small wound; therefore the degree of lameness can be a more reliable means of determining the severity. There can sometimes be heat and discharge associated with these injuries. It is also important to remember that damage to structures beneath the skin surface can have also occurred at the same time as a wound, which can often be more significant that the visible swelling. Depending on the location of the wound the healing process can be quite slow, so it is important to manage these cases correctly to optimise recovery from these injuriesSwelling can also be limited to specific structures rather than diffusely spread along the limb. Penetrating injuries can sometimes extend into joints, tendon sheaths or bursae and this can lead to more severe consequences. Clinical signs include lameness and swelling of the associated synovial structure. These require fairly intense treatment such as surgery as systemic antibiotics have very little affect on synovial sepsis. Without treatment the consequences of these injuries can by life threatening so it is important to have any suspicious looking injuries checked by your veterinarian.
Overloading the structures of the limb can also lead to damage, which in turn will cause inflammation. The swelling can either by diffusely spread along the limb or more confined to the injured area. This can also be associated with lameness to different extents. Structures such as tendons are prone to overloading injuries due to the high forces that they are subjected to in work. There are many different structures within the limb that can be injured so it is important to localise the problem to make a diagnosis. Swelling is not always very specific so nerve blocks are an important diagnostic tool. This is a technique that involves injecting small amounts of local anaesthetic into the limb in an attempt to diminish lameness. Once isolating the area responsible for the lameness further imaging techniques such as ultrasound and radiography can be used to investigate the problem area. Some horses can be predisposed to certain injuries either due to their conformation or breeding. Certain types of work can also be more likely to lead to problems due to the high strain placed upon the soft tissue structures. This is why a thorough veterinary history is important and will aid in making a correct diagnosis.
Some skin diseases can also lead to swelling of the legs due to the inflammation that is associated with them. Some metabolic diseases can also lead to swelling of the limbs due to impaired lymphatic drainage, although this is much less common the external trauma or overloading injuries.
Overall lower limb swelling is not always a cause for concern as it can be caused by a number of different processes, some of which don’t even call for any medical treatment. However there are some more serious diseases associated with limb swelling so it is important to differentiate between these different types so that the appropriate treatment can be started.