Swollen Legs

Horses like to give us something to puzzle over, and last week one of my clients had a mystery filled leg with her horse which has prompted me to compose a checklist for anyone in a similar position. After all, fat legs arise for a variety of reasons.

Sometimes you bring your horse out the stable, or in from the field, and they have a filled lower limb. It causes panic, and you think the worst. But calm yourself, and work through a process of elimination to decide whether the filled leg is purely an accumulation of lymph fluid or something more serious. Then you can decide on a course of action and potentially how to prevent it reoccurring.

If one leg is filled and the others not it suggests a knock or injury to that leg which causes a reactive inflammation, but if both hinds or both fores are filled it suggests an accumulation of lymph fluid for physiological reasons. Running through this check list on the lone filled leg will allow you to establish if there’s a more serious cause to the filling or if it’s just a curved ball that horse’s like to throw and get us worried.

  • Firstly, are they weight bearing? A non weight bearing mysterious swollen leg is much more serious than a weight bearing one.
  • Are they sound? Again, a swelling with lameness is more serious than one without lameness. If the horse is not weight bearing and lame then it’s a matter to discuss with the vet.
  • Is there any heat in the leg? Sometimes a knock to the leg, either in the stable or a kick from another horse, doesn’t leave a mark but will leave an area of heat on the leg even if the whole leg is filled with fluid.
  • Are they sensitive on the area? If they’re in pain then there could be a more serious cause to the filled leg.
  • Is the swelling soft or hard? Hard swelling indicates an injury to connective tissue or a localised infection at a wound. Soft swelling suggests lymph fluid.
  • Is there a specific area of swelling or just the whole limb? A specific area means it could be a tendon, ligament, or infection site. A general swelling, particularly without heat, suggests a build up of lymph fluid – for reasons yet unknown. Does the limb resemble a tree trunk, or just have slight filling? A large amount of filling needs to be taken seriously as it suggests infection.
  • Is there a wound? Sometimes you have to look very closely for a small wound which could cause infection to enter and the leg to get swollen in response to the infection. This time of year there could be a small cut or graze which causes mud fever bacteria to enter the limb. Sometimes there can be a tiny wound, such as a thorn, which causes a mild reactive swelling but can’t be identified easily.
  • Are there any clues on the rest of the horse’s body? Mud marks which suggest a kick or a slip in the field, a disturbed bed which suggests they got cast in the night, or a bramble in their tail which hints at a possible thorn in (or was in) the leg causing a reactive inflammation.

With the physical examination done you should feel more confident the level of seriousness of the filled leg. If they’re weight bearing and sound, with general swelling and no heat, pain, or obvious wound or injury then it’s likely to just be a build up of lymph fluid or a mild response to a foreign body, so the best thing is to monitor it for a couple of days and if it doesn’t get any better then call the vet.

Next of course, you need to try and find the possible reason behind the swollen leg or legs, to see if it’s a management issue, or if there is a way to avoid the problem reoccurring.

  • If it’s a swollen hind leg then poor circulation is a potential cause. The lymphatic system has no pump, unlike the circulatory system, so relies on movement to circulate lymph fluid. Combined with the fact the heart is so far away from the hind legs then a lack of movement can cause lymph fluid to build up there.
  • If a horse has suddenly been kept in: on box rest or due to bad weather, then their legs may fill. Turnout and gentle exercise – going on the walker for example – will help reduce swelling.
  • If you link filled legs to more time spent in the stable then you can manage the situation by using magnetic boots, to improve circulation, or stable bandages.
  • Sometimes one leg will fill more when a horse is stabled due to an old injury or previous damage to the lymph system in that limb. If a horse is lame they may load their good limb, which can also cause swelling.
  • High protein diets have also been linked to filled legs, so if your horse suddenly starts having filled limbs, perhaps at the beginning of winter when hard feed is introduced or the rations have changed, then it may be worth checking the levels of protein in their diet and finding alternative food. Young horses, veterans, or those on conditioning feeds require more protein in their diets, so it may be worth speaking to a nutritionist for advice if you think protein levels are the cause of filled legs.
  • If your horse suffers from filled legs on a regular basis, and in more than one leg then they might be suffering from lymphangitis, which is a bacterial infection and needs treatment from the vet, as well as immediate treatment of any cuts by cleaning and applying barrier cream to prevent the entry of infection. If a horse gets lymphangitis then there is a high risk of complications, and they are always susceptible to flare ups so you need to monitor the horse’s legs closely at all times and act quickly if there’s any sign of infection.
  • Check the general health of your horse because an illness that affects the circulatory system can cause the legs to fill as a side effect. But it should be quite clear to you that your horse is under the weather and then you can call the vet.

My client’s horse was a little depressed last week and off his hay for a couple of days, but his bed was disturbed on the days that his leg was filled, suggesting he’d knocked himself, but it went down on turnout each day, and when his appetite picked up again his leg seemed to return to normal. Frustrating as it is because there was no obvious cause, but as it was mild swelling with no pain and it went down quickly we tried not to worry too much. I think the horse was off his hay so fidgeted more in his stable because of boredom and knocked his leg. Perhaps causing a contusion which filled overnight and then went down during the day.

Another horse I know came in from the field with a slightly filled hindlimb earlier this week. Again, not lame or in pain, but we couldn’t find a wound or injury. However, I found a bramble in her tail so I think she was investigating the brambles and got a thorn in that leg, triggering the swelling. The leg just needed monitoring over the following days to see if the swelling reduces and to ensure the thorn comes out, if it already hasn’t.

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