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Swelling in the leg; or is it a clot?


Administrative Staff
Jun 11, 2013
United States United States
By: Josephine (Josephine, Nurse Emeritus)
Updated June 30, 2020 (Jamie)

Many times people get anxious because their leg is swollen. Maybe they expect some swelling around the knee but to see almost the entire leg swollen can be extremely disconcerting. People immediately begin to fear blood clots and infection.

Well, there are many reasons why swelling occurs:

1. the surgery; having tissues cut, handled and pulled around can make fluid build up in the hours afterwards. This can stay or ebb and flow for days and even a couple of weeks.

2. increased blood and lymph flow; healing happens because there is increased circulation bringing plentiful blood cells, plasma and lymph into the area to supply nutrition and oxygen - all needed for the creation of scar and normal tissue.

3. tourniquet; during upper and lower limb surgery, it is common practice to apply a high pressure tourniquet to the upper part of the limb. In the leg it is like this

Before the pressure is applied, an inflated roller is pushed up over the leg to remove most of the free circulating blood from the vessels. Then the tourniquet cuff is inflated. Pressures used are generally around 500mgs mercury (blood pressure is usually about 120 or above).

This has the benefits of
giving the surgeon a blood free area in which to operate​
making surgery easier and faster​
making anatomical points much easier to spot​
minimizing blood loss. This is of great benefit to the patient since these operations would otherwise have a moderately high blood loss.​

However it has the disadvantages of causing post-operative swelling.
When the surgery is done and the tourniquet removed, the reaction is for the blood and lymph to flood back into the leg and a rebound swelling occurs. It's because of this there seems to be a lot of bleeding in the first 48hrs.​

To combat this and prevent the formation of a haematoma (which is simply a collection of blood either inside the joint or within the incision and the soft tissue layers nearby)
vacuum drains are often inserted into the wound​
a compression dressing of wool and crepe is applied to the limb​
the leg is elevated​
the pulse in the foot is monitored to make sure any excessive swelling isn't compromising the circulation of the limb - an event describe as 'compartment syndrome'​

This swelling can continue to occur for 2-3 weeks after surgery, sometimes instigated by spending too much time standing or with feet on the floor when sitting.

It should also be remembered that this swelling can create a mechanical obstruction to flexion of the knee. It's not at all uncommon for patients to get depressed or frustrated when it seems as if they are going backwards. But knowing about and remembering the effects of post-surgical swelling should reassure that this will eventually pass.

Blood clots or deep vein thrombosis (DVT)
Of course, there is always the risk of blood clots, therefore if the symptoms include the following
swelling of the affected leg​
pain and tenderness in the affected leg - you may also find it difficult to stand properly with your full weight on the affected leg​
a change in the colour of your skin, for example, redness​
skin that feels warm or hot to the touch​
then you should seek medical advice at once.

A good test you can try for yourself is to place your open hand over the fullness of the calf and squeeze firmly but gently. If you are unable to do this because it is too painful or doing it causes more pain, then you should seek medical advice at once.

This website has some excellent detail about DVT.
Deep vein thrombosis fact sheet
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