With compartment syndrome, compartment refers to separate sections of the body that contain muscles, nerves, and blood vessels surrounded by a layer of fibrous connective tissue, called fascia.
When the pressure within these compartments rises, normal blood flow can be cut off, leading to tissue damage due to hypoxia, or the lack of oxygen.
Compartment syndrome typically happens in the limbs, usually in the lower leg or the forearm.
Now, if we remove the skin and then we remove the fat tissue from the lower leg, we would uncover the fascia.
Fascia surrounds the muscles, keeping them tightly together while they contract to move the limb, and it also help attach these muscles to the bones.
Now if we look at a cross section of the lower leg, we can see that the fascia sends intermuscular septa that together with the interosseous membrane between the tibia and fibula divide the lower leg into four compartments.
The anterior, lateral, deep posterior and superficial posterior compartments all contain their own muscles, and blood vessels.
For example, the anterior compartment holds the muscles that perform dorsiflexion of the foot and also aid in it’s inversion and eversion; the deep peroneal nerve that innervates them; and its blood supply comes from the anterior tibial artery and veins.
Since the fascia is not elastic it can’t stretch much. Therefore any increase of the cellular and extracellular volume or a decrease of the volume capacity, like with some external compression, will lead to the increase of the pressure inside the compartment.
This will compress the structures within, and the first ones to feel the effect of compression are the veins, because the pressure inside their lumen is normally low.