The muscles of the lower leg are partitioned into four compartments by a layer of separating fascia. This fascia is actually a tough, non-yielding fibrous sheet that holds the nerves, vessels and muscles of the compartment together. These four compartments are named according to their anatomical location as follows:
Compartments of the lower leg
The posterior compartment of the leg is further subdivided into a deep part and a superficial part.
The deep part is located behind the tibia and contains the tibialis posterior muscle and three other muscles that execute downward flexion, as well as inversion of the foot.
The superficial compartment contains the calf muscles, namely the gastrocnemius, soleus and plantaris muscles. All these muscles insert into the heel bone, and when they contract they lift the heel off the ground.
Compartment syndrome refers to a painful condition that develops as a result of rising pressure inside a muscle compartment. An accumulation of blood or fluid will press on the surrounding structures due to the non-resilient nature of the surrounding fasica. This building pressure compresses the small blood vessels, compromising the supply of oxygen and nutrients to the tissues in the compartment. The consequence is severe pain, disability and even permanent tissue damage if not attended to in time.
Posterior Compartment Syndrome may result from an acute injury, in which case it is known as Acute Compartment Syndrome. The injury may cause a bone fracture or a muscle bruise. If the surrounding fasica is intact, the resulting hemorrhage would lead to pooling of blood inside the closed compartment compressing the adjacent structures.
Excessive exertion of the posterior leg muscles, leading to overuse injury and swelling may also produce pressure and pain, in which case it is referred to as Chronic Exertional Compartment Syndrome.
There is severe pain and a feeling of compression on the posterior aspect of the lower leg. The pain is aggravated by activity, especially when the foot is bent downwards. There is also weakness of the posterior leg muscles (difficulty in bending the foot downwards against resistance). The area appears swollen and the overlying skin appears pale, shiny and stretched. There is also decreased or altered sensation in the posterior aspect of the leg.
The signs and symptoms are quite indicative of the disease. An X-ray, CT or MRI may be taken to diagnose the underlying fracture (may also be a stress fracture) or soft tissue injury. The pressure inside the compartment can be measured as well using a simple apparatus.
Treatment depends on the urgency of the situation. Acute compartment syndrome is a medical emergency that requires immediate surgical intervention. The pressure is released by making multiple long incisions in the surrounding fascia. The wound may be left open for 48 to 72 hours and stitched closed in another procedure. A skin graft may be needed to close the wound.
Fasciotomy for posterior compartment syndrome (extreme right)
Chronic exertional compartment syndrome usually results from excessive exertion and can be treated conservatively by reducing the load on the muscle and allowing time to heal. The first line of therapy includes RICE regime, that is Rest, Ice application, Compression and Elevation. Be careful not to elevate the leg above the level of the heart as it may further compromise the circulation.
Massage and stretching exercises for the posterior leg muscles help to relieve muscle stiffness.
It is also necessary to use appropriate footwear and treat any biomechanical or postural abnormalities. Sometimes, surgery may be required to release the tension by incising the fascia (fasciotomy).
