Compartment syndrome is a general term which can cover a variety of different areas in the body but for this discussion we're going to focus on the anterior compartment of the lower leg as this is the primary area that would be affected in runners and triathletes. This article will cover what is typically called Chronic Compartment Syndrome as it is due to overuse and overtraining. Acute Compartment Syndrome is a medical emergency which requires immediate surgical intervention. I'll explain a little more about that later on.
Muscles are surrounded by fascia which act a lot like a sausage casing, holding things in place. In certain areas of the body like the lower leg, bones and fascia combine to form well-defined spaces called compartments. For example, the tibia (shinbone) is bordered by muscles on both sides. The muscles that run up the outside (lateral) margin of the tibia make up the anterior compartment of the lower leg. This anterior compartment is defined by the tibia bone on the inside, the fibula bone to the rear, and the crural fascia surrounding it all. The crural fascia basically wraps the muscles and the bones of the lower leg. Now, the tibia and fibula are bones so they don't offer a lot of 'give', therefore on 2 of the 3 sides of this compartment you have very stiff walls.
By definition, compartment syndrome "occurs in anatomic locations that have unyielding, well defined osteofascial spaces."1 That makes the anterior compartment of the lower leg the perfect place for potential problems because it is bordered on 2 sides by bone. Furthermore, in some individuals the fascia that wraps the muscles is very tight, thereby allowing for little or no expansion, complicating the situation even more. The muscles of the anterior compartment are involved with dorsiflexion (upward movement) of the foot and toes. Also present in the anterior compartment are the deep peroneal nerve which supplies the shin and foot and the anterior tibial artery and vein.
What's Going On
During exercise which involves repetitive dorsi- and plantarflexion of the foot (moving the foot up and down), such as running, swelling can occur in the muscles of the anterior compartment due to increased blood flow. This can create an increased pressure in the compartment. If the fascia surrounding the compartment does not stretch enough (remember, the bony walls of the compartment don't give), the increased pressure will compress the artery and nerve, thereby causing pain or numbness or tingling in the distribution of that nerve.
Signs and Symptoms
Triathletes may experience symptoms with cycling if they are pulling up on the pedals, or during running. Symptoms may be more noticeable while trail running because you need to lift the toes more to clear obstacles such as roots or rocks. I have experienced symptoms during the final miles of the bike in Ironman races and I've attributed that to the anterior shin muscles getting tired during the swim from kicking, followed by a long ride which also worked the same muscles. By the end of the bike, I was having pain and pins and needles in my toes. Thankfully, it did not present a problem once the run started.
What To Do About It
If you have been experiencing symptoms of anterior compartment syndrome your first approach to treatment should be to stretch the anterior muscles of your shin. This can be done kneeling on the ground with your toes pointing behind you and the top surface of your foot flat on the ground. Then you can 'sit' down on your heels and lean your body backwards over your feet. You should feel the front of your shins stretching.
Massage is also a useful approach to treatment because if the muscles are chronically tight they will be more prone to swelling.
When chronic cases do not respond to conservative care, fasciotomy is the treatment of choice. This is a surgical procedure where an incision is made along the length of the affected compartment through the fascia to release the pressure. Properly execute surgery has a success rate of close to 90%2. Prior to surgery, a patient would have to meet certain diagnostic criteria whereby pressure measurements are taken at rest and during activity to insure that the procedure is warranted.
Finally, I mentioned earlier that I would briefly touch on the subject of Acute Compartment Syndrome as this is a very serious condition which requires immediate medical care. The concept behind the condition is the same in that the tissues in a closed space are compromised by pressure in the surrounding area, however the cause is usually the result of significant trauma, fractures, crushing injuries or some kind of clot or other occlusion of a blood vessel. Because these conditions can cause a rapid increase in pressure and thereby damage nerves quickly, proper medical attention is a must. An acute compartment syndrome treated within 12 hours has a complication rate of less than 10 percent. However, after 12 hours the complication rate rises to 80 percent and the amputation rate to 40 percent!3
1. Reid, David C. Sports Injury Assessment and
Rehabilitation. New York: Churchill Livingston, 1992: 285
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