Anterior Shin Splints
The medical term anterior shin splints was replaced several years ago. Now the symptoms that occur in the anterior lateral tibial region (the front of your shin, anterior meaning front side) are assumed to be either stress fractures or a form of compartment syndrome. In understanding the anterior shin splint, it is therefore important to differentiate a shin splint from a stress fracture.
Most injuries that fit the term anterior shin splint are soft-tissue injuries at the muscular origin and bony or periosteal interface of the bone and muscle origin. These usually result in a more vertical area of symptoms, that is, they tend to run up and down the front of your shin.
Most injuries that clinically seem to be stress fractures have what is called a region of pinpoint tenderness and extend in a horizontal direction (side to side at the pain site). This line in many stress fractures of the tibia extends horizontally but might take a tangential course through the tibia. For injuries that are horizontal, no tenderness is found 1 or 2 centimeters above or below this discrete line of tenderness.
The non-stress fracture type injury to this area is thought to be due to micro-tears of the muscle either at the site of attachment to the bone or in the muscle fibers themselves. This may occur because of repetitive traction or pulling of the anterior (front) tibial muscles at the attachment site. Repetitive loading with excessive stress, such as caused by running on concrete, may also play a role in injury to this area. This can result in micro-trauma to the bone structure itself.
Anterior Compartment Syndrome
The muscles in your body are all wrapped in tissue called fascia. This packaging of the muscles forms compartments that encloses the muscle and separates it from adjacent muscles. Anterior compartment syndrome is caused by the muscles swelling within a closed compartment, with a resultant increase in pressure.
This running-related compartment syndrome is usually chronic, caused by repetitive stress, and is in some respects different from the acute compartment syndrome seen after serious muscle injuries. It is vital to seek medical evaluation and treatment if this condition is suspected.
The blood supply can be compromised inside this compartment, resulting in muscle injury and pain. The symptoms include leg pain, unusual nerve sensations (paresthesia), and eventually, muscle weakness. Definitive evaluation measures the pressure in the compartment. In severe cases, surgical decompression of the compartment may be required to relieve pain.
Runners at Risk for Anterior Shin Splints
The usual runners at risk for anterior shin splints are beginning runners whose legs are not yet acclimated to the stresses of running. These runners also may not have been doing an adequate amount of stretching. Poor choice of shoes and running surface (such as concrete) can also play a role. Overtraining, of course, can be a factor, as it is with most running injuries.
The usual mechanical factor seen is an imbalance between the posterior (rear) and anterior (front) muscle groups. The posterior muscles of the calf may be both too tight and too strong. The effect of too tight posterior musculature has ramifications for the gait cycle at two points.
The first period in which too tight posterior muscles impact the anterior muscles is just before and after heel contact by the distance runner. At this time the anterior muscles are acting as decelerators. If the posterior muscles are too tight, they force the anterior muscles to work longer and harder in this deceleration.
The second point in the gait cycle at which the anterior muscles may work too hard is when the foot leaves the ground, just after toe-off. The anterior muscles should be lifting up, or dorsiflexing, the foot at this time so that the toes clear the ground as the leg is brought forward. If the posterior muscles are too tight, the anterior muscles again work harder than they should. Logically, downhill running also has an adverse effect on the anterior muscles. The anterior muscles are working to slow down the foot to keep it from slapping on the ground.
Repetitive impact on hard surfaces is another frequently associated factor. Excessive pronation may be a minor factor, though it is a much greater factor in medial shin splints (now called medial tibial stress syndrome, or MTSS). Overstriding during speed work in underconditioned runners can also contribute to this problem.
Decrease training immediately if you think you are experiencing these symptoms or conditions. Do not run if pain occurs during or following your run. Nonweight-bearing exercise may be necessary. Your goal is to find the distance you can run (if any) that does not produce symptoms, rather than to find your real limit. Swimming, biking, and deep-water running can all be used to maintain fitness.
It's recommended that you do gentle stretching of the calf muscles and the hamstrings. It is also important to be strengthening the muscles in the front of your shin.
Replace shoes with too many miles on them. Shock absorption should be a factor in selecting shoes if you suffer from anterior shin splints. Downhill running can aggravate this problem and should be avoided. A stride that's too long can also delay healing. Most of all, do not run on concrete. After exercise, apply ice to lessen symptoms.
Office Medical Care of Anterior Shin Splints
A thorough evaluation of your training and racing schedule and shoes is followed by a biomechanical evaluation. A bone scan can be used, if necessary, to evaluate the possibility of stress fracture. A wick catheter test can be used, if necessary, to measure post-exercise compartment pressure, if a compartment syndrome is suspected.
Anti-inflammatory medication can be prescribed. A physical therapy consultation and treatments can also be helpful to identify and treat the source of your specific problem.
Sometimes a heel lift is used to reduce the pulling effect of tight posterior muscles. Even though this increases the distance the foot must be dorsiflexed, the duration of action and the effective strength of the posterior muscles is decreased. Orthotics may also be considered when biomechanical abnormalities exist and problems persist.