Shin splints are a very common source of frustration to runners of all abilities, and can strike out of nowhere in people who have run pain free for years. "Shin Splints" is a catch all term for pain in the lower leg which can be felt in front, on the sides, or even behind the lower leg bones. Just like "headache" being a catch all term for pain in the head which can originate in the neck, TMJ and sinuses, shin splints have a number of causes.

Also known as "medial tibial stress syndrome" (sounds expensive to get rid of, doesn't it?!), there are four main causes of shin splints:

1. Strain of the tibailis posterior muscle (most common).
2. Strain to the tibialis anterior muscle.
3. Stress fractures of the tibia (the main weight bearing bone of the lower leg).
4. Compartment Syndrome.

The tibialis posterior muscle assists in holding up the arch of the foot; footwear without enough arch support will allow the arch to drop too far and too fast (which is called over pronation). As the arch drops, it pulls on the tendon that attaches the tibialis posterior muscle to the bone, placing increased strain on the muscle. With 1500 footfalls per mile, the repetitive stress leads to breakdown. Tibialis posterior pain can be felt just to the inside and behind of the ridge made up by your tibia on the front of your leg.

The tibialis anterior muscle pulls your foot and toes upwards (called dorsi-flexion). At heel strike (with 3 to 5 times body weight), the forefoot and toes want to slap down hard, which would lead to increased pronation. This tendency is reduced by quick contraction of the tibialis anterior pulling up on the forefoot and toes. Tight heel cords (calf muscles) will add to the situation. Tibialis anterior pain can be felt to the front and outside of the same tibial ridge.

Stress fractures of the tibia occur after "training through the pain" of shin splints for some time. Stress fractures are fractures or breaks that do not pass completely through the bone. This pain will be felt by touching directly on the tibial ridge in front of the lower leg. These may or may not show up on x-rays, and will show up on a special imaging test called a bone scan. Also, if the strain to the tibialis anterior or posterior muscle is severe enough, pain directly on the tibia itself will be present, even in the absence of stress fractures.

Compartment syndrome is a little more complex. The muscles of your lower leg are separated into four compartments by connective tissue called fascia. This fascia needs to have the ability to expand as the muscles of the lower leg become engorged with blood while running. Without enough room to expand, the muscles begin to choke off their own blood supply and impede their oxygen supply. This creates a condition known as ischemia, which is painful and grows worse as we continue to run. Continued training can cause tissue damage, making this a more serious condition than those mentioned above. Pain associated with compartment syndrome comes on after enough training occurs to create this ischemic condition, and therefore varies with the extent of compartment tightness. This pain should subside as the engorgement of the muscles subsides, and therefore should not be present with just walking.

Preventing Shin Splints

1. Shin splints are usually brought on by training errors, usually too much (distance/intensity) too soon. Increasing your weekly mileage over 10% a week, or increasing your long slow run more than 10% may predispose your to injury. Increases in intensity, such as track workouts and hill running, without a proper base will also predispose you to injury.

2. Improper footwear may also be the culprit, particularly if the shin splints occur on both sides. Shoes that allow excessive pronation (collapsing of the arch) will place added stress on the muscles responsible for supporting the arch or prevent the forefoot from slapping down too hard at heel strike. Harder training surfaces will increase these forces on the feet. Such a change may occur while on vacation. Packed dirt is the most ideal surface, pavement would be approximately twice as hard, and concrete is 33% harder than pavement.

3. The forefoot slapping phenomenon can be diminished by stretching out a tight heel cord. Be sure to stretch the calf with the knee straight and bent 5-6 times throughout the day with one repetition for best results.

4. Post exercise massage of the area by running your fingers along the effected site, followed by ice massage for eight minutes, three times a day will help reduce inflammation.

5. Cross training using an elliptical trainer at the gym will allow you to maintain your aerobic capacity using the same muscles you run with, while taking the pounding stress off your injured tissues.

Dr. Ken Sheridan is a local road and trail runner who competes in a variety of local events, from marathons to duathlons. He practices at Active Care Chiropractic and Rehab in Golden. To ask him your injury questions, call 303-279-0320.