(Medial Tibial Stress Syndrome)
Shin splints is a general term used to describe pain in the front of the shin or tibia bone. This pain can be caused by damage (tiny cracks) to the tibia bone itself, tears in the tibialis anterior muscle, or tears along the tibialis anterior tendon where it attaches to the tibia. It is also referred to as Anterior Compartment Syndrome or Medial Tibial Stress Syndrome, depending on the location of the pain. This condition is often caused by stress to the tibia and surrounding muscles due to an increase in athletic training or demanding training programs (i.e. marathon runners).
Although "shin splints" usually refers to pain that occurs at the outer, front part of the lower leg (anterolateral shin splints), it less commonly refers to pain at the back, inside of the lower leg (called posteromedial shin splints). Both types are painful, with pain occurring anywhere from just below the knee all the way to the ankle, and can take a long time to heal without proper treatment.
The most common cause of shin splints is continued, repeated stress to the tibialis anterior muscle and tendon, the extensor digitorum longus muscle, the extensor hallucis longus, the tibialis posterior muscle and tendon, and the soleus muscle as well as the tissue around the muscles (deep crural fascia) attached to the tibia. Excess wear and stretching of these tendons and muscles can occur with repeated stress or jarring of the tibial bone. In addition, when the muscles swell they put pressure on the fascia which causes more pain. Without an appropriate amount of recovery time or proper conditioning these muscles, the deep crural fascia, and the tibial tendons can become stressed and/or torn to the point of inflammation.
Due to the cause, shin splints are considered a repetitive or cumulative stress injury and are common among runners, gymnasts, dancers and other sports that involve high impact on the foot and lower leg. Approximately 10-15% of all running injuries are attributed to shin splints.
Anterolateral (Anterior) Shin Splints
Anterolateral shin splints affect the tibialis anterior muscle in the outer, front portion of the lower leg. This condition can be the result of a natural imbalance in the size of opposing muscles. Shin muscles pull the foot up, whereas the large and powerful gastrocnemius muscles in the calf pull the foot down when the heel strikes the ground. An imbalance can cause the heel to hit the ground improperly causing excess jarring of the tibia and surrounding muscles.
Anterolateral shin splints will cause pain in the front and outside of the shin which can result from damage to the tibialis anterior muscle itself or the deep crural fascia. Initial pain is felt when the heel strikes the ground though eventually the pain just remains.
To allow this type of shin splint to heal, you should avoid activities that cause stress to the tibia and tibialis anterior muscles and do other kinds of exercise recommended by your doctor or physical therapist. Such exercises usually involve stretching the calf muscle, as tight calf muscles put a lot of pressure on the shin muscle and the anterior tibial tendon.
Posteromedial (Posterior) Shin Splints
Posteromedial shin splints affect the soleus muscle and the tibialis posterior muscles and pain appears in the interior (or medial bone) in the lower leg). These muscle groups are responsible for lifting the heel to support a runner's weight on the ball portion of the foot when running.
Posteromedial shin splints (also called Medial Tibial Stress Syndrome or MTSS) are often caused by running on a sloped track or other non-level running surface or wearing improper shoes that do not protect the foot from rolling (pronation).
Pain begins on the inside, back of the lower leg (usually within 7 inches above the ankles), but will worsen and continue to rise up the leg. Initially, only tendons will become inflamed, but if running continues, the muscles themselves could become affected. In the most severe cases, the tibialis posterior tendon could become detached from the bone - a painful occurrence that causes bleeding and excessive inflammation.
To allow a posteromedial shin splint to heal, the running must temporarily stop and other therapeutic exercises recommended by your doctor or physical therapist can be done. Special shoes may be prescribed during the healing phase, and it may be advisable to look into potential problems with over-pronation of the feet (flat feet). This can often be solved by wearing shoes that prevent pronation and/or avoid running on side slopes.
Lower Leg Stress Fractures
Stress fractures (or bone trauma) in the tibia and fibula are sometimes related to anterolateral shin splints. Due to excess jarring of the bone, microscopic cracks may form in one or both of the lower leg bones. Avoiding the activity or sport that caused the cracks is advised to allow the bones to rest and repair. Without allowing enough time to recover, these cracks can become a fracture which is very painful.
Shin Splint Causes
Shin splints may be caused by:
- Over training or new runners doing too much too soon.
- Running on side slopes (ie. banked tracks).
- Tight gastrocnemius muscles, exerting extra force on shin muscles.
- A sudden change from soft to hard running surfaces.
- Poor or worn out footwear that doesn't reduce the impact or support your arch when running.
- Excessive uphill running.
- Other conditions in the tibial area such as tendinitis, periostitis, stress fractures and compartment syndrome can all lead to shin splints.
- Not warming up or stretching properly.
- Poor running mechanics which could include; heavy forward lean, excessive weight on the ball of the foot, running with toes pointed outward, landing too far back on the heels causing the foot to flop down, and over-pronation. Pronation (flat feet or pes planus) is the most likely to be the cause.
Shin Splint Symptoms
- Most often, shin spints cause pain in the front of the outer leg below the knee.
- Swelling and redness around the tibia may occur.
- Pain or discomfort in the beginning of the workout that lessens and then reappears towards the end of the training session.
- Increased pain when running (especially on hard surfaces), jumping, running downhill, or climbing uphill.
- The pain is usually at it worst the morning after exercising and when the foot is in plantar flexion (toes are bent downward).
- Tight and inflexible calf muscles due to scar tissue build up and lack of proper stretching.
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