Sore shins or “shin splints” after running may be caused by one of three conditions: medial tibial stress syndrome, tibial stress fracture, or chronic exertional compartment syndrome 2. The underlying cause for each of these conditions is excessive force applied to the lower leg during repetitive activities. Normally, these muscles act to absorb shock as you run. However, when a large amount of force is transmitted to the muscles, they become fatigued and unable to function properly. In response to this stress, the muscles and tissues of the lower leg become painful, swollen and inflamed.

Medial Tibial Stress Syndrome

Medial stress syndrome is caused by inflammation of the tendons, muscles or connective tissue surrounding your tibia, or shin bone. Many runners complain of pain and tenderness along the inner side of the tibia. In some individuals, the pain resolves on its own after several minutes into the run, while in others, it worsens as the run continues or even persists after the workout is completed. Risk factors contributing to this condition include repetitive, high-impact activities such as:

• running
  
• flat feet
  
• high arches
  
• overpronation of the feet
  
• inappropriate shoes
  
• sudden increases in training

Tibial Stress Fracture

A stress fracture is a small crack in your bone. It is not known if tibial stress fractures are caused by medial stress syndrome, but some believe the two are related. Tibial stress fractures present with localized pain or tenderness of the tibia. It is usually suspected in individuals diagnosed with medial stress syndrome that does not improve over time. The underlying causes are similar to those of medial stress syndrome.

Chronic Exertional Compartment Syndrome

Chronic exertional compartment syndrome is a condition in which the muscles of the lower leg swell during exercise and cause restriction of blood flow to the muscles. This is a dangerous condition because the tissues can die from lack of oxygen. CECS is often misdiagnosed as medial tibial stress syndrome, as it tends to present with similar symptoms. The classic pattern of pain associated with CECS is a worsening of pain with activity and then a disappearance of pain after about 30 minutes of rest. In contrast to medial tibial stress syndrome, the pain is also accompanied by numbness, tingling, weakness and swelling. Although it is not known why CECS occurs in certain individuals, risk factors such as engaging in repetitive activities, over-training or increasing training too quickly seem to increase susceptibility to developing this condition.

Recommendations and Treatment

See your doctor if you experience shin pain during or after exercise. Most individuals with medial tibial stress syndrome and tibial stress fractures are able to recover with conservative treatment alone, consisting of rest or avoidance of the causative activity. Conservative therapy may be recommended for CECS, but it is typically ineffective. The mainstay of treatment for CECS is surgery, which involves releasing or removing the connective tissue surrounding the muscle.