One of the most common running injuries we treat in our clinic is shin splints or Medial Tibial Stress Syndrome (MTSS). Shin splints cause one in five athletes to stop running. In addition to running, engaging in soccer, rugby, basketball, volleyball, or any sport that involves running or jumping can cause shin splints.
Most people would describe the initial pain of shin splints as a dull ache along the inside of the the lower leg (tibia). Shin splint pain is often felt at the beginning of a run and then diminishes as the run continues, only to return near the end of the run. In this initial stage the pain from shin splints will often dissipate completely with rest. If the shin splints progress, the pain will often be present with both activity and rest. Once shin splints reach the stage of constant pain, a medical professional should be seen to determine if additional injuries are present (stress fractures or compression syndrome).
The exact location of shin splints is often hard to find, because it is usually more of a diffused pain in the soft tissue (fascia, tendon, muscle) rather than on the bone (tibia) itself.
Causes of Shin Splints
The most common cause of shin splints is repetitive motion. This is not surprising considering the force of impact of each runner’s stride. A runner’s shins are subject to two to three times the runner’s body weight on foot impact. This high level of force can easily overwhelm the shin muscles (dorsi flexors) if they are not strong.
Shin muscles are called dorsi flexors because of the motion they perform with contraction. On contraction the dorsi flexors pull the foot up towards your shins, this is what is referred to as dorsi flexion.
During running, the dorsi flexor muscles also control plantar flexion, through the process of eccentric contraction. Eccentric contraction occurs when a muscle elongates while under tension. Controlling plantar flexion of the foot is not an exclusively linear motion. As the foot strikes the ground it is subjected to both rotational forces (pronation and supination) and side to side motions.
Any type of muscle imbalance, or abnormal motion pattern in the ankle, knee or hip could cause increased stress on the dorsi flexors as they try to control motion. In other words, the dorsi flexors may be the site of the shin splints, but the root cause could be far from the location of symptoms. For example, we know that excessive pronation (flat feet) will increase the load placed on the dorsi flexors as they try to control plantar flexion. We also know that weak or imbalanced external hip rotators (gluteus muscles) will increase pronation of the foot. Though it may not be a direct connection, weak external hip rotators could be part of the development and continuation of shin splints.
When it comes to shin splints, it is important to address the problems in all potential problem areas as well as the symptomatic structures in order to identify the root cause of the problem.
In Part Two of Shin Splints we will cover: Differential Diagnosis (Stress Fractures and Compartment Syndrome).