Shin splints or medial tibial stress syndrome (MTSS) is defined by the American Academy of Orthopedic Surgeons as pain along the inner edge of the tibia. Shin splints injuries are specifically located in the middle to lower thirds of the medial side of the tibia. They are common injuries in athletes and military recruits who engage in running sports or other forms of physical activity, including running and jumping. The pain associated with shin splints is caused from a disruption of strong fibers that connect the muscle through the connective tissue covering of the tibia where it inserts into the bone. With repetitive stress, the impact forces fatigue the muscle and create recurrent tibial bending or bowing. The impact is made worse by running uphill, downhill, on uneven terrain, on hard surfaces or improper footwear.
The hypothesis of the development of the syndrome is that the body adapts to loading stresses to the tibia which is exacerbated by pulling the muscle away from the bone. Shin splints can be attributed to overloading the lower leg due to biomechanical irregularities and an increase in stress exerted on the tibia. A sudden increase in intensity or frequency in activity level fatigues the muscles, hindering proper shock absorption and forcing the tibia to absorb most of that shock. Also muscle imbalances, including weak core muscles, inflexibility and tightness of lower leg muscles can increase the possibility of shin splints. The most likely cause is repeated trauma to the connective muscle tissue surrounding the tibia. While the exact cause is unknown, factors that are associated with the development of MTSS include: increased rotation of the hip, prior use of orthotics, previous history of MTSS, increased BMI, misaligned foot bones, excessively tight calf muscles engaging the shin muscle in excessive amounts of muscle activity, undertaking high-impact exercises on hard, noncompliant surfaces (ex: running on asphalt or concrete), smoking and low fitness levels. A study showed that the position of the ankle joint upon movement was the most significant factor to contribute to the onset of MTSS. This abnormal movement causes muscles to fatigue more quickly and they're unable to absorb any shock from the foot hitting the ground.
Treatment for shin splints is not always successful because the exact cause of shin splints is still unknown. MTSS should be treated by restoring proper biomechanics and alignment to the foot and lower extremity through massage and adjustments. The primary objective of treatment should be to enhance shock absorption to the lower extremity. It is important to significantly reduce any pain or swelling before returning to activity and to decrease the activity level if any pain returns. Individuals should consider running on other surfaces besides asphalt, such as grass, to decrease the amount of force the lower leg must absorb. Orthotics and insoles help to offset biomechanical irregularities. Surgery is only performed in extreme cases where more conservative options have been tried for at least a year. However, surgery does not guarantee 100% recovery.
References
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Newman P, Witchalls J, Waddington G, Adams R. Risk factors associated with medial tibial stress syndrome in runners: a systematic review and meta-analysis. OA J Sports Med. 2013; 4: 1-14.
Yuksel O, Ozgurbuz C, Ergun M, Islegen C, Taskiran E, Denerel N, Ertat A. Inversion/eversion strength dysbalance in patients with medial tibial stress syndrome. J Sport Med. 2011; 10: 737-742.
Krenner B. Case report: comprehensive management of medial tibial stress syndrome. J Chiro Med. 2002; 1(3): 122-124.