Previously it was thought the cause of MTSS involved underlying inflammation (periostitis) of the connective tissue that surrounds shin bone (tibia) due to tibial strain when under a load.
However, more recently new evidence indicates that there is a variety of causes including; tendinopathy, and dysfunction of the tendons and muscles that run behind the shin bone. (Tibialis posterior, Tibialis anterior, and Soleus muscles).
These have been shown to alter the load going through the tibia and as repeated loading occurs chronic, repetitive loads cause abnormal strain and bending of the tibia.
MTSS is also associated with biomechanical abnormalities and alignment of the knees (especially genu varus or valgus), legs (tibial torsion, femoral anteversion) and feet (foot arch abnormalities). Leg-length differences and reduced ankle movement and motion of the rearfoot.
Inflexibility and muscle tightness, especially tightness of the triceps surae (gastrocnemius, soleus, and plantaris muscles), is commonly associated with MTSS.