Posterior Tibial Tendonitis is an injury affecting a primary stabilizing structure in the foot and ankle. The posterior tibial tendon begins as a muscle deep in the calf and runs down the inside of the lower leg. It wraps behind the prominent inner ankle bone (the medial malleolus) before attaching to bones in the midfoot, particularly the navicular bone. This position allows the tendon to perform two primary functions: supporting the arch of the foot and helping to turn the foot inward (inversion). When the tendon becomes damaged, inflamed, or degenerates, the resulting condition (Posterior Tibial Tendonitis or Dysfunction) compromises the foot’s ability to maintain its proper shape.
Repetitive Strain and Activity Errors
The most common cause of posterior tibial tendon damage is repetitive microtrauma over time. While the tendon is designed to handle stress, mechanical load exceeding its capacity for self-repair leads to tiny tears within the fibers. These cumulative injuries occur frequently in individuals engaging in high-impact activities that strain the arch and ankle. Sports involving running, jumping, or sudden side-to-side movements, such as basketball, soccer, and tennis, often cause this repetitive overloading.
A sudden and significant increase in the volume or intensity of physical activity can also overwhelm the tendon. Rapidly increasing running mileage or abruptly changing training surfaces introduces excessive force before the tendon can adapt. Poor biomechanics or athletic technique, such as an abnormal walking or running gait, further contributes to the problem. For example, running on a banked road surface forces the foot into an unnatural position, increasing the tension required for stabilization. Without adequate rest and recovery periods, the inflammation and degeneration progress, leading to chronic tendon failure.
Structural Issues in the Foot and Ankle
Underlying anatomical characteristics of the foot often predispose the tendon to failure. A primary biomechanical risk factor is hyperpronation, defined as the excessive inward rolling of the foot during walking or running. This instability forces the posterior tibial tendon to work harder and longer than normal to prevent the arch from collapsing. This constant tension ultimately causes chronic strain and elongation of the tendon fibers.
Sustained overwork of the tendon is associated with the progression of acquired adult flatfoot deformity (progressive collapsing foot deformity). As the tendon weakens and stretches, it loses its ability to dynamically support the arch, causing the foot to gradually flatten. Existing structural imbalances, such as inherited flexible flatfoot or generalized joint hypermobility, exacerbate this issue. These pre-existing conditions keep the tendon constantly strained, making it vulnerable to microtraumas from normal daily weight-bearing activities.
Systemic Risk Factors
Internal and lifestyle factors can compromise the tendon’s intrinsic strength and ability to heal, making it susceptible to injury. Advanced age is a factor, as natural degenerative changes weaken the tendon structure and diminish its blood supply, reducing its resilience and repair capacity. The position of the tendon around the medial malleolus is already known to be a hypovascular area, and decreased circulation further compounds this vulnerability.
Obesity places an increased load on the foot and ankle, stretching the posterior tibial tendon with every step. This higher mechanical force accelerates the degenerative process. Certain underlying medical conditions, including diabetes, hypertension, and inflammatory diseases like rheumatoid arthritis, directly compromise tendon health throughout the body. These systemic issues impair circulation, interfere with cellular healing mechanisms, and increase the likelihood of chronic inflammation and structural failure.