The posterior tibial tendon (PTT) connects a calf muscle to the bones in the foot. This deep-seated tendon plays a substantial role in maintaining the mechanical integrity of the ankle and foot during movement. Understanding the location and function of the PTT offers insight into its importance for mobility and overall foot posture. The PTT is one of the largest tendons that crosses the ankle joint, contributing substantially to the body’s ability to stand and walk.
Precise Location and Path in the Lower Leg
The PTT begins as the extension of the tibialis posterior muscle, which originates in the deep posterior compartment of the lower leg. This muscle is anchored to the back surfaces of the tibia (shin bone), the fibula, and the interosseous membrane that spans between them. The tendon then descends toward the ankle, traveling along the inner side of the leg.
It makes a sharp, nearly 90-degree turn immediately behind the medial malleolus, the prominent bony bump on the inside of the ankle. This turn is a high-stress area. After passing this point, the tendon fans out and extends across the bottom of the foot.
The PTT has multiple insertion points, allowing it to exert force across several bones for foot stabilization. Its main attachment is to the navicular bone, located on the inner side of the arch. It also sends smaller slips of tendon to the plantar surfaces of the cuneiform bones, the cuboid, and the bases of the second, third, and fourth metatarsals. This widespread attachment pattern explains the tendon’s broad stabilizing influence on the foot structure.
Essential Role in Foot Biomechanics
The primary mechanical function of the PTT is to provide dynamic support for the medial longitudinal arch, the main arch of the foot. It acts like a suspension cable, preventing the arch from collapsing under the weight of the body during standing and walking. This support is particularly noticeable during the midstance phase of the gait cycle, where the foot must be rigid for pushing off the ground.
The PTT is also responsible for foot inversion, the motion of turning the sole of the foot inward. By pulling the foot inward and slightly downward, the tendon contributes to the locking mechanism that makes the foot a stiff lever for propulsion. Without the proper function of this tendon, the foot loses stability, leading to an altered walking pattern. The force it generates helps to counteract the natural tendency of the foot to roll inward, a motion called pronation, which is necessary for shock absorption.
Understanding Posterior Tibial Tendon Dysfunction
When the PTT is compromised, Posterior Tibial Tendon Dysfunction (PTTD) occurs, which is the most common cause of adult-acquired flatfoot deformity. This dysfunction usually arises from chronic overuse, leading to a progressive breakdown of the tendon fibers. Risk factors such as advanced age, obesity, diabetes, and hypertension contribute to the tendon’s degeneration and failure.
Initial symptoms of PTTD include pain and swelling along the tendon, particularly on the inner ankle just behind the medial malleolus. As the tendon weakens and loses its ability to support the arch, the foot begins to flatten and the heel rolls outward. Patients often experience difficulty performing a single-leg heel raise, unable to stand on their toes on the affected foot due to weakness and pain.
As the condition advances, the collapse of the arch becomes more pronounced, causing the foot to look visibly flatter. At this later stage, pain may migrate from the inner ankle to the outside of the foot, below the ankle bone. This shift occurs because the bones on the outside of the foot begin to bump against each other due to severe misalignment. If left unmanaged, the progressive deformity can lead to secondary issues like arthritis in the foot and ankle joints.
Management and Recovery Approaches
Treatment for PTTD typically begins with conservative methods aimed at reducing pain and inflammation and restoring the tendon’s function. Early-stage management involves rest, applying ice to the affected area, and using non-steroidal anti-inflammatory drugs (NSAIDs) to alleviate discomfort. Activity modification is also recommended, substituting high-impact exercises like running with low-impact activities such as swimming or cycling.
A primary component of conservative care is the use of supportive devices to control the foot’s mechanics and reduce strain on the tendon. Custom-molded orthotics are prescribed to support the arch and prevent the foot from collapsing. In some cases, a walking boot or a specialized ankle-foot orthosis (AFO) may be used for immobilization to allow the tendon to rest and heal.
Physical therapy focuses on strengthening the PTT and other surrounding muscles, often through exercises like heel raises and calf stretches. If conservative treatments fail after several months, or if the deformity is severe, surgical intervention may be considered. Surgical options can range from debridement and repair of the tendon to more complex procedures like tendon transfers or bone-cutting procedures (osteotomies) to realign the foot structure.