A tendon is a strong, cord-like structure composed of collagen fibers that connects muscle tissue to bone. These structures transmit the force generated by muscle contraction, allowing for movement across a joint. The lower leg supports the body’s weight and places tremendous mechanical stress on its tendons during activities like walking, running, and jumping. This high-load environment makes the lower leg tendons particularly susceptible to injury from both sudden trauma and chronic overuse.
The Major Tendons and Their Functions
The Achilles tendon, located at the back of the ankle, is the largest and thickest tendon in the human body. It attaches the calf muscles to the heel bone and is responsible for plantar flexion, the downward pointing motion of the foot that creates the propulsive force for walking. This tendon can withstand tensile loads several times a person’s body weight during running.
The posterior tibial tendon is located on the medial side of the ankle, attaching to bones on the underside of the foot. Its primary function is to support the medial longitudinal arch of the foot and provide inversion, the movement that turns the sole of the foot inward. It plays a stabilization role fundamental to proper foot mechanics during gait.
Along the lateral side of the ankle run the two peroneal tendons (peroneus longus and peroneus brevis), which originate from the fibula. These tendons perform eversion, turning the sole of the foot outward, and provide dynamic lateral stability to the ankle joint. They counterbalance the inverting action of the posterior tibial tendon, protecting the ankle from excessive rolling.
The anterior tibial tendon runs down the front of the leg and attaches to the midfoot. This tendon is responsible for dorsiflexion, the action of lifting the foot toward the shin. Dorsiflexion is necessary to clear the toes off the ground during the swing phase of walking.
Understanding Common Tendon Pathologies
The most common lower leg tendon injury is tendinopathy, a chronic condition characterized by degeneration rather than simple inflammation. This process involves the disorganization of the tendon’s collagen fibers, a proliferation of cells, and the formation of new, abnormal blood vessels within the tissue. Tendinopathy occurs when the mechanical stress placed on the tendon exceeds its capacity to adapt and repair.
Achilles tendinopathy typically presents as a dull ache and stiffness, often worse in the morning or after activity, and commonly affects the mid-portion of the tendon. Acute injuries like an Achilles tendon rupture are sudden events that usually happen during forceful, eccentric movements such as sprinting or jumping. Patients often describe hearing a loud “pop” and feeling as though they were kicked in the back of the leg.
The posterior tibial tendon is frequently affected by Posterior Tibial Tendon Dysfunction (PTTD), which can lead to adult-acquired flatfoot deformity. The condition progresses through stages, beginning with pain and swelling, then advancing to a flexible flatfoot deformity as the tendon weakens and fails to support the arch. If left untreated, the deformity can become rigid, leading to significant arthritic changes in the foot and ankle joints.
Biomechanical factors, such as excessive foot pronation, create a twisting force on the Achilles and posterior tibial tendons during gait. Systemic conditions like uncontrolled diabetes and obesity increase risk by leading to changes in tendon tissue composition, reducing its strength and elasticity. Furthermore, certain medications, such as fluoroquinolone antibiotics, are known to increase the risk of tendon damage, particularly in the Achilles tendon.
Clinical Approach to Diagnosis and Recovery
The clinical diagnosis of a lower leg tendon injury begins with a thorough physical examination, which includes specific tests to assess tendon integrity and function. For instance, an acute Achilles rupture is typically identified using the Thompson test, where a positive result is the absence of the expected ankle plantar flexion when the calf muscle is squeezed. For PTTD, the single-leg heel raise test is routinely used, as the inability to lift the heel fully often indicates a functional failure of the arch-supporting tendon.
Following the initial physical assessment, medical imaging is often utilized to confirm the diagnosis and determine the extent of the damage. High-resolution ultrasound is frequently the preferred first-line imaging modality because it is excellent for visualizing the tendon structure in real-time, allowing for the detection of tears, thickening, and neovascularization associated with tendinopathy. While Magnetic Resonance Imaging (MRI) is considered the gold standard for soft tissue, it is often reserved for complex cases or surgical planning.
Conservative Management
Conservative management is the initial approach for most tendinopathies and partial tears, beginning with the modification of activity and the use of over-the-counter anti-inflammatories to manage pain. The cornerstone of physical therapy for chronic tendinopathy is the use of therapeutic loading exercises, specifically eccentric training, where the muscle-tendon unit is lengthened under tension. This targeted loading stimulates the tendon cells to remodel the collagen structure, improving the tendon’s tensile strength and overall load capacity.
Other non-surgical treatments include prescription orthotics or bracing to mechanically support the arch and reduce strain on the tendon, particularly in early-stage PTTD.
Surgical Intervention
Surgical intervention is generally reserved for cases involving a complete Achilles tendon rupture, advanced stages of PTTD where the foot deformity is rigid, or when a patient’s symptoms fail to improve after an extensive course of conservative therapy. The recovery timeline following surgical repair of a complete rupture typically involves a lengthy period of immobilization followed by months of rehabilitation to regain full strength and function.