What is the Tibialis Posterior?

The tibialis posterior (or posterior tibialis) is a vital muscle in the lower leg, playing a crucial role in stabilizing the foot and ankle. It is instrumental in controlling the inward movement of the foot (inversion) and supporting the arch during walking or running. While is is quite hidden, it is one of the more important muscles of the leg.

Where is the Tibialis Posterior?

Located deep in the calf, behind the shin bone, the tibialis posterior is part of the deep posterior compartment of the leg along with the flexor digitorum longus, flexor hallucis longus., and popliteus muscles.

It lies between the interosseus membrane and the soleus muscle. It is one of the key muscles responsible for foot and ankle stability. The tibialis posterior functions to control the movements of the foot, aiding in inversion (turning the sole of the foot inward) and plantar flexion (pointing the toes downward).

Posterior Tibialis Function

The primary function of the tibialis posterior muscle is to control overpronation during the midstance phase of walking. This action of posterior tibialis is crucial for avoiding excessive pressure on the foot's medial side and for evenly distributing body weight across the metatarsal heads.

The posterior tibialis action is mainly to invert the foot, while also playing a supporting role in the plantar flexion of the foot. A weakened or non-functional tibialis posterior muscle can lead to a pronated foot condition, characterized by a severe and valgus deformity.

This condition needs to be addressed within a few months of its onset to prevent lasting damage to the foot's structure.

Anatomy of the Posterior Tibialis Muscle

Tibialis Posterior Origin and Insertion

The tibialis posterior muscle origin is from the interosseous membrane, the tibia, and the fibula bones of the lower leg. The tendon goes down the leg, behind the medial malleolus (anke) and then the insertion tibialis posterior is into the all five tarsal bones of the foot, including the navicular, cuneiform, and the bases of the second to fourth metatarsal bones.

Origin of posterior tibialis:

• The muscle origin is at the proximal, posterior shafts of the tibia and fibula and the interosseus membrane.

Insertion of posterior tibialis:

• The tibialis posterior insertion is at all five tarsal bones and the bases of the second through fourth metatarsals.

Due to its deep location, it is not visible like the more superficial calf muscles, but its functionality is crucial in activities such as walking, running, and jumping.

Posterior Tibialis Tendon

The tibialis posterior tendon is a critical component in the lower leg’s musculoskeletal structure, playing a vital role in foot and ankle function. This tendon is the extension of the tibialis posterior muscle, which is deeply situated in the calf, and it follows a unique path through the ankle to the foot. Tibialis posterior tendinopathy can occur from muscle overuse or trauma.

Path of the Posterior Tibialis Tendon:

• Origin: The tendon originates from the tibialis posterior muscle, which is nestled between the interosseous membrane and the soleus muscle in the calf.

• Course: After stemming from the muscle, the tendon descends along the inner side of the leg.

• Medial Malleolus: It travels behind the medial malleolus, which is the bony prominence on the inner aspect of the ankle.

• Insertion: The tendon then fans out and attaches to various bones in the foot, including the navicular, cuneiform, and the bases of the second to fourth metatarsal bones.

The tendon's primary function is to support the arch of the foot and aid in movements like inversion (turning the foot inward) and plantar flexion (pointing the toes down). It contrasts with the tibialis anterior tendon, which is positioned in the front of the leg and facilitates opposite movements like dorsiflexion and eversion.

Tibialis Posterior Action

• Invert the foot

• Plantar flex the ankle

The tibialis posterior supports the arch of the foot and plays a critical role in the stability and alignment of the lower leg. It also assists in plantar flexion at the ankle joint, a motion crucial for pushing off the ground during walking or running.

Tibialis Posterior Synergists

• Flexor Digitorum Longus

  • Assists in foot inversion and supports the arch alongside the Tibialis Posterior.

• Flexor Hallucis Longus

  • Works in tandem with the Tibialis Posterior to control foot movements, especially during the toe-off phase in walking or running.

• Gastrocnemius and Soleus (Calf Muscles)

  • These muscles complement the Tibialis Posterior in plantar flexion at the ankle, crucial for propulsion in gait.

• Plantaris Muscle

  • Although small, it aids in plantar flexion and inversion of the foot, supporting the actions of Tibialis Posterior.

• Popliteus Muscle

  • Stabilizes the knee and assists in slight knee flexion, facilitating the Tibialis Posterior's role in lower leg stability.

Tibialis Posterior Antagonists

• Peroneus Longus and Peroneus Brevis (Fibularis Muscles)

  • Responsible for foot eversion and ankle plantar flexion, counteracting the inversion action of the Tibialis Posterior.

• Tibialis Anterior

  • Primarily responsible for dorsiflexion and eversion of the foot, the tibialis anterior and posterior oppose one another in movement of the foot and ankle.

• Extensor Digitorum Longus

  • Aids in foot dorsiflexion and toe extension, balancing the plantar flexion and toe flexion role of the Tibialis Posterior.

• Extensor Hallucis Longus

  • Works in opposition to the Tibialis Posterior by extending the big toe and aiding in dorsiflexion of the foot.

• Peroneus Tertius

  • Assists in dorsiflexion and eversion of the foot, providing a counterbalance to the Tibialis Posterior's actions.

Common Issues with the Tibialis Posterior Muscle

The tibialis posterior muscle can be prone to overuse and injury, particularly in athletes or individuals with improper foot biomechanics. Common issues include:

• Tibialis Posterior Tendinitis: This condition involves inflammation or damage to the tibialis posterior tendon, often resulting from repetitive stress or overuse. It can lead to pain and swelling in the inner side of the ankle and an eventual collapse of the foot's arch if not addressed.

• Posterior Tibial Tendon Dysfunction (PTTD): This is a progressive condition where the tibialis posterior tendon becomes weakened, leading to flatfoot deformity. Early stages may present with pain and swelling along the course of the tendon, while advanced stages can lead to significant medial longitudinal arch collapse and ankle instability.

• Shin Splints: In some cases, shin splints or medial tibial stress syndrome can be associated with dysfunction in the tibialis posterior muscle.

Proper function of the tibialis posterior is essential for maintaining foot structure and function, particularly the arch. Issues with this muscle can lead to a range of foot and ankle problems, affecting mobility and quality of life.

Posterior Tibialis During the Running Gait

The posterior tibialis muscle plays a significant role in the biomechanics of running, influencing the stability and efficiency of the running gait. Understanding its function during running is crucial for both performance enhancement and injury prevention.

Stance Phase of Running Gait

During the stance phase of running, when the foot is in contact with the ground, the posterior tibialis muscle is actively engaged. Its primary role in this phase is to provide stability to the foot and ankle. As the foot strikes the ground, the tibialis posterior helps control pronation – the natural inward roll of the foot. This control is vital in maintaining the structural integrity of the foot's arch.

Eccentric Contraction for Shock Absorption

When the foot initially contacts the ground, the tibialis posterior works eccentrically (lengthening under tension) to absorb the impact. This eccentric contraction helps in decelerating pronation and stabilizing the foot, preparing it for the push-off phase. Proper functioning of the posterior tibialis during this phase is key in reducing the risk of overpronation-related injuries, such as medial tibial stress syndrome or plantar fasciitis.

Support During Mid-Stance and Push-Off

As the gait cycle progresses to mid-stance, the posterior tibialis continues to support the foot's arch, providing a stable platform for the body's weight. During the push-off phase, it works in concert with other calf muscles to facilitate plantar flexion – the action necessary to propel the body forward. This phase demands a strong and resilient posterior tibialis muscle to effectively transfer energy and power the running motion.

Potential Issues and Overuse

Given its critical role in running, the posterior tibialis is susceptible to overuse, particularly in long-distance runners or those with biomechanical irregularities. Inadequate support or excessive strain can lead to issues like tendinopathy or tendon dysfunction, manifesting as pain along the inner ankle and lower leg. Runners may experience discomfort or fatigue in the medial foot and ankle area, particularly during long runs or on uneven terrain.

Importance in Gait Efficiency

An efficient and injury-free running gait relies heavily on the health and function of the posterior tibialis muscle. Weakness or dysfunction in this muscle can compromise gait efficiency, leading to compensatory movements and increased risk of lower extremity injuries. Runners are advised to incorporate exercises that strengthen and stretch the posterior tibialis muscle into their training routines to ensure its optimal performance and resilience.

In conclusion, the posterior tibialis muscle is an unsung hero in the running gait, playing a crucial role in foot stabilization, shock absorption, and propulsion. A strong and healthy posterior tibialis not only enhances running performance but also significantly reduces the risk of injuries associated with running.

Tibialis Posterior and Common Lower Leg Conditions

The Tibialis Posterior muscle, due to its critical role in foot and ankle stability, is intimately connected with several lower leg conditions. Understanding its involvement in these conditions is key for effective prevention and treatment strategies.

Medial Tibial Stress Syndrome (MTSS)

Medial Tibial Stress Syndrome, commonly known as 'posterior tibialis shin splints,' is a condition characterized by pain along the inner edge of the tibia. The Tibialis Posterior muscle plays a pivotal role in the development of MTSS.

• Mechanism: Repetitive stress on the Tibialis Posterior can lead to MTSS. The muscle's overuse, especially in activities like running or jumping, results in increased traction on its attachment to the tibia. This repetitive pulling can cause inflammation and pain in the area.

• Involvement: The muscle's role in controlling foot pronation and supporting the arch means that any dysfunction can lead to excessive stress on the tibia, contributing to or exacerbating MTSS.

Plantar Fasciitis

Plantar Fasciitis is a common cause of heel pain, often felt during the first steps in the morning or after long periods of rest.

• Link: The Tibialis Posterior helps maintain the arch of the foot. Dysfunction or weakness in this muscle can lead to excessive flattening (pronation) of the foot, putting strain on the plantar fascia.

• Consequence: Chronic stress on the plantar fascia due to poor mechanics of the foot and ankle can result in micro-tears and inflammation, characteristic of plantar fasciitis.

Tarsal Tunnel Syndrome

Tarsal Tunnel Syndrome arises from the compression of the tibial nerve within the tarsal tunnel.

• Link: This nerve descends through the lower leg's posterior compartment, closely following the path of the tibialis posterior tendon behind the medial malleolus and into the tarsal tunnel. This area is notably confined, and any increase in pressure can impact both the tendons and the tibial nerve.

• Consequence: Mimicking carpal tunnel syndrome in the wrist, Tarsal Tunnel Syndrome symptoms include burning sensations, numbness, tingling, and muscle weakness on the plantar side of the foot and toes.

Common Factors and Prevention

• Biomechanical Issues: In all these conditions, improper biomechanics, often stemming from Tibialis Posterior dysfunction, is a key factor. This includes overpronation, flat feet, or an altered gait pattern.

• Preventive Measures: Strengthening and stretching the Tibialis Posterior muscle, along with addressing any biomechanical imbalances, can significantly reduce the risk of these conditions. This could include specific exercises, orthotic support, and modifying training routines.

Treatment Considerations

• Holistic Approach: Addressing the health and function of the Tibialis Posterior should be part of the treatment strategy for these conditions. Nonsurgical treatment may involve physical therapy, targeted exercises, along with acupuncture or dry needling to alleviate muscle tension and improve function.

  • Learn more about Acupuncture for Tibialis Posterior Pain

  • Learn more about Dry Needling for Tibialis Posterior Trigger Points

• Personalized Rehabilitation: Each condition, while linked to the Tibialis Posterior, requires a tailored rehabilitation approach based on the individual's specific symptoms and underlying causes.

In summary, the Tibialis Posterior muscle, by virtue of its location and function, plays a significant role in the onset and progression of Medial Tibial Stress Syndrome, Plantar Fasciitis, and Shin Splints. A comprehensive understanding and targeted approach to this muscle's health are crucial in the effective management and prevention of these common lower leg conditions.

Over to you

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Sources:

• Travell, J. G., Simons, D. G. (1993). Myofascial pain and dysfunction: The trigger point manual. London: Lippincott Williams & Wilkins.

• Biel, A., & Dorn, R. (2010). Trail guide to the body: A hands-on guide to locating muscles, bones and more. Boulder, CO: Books of Dicovery.

• Janda, Vladimír. “Muscle Function Testing.” (1983).

• Corcoran NM, Varacallo M. Anatomy, Bony Pelvis and Lower Limb: Tibialis Posterior Muscle. [Updated 2023 Aug 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK539913/

• Rhim, H. C., Dhawan, R., Gureck, A. E., Lieberman, D. E., Nolan, D. C., Elshafey, R., & Tenforde, A. S. (2022). Characteristics and Future Direction of Tibialis Posterior Tendinopathy Research: A Scoping Review. Medicina (Kaunas, Lithuania), 58(12), 1858. https://doi.org/10.3390/medicina58121858

• Willegger, M., Seyidova, N., Schuh, R. et al. The tibialis posterior tendon footprint: an anatomical dissection study. J Foot Ankle Res 13, 25 (2020). https://doi.org/10.1186/s13047-020-00392-1

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