Lower extremity overuse disorders are painful and can be debilitating. In this article, we look at the function of the posterior tibialis in lower extremity biomechanics and pain conditions. Specifically, we look at a condition called posterior tibial tendon dysfunction. The posterior tibialis plays a crucial role in many foot disorders, but can be overlooked because the muscle is not easily accessible to palpation.

Anatomy

Foot problems often result from dysfunctional biomechanics. Absorbing and distributing the load and ground reaction forces from walking or running puts a heavy demand on the lower extremity. One of the most important stabilizing muscles of the lower extremity is the posterior tibialis (PT), also called tibialis posterior. It lies deep within the posterior compartment of the leg and, as a result, is difficult to reach. It is the deepest of the posterior compartment muscles and originates from the interosseous membrane, posterolateral tibia, and posteromedial fibula (Image 1). Its distal attachment spans across the bottom surface of the foot and has branches that insert into most of the foot bones, including the second, third, and fourth metatarsals; intermediate and lateral cuneiforms; cuboid; and calcaneus (Image 2). 

The PT tendon is the largest and most anteriorly situated of the three tendons that course around the medial ankle and through the tarsal tunnel. There is a region of reduced vascularity where the tendon bends around the medial malleolus. This decreased blood supply makes the tendon prone to overuse injury. In addition, the PT changes its angle of pull from vertical to horizontal as it courses around the medial side of the ankle, causing increased friction on the tendon, which can play a role in degenerative changes. 

The other two tendons from the deep posterior compartment are the flexor hallucis longus and flexor digitorum longus. The flexor retinaculum holds these three tendons in place around the medial ankle. The flexor retinaculum also forms the roof of the tarsal tunnel, and the tendons share the narrow tunnel space with arteries, veins, and nerves. When damaged or dysfunctional, local inflammation of the PT tendon can also cause vascular and nerve compression (tarsal tunnel syndrome) in this region.

Biomechanics

The PT is the main inverter of the foot. However, the majority of load on the muscle-tendon unit occurs not from forceful inversion, but from eccentrically resisting eversion as an eccentric “brake” during the weight-bearing portion of the gait cycle. There is a complex pattern of movement involving the foot, ankle, and leg that occurs when we are walking and running. There are three main stages (or phases) of the gait cycle. The foot strikes the ground with the outside of the heel first (heel-strike phase). Then, the foot’s bottom surface makes contact with the ground (mid-stance phase), and we then push off with the medial side of the foot and big toe (push-off phase). 

As the individual moves through the mid-stance phase of the gait cycle, the leg moves over the planted foot in a diagonal direction. This diagonal plane movement produces a combination of dorsiflexion, eversion, and abduction of the foot called pronation. When an individual is too far onto the medial side of their foot during mid-stance phase, they are overpronating. 

The PT plays a primary role in resisting overpronation. Because the PT is a primary inverter of the foot, it resists the strong foot eversion during pronation through eccentric action of the muscle. It is this strong eccentric load that often leads to chronic overuse of the PT muscle-tendon unit. 

Another crucial function of the PT is its role as the primary dynamic stabilizer of the medial longitudinal arch. The longitudinal arch is created by the shape of the foot bones as well as the dynamic support from muscles and tendons (Image 3). It is critical for shock absorbency and propulsion of the body. When the PT is not functioning properly, the muscle becomes weak and the arch collapses. The collapsed arch is commonly referred to as flatfoot deformity, and dysfunction in the PT is the most common cause. Between 5 percent and 15 percent of people have flatfoot deformity, which would suggest that this condition is more common than many would think.¹

The plantar calcaneonavicular ligament (also called the spring ligament) is also an important support for the arch. When the PT is not functioning with its proper strength, the spring ligament must take on a much greater load in the arch. Overload on this ligament can lead to multiple biomechanical problems in the foot. In addition, excess body weight can overload the PT, as well as the spring ligament, and lead to a collapsed longitudinal arch. 

Loss of integrity in the arch structure can lead to numerous foot and lower extremity problems. Arch collapse is linked to disorders such as forefoot abduction, plantar fasciitis, stress fractures in the leg or foot, calcaneal or hallux valgus, and tarsal tunnel syndrome.² It is important to look at the role of the PT in these conditions because treatments may be aimed only at a local factor without taking into consideration the role of this muscle-tendon unit in the problem.

Muscle-Tendon Dysfunction

Chronic overload of the PT tendon can lead to damage, weakness, and inflammation of the tendon around the medial ankle, called posterior tibial tendon dysfunction (PTTD). Women appear to develop this condition more frequently than men, although it is not clear why.

Tendon degeneration and muscle weakness begin long before symptoms appear. The problem often becomes evident when the flat foot becomes apparent, along with foot or leg pain. It is not clear why the condition progresses so far before the symptoms are recognized. Small tears in the tendon can decrease its pulling strength, so it is likely there is a feedback loop between tendon fiber damage and decreased muscle stimulation. This combination can then lead to the eventual muscle weakness and collapsed longitudinal arch.

Once the arch begins to collapse, more permanent foot deformities may result. For example, calcaneal valgus frequently occurs along with the flatfoot deformity and PT weakness (Image 4). Calcaneal valgus is a postural distortion in which the distal end of the calcaneus tilts in a lateral direction. Once the foot collapses into this position, it is difficult to get the arch restored and back to a normal position. 

It is not just biomechanical stress that leads to the tendon weakness in PTTD. Systemic disorders such as Ehlers-Danlos syndrome routinely produce connective tissue weakness and may lead to tendon dysfunction and collapse of the arch. Other conditions such as lupus or rheumatoid arthritis may also lead to tendon dysfunction, although it is not clear why.³

Assessment and Evaluation

As noted earlier, PTTD can be a precursor to numerous foot problems. As a result, focus is often directed on the resulting problem without appropriate attention to the originating PT muscle-tendon dysfunction. Because medial ankle or plantar foot pain symptoms could be other conditions, PTTD can be underdiagnosed and mistaken for other foot disorders.⁴ Range-of-motion evaluations are not effective with PTTD due to the limited range of foot eversion (caused by the position of the distal fibula). Because there aren’t many signs or symptoms unique to PTTD, there are fewer options for assessing this condition. 

However, there are some indicators to look for. The most prominent sign of PTTD is the collapsed arch and flatfoot deformity. Arch collapse often leads to calcaneal valgus as well. If this postural dysfunction has been present for a while, there may also be pain on the lateral side of the ankle. Lateral ankle pain results from bony compression between the distal fibula and calcaneus due to excessive eversion of the foot.

Pain and visible or palpable inflammation over the medial side of the ankle may also be present. Sometimes increased temperature is palpable in this region if the inflammation is active. Keep in mind that there could be inflammatory reactions within the tendon that may not be evident due to the tendon’s depth in the tarsal tunnel. Pain may also be present on the bottom surface of the foot.

Overpronation in gait is another prominent indicator, and a flatfoot deformity frequently exists in conjunction with overpronation. A common method for identifying overpronation is looking at the wear pattern on the sole of the shoe. Excessive wear on the medial side of a shoe’s sole can be indicative of overpronation and PT weakness. Inability of the client to stand on their toes is another sign sometimes visible during physical examination, particularly standing on the affected side alone. It may be either pain or weakness that prevents a person from standing on their toes.

Treatment Strategies

Generally, the first treatment goal is to reduce any offending activities that are aggravating the PT. If there is a routine occupational or recreational activity, such as running or jumping, that appears to be a precursor, then those activities must be limited or stopped. At later treatment stages, some strengthening activities for the PT may be beneficial. However, additional strengthening is not the best solution early in the symptomatic stages, especially with activity that causes pain. Ankle braces, shoe inserts, and orthotics may also be used to help reduce biomechanical load and reduce stress on the muscle-tendon unit.

This condition results from tendon overuse and muscle overload, so massage can be helpful in reducing either the causative factors or resulting symptoms. It is not possible to fully stretch the PT, as the foot is blocked from going far enough into eversion to really stretch the muscle. As a result, the muscle never gets to lengthen as much as it ideally could. It is possible that this may lead to increased hypertonicity within the muscle and eventual tendon dysfunction. That gives a good rationale for massage treatment aimed at reducing muscular hypertonicity. Unfortunately, due to its location deep in the posterior compartment, it is difficult to access. However, there are some other options for treatment. 

One of the more effective ways to address the tibialis posterior is with the client in a side-lying position and the medial side of the treatment leg facing up. Working along the tibial border anterior to the gastrocnemius and soleus allows the practitioner to apply indirect pressure to the deep posterior compartment, which can effectively address the posterior tibialis. Slow stripping techniques with a small contact surface are applied along the tibial border (Image 5).

An even better treatment is achieved with an active engagement technique that increases the density of the muscle and makes it easier to treat. An active engagement technique can be applied using the same position described above, as long as the client’s foot can move through a full range of motion in dorsiflexion and plantar flexion. The client is instructed to keep a slow and rhythmic movement of dorsiflexion and plantar flexion. The practitioner applies short stripping techniques to the PT along the medial border of the tibia each time the client moves the foot into dorsiflexion. This technique is most effective if it is applied as the muscle elongates (the movement of dorsiflexion). 

One theory about the effectiveness of active engagement techniques is that the process of actively contracting the muscle while it is being worked helps encourage proper neurological signaling of the muscle and may simultaneously reduce some of the noxious sensory input that causes pain. The amount of pressure applied to the PT should be closely monitored with this technique. It is common for PT treatment to be uncomfortable and tender for the client with only a moderate amount of pressure. It’s not helpful to cause additional pain with treatment, so keep pressure levels adjusted accordingly.

Eventually, and once excessive hypertonicity in the muscle is reduced, it may be helpful to encourage strengthening and functional movement activities to restore proper biomechanical function and increase tendon conditioning. A beneficial strengthening exercise for the client is standing on their toes. Also helpful is pulling the foot into inversion against resistance, such as with an elastic resistance band.

In Sum

The PT is a key player in numerous foot and lower leg problems. In addition, biomechanical results from PT weakness, such as collapsed arches, can contribute to problems much further up the kinetic chain. Massage will not reduce the fallen arch, but is an important strategy in managing the condition and decreasing pain and chronic hypertonicity in the muscles. Your understanding of key biomechanical principles and function of the PT greatly benefit your client’s treatment when they face the challenges of this condition.

Notes

1. S. K.-K. Ling and T. H. Lui, “Posterior Tibial Tendon Dysfunction: An Overview,” Open Orthopaedics Journal 11, Suppl-4, M12 (2017): 714–23. https://doi.org/10.2174/1874325001711010714.

2. M. Guelfi et al., “Anatomy, Pathophysiology and Classification of Posterior Tibial Tendon Dysfunction,” European Review for Medical and Pharmacological Sciences 21, no. 1 (2017): 13–19.

3. K. Yao, T. X. Yang, and W. P. Yew, “Posterior Tibialis Tendon Dysfunction: Overview of Evaluation and Management,” Orthopedics 38, no. 6 (June 2015): 385–91. https://doi.org/10.3928/01477447-20150603-06.

4. B. Durrant, N. Chockalingam, and C. Morriss-Roberts, “Assessment and Diagnosis of Posterior Tibial Tendon Dysfunction: Do We Share the Same Opinions and Beliefs?,” Journal of the American Podiatric Medical Association 106, no. 1 (Jan-Feb 2016): 27–36. https://doi.org/10.7547/14-122.