The tibialis posterior muscle originates on the posterior aspect of the tibia and fibula and courses downward and into the inner ankle as a tendon.
It inserts, mainly in the tarsal scaphoid, but also sends expansions to the 1-2 wedge and to the base of the 2nd-3rd and 4th metatarsal.
This tendon, protected from rubbing against the bone by a sheath, has different functions:
- In unloading; it carries the foot into inversion and plantar flexion, inward and downward.
- In standing; it holds the internal arch of the foot when it supports the whole body weight; for this reason it can be said that this muscle is antipronator or pronation controller, besides being in charge of absorbing the impact against the ground.
- To help the take-off of the foot.
Dysfunction of the posterior tibial tendon
Due to its role in supporting the internal longitudinal arch (the bridge of the foot) or antipronator, tibialis posterior tendon dysfunction is one of the most common pathologies in runners.
In continuous running, the tendon is repeatedly stressed, resulting in tenosynovitis (fluid within the sheath) and tendinitis/tendinosis (acute inflammation or deterioration of the collagenous tissue of the tendon).
Outside the sporting arena, the incidence of posterior tibial tendon dysfunction is higher in women (3/1) from the 4th decade onwards, especially patients who are overweight and have a history of diabetes and circulatory disorders.
Posterior tibial tendon dysfunction is classified into 4 phases or stages:
- Asymptomatic.
- Tendinitis. Mild weakness.
- Tendinosis, partial tendon rupture, significant dysfunction: hyperpronation and abduction.
- Progresses rapidly. Great functional impotence with pain and stiffness.
It usually debuts with diffuse edema, hyperalgesia, sensation of weakness and gradual loss of the internal longitudinal arch.
The injury of this tendon maintained over time is one of the most important factors in the development of the so-called “adult acquired flatfoot”, because if the tendon is elongated or ruptured, the important function of supporting the internal longitudinal arch will be lost.
Functional tests in posterior tibial tendon dysfunction:
- Heel rising test on one or both legs.
- The loss of the plantar arch, the sinking of the bridge of the foot can also be observed.
- The “sign of too many toes” is positive if from a posterior view we see more than 3 toes. It is due to loss of function of the posterior tibial tendon and over solicitation of the flexor of the first toe and the common flexor of the toes.
Complementary diagnostic studies:
- X-rays, to evaluate structural changes such as flat feet or osteoarthritis.
- Ultrasound, to determine the state of the tendon.
- Nuclear magnetic resonance.
A differential diagnosis should also be made with diseases that may involve inflammation of this tendon, such as rheumatoid arthritis.
Treatment of the dysfunction of the posterior tibial tendon
The treatment of the dysfunction of the posterior tibial tendon will depend on the phase in which the injury is found.
In the first phase, orthopedic surgeons will start with conservative treatments that include a plantar support or personalized insole, made under a plaster cast and after a biomechanical study of the footprint. While the insoles are being made, a functional bandage will be applied to reduce the workload on the tendon.
On the other hand, and associated with plantar support, non-steroidal anti-inflammatory drugs are prescribed; subsequently, rehabilitation treatment will be continued with manual therapies, joint manipulations and anti-inflammatory physical methods, such as radiofrequency, ultrasound, laser, magnetotherapy, ice.
In more advanced phases, in which there is a deterioration of the tendon (without reaching a total rupture), we will direct the treatment to its regeneration. It can be carried out by infiltration of plasma rich in growth factors or orthokine, since it achieves a very good result and, according to our experience, in a high percentage repair surgery is avoided, although it will always be necessary to do it guided with ultrasound to deposit the growth factors in the exact area of the tendon lesion.
In most patients, the combination of these biological rehabilitation therapies, ultrasound-guided regeneration therapies and orthopedic correction will restore (or even improve) function in most patients, and prevent progression to flatfoot.
If the flatfoot is still flexible, corrective surgeries with medialization osteotomies of the calcaneus coupled with tendon repair or retensioning or other procedures such as subtalar arthorrhosis or, rarely, lengthening osteotomies of the external column of the foot may be necessary. If the foot is unstructured and arthrosed the only solution would be foot arthrodesis.