Posterior Tibial Tendon Dysfunction

Posterior tibial tendon dysfunction (PTTD), also known as posterior tibial tendonitis, is one of the leading causes of acquired flatfoot in adults. The onset of posterior tibial tendon dysfunction may be slow or abrupt. An abrupt onset is typically linked to some form of trauma, whether it be simple (stepping down off a curb or ladder) or severe (falling from a height or automobile accident). PTTD is seldom seen in children and increases in frequency with age.

The characteristic finding of posterior tibial tendon dysfunction include;

Loss of medial arch height.
Edema (swelling) of the medial ankle.
Loss of the ability to resist force to abduct or push the foot out from the midline of the body.
Pain on the medial ankle with weight bearing.
Inability to raise up on the toes without pain.
Too many toes sign.
Lateral subtalar joint (sinus tarsi) pain.

A common test to evaluate PTTD is the 'too many toes sign'. The 'too many toes sign' is a test used to measure abduction (deviation away from the midline of the body) of the forefoot. With damage to the posterior tibial tendon, the forefoot will abduct or move out in relationship to the rest of the foot. In cases of PTTD, when the foot is viewed from behind, the toes appear as 'too many' on the outside of the foot due to abduction of the forefoot.

In advanced cases of PTTD, in addition to the pain of the tendon itself, pain will also be noted in the subtalar joint and sinus tarsi. The sinus tarsi refers to a small tunnel or divot on the outside of the subtalar joint that can actually be felt. This tunnel is the entry to the subtalar joint. The subtalar joint is the joint that controls the side to side motion of the foot, motion that would occur with uneven surfaces or sloped hills. As PTTD progresses and the ability of the posterior tibial tendon to support the arch becomes diminished, the arch will collapse overloading the subtalar joint. As a result, there is increased pressure applied to the joint surfaces of the lateral aspect of the subtalar joint, resulting in pain.

There have been many proposed explanations for PTTD over the years since this condition was first described by Kulkowski in 1936. The most contemporary explanation refers to an area of hypovascularity (limited blood flow) in the tendon just below the ankle. Tendon derives most of its' nutritional support from synovial fluid produced by the outer lining of the tendon. Extremely small blood vessels also permeate the tendon sheath to reach tendon. This makes all tendon notoriously slow to heal. In the case of the posterior tibial tendon, this problem is exacerbated by a distinct area of poor blood flow (hypovascularity). This area is located in the posterior tibial tendon just below or distal to the inside ankle bone (medial malleolus).

Tendon is most susceptible to fatigue and failure at an area where the tendon changes direction. As the posterior tibial tendon descends the leg and comes to the inside of the ankle, the tendon follows a well defined groove in the back of the tibia (bone of the inside of the ankle). The tendon then takes a dramatic turn towards the arch of the foot. If the tendon is put into a situation where significant load is applied to the foot, the tendon responds by pulling up as the load of the body (in addition to gravity) pushes down. At the location where the tendon changes course, the tibia acts as a wedge and may apply enough force to actually damage or rupture the tendon.

Equinus is also a contributing factor in cases of posterior tibial tendon dysfunction. Equinus is the term used to describe the ability or lack of ability to dorsiflex the foot at the ankle (move the toes towards the shin). Equinus is usually due to tightness in the calf muscle, also known as the gastroc-soleal complex (a combination of the gastrocnemius and soleus muscles). Equinus may also be due to a bony block in the front of the ankle. The presence of equinus forces the posterior tibial tendon to accept additional load during gait.

Additional contributing factors that contribute to the onset of posterior tibial tendon dysfunction may include obesity, hypertension, diabetes, peripheral neuropathy, smoking or arthritis.

PTTD is a progressive condition, meaning to say, that if left untreated, PTTD will become worse over time. The progression of PTTD begins with focal tendonitis. If left untreated, tendonitis will progress to partial and then complete tears of the posterior tibial tendon. Several classifications have been developed to describe posterior tibial tendon dysfunction. The classification as described by Johnson and Strom is most commonly used today.

Stage I Posterior tibial tendonitis without tendon tear

Tendon status - Attenuated (lengthened) with tendonitis but no rupture.
Clinical findings - Palpable pain in the medial arch. Foot is supple, flexible. Too many toes sign may be positive or negative.
X-ray/MRI - Mild to moderate tenosynovitis on MRI, no X-ray changes found.

Stage II Posterior tibial tendonitis with partial tendon tear
Tendon status - Attenuated with possible partial or complete rupture.
Clinical findings - Pain in arch. Unable to raise on toes. Too many toes sign positive.
X-ray/MRI - MRI notes tear in tendon. X-ray noting abduction of forefoot, collapse of talo-navicular joint.

Stage III Posterior tibial tendonitis with partial to complete tendon tear.
Tendon status - Severe degeneration of the tendon with likely rupture.
Clinical findings - Rigid flatfoot with inability to raise up on toes. Too many toes sign positive.
X-ray/MRI - MRI shows tear in tendon. X-ray noting abduction of forefoot, collapse of talo-navicular joint

An additional consideration in diagnosing PTTD pain is the presence of an accessory bone called an os tibiale externum. The os tibiale externum, or what is frequently called and accessory navicular, is a small bone that resides within the body of the PT tendon. The os tibiale externum functions to facilitate motion around the navicular. The os tibiale externum functions much in the same way that the knee cap (patella) works to guide the quadraceps tendon around the knee as it bends. The os tibiale externum can undergo degenerative wear called chondromalacia. The os tibiale externum also can fracture. Therefore, the os tibiale externum must also be considered when diagnosing PT tendon pain.

Treatment of posterior tibial tendon dysfunction

Treatment for PTTD is dependant upon the clinical stage and the health status of the patient. It is important to recognize that PTTD is a mechanical problem that requires a mechanical solution. This means that treating PTTD with medication alone is fraught with failure. Prompt introduction of some form of mechanical support is imperative.

PTTD is a condition that increases in frequency with age and the prevalence of poor health indicators such as diabetes and obesity. As a result, many patients with PTTD are poor surgical candidates for correction of PTTD. Prosthetics such as an ankle foot orthotic (AFO), Arizona Brace or other bracing may be very helpful to control the symptoms of PTTD.

Surgical procedures which focus on primary repair of the posterior tibial tendon have been very unsuccessful. This is due to the fact that tendon heals slowly following injury and cannot be relied upon as a sole solution for PTTD cases. Surgical success is usually achieved by stabilization of the rearfoot (subtalar joint) which significantly reduces the work performed by the posterior tibial tendon.

Stage I PTTD may respond to treatment that includes variations of rest. Variations in rest include an ankle brace, walking cast with an elevated heel or a hard, below the knee non-weight bearing cast. Pain and inflammation may be controlled with anti-inflammatory medications. It is important to be sure that Stage I patients realize that the use of shoes with additional arch support and heel elevation is imperative. Arch support and heel elevation should be continued indefinitely. Arch support, whether built into the shoe or added as an orthotic, helps support the posterior tibial tendon and decrease the amount of mechanical load applied to the posterior tibial tendon. Elevation of the heel, reduces equinus, one of the most significant contributing factors to PTTD. If Stage I patients return to low heels without arch support, PTTD will recur.

Stage II patients typically require surgical correction to stabilize the subtalar joint prior to further damage to the posterior tibial tendon. Subtalar arthroeresis is a procedure used to stabilize the subtalar joint. Subtalar arthroeresis may only be used in flexible feet. Arthroeresis is a term that means the motion of the joint is blocked without fusion. Subtalar arthroeresis can only be used in cases of Stage II posterior tibial tendonitis where mild to moderate deformation of the arch has occurred and MRI findings show the tendon to be only partially ruptured. Subtalar arthroeresis is typically performed in conjunction with an Achilles tendon lengthening procedure or endoscopic gastrocnemius recession to correct equinus. These procedures require casting for a period of weeks following the procedure.

The following video shows placement of a subtalar joint implant for control of pronation in a flexible foot with PTTD. The sinus tarsi is dissected free of capsule and ligament and the implant is placed in the sinus tarsi. This procedure is completed in a hospital or out-patient surgery center using a general anesthetic. Patients can walk immediately following subtalar arthroeresis if an Achilles tendon lengthening is not performed. If an Achilles tendon lengthening is performed, a 6 week period of non-weight bearing casting is required. 

 

When an os tibiale externum is present, a modified Kidner procedure is typically performed. The following images show excision of the os tibiale externum and transposition of the posterior tibial tendon. This procedure is performed in a hospital or out-patient surgery center using a general anesthetic. Weight bering following the surgery is dependent upon the integrity of the tendon following excision of the os tibiale externum. Most modified Kidner procedures do require a period of non-weight bearing.

Stage III patients require stabilization of the rearfoot with procedures that fuse the primary joints of the arch and foot. Rearfoot stabilization is used to correct rigid deformities of the foot. These procedures are salvage procedures and require prolonged casting and disability following surgery. A common procedure for Stage III is called triple arthrodesis which is a technique used to fuse the subtalar joint, the talo-navicular joint and the calcaneal cuboid joint (picture at left).

Arthroeresis - to surgically limit or block range of motion of a joint.

PTTD - posterior tibial tendon dysfunction.

Sinus tarsi - a cavity or sinus and the entry of the subtalar joint.

The posterior tibial tendon is the extension of the posterior tibial muscle that lies deep to the calf. The origin of the posterior tibial muscle is the posterior aspect of both the tibia and fibula and the interosseus membrane. The insertion of the posterior tibial muscle is the medial navicular where the tendon divides into nine different insertion site on the bottom of the foot.

The function of the posterior tibial tendon is to plantarflex the foot at the toe off phase of the gait cycle and to stabilize the medial arch and subtalar joint as the body passes over the foot.

As PTTD becomes more severe, the ability of the posterior tibial tendon become less able to support the arch.  Hence the collapse of the arch associated with PTTD.

The symptoms of stage I PTTD include a dull ache of the medial arch. The pain becomes worse with activity and better on days with limited time on the feet. Continued weight bearing may result in a partial rupture of the tendon, moving to stage II. Stage I typically shows no swelling but presents with pain along the course of the PT tendon from the medial ankle to the insertion of the PT tendon on the medial arch.

Stage II symptoms are persistent and only partially relieved by rest. Pain is present at the onset of weight bearing and continues throughout the day. Some limitation of the ability to raise up on the toes will be present and limited by pain in the medial arch. Mild swelling may be present in the medial arch.

Stage III symptoms are severe with an inability to complete most normal daily activities. Collapse of the medial arch will be obvious. Abduction of the forefoot will show 'too many toes sign'. Patients are unable raise up on their toes.

Calcaneal stress fracture

Flexor hallucis longus tendonitis

Gout

Posterior tibial tendon rupture

Shepard's fracture (posterior process of the talus)

Sinus tarsi syndrome

Subtalar joint arthritis

Tarsal tunnel syndrome

Tibial stress fracture

• Achilles Tendonitis

• Ankle Sprain

• Tarsal Tunnel Syndrome

• Flatfeet

This article was written by Jeffrey A. Oster, DPM and last updated 2/8/13.  Additional references include;

1. Cantanzariti, A.R., Lee, M.S., Mendicino, R.W. Posterior Calcaneal Displacement Osteotomy for Adult Acquired Flatfoot. J. of Foot and Ankle Surgery. 39-1: 2-14, 2000

2. Myerson, M.S., Corrigan, J. Treatment of posterior tibial tendon dysfunction with flexor digitorum longus tendon transfer and calcaneal osteotomy. Orthopedics 19:383-388, 1996

3. Myerson, M.S. Adult acquired flatfoot deformity. J. Bone and Joint Surgery. 78-A;780, 1996

4. Johnson, K.A., Tibialis posterior tendon rupture. Clin. Orthop. 177:140-147, 1983