A tendon is a band of fibrous tissue that connects muscle to bone allowing the joint to bend. Tendons enable participation in physical activities such as running, jumping and other movements. The posterior tibial tendon starts in the calf and descends down the leg behind the inside of the ankle and attaches to the foot’s arch. Its function is to support the medial arch and sub-talar joint as the body passes over the foot. When the posterior tibial tendon becomes inflamed or is overstretched, the ability to support the arch is impaired resulting in flattening of the foot.
Posterior tibial tendon (Figure 1) dysfunction, as this phenomenon is called, can be attributed to several factors:
- Tendon overuse.
- exposing the foot to a significant load
- Inflammatory diseases such as rheumatoid arthritis.
Patients with posterior tibial tendon dysfunction will often present with pain and swelling on the inside of the ankle, loss of the foot’s arch (flatfoot), tenderness over the mid-foot and an inability to stand on the toes.
To diagnose posterior tibial tendon dysfunction, physicians will likely use the “too many toes” test (Figure 2). Here, the physician measures abduction of the forefoot. If the
posterior tibial tendon is damaged, the forefoot will deviate outwards in relation to the rest of the foot and will appear to have too many toes when viewed from behind. In addition to the “too many toes” test, the physician may ask patients to do a single heel rise. Here, patients are asked to stand with their hands on the wall and lift the unaffected foot off the ground and raise the toes on the affected foot. If the heel does not rotate inward, there is posterior tibial tendon dysfunction.
Posterior tibial tendon dysfunction can be classified in four stages:
STAGE I – characterized by an inflamed posterior tibial tendon with normal strength. Upon examination, the patient will be tender to palpation but may show little or no change in the arch of the foot. While X-rays will most likely show no changes, an MRI will likely reveal mild to moderate tenosynovitis.
STAGE II – characterized by a partially torn tendon or degenerative changes. Here, the physician will note considerable flattening of the arch without arthritic changes and will have a positive too many toes sign. X-rays will reveal abduction of the forefoot while an MRI will reveal a partial tear.
STAGE III – characterized by severe tendon degeneration with a rupture likely. Patients with stage III posterior tibial tendon dysfunction will present with rigid flatfoot. X-rays will likely reveal abduction of the forefoot and collapse of the talo-navicular joint while an MRI will show a tear in the tendon.
STAGE IV – is similar to stage III with the addition of an arthritic ankle joint.
Treatment for posterior tibial tendon dysfunction can range from conservative to surgical depending on how far the condition has progressed. In its early stages, physicians will often utilize rest, anti-inflammatory medications, and immobilization. If the foot fails to respond to conservative treatment or the condition has progressed too far, there are several surgical procedures that can be utilized. First, physicians may perform a tenosynovectomy. Here, the surgeon will debride and excise inflamed tissue surrounding the tendon. A second option is an osteotomy. Here, the surgeon changes the alignment of the calcaneus and may remove a portion of the bone. A third option is a tendon transfer where fibers from another tendon are used to repair the posterior tibial tendon. Finally, surgeons may fuse one or more bone together, eliminating movement in the joint through a process called arthrodesis. During this procedure, the forefoot is stabilized.