One foot tendon that becomes painful more frequently than other tendons is the posterior tibial tendon. It usually is hard at work, helping to hold the arch up and prevent overpronation or rolling in of the foot. The posterior tibial tendon runs behind the inner ankle bone (the medial malleolus), across the instep, and attaches to the bottom of the foot.

A condition called posterior tibial tendon dysfunction can occur with age due to degeneration that begins within the tendon. Tendonitis, or inflammation of the tendon and tendon sheath, can also occur. In many cases, the two conditions, tendonitis and tendinosis, the degenerative condition, are present simultaneously. The weakened tendon sets the stage for tearing, stretching, or rupture. Spontaneous tendon rupture can occur without any previous history of pain or injury.

The symptoms of posterior tibial tendonitis include pain in the instep area of the foot and swelling along the course of the tendon behind the inner ankle.

Pain when walking steadily worsens toward the end of the day. In cases where the condition progresses to the extent that there is a partial tear or rupture of the tendon, this will lead to a pronounced flatfoot deformity. At this stage, the spring ligament deep in the foot’s arch is also often involved.

Diagnostic ultrasound is beneficial in assessing the extent of the injury and which structures are involved. Other imaging, such as MRI, is also helpful. If the arch collapses, X-rays may also be used.

A differential diagnosis for other causes of pain in this area is Tarsal tunnel syndrome. The nerve that passes through the same location as the tendon can become irritated, leading to burning, shooting, tingling, or stabbing pain.

Not treating the problem and allowing the condition to worsen and the arch to collapse will affect a person’s ability to run and walk, leading to arthritis, severe foot pain, and straining of other joints in the leg.

Initially, treatment is to help relieve inflammation and pain and will generally involve Rest, Ice, Compression and Elevation, and anti-inflammatory medication. Prevention of the tendon from stretching out further to stop the arch from collapsing is necessary. It includes using either one or a combination of custom orthotics, footwear modification through additional support, or a walking splint/brace if shoes and orthoses are not supportive enough. After the inflamed tendon has settled, exercises are necessary to strengthen the muscle and the tendon.

If the treatment is not helpful in calming the pain and restoring function, or if the tendon has torn or ruptured, surgery may be required. This may consist of tendon repairs or relocation (tendon transfer) of another tendon to reduce the workload of the weakened tendon. Osteotomies (cutting of the bone) to improve foot alignment may also be necessary.

In cases that have been neglected, and a painful flatfoot deformity is present, a fusion (arthrodesis) of one or more joints in the foot to correct the position of the foot may be necessary. A fusion is an operation where a joint between two bones is removed, and the two bones on either side of the joint can grow together – or fuse. This type of operation is generally used to stop pain from joints that are worn out. Usually, several joints must be fused to control the flatfoot deformity occurring after posterior tibial tendon rupture.

This is often a painful progressive deformity, which, like many problems, is best dealt with earlier rather than later. With early intervention, surgery, and long-term complications can be avoided.

The severity of posterior tibial tendon dysfunction depends on factors such as age, activity level, weight, the time the condition has been present, and abnormalities in foot mechanics, such as a pre-existing flat foot.