Posterior Tibial Tendon Dysfunction (PTTD) is a common foot and ankle condition and a common cause of adult-acquired pes planus (“flat foot”). It can affect people of all ages and activity levels, although it is very common in obese, middle-aged women, affecting approximately 1 in 10 people within this demographic. Around 60% of people with PTTD also have diabetes, high blood pressure, a history of ankle and foot surgery or trauma, or steroid use, beither systemic use or local injections. People with seronegative spondylarthropathies and Rheumatoid Arthritis as well as Psoriatic Arthritis are also at higher risk of developing PTTD. Usually only one side is affected; bilateral cases are rarely reported in the literature.
The Tibialis Posterior muscle originates (begins) on the postero-lateral aspect of the Tibia (back of the shin-bone, on the outside), the postero-medial Fibula (back and inside of the fibula) and interosseous membrane between the Tibia and Fibula. It runs through the deep posterior compartment of the leg and its tendon passes behind the medial malleolus (inside of the ankle). Blood supply to the tendon is poorest in this area and is the most common site for rupture. After the medial malleolus, the tendon splits just proximal (just before) the sites of insertion on navicular tuberosity, the plantar portion of the second, third, fourth metatarsals, second and third cuneiforms and cuboid. The recurrent part also attaches to the calcaneus at the sustentaculum tali.
The Tibialis Posterior is the primary stabiliser of the medial longitudinal arch of the foot (your “instep”), as well as the primary inverter of the midfoot. It contracts to elevate the medial longitudinal arch, causing the hind foot and midfoot to become a rigid structure. This allows the gastrocnemius to act with greater efficiency during the gait cycle.
PTTD is described as a chronic condition where the tendon of the Tibialis Posterior muscle slowly and progressively degenerates, most often under the influence of biomechanical stresses due to “training load errors” (aka “overuse injuries”) or abnormal lower leg biomechanics. Either of these can lead to microtraumas, the replacement of healthy tissue with fibrotic tissue, lengthening of the tendon, and in some cases, rupture of the tendon, although some people with PTTD can develop a pes planus foot without the tendon rupturing. As the tendon lengthens and stops functioning correctly, the medial arch of the foot begins to collapse, causing the talus and tibia to rotate internally. This leads to eversion of the subtalar joint, which forces the heel into a valgus alignment and abducts the talonavicular joint. The everted heel causes the normal axis of the Achilles tendon to move laterally, which in time will lead to a contracture. As the deformity progresses, the distal part of the Fibula (the end of the Fibula bone) comes into contact with the lateral aspect of the Calcaneus (outside of the heel bone), causing lateral hindfoot pain.
PTTD can also develop because the tendon is intrinsically abnormal or from trauma to the ankle, usually an ankle fracture, or direct trauma to the tendon itself.
It has been suggested that the significant increase in PTTD in recent years is associated with an increased number of people of all ages taking part in sports or exercise (including walking), especially those in older people age demographics. While PTTD is more obvious in its advanced stages, notable by the present of foot deformity, the tendon begins degenerating long before the condition is apparent clinically. Recognising PTTD in its early stages is very important as conservative management may prevent the person developing a rupture of the tendon and/or foot deformities that can only be managed surgically.
Symptoms vary depending on how severe the conditions is. People with PTTD usually experience the pain and swelling along the medial aspect of the foot and ankle, which is worse for walking or running and better for resting. As the medial longitudinal arch collapses, the deformity of the foot increases; in this instance patients may describe abnormal wear on their shoes. In severe cases of deformity the distal fibula (bottom part) will come into contact with the calcaneus (heel bone), and pain will move to the lateral aspect of the foot (outside); patients at this stage may describe the feeling of walking on the medial aspect of the ankle. As the condition progresses, chronic inflammatory processes degenerate the tendon, leading to it elongating, developing interstitial tears, and eventually rupturing. It also appears that people who have chronic tendosynovitis before developing PTTD are more likely to experience ruptures of the tendon.
PTTD is often classified into 5 stages:
In stage I PTTD, there is swelling, inflammation and/or pain along the course of the tendon or at the sinus tarsi, but the tendon is intact and there is no foot deformity or loss of function.
Stage IIA involves some loss of function or rupture the Tibialis Posterior tendon and acquired pes planus which can be correct (is flexible).
Stage IIB involves loss of function, acquired pes planus and forefoot abduction (both can be corrected – are flexible).
Stage III involves fixed deformities that cannot be corrected (inflexible), more advanced deformity, namely forefoot abduction and rearfoot eversion, much more severe pain including sinus tarsi pain, and subtalar joint arthritis.
Stage IV involves a compromised deltoid ligament, ankle pain with tibio-talar degeneration.
Conservative methods can be used at any of these stages, as can surgery. At Stage I, conservative management using in-shoe orthotics (insoles), soft-tissue rehabilitation (stretches, strengthing), acupuncture, and changes to footwear may be sufficient. If these fail to resolve the condition after 4 months, then surgery may be required. Conservative measures can still be trialed in Stage II, but these often fail and surgery is often required. Conservative management at Stages III and IV are aimed more at managing pain and slowing the progression of the condition. Surgery is almost always needed at these stages.