Posterior Impingement Syndrome
(Impingement at the back of the ankle)
Posterior impingement syndrome refers to pain at the back of the ankle when the foot is plantarflexed (bent downwards) to the maximum, such as when one stands on tiptoe. The cause of the pain is compression or impingement of the bony and soft tissue structures located at the back of the ankle
If we look at the anatomy of the ankle joint, it is mainly formed by the ankle bone called the talus, joining upwards with the lower leg bones, tibia and fibula. On the underside of the anklebone, there is the heel bone (calcaneus), the posterior end of which extends backwards to a greater extent than the talus. When the foot bends downwards, the back of the heel bone moves upwards, narrowing the angle between the heel bone and the lower leg bones and compressing the structures between them, especially any accessory bones or bone fragments in the area.
For this reason, the problem mainly affects individuals engaged in activities that involve repeated downward flexion of the foot such as ballet dancers, during their pointe work. This syndrome is quite common among ballet dancers and is also known as Dancer’s Heel.
Apart from dancers, football players, basketball players, skaters and gymnasts are also prone to developing this problem, as they also need to constantly flex the feet forcefully during push-off manoeuvres.
Posterior impingement syndrome can occur due to a number of reasons.
Symptomatic Os Trigonum:
The os trigonum or accessory talus is a small bean-sized bone located at the back of the anklebone (talus), which is present in only about 10 % of the population. This bone is attached to the talus through the cartilage joint.
The presence of an os trigonum does not cause any symptoms under usual circumstances; the problem arises with repeated forced downward flexion of the foot. When the foot is plantarflexed to the end range of motion, the os trigonum becomes compressed between the lower leg bone (tibia) and the heel bone (calcaneus) and mildly limits the complete flexion of the foot. This compresses the soft tissues located in between, causing pain and inflammation. There may also be inflammation (periostitis) of the os trigonum.
Prominent bony process at the back of the talus (Stieda’s Process):
At the rear surface of the talus, there is a large bony process with two prominent projections; one at the inner end called the medial tubercle and one at the outer side called the lateral tubercle. In some individuals, the medial tubercle is unusually large and is known as the Process of Stieda. Just like the os trigonum, this bony prominence can also become compressed during repeated plantarflexion of the foot, leading to pain and inflammation.
Fracture of the trigonal process:
The lateral tubercle on the posterior surface of the talus is also known as the trigonal process. Repeated flexion also predisposes this process to repeated stress, which may result in fracture of this small projection if it gets dislocated. A trigonal process fracture may also result from a sudden injury such as an ankle sprain.
This dislocated fragment produces the same symptoms and is hard to distinguish from an os trigonum. As in normal anatomy, the os trigonum when present is located just behind the trigonal process.
A bony projection on the upper surface of the heel bone (calcaneus) may also lead to crushing of the bony and soft tissue structures during flexion of the foot.
Upper left: Os Trigonum Upper right: Bony prominence on the heel bone (calcaneus)
Lower left: Process of Stieda Lower right: The normal anatomy of ankle
Ankle joint instability resulting from a previous ankle sprain may cause the talus to shift forward during maximum flexion of the foot; as a result, the back of the calcaneus comes in contact with the back of the tibia, crushing the soft tissue structures in between.
Pain at the back of the ankle during and after activities involving forced downward bending of the foot, such as running down slopes, dancing on toes or kicking
There may be a sharp pain or a dull ache in the region
Tenderness and swelling in the area
Sometimes the pain extends upwards to the calf region or downwards towards the foot.
The history of the patient, as well as a thorough clinical examination is important for diagnosing the condition.
Pain can be elicited by turning the foot to the maximum flexed position. A local anesthetic injected at the back of talus eliminates the pain associated with downward flexion of the foot and is a significant diagnostic test for posterior impingement syndrome.
X-rays help to clarify the presence of bony projections, accessory bone or fractured bone fragments in the area.
CT scan and MRI are great diagnostic tools that clearly show the bone and soft tissue condition in the area.
Conservative treatment usually produces significant improvement in the condition and involves giving the sore tissues rest and reducing the pain and inflammation.
The RICE regime is advised and includes:
Rest: Avoiding any activities that cause the pain for about four to six weeks, use of crutches may also be advised
Ice Application: for about 20 minutes at a time, 3-4 times a day for the first two to three days, to reduce swelling and pain in the area .
Compressing the area with the help of elastic bandages; this supports the ankle and prevents inflammation. However, the bandage should not be too tight.
Elevating the leg off the ground above the heart level also reduces inflammation.
Non-steroidal anti-inflammatory painkillers such as ibuprofen, or naproxen may be prescribed.
Steroid (cortisone) injections may be given in the area to reduce inflammation.
If the symptoms are severe, the ankle may be immobilized using a rigid cast or splint.
Ultrasonic and manual massage therapies improve blood flow to the area and speed up healing.
If the condition does not respond well to rest and anti-inflammatory therapy, surgical correction of the cause is required, which entails removing the os trigonum or any bony protuberances and fractured fragments of bone.
Surgery may be performed through an open incision or by using a camera inserted through a small incision. The latter procedure involves fewer complications and a rapid recovery.
In the post-operative healing period, physiotherapy helps to improve strength and control of the ankle as well as increasing the range of motion at the joint.