Pretest

I. Posterior ankle impingement-compression of the talus and surrounding soft tissues between the tibia and calcaneus

1. Cause-forced or repetitive plantar flexion of the foot
2. Occurs in dancers and athletes
3. Presentation-pain in the medial or lateral aspect of the ankle posteriorly with activities, especially plantar flexion
4. Physical examination-tenderness medial or lateral to the Achilles tendon
5. Diagnosis is difficult to make and often missed because of the following:
1. Symptoms are reproduced by plantar flexion of the ankle
2. Injections can be performed to see if the injection relieves the symptoms

II. Causes of posterior impingement

1. Os trigonum
2. Enlarged lateral process of the talus
3. Enlarged posterior process of the calcaneus
4. Posterior intermalleolar ligament
5. Soft tissue impingement
6. Loose bodies
7. Ganglia
8. Low lying flexor hallucis longus muscle body
9. Anomalous muscle bodies

III. Anomalous muscles about the ankle

1. Most common is the peroneus quartus (prevalence of the muscle between 7% and 22%)
1. Arises from peroneus brevis and inserts into retrotrochlear eminence of the calcaneus
2. Peroneocalcaneus internus (1%)
1. Arises from the fibula and inserts into under surface of sustentaculum tali
3. Long accessory to the long flexors or quadratus plantae (1%-8%)
4. Tibiocalcaneus internus
5. Accessory soleus

IV. Recent report-three elite athletes with four symptomatic ankles, mean age was 21 years with a mean of 16 months of symptoms

1. Magnetic resonance imaging (MRI) showed the anomalous muscles and there was fluid in the tendon sheath of each
2. For each patient, the anomalous muscle was resected and the patients had excellent pain relief

V. Take home Message:

1. These anomalous muscles may cause ankle pain and should be considered in athletes with chronic ankle pain.
2. These muscles may be hard to detect on MRI and one should review MRIs with an experienced musculoskeletal radiologist when one is uncertain of the diagnosis.
3. Release of excision of these muscles may resolve an athlete's pain.

Reference

1. Best A, Giza E, Linklater J, Sullivan M. Posterior impingement of the ankle caused by anomalous muscles: A report of four cases. J Bone Joint Surg Am. 2005; 87:2075-2079.