Posterior Ankle Impingement

Posterior ankle impingement is pain at the back of the ankle caused by bone or soft tissue being pinched when the foot points downwards. It is common in dancers, gymnasts and footballers, and is often linked to an os trigonum, a small extra bone. Many cases settle with rest and physiotherapy, and keyhole surgery can help if not.

When the foot points down (plantarflexion), the back of the shin bone (tibia) and the heel bone come close together. Any structure caught between them can be squeezed. The condition is sometimes called talar compression syndrome and is common in ballet dancers.

What are the symptoms?

• Pain at the back of the ankle when pointing the foot down
• Tenderness behind the ankle, between the Achilles tendon and the heel bone
• Pain that is worse with ballet en pointe, kicking or going downstairs
• Swelling at the back of the ankle
• A feeling of catching or restriction during ankle movement

Walking downhill and wearing high-heeled shoes are also typical triggers. The condition can be confused with Achilles tendon problems, tendinopathy of the big-toe flexor tendon (FHL) or arthritis of the joint below the ankle.

What causes posterior ankle impingement?

• Os trigonum: a small extra bone at the back of the ankle bone (talus) that can become painful
• Soft tissue thickening: enlargement or inflammation of the joint capsule or soft tissues at the back of the ankle
• Injury: repeated ankle injuries or sprains
• Sport and dance: repeated pointing of the foot in dance, gymnastics or football

How common is an os trigonum?

A study of CT scans in 628 patients in Foot & Ankle International (Zwiers and colleagues) found an os trigonum in 32.5% of the patients scanned. In patients without posterior ankle impingement the figure was 30.3%, and in ankles that had no symptoms it was 23.7%. Patients with posterior ankle impingement were more likely to have one. The authors concluded that the os trigonum is more common than previously reported.

How is it diagnosed?

Diagnosis is based on the history and examination, including a test in which the foot is pushed firmly downwards to reproduce the pain. Standing X-rays can show an os trigonum or an enlarged bone at the back of the ankle. A CT scan gives detailed images of the bone. An MRI scan shows inflammation, soft tissue changes and the tendons nearby.

Non-surgical treatment

Treatment usually starts without surgery:

• Changing activity and resting from the movements that cause pain
• Anti-inflammatory medication
• Physiotherapy and ankle mobilisation exercises
• An ultrasound-guided steroid injection into the back of the ankle

When is surgery recommended?

When non-surgical treatment has not helped, keyhole surgery is performed. It removes the os trigonum, the impinging soft tissue, or both. Mr Hester performs this as a day case under general anaesthetic through small incisions at the back of the ankle.

Surgery at the back of the ankle can be done through an open incision or endoscopically, using a camera. A meta-analysis of 32 studies in The American Journal of Sports Medicine (Zwiers and colleagues) compared the two. It found no significant difference in function scores, patient satisfaction or time to return to activity. In the endoscopic studies, 86% of patients rated their satisfaction as good or excellent (91% after open surgery), and return to full activity took about nine weeks on average. When poorer-quality studies were excluded, both total and minor complications were significantly less common after endoscopic surgery.

General risks of keyhole ankle surgery include stiffness or persistent pain, nerve damage, infection and a very low risk of a blood clot.

What is recovery like?

• 0–2 weeks: post-operative boot; rest and elevation
• 2 weeks: wound review; weight-bearing and physiotherapy begin
• 4–6 weeks: return to normal walking; swelling settling
• 8–12 weeks: return to sport and dance

How Mr Hester can help

Mr Hester is a dual fellowship-trained foot and ankle surgeon (FRCS Tr&Orth), trained at Guy's and St Thomas' and in Toronto and Calgary, and a member of BOFAS and EFAS. He sees patients privately at The London Clinic, Cromwell Hospital, King Edward VII's Hospital and HCA The Shard. His NHS practice is at King's College Hospital.

Insured patients need a GP referral and an authorisation code from their insurer. Self-pay patients are welcome. To book, call 020 7046 8004.

Frequently Asked Questions

Sources

1. Zwiers R, Baltes TPA, Opdam KTM, Wiegerinck JI, van Dijk CN. Prevalence of Os Trigonum on CT Imaging. Foot Ankle Int. 2018;39(3):338–342. PMID: 29272144. https://pubmed.ncbi.nlm.nih.gov/29272144/
2. Zwiers R, Miedema T, Wiegerinck JI, Blankevoort L, van Dijk CN. Open Versus Endoscopic Surgical Treatment of Posterior Ankle Impingement: A Meta-analysis. Am J Sports Med. 2022;50(5):1449–1456. PMID: 34048272. https://pubmed.ncbi.nlm.nih.gov/34048272/
3. Sprains and strains. NHS. https://www.nhs.uk/conditions/sprains-and-strains/