Posterior ankle impingement causes pain at the back of the ankle when pointing the foot downwards, into plantarflexion. It’s easily confused with Achilles tendon pain. So what causes posterior ankle impingement, and how do we diagnose and manage it?
This is the umbrella condition. Its single commonest bony cause is an os trigonum — covered in full on its own page.
What causes posterior ankle impingement?
Posterior ankle impingement happens when structures at the back of the ankle are pinched, causing pain. The pinching comes from bone, soft-tissue swelling, or anatomical variations.
Bony causes include an os trigonum, an abnormally elongated back of the talus (a Stieda process), bony spurs from ankle arthritis, and fractures. Soft-tissue causes include tendonitis and joint swelling after an ankle sprain.
How do we diagnose posterior ankle impingement?
Several features separate posterior ankle impingement from other causes of posterior ankle pain. The pain is deep in the back of the ankle and occurs when the foot is pointed down (plantarflexion). It can start suddenly after an ankle twist or build gradually with repetitive plantarflexion—common in dancing and football.
It’s essential to distinguish it from other causes of pain at the back of the ankle, such as Achilles tendonitis, posterior tibial tendonitis, an accessory soleus muscle, and Kager’s fat pad oedema. On examination, we usually find restricted ankle movement and sometimes swelling around the Achilles tendon.
The posterior ankle impingement test
Forcing the ankle into full plantarflexion pinches the back of the ankle and reproduces the pain. We don’t know exactly how sensitive this test is, so we confirm the cause with imaging.
An X-ray shows bony causes — os trigonum, Stieda process, loose bodies, and spurs. An MRI shows soft-tissue causes such as joint swelling or soft-tissue impingement.
How do we treat posterior ankle pain?
We always start with conservative management.
- Activity modification to reduce the provoking movements
- Regular NSAIDs such as ibuprofen to settle swelling at the back of the ankle
- Physiotherapy — an underrated treatment — using soft-tissue massage, joint mobilisation, and strengthening of the muscles around the ankle to reduce pinching
A study found that 60% of patients with posterior ankle pain responded to conservative treatment.
Injections for posterior ankle pain
In persistent cases, a cortisone shot directed to the area of swelling at the back of the ankle helps. We strongly suggest an ultrasound-guided injection to improve accuracy and reduce side effects — the structures here are deep and close to important nerves and tendons.
Surgery
We only recommend surgery when conservative treatment, including injections, has failed. Open or arthroscopic (keyhole) techniques remove the bony and soft-tissue causes — an os trigonum can be excised at the same time as treating joint swelling or synovitis.
Surgery isn’t to be taken lightly. Recovery is long, often 3–6 months. Removing a bony cause, such as an os trigonum, may also raise the risk of arthritis from an uncovered calcaneus at the back of the subtalar joint. One study of os trigonum excision reported a 13–14% complication rate, primarily due to postoperative subtalar arthritis.
Frequently asked questions about posterior ankle impingement
What does posterior ankle impingement feel like?
Deep pain at the back of the ankle that comes on when you point your foot down — pushing off, going on tiptoe, pointing in ballet, or striking a ball. It’s often mistaken for Achilles pain, but Achilles pain rises with tendon loading, whereas the pointing movement itself provokes impingement pain.
What’s the difference between posterior ankle impingement and Achilles tendonitis?
Achilles tendonitis causes pain along the tendon that worsens with loading (running, hopping). Posterior impingement causes deeper pain at the very back of the ankle, brought on by full plantarflexion. The two can coexist, which is why an accurate, often ultrasound-based, assessment matters.
Who gets posterior ankle impingement?
It’s common in dancers (especially ballet), footballers, and other athletes who repeatedly point the foot, and in anyone after an ankle twist that swells the back of the joint. An underlying bony variant, such as an os trigonum, makes it more likely.
Will posterior ankle impingement settle without surgery?
Often, yes. Around 60% settle with activity modification, physiotherapy, and — where needed — an ultrasound-guided cortisone injection. Surgery is reserved for cases that fail this.
Final word from Sport Doctor London about posterior ankle impingement
Posterior impingement causes pain at the back of the ankle and is easily confused with Achilles or tibialis posterior tendonitis. Most cases settle without surgery. See an experienced sports doctor for an accurate diagnosis and the right management.
To book an ankle assessment with Dr Masci in London, contact the team here or call +44 (0) 203 488 0350.
Leave A Comment