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Posterior impingement (Os trigonum syndrome)

What is Posterior impingement (Os trigonum syndrome)

This condition is observed in athletes such as ballet dancers. The patient experiences pain at the posterolateral aspect of the ankle posterior to the peroneal tendon due to compression of the bone or soft tissue structures during activities that involve maximal ankle plantarflexion motion. It may also be seen in association with Flexor Hallucis Longus Tenosynovitis.

During the movement of plantar flexion, the foot and ankle are pointed maximally away from the body, the ankle is compressed posteriorly. This may result in tissue damage and pain if the compressive forces are too repetitive or forceful.

Posterior impingement often occurs due to inadequate rehabilitation following an acute ankle injury. In some cases, an individual may have an anatomical variant in their talus bone, known as an os trigonum, which is quite normal. However, such individuals have an increased likelihood of developing this condition, particularly in athletes..

Symptoms of Os trigonum syndrome

Individuals that suffer Posterior Ankle Impingement typically present with:

  • Sharp pain at the back of the ankle joint during activities that require maximal plantar flexion (pointing).
  • Ache at rest or following provocative activities

Examples of provocative activities include :

  • Kicking a ball
  • Pointe work (dancing)
  • Walking or running (especially downhills)
  • Jumping or hopping
  • Activities like toe walking

Diagnosis of Posterior impingement

Posterior ankle impingement can be diagnosed on the basis of history and physical assessment findings. In some cases, imaging may be required.

Diagnostic Imaging

An X-Ray can be utilized when imaging posterior ankle impingement. The x-ray view of the ankle from the sideshows bone spurs. At times an x-ray taken at a slight angle (oblique radiograph) can be helpful in seeing anteromedial bone spurs.

MRI is a useful test for a couple of different reasons. First, it can be useful in being sure there is no other cause of foot or ankle pain present that can mimic posterior ankle impingement or additional symptoms.

Treatment of Os trigonum syndrome

  • PHASE I – Pain Relief, Minimize Swelling & Injury Protection

Rest: Our first aim is to provide the patient with some active rest from pain-provoking postures and movements. Stop doing the movement or activity that provokes the ankle pain.

Ice is a simple and effective modality to reduce pain and swelling. Apply for 10-15 minutes each 2 to 4 hours during the initial phase.

Compression: A compression bandage, ankle binder, compression stocking, or kinesiology supportive taping will help to both support the injured soft tissue and reduce excessive swelling.

Elevation: Elevating the injured ankle will assist to reduce excessive swelling around the ankle.

Physiotherapy treatment variants are used to reduce pain and inflammation. These may include ice, electrotherapy, acupuncture, unloading taping techniques, soft tissue massage, and temporary use of a mobility aid (e.g. brace) to off-load the injured structures.

Anti-inflammatory medication and creams can help reduce your pain and swelling.

  • Phase 2: Restore Full Range of Motion

As soon as it is comfortable, the Physiotherapist should start rehabilitation aiming at regaining full active range of motion of the ankle.

  • Phase 3: Restore Muscle Strength and length

The calf, intrinsic muscles of the foot, and plantar fascia can hold the calcaneum in a fixed position and needs to be stretched to increase space in the posterior ankle region. Ankle and foot muscles will require strengthening to recover from the injury and prevent future episodes. It is important to regain normal muscle strength to provide normal dynamic ankle control and function. The strength and power training should be gradually progressed from non-weight bear to partial and then full weight-bearing and resisted exercises. Strengthening for another leg, gluteal and lower core muscles may be required depending on assessment findings.

  • Phase 4: Restore High Speed, Power, Proprioception, and Agility

Most cases of posterior ankle impingement occur during high-speed activities, which place enormous forces on the ankle and adjacent structures. Balance and proprioception exercises are required to ensure a full recovery and also to prevent re-injury.

  • Phase 5: Return to Normal Daily Function and Sport

A sport-specific exercise program and a progressive training regime should be planned by the physiotherapist to ensure a safe and injury-free return to sport.

Surgery for Posterior impingement

Surgery is opted in persistent cases of posterior ankle impingement who don’t show improvement with non-operative treatment over 6-8 weeks, particularly for the high-level athlete.

Surgical treatment involves removing the prominent bone spurs and/or soft tissue either arthroscopically or by opening up the ankle joint with an incision. If the bone spurs are large it is often more effective to make a larger incision and open up the ankle joint and remove the bone spurs.

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