Os Trigonum Syndrome or Posterior Ankle Impingement (PAI)

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Published: Feb 20, 2014
DOI: https://doi.org/10.31524/bkkmedj.2014.02.019

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Pornthep Mamanee, MD
Orthopaedic Center, Bangkok Hospital, Bangkok Hospital Group, Bangkok, Thailand.
Nathapon Chantaraseno, MD
Orthopaedic Center, Bangkok Hospital, Bangkok Hospital Group, Bangkok, Thailand.
Somsak Geraplangsub, MD
Imaging Center, Bangkok Hospital, Bangkok Hospital Group, Bangkok, Thailand

Abstract

Os Trigonum is an normal variant of an accessory bone found posterior to the talus. The os trigonum is present in around 5-15% of normal feet. Usually it is asymptomatic, until there is a minor to blunt injury on the anterior aspect of the foot. The injury becomes painful on the hyperplantarflexion test. The pain is located at posterolateral aspect of the ankle associated with swelling known as the ‘os trigonum syndrome’1,2 or posterior ankle impingement (PAI).

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How to Cite
1.
Mamanee P, Chantaraseno N, Geraplangsub S. Os Trigonum Syndrome or Posterior Ankle Impingement (PAI). BKK Med J [internet]. 2014 Feb. 20 [cited 2026 Feb. 28];7(1):94. available from: https://he02.tci-thaijo.org/index.php/bkkmedj/article/view/219633
Issue
Vol. 7 (2014): February
Section
Medical Images
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References

1. Sainani IN, Lawande AM, Pawar A, et al. Posterior ankle impingement syndrome due to os trigonum. Appl Radiol 2011;40:28-30.
2. Karasick D, Schweitzer ME. The os trigonum syndrome: imaging features. AJR Am J Roentgenol 1996;166:125-9.
3. Kose O, Okan AN, Durakbasa MO, et al. Fracture of the os trigonum: a case report. J Orthop Surg (Hong Kong) 2006;14:354-6.
4. American College of Foot and Ankle Surgeons (ACFAS). Os Trigonum Syndrome (Accessed December 15, 2013, at https:// www.foothealthfacts.org/footankleinfo/os_trigonum_syndrome.htm?terms=os%20trigonum).
5. American Academy of Orthopaedic Surgeons (AAOS). Posterior Tibial Tendon Dysfunction. (Accessed December 15, 2013, at https://orthoinfo.aaos.org/topic.cfm?topic=A00166).