Os Trigonum Syndrome: Causes and Management introduction Os trigonum syndrome, sometimes called posterior ankle impingement syndrome (PAIS), is a potentially underrecognized condition and cause of posterior ankle pain.
Os Trigonum Syndrome: Causes and Management introduction Os trigonum syndrome, sometimes called posterior ankle impingement syndrome (PAIS), is a potentially underrecognized condition and cause of posterior ankle pain. This has been increasing in clinical practice secondary to awareness, increased interest in physical fitness and the use of exercise machines. The name comes from an accessory ossicle and how it is oriented between the medial navicular bone and posterior tibial tendon.
In 1804, Rosenmuller first described the os trigonum as an accessory ossicle. The name originated from the trigonal contours of its three surfaces: the anterior surface adjacent to the talus, the posterior surface with its ligamentous attachment, and the inferior surface adjacent to the calcaneus. An elongated lateral tubercle to the talus (Stieda process) may cause symptoms similar to os trigonum syndrome.
An os trigonum syndrome originates from a stress fracture of the Stieda process or failed fusion of a secondary ossification center of the lateral tubercle, creating a synchondrosis with the talus. It can also originate from an acute fracture of the Stieda process (posterior process fracture of the talus). Laterally, the os trigonum and the trigonal process receive fibers from the posterior talofibular ligament whilst immediately medially lies the thick, fibrous tendon sheath of flexor hallucis longus, both of which may contribute to the clinical picture in os trigonum syndrome.
In radiologic studies of normal feet and ankles, the prevalence of os trigonum syndrome ranges from 14% to 25% in patients with an ununited lateral tubercle. Reported a prevalence rate of 30% in ballet dancers, which may be attributed to repetitive forced plantar flexion in ballet training during the skeletal maturation phase of development that precedes the closure of the ossification center. The prevalence is higher in sports and activities with repetitive plantarflexion including ballet, soccer, downhill running.
Any ankle trauma can initiate or exacerbate the condition. Almost three quarters of patients report an acute ankle injury as the initiating cause of symptoms. Symptoms of os trigonum syndrome include stiffness, particularly while in plantar flexion, chronic pain, and swelling behind the ankle.
If you are experiencing symptoms that may be related to os trigonum syndrome, it is important to see a sports medicine physician. Early evaluation and treatment typically lead to better outcomes. Do not ignore pain or symptoms that are limiting your activity.
*This article is for educational purposes only and does not substitute for professional medical advice. Always consult a qualified healthcare provider.*
Connect with a doctor, physical therapist, or imaging center near you.
Find a Provider Near You โ