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Posterior Ankle Impingement Syndrome

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Other Names

  • Posterior Ankle Impingement Syndrome (PAIS)
  • Posterior block of the ankle
  • Posterior triangle pain
  • Talar compression syndrome
  • Os trigonum syndrome
  • Os trigonum impingement
  • Posterior tibiotalar impingement syndrome
  • Nutcracker-type syndrome


  • This page refers to Posterior Ankle Impingement Syndrome (PAIS)



  • True incidence is unknown
  • Reported to be 18% in all ankle impingement-type problems in runners[1]


  • Definition
    • There is a lack of consensus regarding the definition of PAIS
    • Generally considered to be the clinical disorder characterized by posterior ankle pain in forced plantar flexion.
    • It has been referred to as "soft tissue impingement"[2] or "bony impingement"[3] occurring within the anatomic interval between the posterior tibial articular surface and the calcaneus
  • Diagnosis
    • Challenging due to the wide variety of causes of posterior ankle pain
    • Anatomic structures are deeply positioned, which makes physical exam limited
    • Must consider age, sex, mechanism, prior treatments, associated conditions


Osseous Lesions

  • Stieda process
  • Os trigonum
  • Osteoarthritis with osteophytes
  • Osteochondral lesion
    • Can occur in the tibiotalar space or subtalar space
    • Often missed or delayed in up to 81% of unexplained chronic ankle pain (need reference)
    • Patients often complain of swelling, pain and mechanical symptoms including locking, catching
  • Loose bodies
  • Chondromatosis
  • Subtalar coalition
  • Synchondrosis injury to Os Trigonum
  • Prominent Calcaneus posterior process

Soft Tissue Lesions

  • Flexor Hallucis Longus Tenosynovitis
    • Seen in runners, tennis players, and those involved in repetitive push-off maneuvers, such as ballet dancers
    • Typically begins insidiously
    • Pain at the posteromedial ankle, can radiate along the worse, worse with manipulation of hallux
  • Synovitis
  • Impingement of the joint capsule
  • Posterior capsuloligamentous injury
  • Impingement of the anomalous muscles
  • Calcified inflammatory tissue


  • Posterior region of ankle
    • Includes soft tissue structures between Ankle Joint (Tibiotalar Joint) and Calcaneus
    • Superior border: horizontal line 4 cm above the tip of the malleolus
    • Inferior border: curved line 4 cm below the lateral malleolus
    • Achilles Tendon is central axis
  • Os Trigonum
    • Secondary ossification center of the Talus
    • Mineralizes between age 7 and 13, fuses within 1 year, forms Steida process
    • Remains separate ossicle in 7-14% of patients, often bilaterally[4]

Risk Factors

  • Sports[5]
    • Ballet Dancers
    • Soccer
    • Downhill running

Differential Diagnosis

Clinical Features

  • History
    • Typically chronic or recurrent posterior ankle pain
    • Exacerbated by push off activities, forced plantar flexion
    • Offending activities include dancing, kicking, downhill running, sliding, high heels
    • History can be traumatic (acute or chronic), or overuse
    • Pain is described as consistent, sharp, dull and radiating
    • Patients have a hard time pinpointing the exact location of pain
  • Physical Exam: Physical Exam Ankle
    • Inspect for Pes Planus, Pes Cavus
    • Pain or tenderness deep to the Achilles tendon
    • Pain is worse with plantar flexion
  • Special Tests



  • Standard Radiographs Ankle
    • Lateral view is most helpful observe osseous lesions of hindfoot
  • Posterior impingement (PIM) view
    • Recommended instead of a conventional lateral view for symptomatic hindfoot pain
    • lateral, 25-degree external rotation, oblique view of the ankle
    • Significant superior diagnostic accuracy compared with the lateral view in the detection of os trigonum[6]
  • Potential findings
    • May show acute or chronic fracture of Trigonal Process
    • Presence of Os Trigonum
    • Impingement on dynamic view
    • Posterior ankle calcified tissue


  • Can be useful to clarify osseous dysfunction
    • Provides fine detail regarding the size, location, and number of anatomical bony abnormalities[7]
  • May not differentiate between old fracture and os trignoum

Bone Scintigraphy

  • Can help clarify acuity of fracture of the trigonal process


Ultrasound guided diagnostic injection of the FHL tendon[8]
  • Imaging study of choice in patients with PAIS[9]
  • Potential findings
    • Bone contusion
    • Pseudarthrosis
    • Fragmentation
    • FHL Tenosynovitis
    • Identify anomalous muscles
  • Can exclude other causes of posterior ankle pain

Diagnostic Injection

  • Can be performed with local anesthetic to confirm the suspected diagnosis
    • Generally under ultrasound guidance


  • Generally classified based on etiology


Proposed treatment algorithm from Maquirriain[10]


  • General
    • Approach is generally driven by etiology
    • Maquirriain proposed a treatment algorithm[10]
  • Indications
    • Trigonal process disease
    • FHL tenosynovitis
  • Relative rest and activity modification
    • PAIS often improves with rest alone[11]
    • Avoidance of forced plantar flexion
  • Ice Therapy
  • Immobilization
    • Occasionally, casting for 4 to 6 weeks for trigonal process disease
  • Physical Therapy
    • Progressive resistive exercises and strengthening
  • Orthotics
    • For FHL tenosynovitis, consider strapping of the foot, and longitudinal arch supports placed in firm-sole shoes
  • Corticosteroid Injection
    • Can be performed for FHL tenosynovitis


  • Indications
    • Failure of non-surgical approach after 3 months
    • Prominent calcaneus posterior process
    • Severe stenosis of the fibro-osseous tunnel
    • Posterior osteochondral ankle lesions
  • Technique
    • surgical excision of the fractured trigonal process or os trigonum
    • Resection of prominent calcaneus posterior process

Rehab and Return to Play


  • Needs to be updated

Return to Play/ Work

  • Consider protective dorsiflexion taping

Complications and Prognosis


  • Nonsurgical
    • Treatment reportedly has been successful in approximately 60% of patients[12]
  • Need for surgery
    • Approximately 40% patients eventually require surgical intervention due to intractable hindfoot pain (need citation)
  • Surgical outcomes
    • A majority of studies have reported post-operative American Orthopaedic Foot and Ankle Society (AOFAS) Scores greater than 85[8]
    • Zwiers et al: mean time to return to full activity was on average 11.3 wk (5.9-12.9 wk) following arthroscopic treatment[13]


See Also


  1. McBryde A: Disorders of the ankle and foot, in Brana WA, Kalenak A (eds): Clinical Sports Medicine. Philadelphia, PA: WB Saunders, 1991, pp 466-489.
  2. Jaivin, Jonathan S., and Richard D. Ferkel. "Arthroscopy of the foot and ankle." Clinics in sports medicine 13.4 (1994): 761-783.
  3. Hamilton, William G., Mark J. Geppert, and Francesca M. Thompson. "Pain in the posterior aspect of the ankle in dancers. Differential diagnosis and operative treatment." JBJS 78.10 (1996): 1491-1500.
  4. Lawson, J. P. "Symptomatic radiographic variants in extremities." Radiology 157.3 (1985): 625-631.
  5. Smyth NA, Zwiers R, Wiegerinck JI, Hannon CP, Murawski CD, van Dijk CN, Kennedy JG. Posterior hindfoot arthroscopy: a review. Am J Sports Med. 2014;42:225–234.
  6. Wiegnerinck JI, Kerkhoffs GMM, Struijs PAA, van Dijk CN. The posterior impingement-view: An alternative conventional projection to detect bony posterior ankle impingement. Arthroscopy. 2014;30:1311–1316
  7. Burghardt AJ, Link TM, Majumdar S. High-resolution computed tomography for clinical imaging of bone microarchitecture. Clin Orthop Relat Res. 2011;469:2179–2193.
  8. 8.0 8.1 Yasui Y, Hannon CP, Hurley E, Kennedy JG. Posterior ankle impingement syndrome: A systematic four-stage approach. World J Orthop. 2016;7(10):657-663.
  9. Wakeley, C. J., D. P. Johnson, and I. Watt. "The value of MR imaging in the diagnosis of the os trigonum syndrome." Skeletal radiology 25.2 (1996): 133-136.
  10. 10.0 10.1 Maquirriain, Javier. "Posterior ankle impingement syndrome." JAAOS-Journal of the American Academy of Orthopaedic Surgeons 13.6 (2005): 365-371.
  11. Frey C: Injuries to the subtalar joint, in Pfeffer GB (ed): Chronic Ankle Pain in the Athlete. Rosemont, IL: American Academy of Orthopaedic Surgeons, 2000, pp 21-42.
  12. Hedrick MR, McBryde AM: Posterior ankle impingement. Foot Ankle 1994; 15:2-8.
  13. Zwiers R, Wiegerinck JI, Murawski CD, Smyth NA, Kennedy JG, van Dijk CN. Surgical treatment for posterior ankle impingement. Arthroscopy. 2013;29:1263–1270.
Created by:
John Kiel on 20 September 2021 06:35:01
Last edited:
3 October 2022 23:52:30
Lower Extremity | Ankle | Acute | Overuse | Chronic