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Posterior Ankle Impingement

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(Redirected from Os Trigonum Syndrome)

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

Background

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

History

  • The first case was published by Johann Rosenmuller in 1804 due to Os Trigonum[1]
  • The syndrome was later described by Howse in 1982 referring to a cluster of dancers[2]

Epidemiology

  • True incidence is unknown
  • Reported to be 18% in all ankle impingement-type problems in runners[3]
  • In a cohort of male professional soccer players, ankle impingement syndromes accounted for less than 0.5% of all injuries[4]
    • Posterior impingement was more common than anterior impingement

Introduction

Vicious circle of the repetitive plantar flexion with the presence of anatomical factors, which cause local soft-tissue changes posterior to the ankle joint resulting in more space restriction, and aggravating patient symptoms.[5]
Medial view of posterior ankle with the presence of os trigonum[6]
Os trigonum on (a) Lateral foot radiograph; (b) 2D CT; (c) 3D CT[7]
Illustration of posteromedial impingement, with entrapment of fibrotic scar tissue in the posteromedial ankle gutter (circled).[8]
Hindfoot extra-articular structures divided into quadrants as defined by the intermalleolar ligament. (1) Fibula, (2) tibia, (3) posterior-inferior tibiofibular ligament (transverse ligament), (4) flexor hallucis longus tendon, (5a) intermalleolar ligament, (5b) superior tibial insertion of the intermalleolar ligament, (6) tibiotalar joint, (7) subtalar joint, (8) posterolateral talar process, (9) flexor hallucis longus retinaculum, (10) calcaneofibular ligament, and (11) posterior talofibular ligament[9]

General

  • Clinical disorder characterized by posterior ankle pain that occurs during forced plantar flexion
  • Can result from either bony or soft tissue structures in the posterior ankle
  • The condition can evelop acutely following traumatic hyperplantarflexion or chronically from repetitive stress
  • Patients present with posterior ankle pain made worse with plantarflexion and push off manuevers
  • Treatment is primarily conservative, with surgical intervention reserved for those who do not improve

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"[10] or "bony impingement"[11] 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

Etiology: 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
    • Os trigonum is present in 63.3% of patients with isolated PAIS[12]
    • May be related to degenerative changes at the synchondrosis, fracture of the posterior lateral talar process, local synovitis, flexor hallucis longus tenosynovitis or intra-articular loose bodies
    • Repetitive plantarflexion predisposes to this condition as seen in ballet dancers, basketball, football
  • Prominent Calcaneus posterior process

Etiology: Soft Tissue Lesions

  • Flexor Hallucis Longus Tendinopathy
    • 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

Associated Conditions

Anatomy of the Posterior Ankle Joint

  • 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[15]

Risk Factors

Sports[16]

  • Ballet Dancers[17]
  • Soccer[18]
  • Downhill running
  • Basketball
  • Football

Differential Diagnosis

Differential Diagnosis Ankle Pain

Clinical Features

Typical pain distribution although patients often have trouble localizing
Heel Thrust Test

History

  • Patients typically report 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
  • Athletes in high risk sports include (ballet dancers performing "en pointe," soccer players, gymnasts, javelin throwers)[17]
  • Patients may describe a sensation of something catching in the back of the ankle during plantar flexion

Physical Exam: Physical Exam Ankle

  • Inspect for Pes Planus, Pes Cavus
  • Pain or tenderness deep to the Achilles tendon
    • Particulary in the region between the Achilles tendon and the peroneal tendons
    • Direct palpation of the posterolateral or posteromedial ankle may reproduce symptoms
  • Pain is worse with plantar flexion, characteristically beond 50 degrees of motion
    • This is true in both passive and active motion

Special Tests

  • Plantar Flexion Test: Hindfoot pain aggravated by plantar flexion of the ankle
  • Heel Thrust Test: painful forced dorsiflexion
  • Single Leg Heel Raise: endurance capacity and perceived ankle stability may be reduced[19]

Evaluation

Ultrasound guided diagnostic injection of the FHL tendon[20]
A 25-year-old female ballet dancer with posterior ankle impingement due to presence of an Os trigonum. Sagittal proton density-weighted fat-suppressed MRI shows moderate bone marrow oedema in the Os trigonum but also the talar body (short white arrows). There is fluid-equivalent signal at the synchondrosis indicating a partial destabilization (black arrow). In addition there is marked synovitis surrounding the Os trigonum and extending to the subtalar joint consistent with an acute inflammatory response due to chronic irritation of the posterior subtalar joint and surrounding structures (long white arrows).<[17]
Lateral right ankle radiography (A), T1 weighted sequence (B) and sagittal STIR MRI sequence (C) images demonstrating an enlarged Stieda's process (arrows) with mild bone marrow and soft tissues edema.[21]

Diagnosis

  • The diagnosis is primarily clinical and takes precedence over imaging findings
  • One study of elite Ballet dancers and athletes compared imaging findings to clinical exam[22]
    • Imaging was not associated with posterior ankle pain or a positive plantarflexion pain provocation test
    • This included os trigonum, Stieda process, bone marrow edema, and flexor hallucis longus pathology
    • Imaging findings did not differ between PAIS-positive and PAIS-negative groups

Radiographs

  • Standard Radiographs Ankle
    • Lateral view is most helpful observe osseous lesions of hindfoot
    • Radiographs were reported as normal in 72% of pediatric and adolescent patients with surgically confirmed PAIS[23]
  • 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[24]
  • Potential findings
    • May show acute or chronic fracture of Trigonal Process
    • Presence of Os Trigonum
    • Impingement on dynamic view
    • Posterior ankle calcified tissue

CT

  • Can be useful to clarify osseous dysfunction
    • Provides fine detail regarding the size, location, and number of anatomical bony abnormalities[25]
  • May not differentiate between old fracture and os trignoum

Bone Scintigraphy

  • Can help clarify acuity of fracture of the trigonal process

MRI

  • Imaging study of choice in patients with PAIS[26]
  • Potential findings
    • Bone contusion
    • Pseudarthrosis
    • Fragmentation
    • FHL Tenosynovitis
    • Identify anomalous muscles
  • Can exclude other causes of posterior ankle pain

Ultrasound

  • Can aid in both diagnosis and therapeutic intervention
  • Potential findings
    • Os trigonum
    • Assess for fluid collections
    • Evaluate the flexor hallucis longus tendon dynamically
  • Diagnostic injection can be performed with local anesthetic to confirm the suspected diagnosis
    • Generally under ultrasound guidance

Classification

  • Generally classified based on etiology

Management

Proposed treatment algorithm from Maquirriain[27]

Nonoperative

  • General
    • Approach is generally driven by etiology
    • Maquirriain proposed a treatment algorithm[27]
  • Indications
    • Trigonal process disease
    • FHL tenosynovitis
  • Relative rest and activity modification
    • PAIS often improves with rest alone[28]
    • Avoidance of forced plantar flexion
  • Ice Therapy
  • NSAIDS
  • Immobilization
    • Occasionally, casting for 4 to 6 weeks for trigonal process disease
  • Physical Therapy
    • Focus on ankle range of motion, strengthening, and proprioception
    • Progressive resistive exercises and strengthening
  • Orthotics
    • For FHL tenosynovitis, consider strapping of the foot, and longitudinal arch supports placed in firm-sole shoes

Procedures

  • Corticosteroid Injection
    • Can be performed for FHL tenosynovitis
    • Can serve both diagnostic and therapeutic purposes
    • Should be performed under ultrasound guidance

Operative

  • 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

Intermediate level exercises for posterior ankle impingement
Advanced exercises for posterior ankle impingement

Example Postoperative Rehabilitation Protocol

  • Phase 1: Immediate Postoperative (Weeks 0-2)[18]
    • Weight-bearing as tolerated with crutches (most endoscopic protocols allow immediate weight-bearing)
    • Compression dressing and elevation for edema control
    • Gentle active range of motion exercises (dorsiflexion/plantar flexion within pain-free limits)
    • Ankle pumps and toe curls for circulation
    • Ice application for pain and swelling management
    • Portal site care and wound monitoring
  • Phase 2: Early Rehabilitation (Weeks 2-4)
    • Progressive weight-bearing, weaning from crutches
    • Full active and passive range of motion exercises
    • Initiation of Achilles tendon and gastrocnemius-soleus stretching
    • Intrinsic foot muscle strengthening
    • Stationary cycling (low resistance)
    • Proprioceptive training: single-leg stance on stable surfaces
    • Scar mobilization once wounds healed
  • Phase 3: Intermediate Rehabilitation (Weeks 4-8)[29]
    • Full weight-bearing without assistive devices
    • Progressive resistance exercises (theraband, calf raises)
    • Single-leg heel raise progression (given documented deficits in SLHR capacity in PAIS patients)
    • Balance and proprioception: unstable surfaces (wobble board, BOSU)
    • Pool-based exercises and aqua jogging
    • Light jogging on treadmill (typically week 6+)
    • Sport-specific movement patterns introduced
  • Phase 4: Advanced Rehabilitation (Weeks 8-12)
    • Plyometric exercises (jumping, hopping, bounding)
    • Agility drills (ladder, cone drills, cutting)
    • Sport-specific training at submaximal intensity
    • Progressive running program (straight-line → directional changes)
    • Eccentric strengthening of posterior chain
    • Full plantar flexion activities without pain

Exercise Therapy and Handout PDFs

Return to Play/ Work

  • Estimated time frame[30]
    • Endoscopic surgery: Return to training at 4-5 weeks, return to competition at 6-8 weeks
    • Open surgery: Return to training at 9-10 weeks, return to competition at 11-12 weeks
    • Full unrestricted activity: 70-80% of patients by 13-18 weeks
  • General RTP criteria
    • Pain-free full range of motion (including terminal plantar flexion >50°)
    • No tenderness on palpation of posterior ankle
    • Negative passive plantar hyperflexion test
    • Single-leg heel raise endurance equal to contralateral limb (≥90%)
    • Single-leg hop test ≥90% of contralateral limb
    • Completion of sport-specific drills at full intensity without symptoms
    • AOFAS score ≥90 or return to preinjury baseline
    • Psychological readiness and confidence in ankle
  • Sport specific
    • Soccer players: Mean return to training 34 days (5 weeks), return to playing 41 days (6 weeks) after endoscopic surgery[18]
    • Ballet dancers: Gradual return to relevé, demi-pointe, then en pointe positions; may require longer timeline (12-16 weeks)
    • High-demand athletes: Sport-specific functional testing before clearance

Prognosis and Complications

Prognosis

  • General
    • Overall prognosis for PAIS is excellent
    • The majority of patients achieving significant symptom improvement regardless of treatment approach
  • Nonsurgical
    • Treatment reportedly has been successful in approximately 60% of patients[31]
    • Patients can expect return to activity within 3-4 weeks following injection therapy
  • 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[20]
    • Zwiers et al: mean time to return to full activity was on average 11.3 wk (5.9-12.9 wk) following arthroscopic treatment[32]
  • Prognostic factors
    • Overuse-related PAIS have better outcomes than trauma-related PAIS[33]
    • Longer preoperative symptom duration correlates with longer time to return to training and playing[18]
    • Bony impingement requiring excision is associated with longer recovery compared to soft tissue debridement alone

Long Term Outcomes

  • Durability of results[34]
    • 5-year follow-up data from a randomized controlled trial confirms sustained improvement with both open and endoscopic techniques
    • Medium- to long-term outcomes (median 4.8 years) demonstrate maintained pain relief and functional improvement
    • No reoperations reported at average 23-month follow-up in elite athletes
    • All patients in one series reported they would undergo the surgery again if needed
  • Return to Previous Level of Activity[35][36]
    • 100% of athletes returned to their previous level of competition in some series
    • 94% of patients able to return to previous sport/physical activity
    • Professional athletes: All returned to their previous level of professional activity

Complications

See Also

Internal

External

References

  1. ↑ Rosenmüller, Johann Christian. De nonnullis musculorum corporis humani varietatibus. Klaubarth, 1804.
  2. ↑ Howse, A. J. G. "Posterior block of the ankle joint in dancers." Foot & ankle 3.2 (1982): 81-84.
  3. ↑ 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.
  4. ↑ D’Hooghe, Pieter, et al. "Anterior ankle impingment syndrome is less frequent, but associated with a longer absence and higher re-injury rate compared to posterior syndrome: a prospective cohort study of 6754 male professional soccer players." Knee Surgery, Sports Traumatology, Arthroscopy 30.12 (2022): 4262-4269.
  5. ↑ Albtoush, O. M. "Posterior Ankle Impingement Syndrome." European Congress of Radiology-ESSR 2017, 2017.
  6. ↑ Preinl, Maciej, et al. "Prevalence and clinical aspects of os trigonum: a meta-analysis: Prevalence and clinical aspects…." Anatomical Science International 100.3 (2025): 287-297.
  7. ↑ Keles-Celik, Nigar, et al. "Accessory ossicles of the foot and ankle: disorders and a review of the literature." Cureus 9.11 (2017).
  8. ↑ Giannini, Sandro, et al. "Posterior ankle impingement." Foot & Ankle International 34.3 (2013): 459-465.
  9. ↑ Yasui, Youichi, et al. "Posterior ankle impingement syndrome: a systematic four-stage approach." World journal of orthopedics 7.10 (2016): 657.
  10. ↑ Jaivin, Jonathan S., and Richard D. Ferkel. "Arthroscopy of the foot and ankle." Clinics in sports medicine 13.4 (1994): 761-783.
  11. ↑ 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.
  12. ↑ Özer, Mustafa, and Ahmet Yıldırım. "Evaluation of the prevalence of os trigonum and talus osteochondral lesions in ankle magnetic resonance imaging of patients with ankle impingement syndrome." The Journal of Foot and Ankle Surgery 58.2 (2019): 273-277.
  13. ↑ Sharpe, B. Dale, et al. "Posterior ankle impingement and flexor hallucis longus pathology." Clinics in Sports Medicine 39.4 (2020): 911-930.
  14. ↑ Kalbouneh, Heba M., et al. "Incidence of symptomatic os trigonum among nonathletic patients with ankle sprain." Surgical and Radiologic Anatomy 41.12 (2019): 1433-1439.
  15. ↑ Lawson, J. P. "Symptomatic radiographic variants in extremities." Radiology 157.3 (1985): 625-631.
  16. ↑ 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.
  17. ↑ 17.0 17.1 17.2 Hayashi, Daichi, et al. "Posterior ankle impingement in athletes: pathogenesis, imaging features and differential diagnoses." European journal of radiology 84.11 (2015): 2231-2241.
  18. ↑ 18.0 18.1 18.2 18.3 Calder, James D., Shaun A. Sexton, and Christopher J. Pearce. "Return to training and playing after posterior ankle arthroscopy for posterior impingement in elite professional soccer." The American Journal of Sports Medicine 38.1 (2010): 120-124.
  19. ↑ Baillie, Peta, et al. "Single-leg heel raise capacity is lower, and perceived ankle instability is greater, in dancers and athletes with posterior ankle impingement syndrome." Clinical Journal of Sport Medicine 34.4 (2024): 376-380.
  20. ↑ 20.0 20.1 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.
  21. ↑ Martins, Nádia, et al. "Posterior Ankle Impingement Syndrome." Reumatologia clinica 14.4 (2017): 244-245.
  22. ↑ Baillie, Peta, et al. "Posterior ankle impingement syndrome clinical features are not associated with imaging findings in elite ballet dancers and athletes." Clinical journal of sport medicine 32.6 (2022): 600-607.
  23. ↑ Kushare, Indranil, Matthew G. Ditzler, and Siddharth P. Jadhav. "Delayed diagnosis of posterior ankle impingement in pediatric and adolescent patients: does radiology play a role?." Pediatric Radiology 50.2 (2020): 216-223.
  24. ↑ 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
  25. ↑ Burghardt AJ, Link TM, Majumdar S. High-resolution computed tomography for clinical imaging of bone microarchitecture. Clin Orthop Relat Res. 2011;469:2179–2193.
  26. ↑ 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.
  27. ↑ 27.0 27.1 Maquirriain, Javier. "Posterior ankle impingement syndrome." JAAOS-Journal of the American Academy of Orthopaedic Surgeons 13.6 (2005): 365-371.
  28. ↑ 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.
  29. ↑ Smyth, Niall A., et al. "Hindfoot arthroscopic surgery for posterior ankle impingement: a systematic surgical approach and case series." The American journal of sports medicine 41.8 (2013): 1869-1876.
  30. ↑ Georgiannos, Dimitrios, and Ilias Bisbinas. "Endoscopic versus open excision of os trigonum for the treatment of posterior ankle impingement syndrome in an athletic population: a randomized controlled study with 5-year follow-up." The American journal of sports medicine 45.6 (2017): 1388-1394.
  31. ↑ Hedrick MR, McBryde AM: Posterior ankle impingement. Foot Ankle 1994; 15:2-8.
  32. ↑ Zwiers R, Wiegerinck JI, Murawski CD, Smyth NA, Kennedy JG, van Dijk CN. Surgical treatment for posterior ankle impingement. Arthroscopy. 2013;29:1263–1270.
  33. ↑ van Dijk, C. Niek, Peter AJ de Leeuw, and Peter E. Scholten. "Hindfoot endoscopy for posterior ankle impingement: surgical technique." JBJS 91.Supplement_2 (2009): 287-298.
  34. ↑ Georgiannos, Dimitrios, and Ilias Bisbinas. "Endoscopic versus open excision of os trigonum for the treatment of posterior ankle impingement syndrome in an athletic population: a randomized controlled study with 5-year follow-up." The American journal of sports medicine 45.6 (2017): 1388-1394.
  35. ↑ Carreira, Dominic S., et al. "Outcome of arthroscopic treatment of posterior impingement of the ankle." Foot & Ankle International 37.4 (2016): 394-400.
  36. ↑ Smyth, Niall A., et al. "Hindfoot arthroscopic surgery for posterior ankle impingement: a systematic surgical approach and case series." The American journal of sports medicine 41.8 (2013): 1869-1876.
  37. ↑ Zwiers, Ruben, et al. "Open versus endoscopic surgical treatment of posterior ankle impingement: a meta-analysis." The American Journal of Sports Medicine 50.2 (2022): 563-575.
Created by:
John Kiel on 20 September 2021 06:35:01
Authors:
Last edited:
4 March 2026 01:34:43
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Lower Extremity | Ankle | Acute | Overuse | Chronic | Featured
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