Urgent Peroneal Tendon Subluxation/Dislocation
This patient requires immediate clinical examination for peroneal tendon subluxation or dislocation, with urgent imaging (dynamic ultrasound or MRI) and orthopedic referral, as this injury has a low success rate with conservative treatment and typically requires surgical intervention to prevent chronic instability and restore function.
Clinical Presentation Analysis
The combination of:
- Inversion ankle injury with audible "pop"
- Sensation of "something moving" on the lateral foot
- Altered gait pattern
This triad is pathognomonic for peroneal tendon subluxation/dislocation rather than a simple lateral ankle sprain 1, 2. While both injuries share similar inversion mechanisms, the "popping" sensation with palpable movement distinguishes peroneal tendon pathology from standard ligamentous injury 3.
Immediate Diagnostic Steps
Physical Examination Priorities
Specific findings to assess:
- Palpate the retromalleolar groove while having the patient actively dorsiflex and evert the ankle—you should feel the tendons subluxing or dislocating over the lateral malleolus 2, 4
- Test for tenderness directly over the peroneal tendons posterior to the fibula (not just over the lateral ligaments)
- Assess for cavus foot deformity, which predisposes to this injury 5
- Perform resisted ankle eversion to reproduce the painful "snapping" sensation 5
Critical pitfall: Do not assume this is a simple ankle sprain based on mechanism alone—peroneal tendon injuries are frequently missed in acute settings because clinicians focus solely on lateral ligament assessment 2, 3.
Imaging Protocol
Dynamic ultrasound is the gold standard for acute diagnosis 4. A 2004 study demonstrated 100% positive predictive value for dynamic ultrasound in detecting peroneal tendon subluxation when performed during active dorsiflexion and eversion maneuvers 4. Static imaging (standard X-rays or MRI without stress positioning) will miss episodic subluxation 2, 4.
If dynamic ultrasound is unavailable, obtain MRI to evaluate:
- Superior peroneal retinaculum integrity
- Associated peroneal tendon tears (present in up to 40% of cases) 4, 6
- Retromalleolar groove anatomy 1
Plain radiographs should still be obtained initially to rule out fractures, but they will not diagnose the tendon pathology 1.
Management Algorithm
Conservative Treatment (Limited Role)
Conservative management has a low success rate for preventing recurrent subluxation 2, 6. It may be attempted only in truly acute first-time injuries with:
- Short-term immobilization (boot or cast) for 2-3 weeks
- Transition to ankle brace
- Supervised physical therapy focusing on peroneal strengthening
However, you should set realistic expectations with the patient that conservative treatment frequently fails 2.
Surgical Intervention (Definitive Treatment)
Operative management has high success rates and faster return to function 1, 2, 6. Surgery is indicated for:
- Recurrent subluxation after conservative trial
- Acute injuries in high-demand patients/athletes
- Associated peroneal tendon tears >50% 6
Surgical options include 1, 6:
- Superior peroneal retinaculum repair (primary approach for acute injuries)
- Groove-deepening procedures (for shallow retromalleolar groove)
- Tendon repair/tubularization (if <50% torn) or tenodesis (if >50% torn) 6
Urgent Referral Criteria
Refer to orthopedic surgery within 1-2 weeks for:
- Confirmed or highly suspected peroneal tendon subluxation
- Any patient with persistent lateral ankle pain and "snapping" sensation after inversion injury
- Failed conservative management after 4-6 weeks
Common pitfall: Delaying diagnosis by treating this as a routine ankle sprain leads to chronic instability, persistent pain, and more complex reconstructive procedures 2, 5.
Immediate Management Pending Referral
- Immobilize in walking boot or posterior splint
- Non-weight-bearing or protected weight-bearing as tolerated
- NSAIDs for pain control (though note they may suppress natural healing—use judiciously) 7
- Arrange urgent dynamic ultrasound or MRI
- Expedite orthopedic referral—do not wait for "failed conservative treatment"
The key distinction: Unlike standard lateral ankle sprains where supervised exercise programs are preferred 7, peroneal tendon subluxation typically requires surgical stabilization to restore function and prevent chronic disability 2, 6.