What structure can pop in the midfoot causing lateral foot pain after an inversion injury?

Midfoot "Pop" with Lateral Pain After Inversion Injury

The most likely structure that "popped" in your midfoot causing lateral pain after an inversion injury is the peroneal tendons subluxating or dislocating from their normal position behind the lateral malleolus, though an isolated cuboid dislocation is also possible but much rarer. 1, 2

Primary Diagnosis: Peroneal Tendon Subluxation/Dislocation

Peroneal tendon subluxation occurs when the superior peroneal retinaculum (the fibrous band holding these tendons in place) tears during forced dorsiflexion combined with hindfoot eversion. 1 This creates the characteristic "popping" or "snapping" sensation patients describe, often accompanied by lateral ankle and foot pain. 3, 2

Key Clinical Features to Identify This Injury:

• History of a "pop" or "snap" felt during the injury, often misdiagnosed initially as a simple ankle sprain 3, 2
• Visible or palpable subluxation of tendons over the lateral malleolus during ambulation or resisted eversion 3
• Sensation of ankle "giving way" or instability with a snapping feeling 3
• Pain localized to the retromalleolar groove (behind the lateral ankle bone) 4
• Tenderness on palpation of the peroneal tendons during resisted ankle dorsiflexion and eversion 4

Why This Gets Missed:

The mechanism of injury (inversion) mimics a standard lateral ankle sprain, and both conditions frequently coexist because disruption of lateral ankle ligaments places additional strain on the superior peroneal retinaculum. 3 Standard ankle radiographs may appear normal or show only soft tissue swelling. 2

Alternative Diagnosis: Isolated Cuboid Dislocation

If the pain is specifically in the lateral midfoot (not at the ankle), consider an isolated cuboid dislocation—a rare injury that presents with lateral midfoot pain, inability to bear weight, and a palpable gap at the cuboid level. 5

Critical Features of Cuboid Dislocation:

• Lateral midfoot pain (not ankle pain) 5
• Palpable gap or deformity at the cuboid level 5
• Complete inability to bear weight since injury 5
• Initial radiographs may be inconclusive or appear normal 5

Diagnostic Approach

Immediate Evaluation:

1. Obtain three-view ankle radiographs (AP, lateral, mortise) if the patient meets Ottawa Ankle Rules criteria: inability to bear weight immediately or for four steps, point tenderness over malleoli/talus/calcaneus, or inability to walk at presentation. 6

2. For peroneal tendon subluxation, the diagnosis is primarily clinical—watch for visible tendon subluxation during active ankle eversion or ambulation. 3, 2

Advanced Imaging When Needed:

• Order non-contrast MRI for persistent lateral pain despite negative radiographs, suspected grade II-III ligament injury after 4-5 day re-examination, or when clinical suspicion for peroneal tendon pathology remains high. 7, 6

• MRI is the gold standard for visualizing peroneal tendon pathology and superior peroneal retinaculum tears. 7, 1

• Point-of-care ultrasound with dynamic viewing can capture episodic subluxation in real-time. 2

• For suspected cuboid dislocation with inconclusive radiographs, CT scanning is indicated. 5

Management Recommendations

For Peroneal Tendon Subluxation:

• Acute first-time dislocations may be managed conservatively with immobilization, but success rates are only 50% and recurrence is common. 3, 2

• Recurrent subluxations require surgical repair—anatomical reattachment of the superior peroneal retinaculum has excellent recovery rates and faster return to sport. 3, 2

• Athletes should be managed surgically even for acute injuries due to higher functional demands and better outcomes with early operative intervention. 3

For Cuboid Dislocation:

• Open reduction and internal fixation with Kirschner wires is usually necessary, as closed reduction is often blocked mechanically by the extensor digitorum brevis muscle or peroneus longus tendon. 5

Common Pitfalls to Avoid

Do not dismiss persistent lateral foot pain after an inversion injury as "just a sprain"—peroneal tendon subluxation and cuboid dislocation are frequently missed at initial presentation because they share the same mechanism as common ankle sprains. 5, 3, 2

Do not rely solely on initial radiographs to rule out these injuries—both conditions can have normal or subtle findings on plain films. 5, 2

Re-examine the patient 4-5 days after injury when swelling has subsided to reliably differentiate simple sprains from more complex pathology. 6