Peroneal Tendon Subluxation and Dislocation

Peroneal tendon subluxation is an uncommon but frequently missed cause of lateral ankle pain in young athletes. The superior peroneal retinaculum (SPR) tears, allowing the peroneus longus and brevis tendons to dislocate anterolaterally out of the fibular groove. Patients describe a painful "snap" or "pop" over the lateral malleolus, which is pathognomonic when reproduced on examination.

The controversies section mentions tendoscopic treatment of intrasheath subluxation — this distinct, easily-missed entity deserves separating from frank (subsheath) dislocation.

• What it is. In intrasheath subluxation the superior peroneal retinaculum is intact and the tendons never leave the retromalleolar groove — instead they snap against each other within the sheath. It is the reason a patient can have a convincing painful snap yet a normal static MRI and no visible dislocation over the fibula.
• The Raikin classification. Type A - no tendon tear: the peroneus longus and brevis reverse their positions (flip past each other) within an intact sheath. Type B - with a tear: the peroneus longus subluxes through a longitudinal split in the peroneus brevis, snapping in and out of the split.
• Diagnosis is dynamic. Because static imaging is typically normal, the key test is dynamic ultrasound (or dynamic MRI) during active circumduction/eversion, which shows the tendons flipping or the longus moving through the brevis split in real time — the same reason it is under-recognised.
• Management. A conservative trial as for frank subluxation; when refractory, tendoscopic or open groove deepening (with repair of any brevis split) addresses the crowded sheath — an isolated SPR repair does not help, because the SPR was never torn.

The classification lists a Type IV / habitual variant and the outcomes section flags it as hard to correct — the atraumatic subluxer behaves differently enough to manage on its own terms.

• A different patient. Unlike the traumatic dislocator (a discrete injury), the habitual subluxer has no significant trauma; the tendons sublux repeatedly with ordinary activity, often bilaterally and relatively painlessly, and some patients can voluntarily sublux the tendons on demand. The underlying problem is usually a congenitally shallow, flat, or even convex (retro-fibular) groove rather than an acute SPR tear.
• Why SPR repair alone fails. With a flat or convex fibula there is no competent groove to contain the tendons, so an isolated retinacular repair predictably re-fails — this is the one scenario where bony work is mandatory, not optional.
• Management. Groove deepening (or a fibular osteotomy to create or rotate a groove) combined with retinacular reconstruction is the mainstay; historical sling/rerouting or bone-block procedures are reserved for the rare failed reconstruction.
• A counselling caveat. A voluntary or psychogenic subluxer with minimal pain may do poorly after surgery and needs careful selection — operate for genuinely disabling, involuntary symptoms, not for the "party trick" alone.

Peroneal tendon dislocation is rare (roughly 0.3-0.5% of ankle injuries) and there are no formal disease-specific society guidelines or arthroplasty/implant registries — it is a soft-tissue tendon problem managed by surgeon judgement and small-series evidence. Practice is shaped by the foot-and-ankle literature and by sports-medicine consensus rather than by national protocols.