Snapping phenomenon around the ankle: An anatomy-based review

Table 1 Summary of ankle snapping phenomena, categorized by anatomical region, includes the involved structures, pathologic findings, clinical presentation, relevant imaging findings, and both conservative and surgical management strategies

Type		Involved structures	Pathologic findings	Clinical findings	Imaging findings	Conservative management	Surgical management
Lateral	Prefibular (anterior)	PL and PB	SPR tear; PL and PB dislocation	Snapping behind lateral malleolus during resisted eversion in dorsiflexed ankle	US: Tendon dislocation out of retromalleolar groove; MRI: Tendon tears, retinacular avulsions, tenosynovitis, and retromalleolar groove morphology	Immobilization with taping/plaster cast for 4-6 weeks (< 50% successful rate)	SPR repair/reconstruction ± groove deepening (open or endoscopic)
	Distal	PL	IPR tear; PL dislocation	Snapping tendon at peroneal tubercle with foot eversion	US: Tendon dislocation over peroneal tubercle; MRI: IPR tear		Peroneal tubercle resection, IPR reconstruction ± groove deepening (open or endoscopic)
	Intrasheath	PL and PB	Intact SPR; switching tendon positions	Snapping posterior to lateral maalleolus with ankle circumduction	US: Switching of tendon positions; MRI: Tendon split tear, intact SPR		Tendon debridement/repair ± SPR reconstruction and groove deepening (open or endoscopic)
Anterior		TA	Ganglion cyst at naviculocuneiform joint rubbing TA tendon	Snapping at tendon insertion during everted-to-inverted foot motion	Radiograph: Normal, US/MRI: No report	No report	Surgical excision
		EDL	IER incompetence; EDL snapping over lateral talar body	Snapping on anterolateral ankle during maximal foot inversion	MRI: No related pathology found	No report	IER repair/reinforcement
		PT	Hypertrophied PT muscle belly snapping over lateral talar dome	Snapping of fusioform mass anterolaterally with ankle plantarflexion-to-dorsiflexion	Radiograph: Normal, US/MRI: No report	No report	Arthroscopic myoplasty
		Talar head	Hypertrophied lateral talar head impinging on IER	Snapping anterolaterally in ankle dorsiflexion-plantarflexion, with foot inversion	Radiograph: Dorsolateral prominence of talar head; US: IER snaps over lateral prominence of talar head	No report	Arthroscopic taloplasty
Medial		PTT	Flexor retinaculum tear/pseudoretinaculum; PTT dislocation	Snapping/palpable cord-like structure over medial malleolus with resisted ankle plantarflexion-inversion	US: Tendon dislocation, retinacular tear or avulsion, fluid signal in retromalleolar region; MRI: Tendon dislocation, retinaculum lesions, associated deltoid ligament injury	Not specified (20% successful rate)	Flexor retinacular repair/reconstruction
		FDL	Retinacular detachment; Concurrent PTT and FDL dislocation	Snapping with resisted ankle plantarflexion and inversion	US/MRI: Tendon dislocation, retinacular detachment	No report	Flexor retinacular repair/reconstruction
Posterior		FHL	Stenosing FHL tenosynovitis	Triggering/Locking during great toe flexion, exaggerated in ankle plantarflexion	Radiograph: Os trigonum, Stieda's process, accessory ossicles, synovial chondromatosis; US: FHL tendon pathology/dynamic triggering; MRI: Tenosynovitis, stenosis, and fibrous bands	US-guided intralesional steroid injections (no success rate reported)	Pulley release/tenosynovectomy, excision of anomalous muscle belly
		Plantaris	Subluxable plantaris tendon to Achilles tendon	Snapping at posteromedial ankle or calf during squating maneuver	US: Subluxated plantaris tendon from medial to more posterior margin of Achilles tendon; MRI: Achilles tendon myotendinous junction edema without tendinopathy may be reported	Eccentric gastrocnemius stretching (no success rate reported)	Tendon resection/adhesion release

EDL: Extensor digitorum longus; FDL: Flexor digitorum longus; FHL: Flexor hallucis longus; IER: Inferior extensor retinaculum; IPR: Inferior peroneal retinaculum; MRI: Magnetic resonance imaging; PB: Peroneus brevis; PL: Peroneus longus; PT: Peroneus tertius; PTT: Posterior tibial tendon; SPR: Superior peroneal retinaculum; TA: Tibialis anterior; US: Ultrasound.