Posterior Deep Deltoid Ligament

pars posterior profunda ligamenti deltoidei

The posterior deep deltoid ligament (posterior tibiotalar ligament) is the deepest and strongest component of the deltoid ligament complex, running from the posterior colliculus of the medial malleolus to the posteromedial talar body. It is the primary restraint to external talar rotation.

Region: Lower Leg

Biomechanics

Function & Actions

Primary restraint to talar external rotation and posterior talar displacement; resists valgus tilt; the strongest component of the deltoid ligament.

Clinical Relevance

Clinical Notes

The posterior deep deltoid is the last deltoid component to tear in progressive eversion injuries and is the critical structure assessed in medial ankle instability after bimalleolar or trimalleolar fractures. Its integrity determines whether medial-sided ankle fixation or repair is required. MRI arthrography demonstrates posterior deep deltoid tears at the posterior malleolar attachment.

Pathology

Common Injuries & Conditions

Posterior Deep Deltoid Tear in Ankle Fracture

Disruption of the posterior deep deltoid ligament in bimalleolar equivalent fracture producing medial instability with a widened medial ankle space on stress views, requiring repair or ligament reconstruction alongside fibular fixation.