Injury to the deltoid ligament complex of the medial ankle occurs when the foot is forced into eversion and external rotation.

Medial ankle sprains are less common than their lateral counterpart due to the vast strength of the deltoid ligament:

Grade I sprain results from mild stretching of the deltoid ligament with microscopic tears (1). Patients have mild swelling and tenderness. There is no joint instability on exam, and the patient is able to bear weight and ambulate with minimal pain. Owing to their benign nature, these injuries are not seen frequently in the office.

Grade II sprain is a more severe injury involving an incomplete tear of the deltoid ligament. Patients have moderate pain, swelling, tenderness, and ecchymosis. There is mild to moderate joint instability on exam with some restriction in the range of motion and loss of function. Weight-bearing and ambulation are painful.

Grade III sprain involves a complete tear of the deltoid ligament. Patients have severe pain, swelling, tenderness, and ecchymosis. There is significant mechanical instability on exam and significant loss of function and motion. Patients are unable to bear weight or ambulate.

May progress to chronic ankle instability (constant sensation of ankle “giving away”) if lingering symptoms persist a year after initial ankle sprain (2)

Synonym(s): medial ankle sprain, deltoid ligament sprain

Although the majority of ankle injuries are lateral etiology (> 90%), the incidence of medial ankle sprains is ˜6% (2).

Deltoid ligament sprains are often accompanied by a lateral malleolar fracture and/or syndesmotic injury (1).

Previous ankle sprain

High-risk sports, including football, basketball, and long jumping

Valgus-flat foot deformity (3)

Low arch of the foot (i.e., pes planus)

Dysfunction of the spring ligament

Dysfunction of the posterior tibialis

Extreme fatigue of peroneus (fibularis) longus muscle

Syndesmosis disruption (3)

Fracture of the fibula and/or tibia

Avulsion fracture of the medial malleolus

Bimalleolar and trimalleolar fracture

Severe lateral ligament injury

Spring ligament injury

Posterior tibial tendon injury

Flexor hallucis longus injury

Posterior tibial and/or saphenous nerve traction injury