Ankle Injury Types Explained: Sprains to Achilles Tears

Lateral Ligament Sprains

Ankle sprains account for 85 percent of all ankle injuries. The lateral ligament complex (ATFL, CFL, and PTFL) is most commonly affected during inversion injuries. Sprains range from Grade 1 (stretching) to Grade 3 (complete rupture). Most heal with functional rehabilitation, though chronic instability develops in up to 20 percent of cases. For healing expectations, see our article on ankle ligament healing without surgery.

Ankle Fractures

Ankle fractures involve one or more of the malleoli (medial, lateral, or posterior). The Weber classification categorizes fibula fractures based on their relationship to the syndesmosis: Type A (below), Type B (at the level of), and Type C (above). Stable, nondisplaced fractures may be treated with a boot or cast, while displaced or unstable fractures require surgical fixation. The syndesmosis (high ankle sprain) must be assessed as its injury significantly affects treatment and recovery.

Achilles Tendon Tear

The Achilles tendon is the largest and strongest tendon in the body, yet it is vulnerable to rupture, particularly in middle-aged recreational athletes. Patients often describe a sudden pop followed by difficulty walking and pushing off. The Thompson test (squeezing the calf with absent foot flexion) is highly diagnostic. Treatment is either operative repair or functional bracing with early mobilization, both showing comparable outcomes in recent studies. MRI confirms the diagnosis and shows the gap between torn tendon ends.

Peroneal Tendon Injuries

The peroneal tendons run behind the lateral malleolus and are important for ankle eversion and stability. Injuries include tendinitis from overuse, tears (particularly of the peroneus brevis), and subluxation where the tendons snap over the fibula. These injuries often coexist with chronic ankle instability and may be missed on initial evaluation. MRI demonstrates tendon thickening, splits, or displacement from the retromalleolar groove. Learn how to identify these on imaging in our ankle MRI reading guide.

Osteochondral Defects of the Talus

Osteochondral defects (OCDs) involve damage to the cartilage and underlying bone of the talar dome. They often result from ankle sprains or fractures and cause deep ankle pain, swelling, and mechanical symptoms like catching or locking. MRI is the best imaging modality for detecting and staging OCDs. Small, stable lesions may be managed conservatively, while large or unstable defects typically require arthroscopic treatment.

Key Takeaways

• Lateral ligament sprains are the most common ankle injury and most heal conservatively
• Ankle fracture stability determines whether surgical or conservative treatment is appropriate
• Achilles ruptures can be treated operatively or with functional bracing with similar outcomes
• Peroneal tendon injuries and osteochondral defects are often associated with chronic ankle instability

Frequently Asked Questions