A 45-year-old man comes to the office due to right ankle pain for the past 2 days. The patient was running downhill on a dirt trail when he twisted his ankle inward. Since then, he has had pain and swelling at the right ankle but is able to walk unassisted. The patient has no other medical conditions and takes no chronic medications. On examination, there is bluish discoloration over the lateral aspect of the joint. He has maximal tenderness to palpation at the anterolateral aspect of the ankle joint. Forced inversion of the foot also increases the pain. Which of the following structures is most likely injured in this patient?

Question

A 45-year-old man comes to the office due to right ankle pain for the past 2 days.  The patient was running downhill on a dirt trail when he twisted his ankle inward.  Since then, he has had pain and swelling at the right ankle but is able to walk unassisted.  The patient has no other medical conditions and takes no chronic medications.  On examination, there is bluish discoloration over the lateral aspect of the joint.  He has maximal tenderness to palpation at the anterolateral aspect of the ankle joint.  Forced inversion of the foot also increases the pain.  Which of the following structures is most likely injured in this patient?

Quizplus · Accepted Answer

11ec160b_35e0_8341_9249_15d16fcafd54_MD0001_00 This patient has a right lateral ankle sprain, which is most often due to inversion of a plantar-flexed foot. The ankle is stabilized laterally by the anterior inferior tibiofibular, anterior talofibular, posterior talofibular, and calcaneofibular ligaments. The lateral ankle ligaments are weaker and are injured more often than the medial ligaments. The most common ankle sprains involve only the anterior talofibular ligament and present with pain and ecchymosis at the anterolateral aspect of the ankle. However, stronger forces can injure multiple ligaments, leading to significant joint instability with possible nerve injury and joint dislocation/fracture. (Choice A) The soleus and gastrocnemius muscles combine to form the Achilles tendon, which inserts on the posterior calcaneus and acts in ankle flexion. The tendon can be injured with sudden forces during strenuous activities (eg, sudden pivoting on a foot or rapid acceleration). (Choice B) The medial deltoid ligament complex is stronger than the other ligaments and is not commonly injured. Forced eversion of the ankle can damage the deltoid ligament but more commonly causes an avulsion fracture of the medial malleolus. (Choice C) The subtalar joint is at the posterior junction between the talus and the calcaneus and is reinforced by the talocalcaneal ligaments. The joint is involved with inversion, eversion, dorsiflexion, and plantar flexion of the foot, but is infrequently injured. (Choice E) Dorsiflexion and/or eversion of the ankle can cause a high ankle sprain affecting the syndesmotic structures (interosseous membrane and anterior, posterior, and transverse tibiofibular ligaments), which connect the tibia and fibula. Injury to these structures is uncommon as they can withstand severe forces. Patients usually have an unstable ankle joint with tenderness at the distal tibiofibular joint, but no significant swelling. Educational objective: Lateral ankle sprain is due to inversion of a plantar-flexed foot and most commonly involves the anterior talofibular ligament. Stronger forces can cause joint instability by injuring additional ligaments. __________ References: Ankle sprains and instability. (http://www.ncbi.nlm.nih.gov/pubmed/24559877)

A 45-Year-Old Man Comes to the Office Due to Right