Ankle Sprain
Ligaments are band-like structures that hold bones together.  There are several ligaments in the ankle.  When the ankle is twisted in such a way as to stretch or tear these ligaments, it is known as an ankle sprain.
Ankle sprains usually occur as the result of “rolling” or twisting the ankle.  Injuries that cause the ankle to turn inward (inversion injuries) lead to sprains of the ligaments on the outer (lateral) ankle.  They are the most common ankle sprains.  Injuries that cause the ankle to turn outward (eversion injuries) lead to sprains of the ligaments on the inner (medial) ankle.  Injuries that rotate the foot to the side (external rotation) and push the foot upwards (dorsiflexion) lead to sprains of the ligaments that hold the tibia and fibula together (syndesmosis).  This is known as a high ankle sprain.
Sprains are graded by severity.  When the ligament is stretched, but not grossly torn, it is known as a grade 1 sprain.  A partial tear is a grade 2 sprain.  A complete tear is a grade 3 sprain.
Ankle sprains are diagnosed based on a history, physical exam, and sometimes x-rays.  Patients usually report twisting or rolling the ankle.  They may or may not feel or hear a pop.  It may be difficult to bear weight on the injured ankle.  Knowing the direction in which the ankle has twisted can help in identifying which ligament is injured.
Upon physical exam, the ankle is usually bruised and swollen.  The injured ligament(s) will be tender to push on.  Stability of the ankle is checked using tests such as the anterior drawer test and talar tilt test.  The syndesmotic squeeze test and external rotation test can help to identify a high ankle sprain.
X-rays can be helpful to rule out an ankle fracture (broken ankle).  They can also be helpful in evaluating the stability of the ankle.  Stress views may be obtained which, if they demonstrate too much movement of the bones in relation to each other, may indicate a more serious injury and instability.
The vast majority of ankle sprains are treated non-surgically.  The first phase of treatment is immobilization.  The ankle is put at rest in a splint, boot, cast, or brace.  Weight-bearing is permitted, although crutches may be necessary at first if the ankle is too painful to walk on.  Anti-inflammatory medications, ice, and elevation help with pain and swelling.  Strenuous activity should be avoided to allow the injured ligaments to heal.  After a few weeks of immobilization, the splint, boot, or cast should be discontinued to allow ankle range-of-motion.  As motion improves, strengthening and balance exercises can begin.  Rehabilitation may be more effective under the supervision of a physical therapist or athletic trainer.
If there is too much instability in the ankle, an MRI may be obtained to evaluate torn ligaments.  Ligaments may need to be repaired or reconstructed.  If there is a high ankle sprain resulting in gapping between the tibia and fibula (syndesmosis tear), screws may be used to fix the tibia and fibula back together so the syndesmosis can heal.
ankle x-ray anterior-posterior
ankle x-ray lateral
tibia fibula
talus
anterior talofibular ligament
calcaneofibular ligament
deltoid ligament
anterior tibiofibular ligament (part of syndesmosis)
lateral ligaments
medial (deltoid) ligaments
inversion
eversion
external rotation & dorsiflexion
grade 1
grade 2
grade 3
ankle x-ray mortise