Twisted Ankle

Ow, my ankle! It twisted like the pretzel, Igor.

—Heidi, Igor

Tony: Ah, let me guess... You're that person in horror movie that decides that since all your friends are dead, you really need to go check out the demonic, breathing noise down in the basement.

Kate: Well, it beats being the girl who twists her ankle and gets everybody else killed.

—NCIS

Any injury which causes a fleeing victim to fall or become slowed to allow a pursuer a better chance to catch up. If the injury is severe, another character may need to be depended upon for transportation (often in a fireman's carry), thus slowing down additional characters.

See also Broken Heel. Contrast Dramatic Slip.

Examples of Twisted Ankle include:

Anime and Manga

Happened to Teana on the first episode of Magical Girl Lyrical Nanoha Striker S, adding some complications to her B-Rank qualifying mage exam. Later gets mirrored in the last episodes of the season, though that one was less of a twisted ankle and more of a slashed up one courtesy of Deed.
In the Library Island Story Arc of Mahou Sensei Negima, this happened to Yue while the group was trying to get out of the place. Negi tried to give her a piggy-back only to immediately collapse under her weight. Huge Schoolgirl Kaede carried her instead.
In the Umineko no Naku Koro ni VN, this was originally the reason Rosa decided to stay put and try to fight the goat-headed butlers. While she and Maria were running through the rose garden, Rosa tripped on the steps and broke her ankle, so she couldn't make it to the beach, which was originally her plan.

Film

Parodied in Scary Movie, where a very Genre Savvy victim mocks this trope while demonstrating it in a very extreme manner to the increasingly horrified killer, complete with a sickening snap and a protruding fracture.
In Monsters vs. Aliens a teenage boy twists his ankle (with the foot turned all the way around!) and has to be carried by his date.
In Igor, Heidi fakes a twisted ankle to get Igor away from Eva.

Literature

Septimus Heap: In Flyte, it's a twisted ankle that slows down Septimus to the point that he gets almost taken by the wolverines.
In Harry Potter and the Order of the Phoenix, Ginny injures her ankle while fighting in the Department of Mysteries. Luna helps her along for a while, but when most everyone in the group is incapacitated, Ginny's left on the ground, SOL.

Live Action TV

Twisted ankles were the main method The Doctor's companions used to advance the plot and increase the tension in an episode: when being chased through the BBC Quarry by People in Rubber Suits, Sarah Jane Smith especially could be counted upon to twist her ankle at just the right moment. Fans accuse Susan of being the worst for this.
- Happened to a male companion of the Eighth Doctor in the Expanded Universe, due to a gunshot wound to the leg, and the Doctor proceeded to carry him around bridal-style.
- When it happened (yes, to Susan) in The Five Doctors, it was a deliberate bit of Self-Parody, with no dramatic effect. Although the same can't be said of Sarah Jane's "needing" to be hauled up the gentlest slope in Wales with a rope and Bessie the car.
This happens to Dr. Keller while evading hostile aliens in the woods in one episode of Stargate Atlantis.
Kat falls victim to this in Power Rangers Zeo.
Buffy the Vampire Slayer. Willow twists her ankle after her Crash Into Hello with Tara while fleeing from the Gentlemen. The injury is not emphasised, but is just one more thing to add to the terror of the scene.
Discussed (and ranted on) at length by Mary Jo in an episode of Designing Women.

Video Games

In one Valkyria Chronicles mission, Alicia (who, as a Scout, is usually one of the fastest characters available) twists her ankle after being thrown off a cliff by an artillery bombardment, drastically reducing her foot speed and cutting her action bar to a fraction of its normal length. For some reason, the magic healing rocks that can fix bullet wounds don't help with this, but some ground-up flowers will. We later learn that Alicia's a Valkyria with an innate Healing Factor, and has "always healed quickly"; while this does explain how she's back up to full speed the next day, by and large it only raises more questions.
Happens at least twice to Fiona Belli in the game Haunting Ground as part of her massive amounts of Cutscene Incompetence.
- Kinda justified because she actually gets up and runs even if hurt. The second time she tries to get away on all fours. She also trips a lot when scared in gameplay, too.

Webcomics

Starslip Crisis:

Zillion: "O'ch! My foot-knee most tender!"

Eerie Cuties parodied a stereotypical horror movie in Chapter 5, so yes, there was "Aow! I... sprained my ankle!", too.

Western Animation

Parodied in the Angry Beavers Halloween special "The Day the Whole World Got Really Screwed Up". In one scene, the beavers and a generic B-movie damsel-in-distress are trying to flee a horde of monsters, only for the woman to injure one ankle, then the other, then both at once somehow as the beavers try to help her along.
It happens to Carly in one episode of Transformers Generation 1.