An ASO brace is an Ankle Stabilizing Orthosis, a lightweight fabric brace designed to limit excessive side-to-side movement in the ankle joint. It’s one of the most commonly recommended ankle braces for both injury recovery and prevention, particularly in court sports like basketball and volleyball where ankle sprains are frequent.
How the ASO Brace Works
The ASO brace uses two separate support systems layered on top of each other. First, a lace-up shell wraps around the foot and lower leg, similar to a shoe. Over that, a pair of figure-eight straps cross over the top of the foot, loop under the arch, and pull the ankle into a neutral, stable position. This combination locks the ankle against the two movements that cause most sprains: rolling inward (pronation) and rolling outward (supination).
The figure-eight straps are the defining feature. They mimic the wrapping pattern athletic trainers use when taping an ankle, but with the advantage of being adjustable and reusable. You can tighten or loosen the straps independently of the laces, which lets you dial in the level of restriction you need. The laces alone offer mild support. Adding tension to the figure-eight straps increases stability significantly.
The brace is made from thin, semi-rigid fabric (typically ballistic nylon) that fits inside a regular shoe. It sits low-profile enough that most people can wear it during athletic activity without switching to a larger shoe size.
Who Uses an ASO Brace
Orthopedic specialists typically recommend the ASO brace in two situations: recovering from an ankle injury and preventing a repeat one. After an ankle sprain, it provides external stability while the damaged ligaments heal. For ankle fractures, patients are often transitioned from a rigid walking boot to an ASO brace once they regain range of motion and can bear weight with less pain. The brace serves as an intermediate step between full immobilization and returning to normal activity.
Athletes with a history of ankle sprains make up the other major group. Once you’ve sprained an ankle, the ligaments remain slightly looser than before, raising the risk of spraining it again. Wearing an ASO brace during sports provides ongoing mechanical support that compensates for that residual looseness. Basketball, volleyball, soccer, and tennis players are among the most common users because of the cutting, jumping, and lateral movements those sports demand.
ASO Brace vs. Athletic Tape
The traditional alternative to a brace is athletic tape applied by a trainer before practice or a game. Research comparing the two approaches has generally found that braces are slightly more effective than taping, though both reduce injury rates compared to no support at all. The practical advantages of a brace are more clear-cut: tape loosens within 20 to 30 minutes of activity and needs to be reapplied, while a brace maintains its tension throughout a session and can be retightened on the fly.
Cost also favors the brace over time. A single roll of athletic tape lasts a few applications, and taping requires either a trained person or significant practice to do correctly. An ASO brace costs roughly $30 to $50 and lasts months with regular use. Interestingly, one study found that simply wearing high-top sneakers instead of low-tops prevented some ankle injuries, and combining high-tops with taping reduced injuries by more than 50% compared to low-tops with taping.
Finding the Right Size
ASO braces are sized by measuring around your heel, with the tape measure looping from the front of the ankle, under the heel, and back up. Sizes range from X-Small (10 to 11 inches) through XX-Large (15 to 16 inches). If you don’t have a flexible measuring tape handy, you can also go by shoe size:
- Men’s US 7.5 to 9: X-Small
- Men’s US 9.5 to 11: Small
- Men’s US 11.5 to 13: Medium
- Men’s US 13.5 to 15: Large
- Women’s US 6.5 to 8: X-Small
- Women’s US 8.5 to 10: Small
- Women’s US 10.5 to 12: Medium
- Women’s US 12.5 to 14: Large
If you fall between sizes, sizing up typically works better. A brace that’s too small will be difficult to lace and may create pressure points, while a slightly larger one can be cinched down with the laces and straps.
How to Put On an ASO Brace
Getting the brace on correctly matters for both comfort and function. Start by wearing a clean pair of athletic socks and making sure your feet are completely dry, including between the toes. Moisture against the skin increases the chance of blistering during activity.
Loosen the laces fully before sliding your foot in. This is the most common mistake people skip, and forcing your foot into a partially laced brace stretches out the material over time. Once your foot is inside, press your heel firmly against the back of the brace so there’s no gap. Then tighten the laces from the bottom up, pulling snug but not so tight that you feel numbness or tingling in your toes.
After the laces are set, pull each figure-eight strap across the top of your foot, under the arch, and secure it. These straps should feel firm. They’re doing the real stabilization work, so don’t leave them loose. Once everything is fastened, stand up and walk a few steps. You should feel supported through the ankle with no pinching or bunching. The brace goes on before your shoe, and the tongue of the brace should sit flat under the shoe’s tongue so it doesn’t fold or create pressure spots.
What It Feels Like to Wear
The first thing most people notice is how much the brace limits side-to-side ankle movement while still allowing you to point your toes and flex your foot up and down. This is intentional. Forward and backward motion (the kind you need for walking, running, and jumping) stays largely unrestricted, while the inversion and eversion movements that lead to sprains are significantly reduced.
There’s an adjustment period of a few days, especially if you’ve never worn an ankle brace before. The figure-eight straps can feel unfamiliar, and some people find the brace slightly warm during extended activity. Over time, the material conforms to your foot shape and breaks in. The brace is designed to be hand-washed and air-dried, which helps maintain the integrity of the straps and keeps the fabric from breaking down prematurely.