How to Choose an Össur CTi®3 Knee Brace: Sizing and Custom vs Off-the-Shelf
The Össur CTi®3 is a rigid, off-the-shelf ligament knee brace with a carbon composite frame and Accutrac® hinges. It is made in four sizes, each built for the left or the right leg. This guide covers who typically considers this style of brace, how it differs from a custom CTi, how to measure and what to review before you order.
We sell equipment, not medical advice. A brace is not a substitute for an exam. Ask a physician, orthotist or physical therapist whether this model is suitable.
What the CTi®3 is, in plain terms
Össur makes the CTi®3 as a prefabricated, double-upright brace for daily activity and sport. Prefabricated means you select a standard size rather than a frame molded to one person's leg. Each brace is side-specific: choose Left for the left knee or Right for the right knee. The four sizes are Small, Medium, Large and Extra-Large.
The company lists the brace for people who may need more front-to-back and side-to-side stability at the knee, including after injuries involving the ACL, MCL, LCL or PCL, or when more than one ligament is involved. Those are the manufacturer's listed uses, not a promise of a particular result. A clinician should confirm whether the brace is a good match and how it should be worn.
What sets the CTi®3 apart
Össur's official product information lists these design details:
- Frame. A carbon composite structure. Össur lists the brace weight at 16.5 ounces, and the standard color is black.
- Hinges. Accutrac® hinges are designed to track how the knee bends.
- Range of motion. Stops can be changed without tools. A clinician should decide whether motion needs to be limited and by how much.
- Liners. A raised tread-block pattern is used to combine cushioning with airflow.
- Water use. The materials are described as water-friendly. Follow the official instructions for use for cleaning and care.
- Alignment cue. A mark on the hinge gives a visual reference when you put the brace on.
Each CTi®3 ships with a condyle pad set and an extension stop set. The 0° extension stop and the standard condyle pads are already installed. Add-on parts are available, including an MX kit plus spare straps, liners and flexion stops.
CTi®3 compared with a custom CTi
The CTi family includes this prefabricated model and a separately made custom CTi. They share the Accutrac® hinge concept, but they are not the same product. The custom brace is built to the wearer's anatomy, usually through a clinician. The CTi®3 is the stock-size option: accessories can be added, but the frame itself is not custom-molded.
| CTi®3 (off-the-shelf) | CTi® Custom | |
|---|---|---|
| How it is made | Prefabricated in four sizes, left or right | Built to the wearer's measurements |
| Frame | Carbon composite; listed weight 16.5 oz | Carbon fiber; listed weight 20 oz |
| Color options | Black | Standard colors or a custom finish |
| Models | One standard model | Several, including Vapor, Standard, Pro Sport and OA |
| How you order | By size and side, using the measurement chart | Usually through a clinician who records a mold or detailed measurements |
| Extras | An MX kit and replacement parts can be added | Options, colors and accessories can be specified when it is made |
If a clinician has recommended a molded brace, or your measurements fall outside the four stock sizes, discuss the custom path. If a stock size matches and a clinician agrees, the CTi®3 is the off-the-shelf route.
How to measure and choose a size
Össur's preferred measurement is the medial-lateral width of the knee (straight across the joint) while standing and bearing weight. Take it at the joint line, not above or below the joint.
A second measurement, used when you land between sizes, is the thigh circumference 8 inches (20 cm) above mid-kneecap.
A third measurement, the circumference just below the lower edge of the kneecap, can be used in place of the knee-width figure. Össur notes that the circumference values are approximate.
| Size | Knee width (preferred) | Thigh, 8" above mid-kneecap | Just below the kneecap |
|---|---|---|---|
| Small (S) | 3.5"–4" (8.9–10.2 cm) | 15.7"–18.5" (40–47 cm) | 11"–13.4" (28–34 cm) |
| Medium (M) | 3.9"–4.5" (10–11.4 cm) | 17.7"–21.7" (45–55 cm) | 13.4"–15" (34–38 cm) |
| Large (L) | 4.4"–5" (11.2–12.7 cm) | 20.5"–24" (52–61 cm) | 15"–16.1" (38–41 cm) |
| Extra-Large (XL) | 4.9"–5.5" (12.5–14 cm) | 22.8"–26.4" (58–67 cm) | 16.1"–17.3" (41–44 cm) |
The width ranges overlap. For example, a knee width of 3.9" to 4" appears in both Small and Medium. If your width fits two sizes, use the thigh measurement to decide, then cross-check the figure taken just below the kneecap. If the three numbers still disagree, ask a clinician or the retailer before you order.
The condyle pad set lets you fine-tune how the brace sits at the sides of the knee. Standard pads come installed; thinner or thicker pads from the same set can be swapped if a clinician or the fitting instructions call for it. Do not use the extension stops to pick a size. Adjust those only if a clinician tells you to.
How to order
- Confirm with a clinician that a rigid ligament brace is appropriate, and whether an off-the-shelf CTi®3 or a custom CTi is the better route.
- Record the three measurements, or have them taken in clinic.
- Choose the side (Left or Right). If both knees need a brace, plan on a pair of opposite sides.
- Decide whether you want the brace alone or a kit that adds an MX package or sleeves.
- Place the order. The current CTi®3 listing at The CTI Shop shows the single brace and bundled kits. You can also start at The CTI Shop home page.
What to check before you buy
- A clinician has reviewed fit and suitability.
- You have the knee width, the thigh circumference and the measurement just below the kneecap.
- Size was chosen using knee width first, with the other figures used only to break a tie.
- Left versus right is correct for the knee that will wear the brace.
- You know what ships in the box: pads and extension stops are included; an MX kit and extra sleeves are optional.
- You have read the official instructions for use, plus the return and warranty terms, before you pay.
- If a prescription or plan estimate matters, ask the clinician and the insurer; coverage is not automatic.
Other braces at Medical Supplies Now
If you are comparing other styles of knee support, or you need a brace for a different joint, browse our knee braces, knee bracing and support, braces and supports, and post-op braces.
Questions?
Call us at 1-877-861-8000, Monday-Friday, 9 AM-6 PM Pacific, or email contactus@medsupplynow.com. For CTi®3 purchases, use The CTI Shop links above.
Frequently asked questions
Is the CTi3 an off-the-shelf or a custom brace?
The CTi®3 is prefabricated in four stock sizes, Small, Medium, Large and Extra-Large, each made for either the left or the right leg. The custom CTi is a separate product built to the wearer's measurements, usually ordered through a clinician.
How do I measure for a CTi3?
Össur's preferred measurement is the side-to-side width of the knee at the joint line, taken while standing. If that width fits two sizes, use the thigh circumference 8 in (20 cm) above mid-kneecap to decide.
What comes in the box with a CTi3?
Condyle pads and extension stops. The standard pads and the 0° extension stop are fitted at the factory, and the extra pads and stops come in the box. An MX kit, sleeves and spare parts are sold separately.
How much does the CTi3 weigh?
Össur gives a weight of 16.5 oz for the brace. The frame is carbon composite and the standard color is black.
Should I talk to a clinician before ordering?
Yes. A physician, orthotist or physical therapist should confirm the brace suits you and decide whether motion needs to be limited. For questions about this guide, our team is available at 1-877-861-8000, Monday to Friday, 9 AM to 6 PM PT.