Sizing
Four sizes, fitted to your child.
Theo is sized to leg length and weight, not age. Your child's therapist takes the measurements during the assessment, and our clinical team chooses the size before anything is built. The chart below shows what each size covers.
Trexo Theo is a prescription device for patients 12 years and older with cerebral palsy. Meeting a size range alone does not establish suitability. Your clinician assesses fit and safety. Indications and safety information.
The sizing chart.
Lengths are in centimeters, measured lying down with shoes and orthotics on. The largest size supports up to 150 lb.
| Size | Hip to floor | Hip to knee | Knee to floor | Max weight |
|---|---|---|---|---|
| Small | 40–47 cm | 18 cm | 22–29 cm | 80 lb (36 kg) |
| Medium | 43–53 cm | 21–24 cm | 22–29 cm | 80 lb (36 kg) |
| Large | 55–76 cm | 26–34 cm | 29–42 cm | 125 lb (56 kg) |
| Extra Large | 62–90 cm | 29–39 cm | 33–51 cm | 150 lb (68 kg) |
Each size adjusts within its range, so one device grows with your child, and a size upgrade is available when they outgrow it. Ranges are from the Trexo Theo Instructions for Use, which is the authoritative source.
What gets measured
Four measurements, taken by your therapist.
They are part of the assessment package we send after you reserve. Want a rough idea today? A tape measure from hip joint to floor, with shoes on, is enough to see which row of the chart your child is near. It is not required and it does not replace the assessment.
Step 01
Lying down, shoes and orthotics on
Measurements are taken with your child lying on their back, wearing the shoes and ankle-foot orthoses they will wear in Theo, since both add height.
Step 02
Hip to knee
Theo's robotic legs rotate at the hip and the knee, and they need to line up with your child's own joints. The therapist measures from the hip joint to the center of the knee, in centimeters. This sets the thigh section.
Step 03
Knee to floor
From the knee joint to the sole of the shoe, in centimeters. This sets the shin section. Hip to floor is the two added together and is the quickest check against the chart.
Step 04
Foot
The length of the foot in the shoe or orthosis your child will wear, which sets the footplate. If new orthotics are still being made, the footplate is finalized before delivery.
What happens next
We confirm the fit before we build.
Our clinical team reviews the therapist's measurements alongside the assessment and prescription and confirms the size. About a month before shipping, the measurements are taken again so the device matches your child on the day it arrives, not the day you reserved.
Fit is checked again at training, when the device is set up on your child by a Trexo Certified Trainer, and at each size adjustment as they grow. If you are not sure whether your child fits today, the quickest route is to ask us.
Trexo Theo is a prescription device. Sizing is one part of the assessment, and the whole path from reservation to home is on the how it works page.
Wondering about size?
A refundable reservation holds your place in the US build queue. Your child's therapist measures, and our clinical team confirms the size before purchase.