There are no previously published studies measuring functional outcomes of orthoses, specifically knee orthoses, to treat hypermobility and instability in Ehlers-Danlos syndrome. A patient with Ehlers-Danlos syndrome type I, hypermobility, and instability was provided with bilateral custom knee orthoses and evaluated using the timed up and go test and the Locomotor Capabilities Index. The patient showed substantial improvement with both measurements. Over a 15-week period, the patient showed a 21.7% improvement in the timed up and go test and a 105.6% improvement in her Locomotor Capabilities Index score. The outcome measures in this study suggest that the patient showed improvement in her gait speed and mobility and her reported stability, independence, and safety when fit with bilateral custom knee orthoses. These improvements suggest a substantial medical benefit for patients with hypermobility and instability of the knee, such as seen with Ehlers-Danlos syndrome, to be treated with custom knee orthoses to increase their gait speed and mobility and their perceived stability, independence, and safety.