A support device provides elevation and support for a patient's foot and limits lateral and medial rotation of the foot relative to the knee. This protects the knee from injury during healing. The device includes a generally flat main body, two spaced-apart lateral ridges, and a medial depression between the lateral ridges that provides a support surface on which the foot may be positioned. The lateral ridges can extend to a height above the support surface so that inner side surfaces of the lateral ridges are adjacent to a majority of a foot placed in the medial depression. The support surface can include a heel aperture extending through the main body to provide a continuous heel pocket allowing the heel to remain freely suspended when the foot is placed in the device. The device can additionally or alternatively include a slidable base allowing the device to better slide on a surface enabling the user to perform therapeutic exercises.