Abstract: The presently disclosure describes a motion assistance system for a wheelchair, for example, a powered drive wheel system that can continually drive a wheelchair in a circular or elliptical path. The motion assistance system comprises a mounting mechanism attachable to one or more structural elements of the wheelchair, and a drive linkage pivotable with respect to the mounting mechanism. A drive wheel can be mounted to an end of the drive linkage such that the drive wheel contacts the ground when installed on the wheelchair. The drive wheel comprises a plurality of lateral rollers positioned radially about the circumference of the power drive wheel. The lateral rollers can rotate about an axis tangential to the circumference of the drive wheel in order to facilitate driving the wheelchair in a radial direction.