Provided is a wheel assembly (10), which finds particular application for use with a wheelchair (30). The wheel assembly (12) typically comprises an inner hub (12) which is configured for attachment to the wheelchair (30), along with an outer rim (14) which generally defines a contact surface (16). The wheel assembly (10) further comprises a plurality of spokes 18 that supports the outer rim (14) on the inner hub (12). The spokes (18) are generally configured to extend between the hub (12) and the rim (14) in an arcuate manner, with a bulge (24) of each spoke's arc directed away from a preferred direction of rotation of the wheel assembly (10). This configuration produces a digging, scooping or paddling action when the wheel assembly (10) travels through a particulate material, such as sand, soft soil, snow, etc., or a liquid, such as water.