The present invention provides an orthopedic device assembly comprising a first assembly element, a second assembly element, and a retaining mechanism. The first assembly element has a recess that receives the second assembly element, and the retaining mechanism holds the second element in an assembled state with the first assembly element. The retaining mechanism includes a retaining member with an angular cross-section defined by a base portion and a lateral flange portion projecting from the base portion. The retaining member is inserted through an aperture of the first assembly element into a groove in a wall of the recess of the first assembly element, with the flange portion projecting laterally of the groove and overhanging a shoulder portion of the second assembly element so as to retain the second assembly element in the assembled state with the first assembly element.