A carriage for a limb support includes a space for receiving a longitudinal member of a patient support apparatus, a plurality of rollers configured to engage the longitudinal member and a locking mechanism. The plurality of rollers is configured to maintain alignment of the carriage during movement of the carriage along the longitudinal member. The carriage also includes an elastomeric member that resists rotation to prevent unwanted motion of the carriage. The locking mechanism is configured to secure the carriage to the longitudinal member at any of an infinite number of positions along the length of the longitudinal member, the locking mechanism being lockable with a single action.
