One example provides a system for selectively restricting motion of an articulable joint, the system comprising a base having a first portion configured to be positioned at a first side of the articulable joint and a second portion configured to be positioned at a second side of the articulable joint, a clutch mechanism comprising a flexible portion having a first end coupled to the first portion of the base and a second end coupled to the second portion of the base, and a guide coupled to the base, the guide comprising a support surface that supports the flexible portion between the first end and the second end as the flexible portion moves during articulation of the articulable joint, the support surface of the guide comprising an angular transition in a dimension transverse to a travel direction of the flexible portion as a function of distance along the travel direction.