Stance-control orthotic knee joints stabilize the knee joint during the weight-bearing portion of gait without restricting swing-phase flexion, thus achieving a more normal gait for individuals with quadriceps muscle weakness. These devices must be designed around well-defined stance-control strategies that enable or hinder joint motion at specific events during the gait cycle. This paper presents a new type of stance-control strategy and a novel stance-controller design. Pilot clinical testing was performed on a prototype, demonstrating feasibility of this approach for providing reliable knee stability while facilitating swing-phase flexion. In particular, 44 deg of swing-phase flexion and 15 deg of stance-phase flexion were achieved during level walking. Further testing is needed in situ to provide additional validation and assess other mobility conditions.