Until recently, robotic devices for stroke rehabilitation had multi-joint designs that were often tethered to a treadmill for gait training. A new single-joint wearable robotic knee orthosis (RKO) has been designed that provides patient-initiated powered-assistance in untethered functional mobility. This case-series documents application of the wearable RKO in untethered functional training with stroke survivors. Three ambulatory adult stroke survivors used a wearable RKO during 18 one-hour sessions within a six-week physical therapy programme. Subjects were assessed with a variety of balance, gait and functional tests including the Berg Balance Scale (BBS); six-minute walk test (6MWT); and Emory Functional Ambulation Profile (EFAP) at pre-treatment, post-treatment, one-month and three-month follow-up. All subjects improved balance, gait and functional performances with mean individual improvements of 12.6% for BBS, 12.0% for 6MWT and 16.7% for EFAP post-treatment. No adverse events occurred. These three stroke survivors may have benefited from the task-specific functional training programme augmented by RKO use.