Muscle weakness of older adults makes daily living activities (ADLs) difficult. Designing and developing a knee exoskeleton to assist them during these ADLs is still one of the engineering challenges. In the human-centered design laboratory, we have designed and developed an entirely passive knee exoskeleton capable of giving more than 25% assistance during the sit-to-stance movement. Since there are rotational and translational movements in the knee joint biomechanics, using a cam slot in the knee joint makes the misalignment of this exoskeleton minimum in both directions during the sit-to-stand task.