Patients who have suffered severe damage to their nervous system, as caused by diseases such as stroke, sclerosis, or cerebral palsy, often experience spasticity. Spasticity is marked by forced contraction of the muscles, limiting the patient’s bodily control and movement. Medical exoskeletons have been designed and utilized to help rehabilitate patients to restore the lost Degree-Of-Freedom (DOF); however, most of the existing exoskeletons are too expensive, bulky, or mechanically complex and difficult to align and properly fit to the users. In this research, we have developed a cost-effective, compact, and adjustable 4-DOF exoskeleton to fit various sizes of the upper arm. The design offers patients enough range of motion to accomplish most tasks of daily living while eliminating the risk of singularities and collision with the user’s body. The design is lightweight and compact. Each DOF utilizes an RMD-X8 motor, which is built to withstand 300 N of axial loading and 1000 N of radial loading. The links and joints were 3D-printed using PLA, with some being reinforced with 3003 H14 Aluminum sheet metal. This reinforcement minimizes bending by handling the bulk of the exoskeleton’s load and prevents damage to the 3D prints and motors. The alignment of the exoskeleton to the human anatomical joints has been analyzed through musculoskeletal modeling. Results are promising and further analysis will be done through human subject testing to assess the exoskeleton’s effectiveness in rehabilitating patients, as well as gauge what modifications to make in future designs.