Participants will be treated for symptomatic shoulder instability with the evidence-based, targeted treatment intervention. For eight weeks, there will be two treatment sessions per week lasting 30-45 minutes. Exercises in the ARP include: Low-load and high-duration rotator cuff strengthening exercises, progressive scapular muscle endurance training, plyometric strengthening exercises, and surface electromyographic (EMG) biofeedback. Each prescribed exercise in the ARP will be increased to match the participant's function at the discretion of the study clinician. Although the components of the ARP will be pre-determined, the parameters and volumes of the components will be determined and documented over the treatment phase.

Participants will be treated for symptomatic shoulder instability with the non-specific, generalized treatment intervention. For eight weeks, there will be two treatment sessions per week lasting 30-45 minutes. The NPI consists of a general approach to treating shoulder pain with passive modalities for pain modulation. These interventions are commonly practiced but have little evidence to support their use in the treatment of symptomatic shoulder instability. Although the components of the NPI will be pre-determined, the parameters and volumes of the components will be determined and documented by a study clinician over the treatment phase.

The ARP intervention consists of therapeutic exercises designed to increase shoulder strength and endurance using a cluster of common exercises used for the treatment of shoulder pain. Specifically, the ARP program will focus on increasing scapular motor-control through a phasic program of common therapeutic exercises. This concept has been shown in the literature as capable of reducing shoulder pain and improving function in a variety of pathological conditions, however, the effect of this approach to reducing pain and increasing function for symptomatic shoulder instability is unknown. The selection of exercises and application for each exercise included in the ARP is based on recommendations from the literature and will incorporate participant feedback to customize dosages.

The magnitude of humeral head translations will be measured as the distance traveled by the humeral head relative to the scapular glenoid. The units of measure for this variable is distance, recorded in millimeters (mm). These measurements will be recorded with biplane radiographic motion analysis.

The magnitude of 3D scapular rotations will be measured as scapular rotations in each anatomical plane relative to the thorax. The three scapular rotations that will be measured are: scapular upward/downward rotation, scapular internal/external rotation, and scapular anterior/posterior tilting. These rotations are measured in degrees. These measurements will be recorded with biplane radiographic motion analysis.

Pain ratings will be measured with a 10cm VAS. The VAS will not have numbers on the scale, as a numeric pain scale would have. Participants will report their pain rating on the VAS scale weekly by sliding the marker along the line on the electronic survey throughout the duration of the study.

The WOSI contains 21 items, each rated on a scale of 0 to 100, and four overarching groups: physical symptoms, sports/recreation/work, lifestyle, and emotion. Composite scores range from 0-2100, where greater scores indicate a reduced quality of life.