Here’s some information regarding Frozen Shoulder aka Adhesive Capsulitis:

Frozen Shoulder (adhesive capsulitis): immobility of shoulder (due to scar tissue build up around the shoulder which reduces ease of movement)

Inflammation, scarring, thickening, and shrink of the glenohumeral joint
Scar tissue can build up due to a long period of inactivity (ex. from injury, illness), making one more vulnerable to inflammation and adhesions
Scar tissue limits range of motion over time
Typically develops slowly, and in three stages:

1. Freezing stage: any movement of shoulder caused pain, and ROM starts to become limited

2. Frozen stage: shoulder becomes stiffer, using it becomes more difficult, and pain lessens

3. Thawing stage: range of motion begins to improve

Early treatment helps keep the condition from getting worse

Treatment:

Gentle shoulder mobility exercises, and increasingly ambitious range of motion exercises as symptoms improve
Transcutaneous electrical nerve stimulation
Shoulder massages
Shoulder manipulation to physically break up scar tissue surrounding the joint capsule
Acupuncture