I was diagnosed with a frozen shoulder (adhesive capulitis) several years ago. I was told the symptoms usually resolve themselves after 12-18 months, but the pain and limited use of my left arm really restricted my activities. I opted for treatment.
After physical therapy to restore range of motion (no relief), Injection of cortisone and air into the joint space (to break up the scar tissue and decrease inflammation, no relief), I had a MOA (manipulation under anesthesia). This essentiall consists of manipulating the shoulder through its normal full range of motion while you are under anesthesia. This breaks loose the scar tissue which then allows you to move your arm again. When I woke up, my symptoms were completely gone. I did need a couple sessions of physical therapy after to learn exercises to maintain my shoulder mobility, but that was all. No recurrence of symptoms after almost ten years. The main risk is that of the anesthesia, so you need to balance that against the severity of your symptoms.
I wish you relief soon!