Had cortisone put in shoulder for frozen shoulder 3 weeks ago. Its stopped working already. Can I have more put in yet?

Cortisone. Cortisone is great to treat inflammation but can weaken structures like tendons and ligaments. For this reason, it is too early for another steroid injection. You need non-steroidal anti-inflammatories and physical therapy. If this fails, an anthroscopic procedure to break up adhesions.