Any injury to the shoulder can lead to
frozen shoulder, including tendonitis, bursitis,
and rotator cuff injury.
Frozen shoulders occur more frequently in patients with diabetes, chronic inflammatory arthritis of the shoulder, or after chest or breast surgery or autoimmunity. Long-term immobility of the shoulder joint can put people at risk to develop a frozen shoulder.
Although, immobility adds to the problem hence continue mild passive exercises. Please continue diclofen too.