Shoulder impingement and pain are very common and can be improved with physical therapy. Partial rotator cuff tears can also benefit from rehab and would be determined on an individual basis with clinical symptoms and imaging guiding the decision process.
Full rotator cuff tears, which are most commonly the supraspinatus and/or infraspinatus should be addressed in a timely manner with surgery. Delayed surgery could cause further retraction of the torn tissue and scarring, which research shows can cause decreased functional performance after surgery.
This picture shows a complete rotator cuff tear that is repaired with a suture bridge technique.
Conservative rehab after surgery is essential to protect the repaired tissue and aggressive therapy that is short sighted in improving ROM and function has demonstrated an increased rate of repair failure with no increased long term functional outcomes.
Therapy may be uncomfortable, but increased pain is usually not required to attain ROM or improved function.