It is often a tough call deciding which cuff problems need surgery and which will get better naturally.
However, if surgery is contemplated, simple scanning of the shoulder by an experienced ultrasonographer is a good predictor of which rotator cuff tears are repairable and which are not, according to a study of 373 patients from a centre in Sydney, Australia.
Tse, A.K., Lam, P.H., Walton, J.R., Hackett, L. & Murrell, G.A.C. (2015) Ultrasound Determination of Rotator Cuff Tear Repairability. Shoulder and Elbow. Published online before print May 12, 2015, doi: 10.1177/1758573215585284.