Free chapter on bursae around the shoulder joint. Wilk, Kevin E.; Andrews, James R. (1994). The Athletes shoulder. Edinburgh: Churchill Livingstone. ISBN 978-0-443-08847-6. Blaine TA, Kim YS, Voloshin I,  et al. (2005). "The molecular pathophysiology of subacromial bursitis in rotator cuff disease". J Shoulder Elbow Surg. 14 (1 Suppl S): 84S–89S. doi:10.1016/j.jse.2004.09.022. PMID 15726092. Brox JI, Gjengedal E, Uppheim G,  et al. (1999). "Arthroscopic surgery versus supervised exercises in patients with rotator cuff disease (stage II impingement syndrome): a prospective, randomized, controlled study in 125 patients with a 2 1/2-year follow-up". J Shoulder Elbow Surg. 8 (2): 102–11. doi:10.1016/S1058-2746(99)90001-0. PMID 10226960. Butcher JD, Salzman KL, Lillegard WA (1996). "Lower extremity bursitis". Am Fam Physician. 53 (7): 2317–24. PMID 8638508. Donatelli, Robert (2004). Physical therapy of the shoulder. Edinburgh: Churchill Livingstone. ISBN 978-0-443-06614-6. Handa A, Gotoh M, Hamada K,  et al. (2003). "Vascular endothelial growth factor 121 and 165 in the subacromial bursa are involved in shoulder joint contracture in type II diabetics with rotator cuff disease". J. Orthop. Res. 21 (6): 1138–44. doi:10.1016/S0736-0266(03)00102-5. PMID 14554230. S2CID 29665718. Hartley, Anne (1990). Practical joint assessment: a sports medicine manual. St. Louis, MO: Mosby Year Book. ISBN 978-0-8016-2050-8. Sports Medicine and Rehabilitation: A Sport-Specific Approach. Hagerstown, MD: Lippincott Williams & Wilkins. 1994. ISBN 978-1-56053-133-3. Lo IK, Boorman R, Marchuk L, Hollinshead R, Hart DA, Frank CB (2005). "Matrix molecule mRNA levels in the bursa and rotator cuff of patients with full-thickness rotator cuff tears". Arthroscopy. 21 (6): 645–51. doi:10.1016/j.arthro.2005.03.008. PMID 15944617.
5% did not improve and declined further treatment.Of the 413 patients who improved, 74 had a recurrence of symptoms during the observation period and their symptoms responded to rest or after resumption of the exercise program.The Morrison study shows that the outcome of impingement symptoms varies with patient characteristics. Younger patients (20 years or less) and patients between 41 and 60 years of age, fared better than those who were in the 21 to 40 years age group. This may be related to the peak incidence of work, job requirements, sports and hobby related activities, that may place greater demands on the shoulder. However, patients who were older than sixty years of age had the "poorest results". It is known that the rotator cuff and adjacent structures undergo degenerative changes with ageing.The authors were unable to posit an explanation for the observation of the bimodal distribution of satisfactory results with regard to age. They concluded that it was "unclear why (those) who were twenty-one to forty years old had less satisfactory results". The poorer outcome for patients over 60 years old was thought to be potentially related to "undiagnosed full-thickness tears of the rotator cuff". References
Anderson, D., M, (2000), Dorland’s Illustrated Medical Dictionary, 29th ed, W.B. Saunders Company, Canada, 965-967. Buschbacher, R., M, Braddom, R., L. (1994). Sports medicine & rehabilitation: A sport-specific approach. Hanley and Belfus Inc, Philadelphia. Hartley, A. (1990). Practical joint assessment: A sports medicine manual, St Louis, Sydney. Further reading
Arend CF. Ultrasound of the Shoulder. Master Medical Books, 2013.