Partial cuff tears may potentially be distinguished on an MRI, but can absolutely be diagnosed at the time of arthroscopic surgery. This is the primary reason that rotator cuff surgery should ideally include a diagnostic arthroscopic assessment.
Inraarticular partial tears are called PASTA lesions (partial articular sided tendon avulsions), and they can be caused by impingement from a bone spur or CA ligament, age-related degeneration, impingement on the glenoid rim from instability, or tension failure from throwing activities, for example.
Surgical treatment begins with arthroscopic debridement. 75-85% of debrided PASTA lesions get better when an outlet obstruction (bone spur) is treated with acromioplasty. If a near complete "partial" tear is felt to be at significant risk of becoming a full tear, repair may be indicated, but it's worth noting that most of the time this is not necessary. In light of the rehabilitative demands following a cuff repair, and the need for a sling for 6 weeks, I think it is attractive to debride PASTA lesions in most cases.
Over the past 5 years I have had to take only 5% of patients back to the OR at 4-6 months to fix a partial tear--which means scraping it off the bone and repairing it. In such cases results are very good over 95% of the time.
By contrast, bursal sided partial tears are easily fixed without having to disrupt the inside part of the tendon that is still attached.Sofor bursal-sided partial tears,I usually recommend repair. Postoperatively you will spend 6 weeks in a sling during which PT will help you keep your motion with passive exercisies. At 6 weeks active motion begins and you can start to drive. Strengthening begins at 10 weeks---but no golf or tennis for a full 4 months.
