Maria, in the hands of someone who knows what they are doing and who has a good grasp on shoulder diagnosis and rehabilitation you will most likely have a successful outcome.
The cuff is effectively intact (intrasubstance only) but degenerative. The bursa is, it seems irritated and reactive.
It is highly likely that your rotator cuff and scapula muscles are dysfunctional but with a graduated physiotherapy program including massage, heat, trigger point therapy, mobilisation, postural correction, scapula stability and rotator cuff activation (loading) drills over an approximate 90 day period you should see some positive results if the diagnosis and therapy are accurate.
However, as has been previously stated shoulder pain is complex and the root cause can be different to the presenting problem and unrelated to the presence of a cuff tear so a thorough assessment is essential.
What we know about cuff tendons is they have a tendency to propagate and become larger tears over time. Likewise as previously stated they become more prevalent as we get older, whether we get symptoms or not is another thing (explanation) all together.
Best thing... get in early, get educated, become more aware of how to engage the right muscles to improve the performance of your shoulder NOW because there are no guarantees. You're only young and have hopefully a healthy biology so you should do well.
Good Luck!
Luke
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