Hello and thank you for your question,
Your MRI report says that you have some minimal arthritis at the point where your clavicle meets your shoulder joint. It also says that you have a tear in rotator cuff. Rotator cuff is the joint which holds your shoulder together. It is responsible for you being able to lift your arm, put it behind your back, etc. Rotator cuff tears are common, we often see them with falls. However, the severity of the tear could not be fully visualized on the MRI because you might have been moving so they are recommending another test called MR arthrogram to get a better look at the extend of the damage.
Often, rotator cuff tears can be treated with physical therapy, cortisone injections and anti-inflammatory medications. Occasionally they will require surgery to be put back together. If the tear is partial, you will only need physical therapy, if the tear is complete, you might need surgery and that is why you might need to get MR arthrogram since MRI was not able to tell if the tear is partial or complete.
I hope you find this information helpful. Please feel free to follow-up with any other questions you might have.
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Best wishes and good luck,