What is the most likely diagnosis in a patient with shoulder pain and weakness during abduction?

In a patient presenting with shoulder pain and weakness during abduction, a rotator cuff tear is a likely diagnosis. Specifically, tears involving the supraspinatus tendon, which is one of the four rotator cuff muscles, can lead to significant impairment in the ability to abduct the arm. This weakness is often most pronounced when the arm is raised between 60 to 120 degrees, as this is when the supraspinatus is most actively engaged in facilitating abduction.

Rotator cuff tears typically result from a combination of acute injuries and degenerative changes, especially in older populations or athletes involved in repetitive overhead activities. Patients may report not only weakness but also pain, especially during specific movements, which helps to differentiate the nature of the tear and its impact on shoulder function.

The other conditions listed, while they can cause shoulder pain, do not typically lead to the same level of weakness during abduction. For instance, subacromial bursitis may present with pain during motion but is less likely to cause significant weakness. Adhesive capsulitis, or frozen shoulder, can cause stiffness and pain but does not primarily lead to weakness in abduction. Supraspinatus tendonitis may also cause similar symptoms, but it typically does not present