## **Core Concept**
The rotator interval is a region in the shoulder joint that is part of the shoulder's rotator cuff. It is an area of the shoulder capsule that is not reinforced by the rotator cuff tendons, specifically between the supraspinatus and subscapularis tendons. This interval is clinically significant because it can be a site of weakness or injury.

## **Why the Correct Answer is Right**
The long head of the biceps tendon passes through the rotator interval. This tendon originates from the supraglenoid tubercle of the scapula, traverses the shoulder joint within the intertubercular groove of the humerus, and is stabilized in place by the transverse humeral ligament. The rotator interval provides a critical area through which this tendon passes to enter the bicipital groove.

## **Why Each Wrong Option is Incorrect**
- **Option A:** The supraspinatus tendon does not pass through the rotator interval; rather, it forms one of the boundaries of the interval.
- **Option B:** The subscapularis tendon also does not pass through the rotator interval; it forms the other boundary.
- **Option C:** While there are other structures in the vicinity, the question specifically asks what passes through the rotator interval, making the long head of the biceps tendon the most relevant.

## **Clinical Pearl / High-Yield Fact**
A significant clinical correlation is that injuries to the rotator interval can lead to instability of the long head of the biceps tendon, potentially causing shoulder pain and weakness. Clinicians often examine and treat this area in patients with shoulder impingement or instability symptoms.

## **Correct Answer:** D. Long head of biceps tendon.