This study looks at whether tightness of a small chest muscle called the pectoralis minor is linked to where rotator cuff tears begin in the shoulder. Rotator cuff tears can start on the bursal side (top surface) or the articular side (joint surface). We want to learn if people with a tighter pectoralis minor are more likely to have tears that begin on the bursal side. Adults aged 18-60 who already plan to have shoulder arthroscopy as part of their usual medical care at Gazi University Hospital may be invited. Taking part does not change their treatment. Before surgery, a trained clinician will measure shoulder posture and pectoralis minor length using simple external tools (a caliper and ruler-like square). We will also review routine shoulder X-rays and MRI scans if available. During surgery, the surgeon will look inside the joint (standard arthroscopy) and record where the tear appears to start. No extra procedures are added for research. We expect to include about 81 participants. The main question is whether people with a shorter (tighter) pectoralis minor more often have bursal-side tear initiation. Results may help doctors understand shoulder mechanics and improve prevention or rehabilitation strategies in the future. Participation is voluntary, and data will be de-identified and kept confidential. There is no direct benefit to participants, and risks are limited to the brief, noninvasive measurements performed before surgery.