Possible causes for the protruding flesh on the outer side of the big arm include trauma to the big arm muscle, lipoma on the big arm, and rupture of the long head of the biceps tendon. 1. Big arm muscle trauma: due to the fall on the outer side of the big arm or the big arm was hit by external force, resulting in big arm muscle contusion, the damaged muscle may appear hematoma, triggering the phenomenon of big arm lateral meat protrusion. 2. Lipoma of big arm: it may be due to abnormal fat metabolism in the body, resulting in fat cells accumulating in the outer side of the big arm, forming lipoma, and the phenomenon of protruding meat on the outer side of the big arm appears. 3. Biceps tendon long head rupture: in most cases, it is due to the degeneration of the biceps tendon. As the strength of the tendon decreases after degeneration, if the biceps tendon slides in the intertrochanteric sulcus during activity, it may lead to rupture of the tendon, forming a muscular bulge in the big arm, and the phenomenon of lateral meat protrusion of the big arm appears. There may also be other reasons for the protrusion of the lateral meat of the big arm, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment under the guidance of the doctor.