The three bones in the proximal row are the scaphoid, the lunate, and triquetrum. There are short ligaments internally that span these bones. The ligaments are mostly in a relaxed state until called upon in strenuous lifting or when batting or playing tennis. Larger external ligaments are at the anterior or palmar aspect of the wrist and span between the radius or ulna and the proximal and distal rows of bones. A triangular fibrocartilage is a triangular cartilage disc the attaches at the edge of the radius and the end of the ulna at the apex of the triangle.
Ligaments can be strained or stretched, and cartilage can be chipped or broken.
Blood flow can dissolve these chips, but it takes time. For the majority of wrist injuries that require treatment are incurred by falling on an outstretched hand, which brings the wrist up into a severely extended posture. This stretches the ligaments or puts extensive pressure on the bones of the wrist. A complete tear will seldom heal with splinting and casting alone and often requires surgery at the earliest date. Early diagnosis and treatment is critical for a complete tear.