The Triangular Fibrocartilage Complex (TFCC) plays a significant role in hand and forearm function. The wrist relies on a coordinated network of bones, ligaments, and cartilage to facilitate its wide range of motion. The TFCC is a collective of soft tissues integral to the stability and smooth operation of the wrist, particularly on the side opposite the thumb.
Precise Location in the Wrist
The TFCC is situated on the ulnar side of the wrist, which is the side closest to the pinky finger. This complex occupies the space between the two forearm bones—the radius and the ulna—and the small carpal bones. Specifically, it originates from the end of the radius and extends across the joint to attach to the distal ulna.
The main component is the triangular fibrocartilage disc, which is shaped like a dome or cushion. This disc rests between the head of the ulna and two carpal bones, the lunate and the triquetrum. The complex is sometimes described as a hammock-like structure because it bridges and supports the connection between the forearm and wrist bones.
The TFCC’s precise placement makes it an integral part of the distal radioulnar joint (DRUJ), which is the connection between the two forearm bones near the wrist. This location is where rotational forces are managed during hand and arm movements. The complex also includes strong ligaments, such as the dorsal and palmar radioulnar ligaments, which provide structural stability.
What the TFCC Does
The primary roles of the TFCC are stability, load transmission, and facilitating forearm movements. It is the main stabilizer of the distal radioulnar joint, ensuring the radius and ulna remain properly aligned when the hand is used. Without this complex, the joint would be prone to instability, particularly during twisting actions.
Another function is to act as a shock absorber for the wrist. The TFCC is a load-bearing structure that helps to cushion the compressive forces transmitted through the wrist, especially those coming from the hand toward the ulna. Approximately 20 percent of the axial load, or force along the length of the arm, is transferred through the TFCC to the ulna bone.
The complex is also instrumental in enabling smooth forearm rotation, specifically pronation (turning the palm down) and supination (turning the palm up). The dorsal and palmar ligaments within the TFCC tighten and relax in a coordinated manner during these movements, maintaining the congruency of the DRUJ. The central disc is made of a type of fibrocartilage that is suited to bearing these compressive loads, much like the meniscus in the knee.
How the TFCC Becomes Damaged
Damage to the TFCC is generally categorized into two main types: traumatic and degenerative injuries. Traumatic injuries, classified as Type 1 tears, usually result from a singular, forceful event. A common cause is falling onto an outstretched hand, which transmits significant axial load and twisting force to the wrist.
Type 1 injuries can also be caused by a sudden, violent twisting of the wrist, such as when an athlete forcefully swings a bat or racquet. These acute tears may involve injury to the main fibrocartilage disc or the reinforcing ligaments. The force may also be associated with a fracture of the radius bone, further complicating the injury.
Degenerative injuries, known as Type 2 tears, are the result of chronic wear and tear over time. These tears frequently occur due to the natural breakdown of cartilage that happens with age. Repetitive motions, especially those involving pronation and gripping, can accelerate this degenerative process.
A congenital condition called ulnar variance, where the ulna is slightly longer than the radius, can predispose a person to Type 2 tears by increasing the compressive load on the TFCC. Conditions like rheumatoid arthritis can also contribute to the gradual deterioration of the complex. Because the central portion of the TFCC has a limited blood supply, tears in this area often do not heal naturally, making them more persistent.