Causes / typical injury mechanism: Triangular fibrocartilage complex (TFCC) injuries are a common cause of ulnar-sided wrist pain. Traumatic tears usually occur following an acute rotational forearm injury or axial loading with an extended and pronated wrist (eg, swinging a racket or a fall on an outstretched pronated hand). Degenerative tears, a more chronic injury, can result from repeated, excessive loading through the ulnocarpal joint and are often seen with positive ulnar variance and ulnar impaction syndrome.

Classic history and presentation: Patients with TFCC injuries present with a complaint of ulnar-sided wrist pain. The pain can typically be recreated with ulnar deviation and rotation of the wrist and manifests as wrist pain and difficulty with tasks such as wringing out a towel, opening a jar, or holding heavy objects such as a pan. Examination will demonstrate focal tenderness between the pisiform and ulnar head or a "clicking" sensation with pronosupination. Forced ulnar deviation of the wrist, a "press test" where the patient presses themself up from a chair, and a "piano key test" can all be useful diagnostic maneuvers to suggest TFCC injury.

Prevalence: The likeliness of TFCC injuries increases with age. However, not all TFCC injuries become symptomatic, and the prevalence of TFCC injuries may be under-recognized.

Risk factors:

• Forced ulnar deviation of the wrist.
• Positive ulnar variance.
• A history of distal radius fracture may predispose patients to positive ulnar variance, in turn leading to TFCC injury.

Pathophysiology: Anatomically, the TFCC describes the confluence of soft tissues that span and support the distal radial ulnar joint (DRUJ) and ulnocarpal joint. It is composed of the articular disk, the palmar and dorsal radioulnar ligaments, the floor of the extensor carpi ulnaris (ECU) tendon sheath, the meniscal homologue, and the palmar ulnocarpal ligaments. The TFCC functions to extend the articular surface of the distal radius to the distal ulna, thereby absorbing and transmitting axial force across the wrist. It also supports the ulnar carpus and serves as a flexible connection between the radius and ulna to allow stable pronosupination. Finally, it is important to understand that the TFCC receives a variable blood supply. The periphery is well vascularized via the anterior interosseous and ulnar arteries, while the central portion remains relatively avascular. This plays an integral role in its healing potential and treatment options.

Grade / classification system: Palmer classification –

• Class 1 traumatic / acute injuries. Largely influenced by variable blood supply to the injury location.
  • 1A: Central perforation or tear
  • 1B: Ulnar / peripheral avulsion
  • 1C: Distal / volar avulsion
  • 1D: Radial avulsion
• Class 2 degenerative / chronic injuries. Progression of degenerative changes.
  • 2A: TFCC wear
  • 2B: TFCC perforation
  • 2C: Lunate or ulnar chondromalacia
  • 2D: Ligament disruption
  • 2E: Ulnocarpal / distal radioulnar joint (DRUJ) arthritis