Triangular fibrocartilage complex

Key points

The triangular fibrocartilage complex (TFCC) sits on the ulnar (little-finger) side of the wrist¹. At its centre is a disc of fibrocartilage (a tough, fibrous kind of cartilage), according to four anatomical studies².
Testing in a study of 61 specimens suggested two jobs: a cushion for the wrist bones on the ulnar side, and a major stabiliser of the distal radioulnar joint³. That joint is where the radius and ulna, the two forearm bones, meet next to the wrist⁴.
Two cadaver (donated body) studies found that the outer 15% to 20% of the articular disc had blood vessels and the rest had none^5,6.
A systematic review (a study that searches for all the research on a question and sums it up) pooled 15 studies of 977 wrists⁷. In people without symptoms, TFCC abnormalities rose from 15% of those under 30 to 49% of those 70 and older⁷.
A randomised controlled trial is a study that assigns people to groups by chance, then compares the groups. The 2024 protocol of a randomised trial of TFCC surgery states that no randomised controlled trial has studied the efficacy of operating on these tears⁸.

Function

Where it sits and what it is made of

The triangular fibrocartilage complex (TFCC) sits on the ulnar (little-finger) side of the wrist¹. It arises from the radius (the forearm bone on the thumb side)¹. It attaches to the far end of the ulna (the forearm bone on the little-finger side) and to the wrist bones on that side¹. The end of the ulna does not touch any carpal bone (small bone of the wrist) directly⁴. The figure labels the central part “Articular disc”.

Engraving of a wrist sliced through from side to side, showing the cut surfaces of the bones. At the top the wide end of the radius sits beside the narrower end of the ulna, with the distal radioulnar articulation labelled between them. A thin band labelled articular disc runs from the edge of the radius across the under side of the ulna, so that the ulna is separated from the lunate and triquetral bones below it. The wrist joint is labelled as the curved gap between the radius and disc above and the first row of carpal bones below. An ulnar collateral ligament is labelled at the little-finger edge, next to the pisiform. — The articular disc, under the end of the ulnaHenry Vandyke Carter, in Henry Gray, Anatomy of the Human Body (1918), Fig. 336. Public domain, via Wikimedia Commons. (source, Public domain)

The paper that named the TFCC studied 61 specimens by dissection and biomechanical testing^2,3. It described one continuous structure whose parts could not be dissected apart^2,3. The parts it listed were:

the articular disc^2,3;
the dorsal (back) and volar (palm-side) radioulnar ligaments^2,3;
the meniscus homologue^2,3;
the ulnar collateral ligament of the wrist^2,3;
the sheath of the extensor carpi ulnaris, a forearm muscle on the little-finger side^2,3.

A scoping review of 24 anatomical studies found that all of them counted four of those parts². These were the radioulnar ligaments, the disc, the extensor carpi ulnaris sheath or subsheath, and the meniscus homologue². The greatest disagreement was over the ulnar collateral ligament². The review’s authors concluded that this ligament is quite likely not a distinct structure². A study of eight cadavers found the meniscus homologue to be dense connective tissue with no identity of its own under the microscope⁹.

The disc and its attachments

The articular disc is made of fibrocartilage, according to four anatomical studies summarised in the scoping review². Seen from above it is triangular, and one anatomical study found its radial part thin and its ulnar part thick².

On the radial side, sections from eight cadavers showed the disc attached to the hyaline cartilage (a smooth, glassy kind of cartilage) of the radius⁹. On the ulnar side, serial sections showed the radioulnar ligament arising from two places¹⁰. One is the base of the styloid process (a bony point), and the other is the fovea¹⁰. The fovea is a hollow between the head of the ulna and its styloid process².

The subsheath of the extensor carpi ulnaris tendon is listed as one part of the TFCC¹¹. The outer edge of the TFCC blends with the subsheath where it attaches to the ulna¹¹.

How it shares load

A review describes the TFCC as a load-bearing structure that passes and spreads axial (lengthwise) load from the carpal bones to the ulna¹². One laboratory study measured the ulna’s share of that load, and what happened when the wrist was altered¹³.

Ulna’s share of the axial load (%). Bars start at zero; the table below gives each value with its source.

Wrist in the laboratory study	Ulna’s share of the axial load
Intact	18.4%¹³
Articular disc removed	6.2%¹³
Ulna lengthened by 2.5 mm	41.9%¹³
Ulna shortened by 2.5 mm	4.3%¹³

Those figures describe an ulna whose length was changed in the laboratory¹³. Ulnar variance is the relative length of the ulna at the wrist¹⁴. In 58 cadaver forearms, the force through the lower ulna was only weakly related to natural ulnar variance (r = 0.44)¹⁵. The authors put that down to a thicker triangular fibrocartilage in arms with a shorter ulna¹⁵.

In nine cadaver forearms, the force through the lower ulna showed no relationship to ulnar variance¹⁴. In those forearms the triangular fibrocartilage was thinner where the ulna was relatively longer¹⁴.

On radiographs (X-ray images) of 120 healthy volunteers, ulnar variance was greatest when gripping in pronation, with the palm turned down¹⁶. It was least when relaxed in supination, with the palm turned up, a mean change of 1.34 mm¹⁶. In nine cadaver forearms, the axial force through the lower ulna was greatest in pronation¹⁴.

How it steadies the forearm bones

In 16 fresh-frozen cadaver arms, the ligament parts of the TFCC were the dominant stabilisers of the distal radioulnar joint¹⁷. The palmar radioulnar ligament was the major restraint on the ulna shifting toward the back of the wrist¹⁷. The dorsal ligament was the primary restraint on it shifting toward the palm¹⁷.

Blood and nerve supply

In 10 cadaver specimens, small vessels entered the TFCC from the joint capsule (the sleeve of tough tissue that encloses a joint)¹⁸. They supplied its outer 10% to 40%¹⁸. The inner portion had no blood vessels, and no vessels crossed its attachment to the radius¹⁸. Two cadaver studies found that the outer 15% to 20% of the articular disc had blood vessels and the rest had none^5,6.

Breakdown

Wear with age

A study of 100 fresh cadavers (180 wrist joints) concluded that degeneration of the triangular fibrocartilage begins in the third decade of life¹⁹. The changes ran from fewer cells and fraying through thinning to perforation, a hole through the disc¹⁹. They were always in the central part of the disc¹⁹. No disc was perforated in the first two decades of life¹⁹.

Discs with a perforation (%). Bars start at zero; the table below gives each value with its source.

Decade of life, 180 cadaver wrist joints	Discs with a perforation
Third	7.6%¹⁹
Fourth	18.1%¹⁹
Fifth	40.0%¹⁹
Sixth	42.8%¹⁹
Over sixty years	53.1%¹⁹

A systematic review pooled 15 studies of 977 wrists⁷. TFCC abnormalities rose from 27% in people younger than 30 to 49% in people 70 and older⁷. In people without symptoms, they rose from 15% to 49% across the same ages⁷. A systematic review of 15 studies concluded that TFCC abnormalities are so common, with and without symptoms, that they may be incidental findings⁷.

Two studies using MRI (a scan that shows soft tissue in detail) in volunteers without symptoms differed over age^20,21:

On MRI of 103 volunteers, the TFCC was judged abnormal in 39 wrists, and greater age was correlated with an abnormal TFCC²⁰.
Of 70 volunteers aged 15 to 78, half had abnormally high signal in the triangular fibrocartilage, and age did not substantially affect that²¹.

A longer ulna and a hole in the disc

In a retrospective study (one that looks back at past records) of 124 patients’ MRI scans, holes in the centre of the disc were counted²². They were seen in 40% of wrists with positive ulnar variance, against 10% of those with negative variance²². Positive ulnar variance means an ulna that stands longer than the radius at the wrist²³.

Tears from injury

The Palmer classification recognises traumatic and degenerative (gradual wear) lesions of the TFCC²⁴. A review of TFCC injuries in athletes sets out its traumatic types by location²⁵:

1A, a hole in the centre of the articular disc alone²⁵;
1B, a tear at the ulnar edge, with or without a fracture of the ulnar styloid²⁵;
1C, a disruption at the far side, from the ulnocarpal ligament²⁵;
1D, a disruption at the radial side²⁵.

The degenerative types run from 2A, wear of the TFCC, to 2E, which adds arthritis between the ulna and the wrist bones²⁵.

One retrospective cohort study covered 500 adults with ulnar-sided wrist pain and a suspected TFCC lesion²⁶. All had arthroscopy (keyhole surgery inside a joint, using a small camera) in one group of 28 clinics, with no standard protocol²⁶. The arthroscopy confirmed a TFCC lesion in 368 (73.6%) and showed no clear abnormality at all in 80 (16.0%)²⁶. The lesions most often recorded were Palmer type 1B (31.6% of all patients), 1D (15.2%) and 2C (10.4%)²⁶. The study states that the Esser Foundation and Xpert Clinics funded it, and that one author holds stocks in Equipe Zorgbedrijven²⁶.

Two series looked inside the wrist with a scope after a displaced fracture of the distal radius, the wrist end of that bone^27,28:

Among 60 patients with a fracture into the joint surface, 26 had a TFCC tear²⁷.
Among 50 fractures in adults, the TFCC was torn in 39 (78%), and its tears were statistically correlated with fractures of the ulnar styloid²⁸.

In sport

A review of TFCC injuries in athletes reports that they make up between 3% and 9% of athletes’ hand and wrist injuries²⁵. It says they are mainly caused by sudden or repeated axial loads on the wrist, particularly on its ulnar side with rotation or side-to-side bending²⁵. The sports it names most often are tennis, padel, table tennis, golf and baseball²⁵.

On MRI of 41 adolescents with no symptoms, 18 of them gymnasts, the TFCC looked no different between gymnasts and non-gymnasts²⁹. Among ten girl gymnasts aged 12 to 16 scanned for wrist or hand pain, three had a tear of the triangular fibrocartilage³⁰.

Recovery

Healing follows the blood supply

Two groups of authors reasoned from the vessels they saw in cadavers^5,18. One suggested that tears at the outer edge may have enough blood supply to mount a repair response¹⁸. Tears in the centre or along the radial attachment have no immediate access to blood, they wrote, and are not likely to heal¹⁸. The other group judged that a repaired tear could heal in the zone with vessels, and not in the central zone without them⁵.

One case series (a report on a group of patients, without a comparison group) covered 35 patients with a repaired tear at the outer edge³¹. Nine had a second look inside the joint, and the repair had healed in seven of them³¹.

What outcome studies can and cannot show

The 2024 protocol of a randomised trial of TFCC surgery states that no randomised controlled trial has studied the efficacy of operating on these tears⁸. It notes that results reported after debridement (trimming away damaged tissue) come from studies without a comparison group⁸. Those results could reflect how the tears behave over time on their own, their natural course, it adds⁸.

A systematic review of 15 studies (478 patients) of scope-assisted repair found that an average of 84% fully returned to their previous work or sport³². The same review concluded that the literature does not say when patients can expect their function to be restored³².

A systematic review of traumatic tears managed without surgery found eight studies of 425 patients³³. It described the data as mixed and scarce³³. The page on wrist sprain reports the debridement, repair and non-surgical studies in more detail.

Connections

The TFCC is part of the wrist, between the head of the ulna and two wrist bones, the lunate and the triquetrum¹². In 50 displaced fractures of the distal radius examined through a scope, it was torn in 39²⁸. The page on distal radius fracture covers that injury. The page on cartilage covers the tissue in general.

In a histological (microscope) study of eight cadavers, the lower layer of the TFCC blended with the sheath of the extensor carpi ulnaris tendon⁹. Among 133 patients with wrist MRI and arthroscopy, an abnormal tendon on MRI was seen in 84.9% of those with a peripheral TFCC tear¹¹.

In the 500-patient arthroscopy study, lesions of the scapholunate ligament were seen in 15.0%²⁶. Across 155 MRI scans of acutely injured wrists with normal X-rays, 15 showed a TFCC injury³⁴. The page on wrist sprain covers those injuries.

Related exercise pages: push-up. In 14 volunteers doing push-ups, forces travelled more toward the ulnar side on a hyperextended (bent far back) wrist than on a neutral wrist³⁵.