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Distal radius

Also called lower radius, lower end of the radius, wrist end of the radius

The wrist end of the radius, the forearm bone on the thumb side. How it is shaped, how much load it carries, who breaks it and how, how it mends and builds up with loading, and what attaches to it.

Region
Wrist & hand
Muscles
brachioradialis, Forearm extensors
Updated
October 14, 2026
Reviewed
October 14, 2026 · how entries are checked

Function

Where the bone sits

The radius runs beside the ulna, on the thumb side of the forearm1. Its upper end is a disc-shaped head that meets the humerus (upper arm bone) at the elbow1. The interosseous membrane, a sheet of dense connective tissue, joins it to the ulna1. The distal radius is the lower end, where the bone meets the ulna and two wrist bones2. A 2020 review states that breaks of this part are usually defined as lying within 3 cm of the wrist joint7.

Engraving of the two bones of the left forearm seen from the front, the ulna on the left of the picture and the radius on the right. At the top the radius shows its round head, a narrow neck and the radial tuberosity marked for the biceps. Outlined areas along the shaft mark where the supinator, flexor digitorum sublimis, flexor pollicis longus and pronator quadratus attach. The radius widens at the bottom, where a curved joint surface is labelled as meeting the lunate and navicular (scaphoid) bones, the styloid process points down on the thumb side and the brachioradialis attaches just above it. The lower end of the ulna is labelled as meeting the radius.
The radius and ulna from the frontHenry Vandyke Carter, in Henry Gray, Anatomy of the Human Body (1918), Fig. 213. Public domain, via Wikimedia Commons. (source, Public domain)

The wrist end and its joint surfaces

An anatomy reference names three joint surfaces at the lower end of the radius8:

  • the scaphoid fossa (a fossa is a shallow hollow in a bone)8;
  • the lunate fossa8;
  • the ulnar notch, also called the sigmoid notch, for the lower ulna8.

The scaphoid and lunate are two of the carpal bones, the small bones of the wrist1. At the wrist joint, both meet the end of the radius directly1. The end of the ulna touches no carpal bone directly1. On the little-finger side sits the triangular fibrocartilage complex, which arises from the radius and attaches to the far end of the ulna9.

Engraving of a wrist sliced through from side to side, showing the cut surfaces of the bones and the joint spaces between them. The ends of the radius and ulna sit at the top, with the distal radioulnar joint between them and a thin articular disc under the ulna. Below, the wrist joint curves over the first row of carpal bones, labelled navicular (the scaphoid), lunate and triquetral, with the pisiform at the edge. A second joint line separates that row from the second row, labelled greater multangular (trapezium), lesser multangular (trapezoid), capitate and hamate, which meet the bases of the five metacarpals. Radial and ulnar collateral ligaments are labelled at the sides.
The joints of the wrist, cut open from the frontHenry Vandyke Carter, in Henry Gray, Anatomy of the Human Body (1918), Fig. 336. Public domain, via Wikimedia Commons. (source, Public domain)

The ulnar notch is a shallow hollow on the inner side of the lower radius1. It meets the head of the ulna to form the distal radioulnar joint1. At the outer end of the radius is a point called the styloid process1. Ligaments that support the thumb side of the wrist attach to it1.

How it is built inside

A bone imaging study describes the lower end of the radius as having a thin cortex (the dense, solid outer layer of a bone)10. Trabeculae, the thin struts of spongy bone, reinforce it from the centre10. They carry load from the joint to the thicker cortex further up the bone10.

How much load it carries

Two sources give figures for how load splits across the wrist. One is a review of wrist biomechanics, for a wrist and forearm in neutral3. The other is a computer model built from 120 normal adult wrist X-rays and loaded to mimic a light grasp with the wrist in neutral11.

Path through the wristReviewComputer model
Between radius and scaphoidAbout 45%355%11
Between radius and lunateAbout 35%335%11
Ulnar side20%310%, through the triangular fibrocartilage11

One study held eight wrists from cadavers (bodies donated for study) in a static push-up position12. A push-up force of 89 N sent an average peak of 69 N along the distal radius12. Scaled up in a straight line to a force of full body weight, that would be 663 N12.

Where the radius grows in length

A growth plate is a layer of cartilage near the end of a growing bone, where the bone grows longer. In X-rays of 200 males and females, about 80% of the radius’s growth in length came from its lower growth plate13. At age five the lower plate gave 85% of total growth, and by age eight 90%13.

Breakdown

Who breaks it

A review of who breaks this bone says children and older adults are at greatest risk4. One study read the wrist X-rays taken in 2016 in a region of southern Sweden with 182,000 residents14.

New lower radius fractures per 10,000 peopleEveryone22 Women34 Men10
New lower radius fractures per 10,000 people. Bars start at zero; the table below gives each value with its source.
Adults in the Swedish region, 2016New lower radius fractures per 10,000 people
Everyone2214
Women3414
Men1014

The review cites a study in which men and women aged 19 to 49 had almost identical rates4. In another study it cites, of people over 65, women’s likelihood of a distal forearm fracture was about 4.88 times men’s4.

How it breaks

A hard fall onto an outstretched hand sends force up the arm, and it may break the humerus, the radius or the scaphoid1. The review states that most of these breaks in older adults follow low-energy trauma, with a fall from standing height the leading cause4. Among 23,394 lower radius fractures in adults in the Swedish Fracture Register, a simple fall caused 75%15.

The sources name three patterns of break1,16,17:

  • Colles fracture. A complete break across the lower radius, with the broken-off end driven backward and upward1. An anatomy textbook calls it the most frequent forearm fracture, common in people over 501.
  • Smith fracture. A break in which the broken-off end shifts or tilts toward the palm; it is the less common of the two16.
  • Torus (buckle) fracture. The report of a trial in children calls this the mildest form of fracture, in which the bone buckles17.

Children and the growth spurt

In Saskatchewan hospital and billing data, lower radius fractures peaked at 11.5 to 12.5 years in girls5. In boys the peak was at 13.5 to 14.5 years5. In Saskatchewan children, the fracture peak almost exactly matched the age of fastest growth in height5. That age was 11.9 years in girls and 14.3 in boys5.

The authors of another population study offer a possible reason18. They suggest activity rises just when fast growth’s demand for calcium leaves a brief shortfall in cortical bone mass18. The review cites data in which sports accounted for 30% of these fractures at ages 10 to 14 and 47% at ages 15 to 174.

Bone density and later fractures

Bone mineral density is how much mineral is packed into a given amount of bone. One study followed 11,392 women aged 50 to 79 for a mean of 8.5 years19. Lower density at the hip and lower spine was associated with a higher risk of wrist fracture19.

One analysis followed postmenopausal women (women after menopause) aged 50 to 79 for a mean of 11.8 years20. Of those who broke a wrist, 15.5% later had a fracture elsewhere20. A wrist fracture was associated with a higher rate of later breaks at other sites20.

Ligaments torn along with the bone

A systematic review (a study that searches for and sums up the research on a question) covered 20 articles21. Their 1,346 patients had acute distal radius fractures examined by arthroscopy, keyhole surgery inside a joint using a small camera21. The overall rate of injury to the scapholunate ligament was 35.3%21. In 50 displaced fractures in adults no older than 60, examined through a scope, the triangular fibrocartilage complex was torn in 3922.

Gymnasts and the growth plate

Eight cross-sectional studies, which look at a group once, examined gymnasts’ wrists23. Depending on the study, between 10% and 85% of the gymnasts examined had X-ray changes consistent with stress reaction of the lower radial growth plate23.

A 1997 critical review of female gymnasts looked at growth arrest, when stress stops the plate growing early24. It judged this plausible, but the evidence too weak to be conclusive24. It found no rigorous studies of whether repetitive loading inhibits growth of the radius in female gymnasts24.

Recovery

How the break mends

An anatomy textbook describes bone healing in stages1. A blood clot forms first, then calluses of cartilage and bone, which are new tissue that bridges the break1. Over several weeks spongy bone replaces the callus cartilage, and remodelling can remove outward signs of the break1. A review of fracture healing reports that about 10% of fractures do not heal normally25.

A literature review of lower radius fractures in adolescents found substantial potential for angled or overlapped fractures to remodel, even in patients older than 1226.

How long it takes at the wrist

Three studies report on union, when the bone has joined across the break27,28,29:

  • Torus fractures in children. A 2026 review states that these wrist breaks heal reliably within three to four weeks27.
  • Adults with a plate. One centre reviewed 494 patients whose break was fixed with a metal plate on the palm side28. Leaving out one surgeon’s 117 patients, X-rayed on a later schedule, the groups compared reached recorded union at about 12.3 to 12.5 weeks28. The authors caution that this mostly reflects when X-ray visits were scheduled, not when the bone truly joined28. Six of the 494 breaks (1.2%) did not unite28.
  • Adults aged 50 or over. In another study of this age group, none of 311 lower radius fractures showed slow healing or non-union on X-ray29.

Trials of wires, plates, casts and soft bandages are covered on the distal radius fracture page17,30,31,32.

How the bone builds up with loading

A review of bone strength reports that bone adapts to the loads it usually bears33. One trial tested this at the radius, with a voluntary task that compressed the forearm6. It measured bone mineral content, the amount of mineral in a bone6.

The trial ran for 12 months in 102 healthy women aged 21 to 40, and 66 completed it6. Slips of paper drawn from an envelope set the groups, and participants were blinded to the study hypotheses6. At the far end of the radius, bone mineral content rose by 2.7% and 3.4% in the two loading groups6. It fell by 1.3% in controls6. The paper states that a United States National Institutes of Health institute fully supported it, with further support from a National Science Foundation graduate fellowship6.

The loading dose was positively related to the change in bone mineral6. Yet the authors concluded that strain size, strain rate and number of loading bouts explained only a small part of the variation6.

Four studies of sport and exercise report on bone in the arm, two of them at the lower radius34,35,36,37:

  • Wrist-loading sports in youth. A 2018 systematic review covered 23 studies of young people in sports such as gymnastics, tennis and rowing34. Athletes had higher bone mineral density and content in the arms than controls34.
  • Gymnastics. A meta-analysis (a study that pools the results of several earlier studies) of 17 studies compared pre-pubertal girls (girls before puberty) in gymnastics with non-gymnasts35. Gymnasts had greater bone properties, and the largest difference was in volumetric bone mineral density at the lower end of the radius35.
  • Impact exercise. A 2023 meta-analysis pooled 28 randomised trials of impact exercise, with ground forces at least those of running36. It found gains in some bone structure measures elsewhere, but no effect at the distal radius36.
  • Resistance training. A 2001 meta-analysis of controlled trials in women reported that this training helped radius bone density after menopause37. It did not single out the lower end37.

In ten cadaver wrists, the bone just under the cartilage was densest in two spots, one in each fossa38. The authors state that such patterns reflect the load carried over the long term38. In healthy adults scanned while bending the wrist, higher density in the lower radius went with larger joint contact areas39.

Connections

Joints it forms

The distal radius forms the wrist joint with the scaphoid and lunate, and the distal radioulnar joint with the ulna1.

Related exercise pages: push-up, in which one cadaver study measured force along the distal radius12.

Muscles and tendons attached to the radius

StructureWhere it meets the radius
Distal biceps tendon, of the biceps brachiiRadial tuberosity, a bump near the elbow1,40
Forearm flexorsPronator teres, a forearm muscle that turns the palm down, inserts at the middle of the shaft’s outer surface41
Forearm extensorsBrachioradialis, a forearm muscle that bends the elbow, inserts at the base of the styloid process41
First dorsal compartment tendonsRun in a groove on the outer side of the lower end41

Distal radius forms part of

Distal radius meets at the wrist joint

Distal radius gives origin to

Distal radius can be injured together with

Distal radius breaks in

Distal radius is attached to by

Distal radius carries in its groove

Distal radius is loaded by

Sources

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Every source the library cites

Changes

  • First published.