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Distal biceps tendon

Also called biceps tendon at the elbow

The tendon that joins the biceps to the radius just below the elbow. How its two parts attach, why it may be weak in the middle, how and in whom it tears, and what studies record afterwards.

Region
Elbow
Muscles
biceps brachii
Updated
September 29, 2026
Reviewed
September 29, 2026 · how entries are checked

Function

What the tendon joins

The biceps brachii is the two-headed muscle on the front of the upper arm1. The short head starts at the coracoid process, a hooked bony point at the front of the scapula (shoulder blade)1. The long head starts at the supraglenoid tubercle, a bump just above the shoulder socket, and at the top of the labrum, the socket’s rim1. Its tendon at the shoulder is the long head of biceps tendon8.

At its lower end, the biceps attaches through this tendon to the radial tuberosity, a bump on the radius1. The radius is the forearm bone on the thumb side. The muscle crosses both the shoulder and the elbow9.

Engraving of the front of the left forearm with the superficial muscles. At the top, the lower end of the biceps brachii narrows into its tendon, which dips into the crease of the elbow, while a flat sheet, the bicipital aponeurosis, fans off its inner side over the forearm flexor muscles. Brachioradialis runs down the outer side and pronator teres crosses the upper forearm.
Biceps tendon and aponeurosis at the elbowHenry Vandyke Carter, in Henry Gray, Anatomy of the Human Body (1918), Fig. 414. Public domain, via Wikimedia Commons. (source, Public domain)

How two heads become one tendon

The two heads often keep separate tendons for part of the way10,11. In 17 cadaver (donated body) elbows, the tendon was in two distinct parts, one from each head, in 1010. In the other seven, the two muscle parts interlocked instead10. On MRI (magnetic resonance imaging) scans of 106 elbows, 96 tendons left the muscle as two11. In 87 of those 96, the two then joined before reaching the radius11.

In 15 cadaver arms, the muscle and tendon turned 90 degrees outward on the way from shoulder to forearm12. The long-head part attached to the upper part of the tuberosity, and the short-head part to the lower part12. In the 17-elbow study, the short head attached further down, placed to be the stronger elbow bender10. The long head attached further from the forearm’s turning axis, placed to be the stronger supinator10.

How big the attachment is

Three studies measured the tendon and its footprint, the patch where it attaches to bone11,12,13:

StudyWhat was measured
15 cadaver armsFootprint about 21 mm long, 7 mm wide and 108 mm² in area12. It began about 23 mm below the joint edge at the top of the radius12
18 cadaver elbowsA ribbon shape on the little-finger side of the tuberosity, covering 63% of its length and 13% of its width13
MRI scans of 106 elbowsTendon about 65 mm long; footprint about 16 mm long and 10 mm wide11

What the tendon does

The biceps bends the elbow and helps turn the forearm palm up, a movement called supination9. With the elbow straight, it acts as a bender of the forearm2. With the elbow bent it becomes the forearm’s most powerful supinator2.

A moment arm is a muscle’s leverage, meaning how far its line of pull sits from the joint it turns. In two donor arms and a computer model, the biceps’ moment arm for bending the elbow peaked with the elbow straighter14. Its peak was larger with the palm turned up14.

Stress is the force in a tendon for each unit of its cross-sectional area. In 11 young men pulling against resistance without moving the elbow, ultrasound showed tendon stress differed with forearm position15. It was about 52% greater with the palm up or the thumb up than with the palm down15.

The flat sheet that fans off it

At its lower end, the biceps also continues as the bicipital aponeurosis, a broad, flat sheet of tendon2. It crosses the elbow and joins the radius and the fascia of the forearm, a sheet of tough tissue that wraps muscles2. In 17 cadaver elbows, it had three layers and fully wrapped the forearm flexor muscles on the little-finger side10. The authors suggest it may help steady the tendons10.

In ten cadaver arms in an elbow machine, an intact sheet lowered the biceps’ leverage for supination at every elbow angle16. With the elbow fully straight, it even made the biceps act as a pronator, turning the palm down16.

Breakdown

Why the tendon may be weak in the middle

An anatomic study found three zones of blood supply along the tendon17. Arteries fed the upper and lower zones, with a poorly supplied zone averaging 2.14 cm between them17. In the same study, the tendon filled 85% of the space at the upper joint between the two forearm bones with the palm fully down17. CT scans are pictures of the inside of the body built from X-rays. In the same study, CT scans showed that space narrowing by half from palm fully up to palm fully down17.

The authors propose that pinching during forearm turning, and the poorly supplied sections, may add to ruptures from wear17. A review lists possible reasons for rupture18. These include earlier inflammation or wear in the tendon, a relatively poor blood supply, and a spur on the tuberosity18. These are suggested explanations, not measured causes18.

Camera checks inside the elbows of 53 cadavers, average age 70, found partial tears with no known injury in 40%19. In every one, the fibres had come away on the tendon’s outer side only19.

How ruptures happen

Studies disagree on the kind of muscle work at the moment of rupture4,20. Eccentric work is muscle work done while the muscle lengthens. In a series of 14 people, all described excessive eccentric tension while the arm was pushed out of a bent position20. In 57 videos of ruptures, 88% happened during an isometric contraction, where the muscle works but the joint does not move4. Just 7% of the 57 were eccentric4.

The two video studies agree on arm position3,4:

  • In 57 videos, 98% of ruptures happened with the palm turned up and 89% with the elbow bent 10 degrees or less4.
  • In 56 videos, 55 of them of men, 96.4% happened with the palm up and the elbow straight or slightly bent3.
  • In those 56 videos, the deadlift was the most common activity, at 71.4%3.

A systematic review sums up the research on a question in a set, checkable way. One review of risk factors found heavy weight lifting the most common way the injury happened, at 53.2%6. In a review of 16 athletes with 18 complete ruptures during athletic activity, weightlifting caused 56%21. One case report, a report on a single patient, describes a recreational lifter tearing both tendons at once during a preacher curl22.

How often it tears

Rates vary by where and how they were counted5,20:

Ruptures per 100,000 people a yearOne health plan, over five years1.2 US insurance database, national estimate2.55 Same US study, regional chart review5.35
Ruptures per 100,000 people a year. Bars start at zero; the table below gives each value with its source.
PopulationRuptures per 100,000 people a year
One health plan, over five years1.220
US insurance database, national estimate2.555
Same US study, regional chart review5.355

Across adults in Finland and Sweden, surgery for this rupture in men rose from 1997 to 201623. Person-years are people times the years each was followed. In Finnish men, it went from 1.3 to 9.6 per 100,000 person-years23. In Swedish men, it went from 0.2 to 5.623.

Who tears it

Most people in these studies were men, with average ages in the mid-forties5,6. In the US study, men made up 95% of cases nationally, and regional patients averaged 46.3 years5. A review of about 7,500 patients found an average age of 46.8, with 96.7% men6. It described 94.7% as having an affinity for sport6. It also found that on average 55.8% had a physical job6.

Some factors went with more ruptures or injuries of this tendon5,20,24. These findings are associations, not proof of cause:

  • In one health plan, 43% of people with a rupture smoked, against 9% of members; smokers had 7.5 times the risk20.
  • In the US study, smoking and higher body mass index went with more ruptures, while diabetes did not5.
  • A database study compared people aged 35 to 75 who filled a testosterone prescription for at least three months with a control group24. Their odds of this injury within a year were about four times higher24.
  • A review found tobacco use in 20.8% of cases and anabolic steroid use, a drug related to testosterone, in 2.5%6.
  • Its authors conclude that steroid use does not seem to raise the risk significantly6.

Tendinopathy

Tendinopathy is local pain in a tendon that comes with activities that load it. Across 1,180 elbow MRI reports, 10% showed signs of tendinopathy in this tendon on the scan25. Of those, 53% were found by chance in people without pain at the front of the elbow25. It was most common at ages 40 to 49.9, then 50 to 59.9, and was significantly linked to rising age25.

Recovery

The studies below record strength in groups of people after a rupture, with or without repair26. A meta-analysis is a study that pools several earlier studies into one answer. Results differed between studies7,27,28:

StudyWhat was found
10 patients, 3 without repairThose three lost on average 40% of supination strength and about 30% of bending strength27
Same study, 4 reattached straight awayNormal bending and supination strength by one year; in the one person checked at four months, not yet27
18 people, 20 unrepaired rupturesMedian (middle value) supination strength 63% and bending strength 93% of the other arm28
Meta-analysis of 53 studies, 1,380 patientsStrength scores with surgery: bending 94.7%, supination 89.2%; without: 83.0% and 62.6%7

In the 18-person study, compared with a historical group who had surgery, the supination gap was significant but the bending gap was not28. Another meta-analysis covered 2,481 ruptures, 79 of them not repaired26. Repair went with higher strength and endurance for both bending and supination26. People’s own questionnaire scores for arm function were also significantly better after surgical repair26.

In a cohort study at one large institution, 36% of people first managed without surgery went on to have surgery29. That rate did not differ significantly between partial tears, at 34%, and complete tears, at 39%29.

Strength after repair

A meta-analysis covered 272 ruptures repaired within 30 days, followed for a mean of 39.6 months30. The repaired arm had significantly lower bending and supination strength than the uninjured arm30. It also had significantly less range: about 1 degree less bending, and about 8 to 9 degrees less turning of the forearm30. In a series of 183 competitive strength athletes after repair, 73% reported full strength in the arm, and 3% tore the tendon again31.

Returning to sport and work

Three reviews and one league study report how many people went back to sport or work32,33,34,35:

Group studiedWhat was found
Review of 1,093 people after surgical repair91.5% returned to sport, and 85.2% to their earlier level or higher, at a mean of 6.3 months32
Review of 157 athletes, all with surgical repair97.5% returned to sport, at a mean of 6.2 months33
NFL (American football) players, 2009–10 to 2022–23 seasons73.1% returned to play, but 52.6% returned to their earlier level of performance34
Review of 1,270 people after surgical repair89% fully returned to work without changed duties, at a mean of about 14 weeks where time was reported35

In the 1,093-person review, the mean age was 44.9 and 99.2% were men32. The injury was linked to sport in 43.5%, and was in the dominant arm in 64.9%32.

Complications after repair

A systematic review pooled 3,091 first-time repairs of this tendon36. Overall, 25% had a complication, 4.6% had a major one, and 1.4% tore again36. The most common problem, in 9.2%, was injury to the lateral cutaneous nerve of the forearm36. This nerve carries feeling and runs along the outer side of the tendon18. Across all nerve injuries in the review, most resolved without further intervention36.

Early movement compared with keeping the arm still

A meta-analysis of 50 studies and 1,577 patients compared outcomes after repair37. It set early movement against a period of immobilisation37. Re-rupture rates, arm-function questionnaire scores and strength did not differ significantly between the two37. The authors rated the quality of the evidence as low to very low37.

Partial tears and tendinopathy

A systematic review looked at partial tears and tendinopathy of this tendon38. Studies reported less elbow pain and better function both with and without surgery38. The evidence was low-level and the studies differed, so results could not be pooled or compared statistically38.

Connections

The muscles that bend the elbow with it

The muscles that bend the elbow include the biceps, the brachialis and the brachioradialis, a forearm muscle9. The brachialis lies under the biceps and adds power to bending the forearm9. In 15 young healthy men bending the elbow as hard as they could, all three were very active39. That held with the palm up, the palm down and the thumb up39.

The other end of the biceps

The long head of biceps tendon starts at the top of the shoulder socket8. In the middle third of the upper arm, it joins the short head as both become muscle8. That muscle then attaches across the elbow to the radial tuberosity, through this tendon1,8.

What studies of the biceps curl show

Related exercise pages: biceps curl. In 11 young men, isometric elbow bending was about 50% stronger with the palm up or thumb up than palm down15. Strain is how much something stretches, as a share of its resting length. In the same men, tendon strain was about 36% greater with the thumb up than palm down15.

Distal biceps tendon is loaded by

Distal biceps tendon shares a muscle with

Distal biceps tendon tore most often in online videos during

Sources

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Every source the library cites

Changes

  • Tidy pass: minor review findings fixed, glosses aligned with the reviewed glossary.
  • First published.