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Fibula

The thin outer bone of the lower leg. How little load it carries, how it breaks at the ankle and under repeated stress, how it responds to training and disuse, and what attaches to it.

Region
Lower leg
Muscles
peroneus longus, peroneus brevis, soleus, hamstrings
Updated
October 5, 2026
Reviewed
October 5, 2026 · how entries are checked

Function

Where it sits

The fibula is a long bone on the outer side of the tibia (shin bone)1. Of the two, the fibula is much the smaller and thinner1. It sits just behind the top of the tibia at the knee and runs down the outer side of the leg to the ankle1.

Engraving of the right tibia and fibula seen from the front. The larger tibia on the inner side shows its condyles and tuberosity at the top, the anterior crest and bare medial surface down the shaft, and the medial malleolus at the ankle, with red outlines marking where muscles such as tibialis anterior attach.
Bones of the lower leg from the frontHenry Vandyke Carter, in Henry Gray, Anatomy of the Human Body (1918), Fig. 258. Public domain, via Wikimedia Commons. (source, Public domain)

Its four parts

The fibula is described in four parts1:

  • Head. The small, knob-like upper end, which meets the underside of the tibia’s outer condyle (a rounded knob at the end of a bone)8.
  • Neck. The place where the head narrows1.
  • Shaft. It has an outer, an inner and a back surface, and the muscles attached to it set its shape1.
  • Lower end. It forms the lateral malleolus, the bony bump that is easily felt on the outer side of the ankle8.

The inner side of the lateral malleolus meets the talus (ankle bone) as part of the ankle joint8.

How it is joined to the tibia

The fibula meets the tibia at two joints, one at each end8. At the top, a capsule covers the joint, and ligaments at the front and back strengthen it9. At the bottom, the rounded lower fibula sits in a matching hollow notch in the tibia10.

Between the two ends, a ridge on the inner surface of the fibula anchors the interosseous membrane that ties it to the tibia1. This connection is a syndesmosis, a joint with very little movement1.

A slight gliding is possible at the upper joint during ankle movement9. In dorsiflexion (pulling the foot up toward the shin), the upper fibula rotates outward9.

How much load it carries

Three experiments on legs from cadavers (bodies donated for study) measured the fibula’s share of load2,3,4:

ExperimentFibula’s share
Autopsy specimens, ankle in a neutral position6.4% of the weight2
Ten specimens with force sensors in both bones, ankle neutral7.12% of the total force, on average3
10 specimen legs under a load of 1500 newtons (a newton is a unit of force) along the leg17% of the load, on average4

In the third experiment, the fibula’s share rose as the total load rose4. In the first, the weight on the fibula rose with dorsiflexion or eversion (turning the sole of the foot outward)2. It fell with plantar flexion (pointing the foot down)2.

The authors of one bone-scan study describe the fibula’s share of the lower leg’s compressive load as small and highly variable, from -8% to +19%11. A review puts it at 10% of body weight, against 90% for the tibia12. The same review calls its role crucial to the stability of the ankle mortise12. The mortise is the socket that the lower tibia and fibula form around the talus.

Breakdown

Breaks at the ankle

In a population study of 9767 ankle fractures, a break of the lateral malleolus was the most common type in every age group5. It made up 55% of all the fractures5. In the same study, falls caused 61% of the fractures and sports 22%5.

A review of lower fibula fractures describes two mechanisms12:

  • Rolling out with outward rotation, the most often reported. The talus rotates and pushes the tibia and fibula apart12. The front ligament between the lower tibia and fibula ruptures first, then the fibula breaks at an angle at the level of the syndesmosis12.
  • Rolling out with the back of the foot forced inward, the second most frequent. The result is a ruptured ligament between talus and fibula, an ankle sprain, or an avulsion fracture at the lower fibula12. An avulsion is a tear in which a tendon or ligament pulls away from the bone.

The Danis-Weber classification sorts these fractures by where the main fibular break lies relative to the syndesmosis12:

TypeWhere the fibula breaksHow a review describes it
ABelow the syndesmosisGenerally stable12
BAt its levelUnstable in some cases12
CAbove itUsually unstable12

Of 1756 adult ankle fractures in one Swedish county, 19.8% were type A (below the syndesmosis), 66.2% type B (across it) and 10.6% type C13.

One source reports injury to the ankle syndesmosis in about half of type B and in all type C ankle fractures10. A review reports that a shortened, outward-rotated fibula can shift the talus sideways12. That shrinks the contact area between tibia and talus and raises peak pressure in the joint cartilage12.

Breaks in sport

  • In a registry of Belgian soccer players over two seasons, fibula fractures were the least common of 1600 lower leg fractures, at 9%15.
  • From 2000 to 2014, 237 lower fibula fractures were reported in National Football League players16. Of the 204 that happened in games, 156 (77%) came during contact with another player16.

Stress fractures

A stress fracture is a small crack in a bone from repeated loading. A systematic review describes fibula stress fractures as moderately common among athletes and military recruits6. It adds that most of the available data on how they are managed come from case reports6. Studies have counted the fibula’s share of stress fractures6,17,18:

Group studiedFibula’s share of stress fractures
320 athletes with stress fractures seen on bone scan6.6%17
Systematic review of 3 studies, 521 stress fractures8.6%6
111 competitive track and field athletes over 12 months12%, the third most common site18

One review gives a range of 7% to 12% of all stress fractures, most often in the lower fibula19. It reports that those of the upper fibula are more common in jumpers than in distance runners19.

One study looked at 635 military recruits who reported leg pain during 6 weeks of basic training20. Twelve had a fibular stress fracture, with 11 of the 13 cases where the upper and middle thirds of the bone meet20. Every fracture followed repeated walking or jumping in a squatting position20.

Recovery

How the fibula responds to training and disuse

Bone adapts to the loads it regularly carries21. Several studies measured the fibula alongside the tibia7,11,22:

  • Runners. Scans compared 30 long-distance runners with 30 untrained people7. The runners’ fibulas had similar or lower cortical area and lower resistance to sideways bending, in contrast to their tibias7.
  • Female athletes. Among 221 premenopausal women, a tibial strength measure was higher in three athlete groups than in an active comparison group22. For the fibula, only the high-impact group differed, by 17%22.
  • Soccer players and runners. In 16 female collegiate soccer players, a measure of the fibula’s structure was about 25% larger than in 16 cross-country runners23.
  • Disuse. Thirteen people were scanned 5 weeks and 12 months after a spinal cord injury24. Bone mineral content near the ankle end fell by 6.9% in the fibula, against 14.8% in the tibia24.

In the study of 221 women, peak jump power tracked the tibial strength measure moderately, but not the fibular one22. The authors conclude that the two bones experience different loading environments despite sitting side by side22.

What studies found after a stress fracture

A systematic review of 3 studies included 45 fibular stress fractures6. All healed without surgery, on average by 7 weeks, and people resumed activity on average by 9 weeks6. No nonunion (a broken bone that fails to join and heal) was reported6.

A meta-analysis (a study that pools the results of several earlier studies) covered 76 studies of bone stress injuries in athletes25. Pooled time to return to sport for the fibula was 56 days, among the shortest of any site25. The fibula was also among the sites with the lowest complication rate25.

What studies found after a break

Studies of athletes reported these times16,26,27:

  • Among 112 elite soccer players, median return to play was 91 days after the fibula alone, 150 after the tibia alone and 183 after both26. The differences between bones were not statistically significant26.
  • Another study followed 31 athletes whose lower leg was broken by a direct blow in soccer27. Return to competitive soccer averaged 18 weeks after the fibula alone, 35 after the tibia alone and 40 after both27.
  • National Football League players with a lower fibula fracture alone missed a mean 93.6 days, and those with combined fracture patterns 132.3 days16.

A systematic review of return to sport after ankle fracture included thirteen retrospective studies, generally of poor quality28. The share returning ranged from 25% to 100%, and reported times from 7 to 43 weeks28. The review found that the optimal time to return remains to be confirmed28.

Connections

Joints and ligaments

At the knee, the upper joint with the tibia is strengthened by the biceps femoris tendon in front and the fibular collateral ligament above9. In 10 cadaver knees, the fibular collateral ligament, also called the lateral collateral ligament, attached below to the head of the fibula29.

At the ankle, the lateral malleolus meets the outer side of the talus and forms part of the outer ankle1. Two of the lateral ankle ligaments start on the front border of the lower fibula, a review of cadaver studies found30. A review reports that many authors see the deltoid ligament as the most important structure holding the talus in place when the fibula is broken12. The deltoid ligament is the fan of ligaments on the inner side of the ankle.

Muscles attached to it

Several muscles start or end on the fibula31,32,33,34,35:

MuscleWhere it attaches
Peroneus longus, one of the peroneals (the muscles on the outer side of the lower leg)Starts from the upper two-thirds of the outer side of the fibula31
Peroneus brevis, also one of the peronealsStarts from the lower two-thirds of the outer surface of the fibula32,33
Soleus (a wide, flat calf muscle)Starts partly from the back of the fibula’s head and from the bone’s outer border34
Biceps femoris, one of the hamstrings, on the outer back of the thighEnds on the top of the fibula and the outer tibia35

The nerve at its neck

Where it wraps around the neck of the fibula, the common fibular nerve lies just under the skin and is vulnerable to compression36.

Exercise

Related exercise pages: running. The authors of the scan study of 30 long-distance runners suggest the greater sideways flexibility of their upper fibulas could improve energy storage7.

Fibula is joined by the interosseous membrane to

Fibula forms part of

Fibula is held to the tibia by

Fibula gives origin to

Fibula is attached to by

Fibula gives origin to part of

Fibula is attached to by the biceps femoris of

Fibula is wrapped at its neck by

Fibula is a site of

Fibula is loaded by

Sources

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  3. Goh JC, Mech AM, Lee EH, Ang EJ, Bayon P, Pho RW (1992). Biomechanical study on the load-bearing characteristics of the fibula and the effects of fibular resection.. Clinical orthopaedics and related research. PMID 1600659
  4. Wang Q, Whittle M, Cunningham J, Kenwright J (1996). Fibula and its ligaments in load transmission and ankle joint stability.. Clinical orthopaedics and related research. doi:10.1097/00003086-199609000-00034 PMID 8804301
  5. Elsoe R, Ostgaard SE, Larsen P (2018). Population-based epidemiology of 9767 ankle fractures.. Foot and ankle surgery : official journal of the European Society of Foot and Ankle Surgeons. doi:10.1016/j.fas.2016.11.002 PMID 29413771
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  7. Lüscher SH, Nocciolino LM, Pilot N, Pisani L, Ireland A, Rittweger J, Ferretti JL, Cointry GR, Capozza RF (2019). Differences in the Cortical Structure of the Whole Fibula and Tibia Between Long-Distance Runners and Untrained Controls. Toward a Wider Conception of the Biomechanical Regulation of Cortical Bone Structure. Frontiers in endocrinology. doi:10.3389/fendo.2019.00833 PMID 31827461
  8. Betts JG, Young KA, Wise JA, Johnson E, Poe B, Kruse DH, Korol O, Johnson JE, Womble M, DeSaix P (2022). Anatomy and Physiology 2e. OpenStax. Link
  9. Sarma A, Borgohain B, Saikia B (2015). Proximal tibiofibular joint: Rendezvous with a forgotten articulation.. Indian journal of orthopaedics. doi:10.4103/0019-5413.164041 PMID 26538753
  10. Hermans JJ, Beumer A, de Jong TA, Kleinrensink GJ (2010). Anatomy of the distal tibiofibular syndesmosis in adults: a pictorial essay with a multimodality approach. Journal of anatomy. doi:10.1111/j.1469-7580.2010.01302.x PMID 21108526
  11. Ireland A, Capozza RF, Cointry GR, Nocciolino L, Ferretti JL, Rittweger J (2017). Meagre effects of disuse on the human fibula are not explained by bone size or geometry.. Osteoporosis international : a journal established as result of cooperation between the European Foundation for Osteoporosis and the National Osteoporosis Foundation of the USA. doi:10.1007/s00198-016-3779-0 PMID 27734100
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  14. Bartoníček J, Fojtík P, Bunganičová E, Tuček M (2023). Maisonneuve ankle fracture.. Rozhledy v chirurgii : mesicnik Ceskoslovenske chirurgicke spolecnosti. doi:10.33699/PIS.2023.102.2.48-59 PMID 37185026
  15. Vanlommel L, Vanlommel J, Bollars P, Quisquater L, Van Crombrugge K, Corten K, Bellemans J (2013). Incidence and risk factors of lower leg fractures in Belgian soccer players.. Injury. doi:10.1016/j.injury.2013.07.002 PMID 23916900
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  22. Rantalainen T, Nikander R, Heinonen A, Suominen H, Sievänen H (2010). Direction-specific diaphyseal geometry and mineral mass distribution of tibia and fibula: a pQCT study of female athletes representing different exercise loading types.. Calcified tissue international. doi:10.1007/s00223-010-9358-z PMID 20383493
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  25. Hoenig T, Eissele J, Strahl A, Popp KL, Stürznickel J, Ackerman KE, Hollander K, Warden SJ, Frosch KH, Tenforde AS, Rolvien T (2023). Return to sport following low-risk and high-risk bone stress injuries: a systematic review and meta-analysis. British journal of sports medicine. doi:10.1136/bjsports-2022-106328 PMID 36720584
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  28. Sinha A, Robertson G, Maffulli N (2022). Doctor, I fractured my ankle. When can I return to play? An updated systematic review.. British medical bulletin. doi:10.1093/bmb/ldac016 PMID 35511134
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  33. Basit H, Shah J, Siccardi MA (2023). Anatomy, Bony Pelvis and Lower Limb, Foot Peroneus Brevis Muscle.. StatPearls. PMID 30571048
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Every source the library cites

Changes

  • First published.