View source for Biology:Malleolus

{{Short description|Ankle bone protrusion}}
{{Infobox bone
| Name        = Malleolus
| Latin       = malleolus, malleoli
| Image       = Gray357.png
| Caption     = [[Biology:Coronal plane|Coronal]] cross-section through the right ankle showing the '''lateral malleolus''' (right) and '''medial malleolus''' (left)
| Image2      = Gray1239.png
| Caption2    = The left leg, with the '''medial malleolus''' labeled at bottom right.
}}
{{wikt}}

A '''malleolus''' is the bony prominence on each side of the human ankle.

Each leg is supported by two bones, the [[Biology:Tibia|tibia]] on the inner side (medial) of the leg and the [[Biology:Fibula|fibula]] on the outer side (lateral) of the leg. The '''medial malleolus''' is the prominence on the inner side of the ankle, formed by the lower end of the tibia. The '''lateral malleolus''' is the prominence on the outer side of the ankle, formed by the lower end of the fibula.

The word ''malleolus'' ({{IPAc-en|m|ə|ˈ|l|iː|ə|l|ə|s|,_|m|æ|-}}{{refn|{{MerriamWebsterDictionary|access-date=2016-01-22|Malleolus}}}}{{refn|{{Cite dictionary |url=http://www.lexico.com/definition/Malleolus |archive-url=https://web.archive.org/web/20200322184451/https://www.lexico.com/definition/malleolus |url-status=dead |archive-date=2020-03-22 |title=Malleolus |dictionary=Lexico UK English Dictionary |publisher=[[Organization:Oxford University Press|Oxford University Press]]}} }}), plural ''malleoli'' ({{IPAc-en|m|ə|ˈ|l|iː|ə|ˌ|l|aɪ|,_|m|æ|-}}), comes from Latin and means "small [[Engineering:Hammer|hammer]]". (It is cognate with ''[[Engineering:Mallet|mallet]]''.)

==Medial malleolus==
The medial malleolus is found at the foot end of the [[Biology:Tibia|tibia]]. The medial surface of the lower extremity of tibia is prolonged downward to form a strong pyramidal [[Biology:Process (anatomy)|process]], flattened from without inward - the medial malleolus.
* The ''medial surface'' of this process is convex and subcutaneous.
* The ''lateral'' or ''articular surface'' is smooth and slightly concave, and articulates with the [[Biology:Talus bone|talus]].
* The ''anterior border'' is rough, for the attachment of the anterior fibers of the deltoid ligament of the ankle-joint.
* The ''posterior border'' presents a broad groove, the malleolar sulcus, directed obliquely downward and medially, and occasionally double; this sulcus lodges the tendons of the Tibialis posterior and Flexor digitorum longus.
* The ''summit'' of the medial malleolus is marked by a rough depression behind, for the attachment of the deltoid ligament.

The  major structure that passes anterior to the medial malleolus is the saphenous vein.

Structures that pass behind medial malleolus deep to the flexor retinaculum:

* Tibialis posterior tendon
* Flexor digitorum longus
* Posterior tibial artery
* Posterior tibial vein
* Tibial nerve
* Flexor hallucis longus

==Lateral malleolus==
The lateral malleolus is found at the foot end of the [[Biology:Fibula|fibula]], of a pyramidal form, and somewhat flattened from side to side; it descends to a lower level than the medial malleolus.
* The ''medial surface'' presents in front a smooth triangular surface, convex from above downward, which articulates with a corresponding surface on the lateral side of the talus. Behind and beneath the articular surface is a rough depression, which gives attachment to the posterior talofibular ligament.
* The ''lateral surface'' is convex, subcutaneous, and continuous with the triangular, subcutaneous surface on the lateral side of the body.
* The ''anterior border'' is thick and rough and marked below by a depression for the attachment of the anterior talofibular ligament.
* The ''posterior border'' is broad and presents the shallow malleolar sulcus, for the passage of the tendons of the Peronæi longus and brevis.
* The ''summit'' is rounded and gives attachment to the calcaneofibular ligament.

A major structure that is located between the lateral malleolus and the Achilles tendon is the sural nerve.

== Clinical significance ==

=== Fracture ===
A '''bimalleolar fracture''' is a fracture of the ankle that involves the lateral malleolus and the medial malleolus. Studies have shown<ref name="tejwani">{{cite journal|last=Tejwani|first=Nirmal|title=Are Outcomes of Bimalleolar Fractures Poorer Than Those of Lateral Malleolar Fractures with Medial Ligamentous Injury?|journal=Journal of Bone and Joint Surgery|year=2007|volume=89|issue=7|pages=1438–1441|doi=10.2106/JBJS.F.01006|pmid=17606780|url=http://www.ejbjs.org/cgi/content/abstract/89/7/1438|access-date=26 November 2010|display-authors=0|archive-url=https://web.archive.org/web/20100215020528/http://www.ejbjs.org/cgi/content/abstract/89/7/1438|archive-date=15 February 2010|url-status=dead}}</ref> that bimalleolar fractures are more common in women, people over 60 years of age, and patients with existing comorbidities.<ref name="tejwani"/>

A '''trimalleolar fracture''' is a fracture of the ankle that involves the lateral malleolus, the medial malleolus, and the distal posterior aspect of the [[Biology:Tibia|tibia]], which can be termed the posterior malleolus. The trauma is sometimes accompanied by ligament damage and dislocation.<ref name="AAOS">{{cite news|title=Ankle Fractures|url=http://orthoinfo.aaos.org/topic.cfm?topic=a00391|author= Orthopaedic Trauma Association|date=September 2007|work=AAOS}}</ref>

==Additional images==
<gallery>
 File:Slide2WIKI.JPG|Ankle joint. Deep dissection. Lateral view.
File:Slide4CEC3.JPG|Ankle joint. Deep dissection.
File:Slide5CEC4.JPG|Ankle joint. Deep dissection.
File:3D Medical Animation Fibula Structure.jpg|Image showing the lateral malleolus as part of the fibula.
File:Left lateral malleolus avulsion fracture.jpg|X-ray avulsion fracture of the summit of the left lateral malleolus.
</gallery>

==References==
{{Gray's}}{{Reflist}}


[[Category:Tibia]]

{{Sourceattribution|Malleolus}}