The word 'cruciate' means 'crossed', and in the knee the term relates to the cruciate ligaments right in the middle of the knee.
Page updated June 2024 by Dr Sheila Strover (Clinical Editor)
![bent knee showing position of cruciate ligaments](/sites/default/files/users/user1/acl.png)
This illustration arrow shows the anterior cruciate ligament in the front, and the posterior cruciate ligament can be visualised behind it.
What is the function of the cruciate ligaments?
The cruciate ligaments are important stabilisers of the knee, and in particular they facilitate rotational stability.
The crossed structure of the two cruciate ligaments allows bending and straightening of the knee, while keeping the knee stable and preventing the two big bones from moving front- and backwards, or rotating excessively, in relation to one another,
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Quote from peer-reviewed paper:
"....The anterior cruciate ligament resists the combined motions of anterior tibial translation and internal tibial rotation, which defines the concept of rotational stability...."
Citation: Noyes FR. The function of the human anterior cruciate ligament and analysis of single- and double-bundle graft reconstructions. Sports Health. 2009 Jan;1(1):66-75. doi: 10.1177/1941738108326980. PMID: 23015856; PMCID: PMC3445115.
Are some people born without cruciate ligaments?
It is rare, but some people are born without cruciate ligaments. Not all of these are symptomatic.
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Quote from peer-reviewed paper:
The condition is "....extremely rare, with a prevalence of 0.017 per 1000 live births....[Orthopaedic surgeons] suggest conservative treatment for asymptomatic patients.....For those who are symptomatic, in order to regain knee stability and function, most clinicians are reported to proceed with cruciate ligament reconstruction or orthopedic surgery"
Citation: Lu R, Zhu DP, Chen N, Sun H, Li ZH, Cao XW. How should congenital absence of cruciate ligaments be treated? A case report and literature review. World J Clin Cases. 2019 Oct 6;7(19):3082-3089. doi: 10.12998/wjcc.v7.i19.3082. PMID: 31624758; PMCID: PMC6795736.
Forum discussions
- Born without ACL's
Some people are born without an anterior cruciate ligament. They may be asymptomatic or suffer from instability.
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