The cruciate ligaments are the important central 'stays' of the knee joint, contributing significantly to the stability of the joint.
Page updated October 2023 by Dr Sheila Strover (Clinical Editor)
The knee joint from the front. The word 'cruciate' means 'crossed', referring to the fact that the two cruciate ligaments cross over one another in the centre of the joint in the area called the 'notch'.
What do the cruciate ligaments do?
There are two cruciate ligaments - anterior (ACL) and posterior (PCL) - and they tether the femur and tibia together while still allowing the knee to bend, There are two of them - anterior (ACL) and posterior (PCL), and they tether the femur and tibia together while still allowing the knee to bend, stabilising the joint from frontwards and backwards forces. The posterior cruciate ligament (PCL) attaches to the tibia at the back of the knee and the anterior cruciate ligament (ACL) attaches to the tibia at the front of the knee.
Note in the sketch on the left how the anterior cruciate ligament attaches, and the anatomy when the knee is bent and straightened. This is one of the reasons why ligament replacements do not do as good a job as the original ligament as this cannot be mimicked by the replacement.
What kind of injuries damage the cruciates?
The ACL is more commonly damaged than the PCL. Injury to the ligaments may be 'non-contact' or 'contact'. Injury to the ACL may occur while cutting and running to that side during a fast non-contact activity like football, or from landing from a twisting jump on that leg while the body still has momentum and continues to twist.
What are the symptoms of a torn anterior cruciate ligament?
During the injury event, the person may hear a loud 'pop', immediately followed by swellling of the knee and instability.
"Injuries to the anterior cruciate ligament (ACL) of the knee are immediately disabling, take a significant amount of time to rehabilitate, are often associated with other concomitant articular injuries, and result in an increased risk of early onset posttraumatic osteoarthritis..."
Citation: Smith HC, Vacek P, Johnson RJ, Slauterbeck JR, Hashemi J, Shultz S, Beynnon BD. Risk factors for anterior cruciate ligament injury: a review of the literature - part 1: neuromuscular and anatomic risk. Sports Health. 2012 Jan;4(1):69-78. doi: 10.1177/1941738111428281. PMID: 23016072; PMCID: PMC3435896.
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Relevant content -
- Anterior cruciate ligament
- Posterior cruciate ligament
From the Journals -
- Journal interpretation - 2009 - Osteoarthritis in patients with anterior cruciate ligament rupture: A review of risk factors - interpreted by Dr Sheila Strover (Clinical Editor)