Expansion
The ACL stops the tibia sliding forward; the PCL stops the tibia sliding backward
Mnemonic
The cruciates are named by their tibial attachment, which makes their function follow automatically:
- Anterior cruciate attaches anteriorly on the tibia, so it prevents the tibia sliding forwards. Tested by the anterior drawer and Lachman
- Posterior cruciate attaches posteriorly, so it prevents the tibia sliding backwards. Tested by the posterior drawer and the sag sign
“LAMP” for the menisci and collaterals: the Lateral meniscus is Attached to Muscle (popliteus) and is therefore More mobile; the Medial meniscus is fixed to the medial collateral ligament, which is why it tears in the unhappy triad.
Expansion
- Anterior cruciate ligament (ACL) - prevents anterior displacement of the tibia on the femur; tested by the anterior drawer and Lachman tests
- Posterior cruciate ligament (PCL) - prevents posterior displacement of the tibia; tested by the posterior drawer test
Remember: each ligament is named by where it attaches to the tibia, and that tells you the direction of tibial movement it resists.