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Anterior Cruciate (ACL)

  1. Attachments of ACL
    1. In tibia immediately behind anterior horn of medial meniscus
    2. Pass upwards, backwards and laterally
    3. Posterior part of medial surface of lateral femoral condyle
ACL has two bundles (Anteromedial is tight in Flexion)
  1. It is major stabilizer of knee. Its mechanism is to stabilize internal rotation and extension of tibia on femur. Its function is multiple in that it limits forward gliding of tibia on femur and limits hyperextension It makes a significant contribution to lateral stability and limits antero lateral rotation of tibia on femur. It is extrasynovial
  2. ACL is most commonly injured with valgus, external (lateral) rotation, hyperextension deceleration, and rotational knee movements. So in nut shell it is injured by occurarce of excessive movements which it limits.

Posterior cruciate (PCL)

  1. Attachments of PCL
    1. In tibia behind posterior horn of medial meniscus.
    2. Posses upwards, forwards and medially.
    3. Posterior part of lateral surface of medial femoral condyle.
  2. It is intracapsular, extra synovial and stouter ligamentous structure.
  3. It limits backward glide of tibia on femur (posterior translation) and checks hyperextension only after the ACL is ruptured.
  4. Classically injured by high velocity trauma with posterior dislocation of tibia on a flexed knee as in a ‘dash board impact’ in a motor car.
  5. Instability is sometimes felt only on climbing stairs.
Extra Edges:
  1. ACL
    • Most difficult action to perform
    • Walking uphill
  2. Posterior Cruciate Ligament (PCL)
    • Walking downhill
  3. Meniscus
    • Full squatting & to walk in the squatting position (Payr’s sign)
    • Deep squat & dulk walking.
  4. Paralysis Of Quadriceps Muscle
    • Rising from a chair & climbing stairs.

Collateral ligament injury

  1. The most common mechanism of ligament disruption of knee is abduction (valgus),flexion and internal rotation of femur on tibia which usually occur in sports in which the foot is planted solidly on the ground and leg is twisted by rotating body (i.e. foot ball, soccer, basket ball, skiing)
  2. The medial structures medial (tibial) collateral ligament (MCL) and medial capsular ligament are first to fail, followed by ACL tear, if the force is of sufficient magnitude. The medial meniscus may be trapped between condyles and have a peripheral tear, thus producing unhappy triad of 0’ Donoghue
  3. Main test for MCL (medial collateral ligament) is valgus (abduction) stress in 30° of knee flexion.
  4. Because in full extension it is indicative of combined MCL, posterior oblique ligament injury & possible cruciate ligament injury.
  5. Varus (Adduction) stress test in 30 degree flexion removes the lateral stabilizing effect of illotibial band so that the lateral collateral ligament can exclusively be examined.

Direction of Force

Position of knee

Ligament Tested

Varus/ Valgus

Full extension

PCL, Posterior capsule



30° flexion Q




90° flexion



30° flexion Q (lachman’s test)

- 90° flexion (anterior drawer)


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