After completing “The Knee Joint” section, you will be able:

  • To describe the 3 bones
  • To explain the 2 joints
  • To summarise the 5 ligaments and explain their origin, attachment and action
  • To describe the 2 meniscus and understand their function
  • To validate knowledge by completing the quiz

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3 BONES

The knee joint is made from 3 bones:

  • Femur:  also known as the thigh bone. It is situated superior to the tibia in the knee joint. FUN FACT: The femur is the longest bone in the body.
  • Tibia: also known as the shinbone. It is situated inferior to the femur in the knee joint and runs down laterally to the ankle joint.
  • Patella: also known as the kneecap. It is situated superficially to (ontop) the femur and tibia. The role of the patella is to protect the knee joint.
  • Knee Joint
    Bones of the Knee Joint
  • Femur
    Femur
  • Tibia 1
    Tibia
  • Patella
    Patella

2 JOINTS

Synovial hinge joint with two articulations:

 1. Tibiofemoral joint/articulation

  • Articulation between the tibia and femur
  • This joint is the weight-bearing joint of the knee joint

 2. Patellofemoral joint/articulation

  • Articulation between the patella and femur
  • This allows the main extensor tendon (from the quadriceps femoris muscle) to be inserted over the joint, and thus increasing the efficiency of the muscle.

5 LIGAMENTS (REMEMBER: LIGAMENTS = BONE → BONE)

There are 5 main ligaments of the knee joint:

 1 Patellar ligament: (1)

  • Continuation of the tendon from the quadriceps femoris muscle.
  • Attaches: tibial tuberosity → patella.
  • Action: Helps to keep the patella in place.

2 Cruciate ligaments:

  • These 2 ligaments attach tibia → femur

TIP: “cruciate” is Latin for cross.

TIP: The cruciate ligaments are named by their origins from the tibia.

  1. Anterior Cruciate Ligament (ACL): (2)

    • Attaches: Anterior tibia → (posteriorly and lateral) to the posterior femur.
    • Also, the ACL attaches to the medial meniscus.
    • Action: Prevents anterior dislocation of the tibia onto the femur.
  2. Posterior Cruciate Ligament (PCL): (3)
    • Attaches: Posterior tibia → (anteriorly and medial) to the anterior femur.
    • Action: Prevents posterior dislocation of the tibia onto the femur.

TIP: * Mnemonic Alert * PAMs APpLes for cruciate ligament insertion on the femur:
Posterior [cruiciate ligament passes] Anteriorly [and inserts] Medially [on the femur].
Anterior [cruciate ligament passes] Posteriorly [and inserts] Laterally [on the femur].

 2 Collateral ligaments:

  • Action: These 2 ligaments help stabilise the hinge motion of the knee joint, preventing medial and lateral movement.

 1. Tibial (medial) collateral ligament (MCL): (4)

  • Attaches: Medial surface of the tibia → medial epicondyle of the femur.
  • Firmly attached to medial meniscus.

 2.Fibular (lateral) collateral ligament (LCL): (5)

  • Thinner than the MCL.
  • Attaches: Lateral surface of the fibula → lateral epicondyle of the femur

2 MENISCUS

These are two fibrocartilage C-shaped structures found between the femur and tibia, one medially and other laterally (hence the names!). They serve 2 functions:

  • SHOCK ABSORBER
  • FORCE DISTRIBUTOR – increases joint stability by deepening the articular surface of the tibia

 1. Medial meniscus:

  • Firmly attached to the tibial (medial) collateral ligament.
  • Hence damage to the MCL is associated with tearing of the medial meniscus.


 2.
Lateral meniscus
:

  • Smaller with no extra attachment and hence more mobile.

References

Moore K, Dalley A, Agur A. (2014). Clinically Oriented Anatomy. 7th ed. Philadelphia: Wolters Kluwer.

Teach Me Anatomy. (2017). The Knee Joint. [online]. Available at: http://teachmeanatomy.info/upper-limb/joints/elbow-joint/ [accessed 1 March 2017].

Tortora G, Derrickson B. (2011). Principles of Anatomy and Physiology. 13th ed. Chichester: John Wiley & Sons.

 

Image References

Bones of The Knee Joint.   Femur.   Tibia.   Patella.   Knee Articulations.   Knee Joints.   Knee Ligaments 1.   Knee Ligaments 2.   Knee Ligaments 3.   Meniscus.