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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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.
Bones of the Knee Joint
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.
- 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.
- 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
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.
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.