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.
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.
- 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
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.
