Ligaments of the Knee Joint

Cruciate, collateral, meniscofemoral and patellar ligaments of the right knee - THIEME Atlas of Anatomy

Classification

1. Patellar Ligament (Anterior)

• The distal continuation of the quadriceps femoris tendon.
• Runs from the apex and adjacent margins of the patella to the tibial tuberosity.
• It is the strongest ligament anteriorly and acts as part of the extensor mechanism.

2. Medial Collateral Ligament (MCL / Tibial Collateral Ligament)

• Shape: Broad, flat; has superficial and deep layers separated by loose connective tissue.
• Attachments: Superficial layer - medial epicondyle of femur → medial surface of proximal tibia, ~7-8 cm below the tibial plateau. Deep layer - inserts into the medial meniscus just above the joint line.
• Function: Resists valgus stress.
• Key point: The deep layer is firmly attached to the medial meniscus, which is why MCL injuries frequently co-occur with medial meniscus tears.
• Tension: Taut in extension; lax in flexion.

Medial view showing the MCL, patellar ligament and medial meniscus

3. Lateral Collateral Ligament (LCL / Fibular Collateral Ligament)

• Shape: Small, rounded cord (unlike the flat MCL).
• Attachments: Lateral epicondyle of femur → head of fibula (runs obliquely downward and backward).
• Function: Resists varus stress.
• Key point: Has no attachment to the lateral meniscus (unlike MCL and medial meniscus), hence isolated LCL injury does not tear the lateral meniscus.
• Tension: Taut in extension; lax in flexion.

4. Anterior Cruciate Ligament (ACL)

• Location: Intra-articular but extrasynovial (covered anteriorly and laterally by synovial membrane).
• Attachments: Anterior intercondylar area of tibia → medial surface of the lateral femoral condyle (runs upward, backward, and laterally).
• Fiber bundles: Two bundles - anteromedial (AM) and posteromedial (PM), allowing some fibers to be taut in every joint position.
• Function: Prevents anterior subluxation of the tibia on the femur. Also limits internal rotation and hyperextension.
• Clinical test: Anterior drawer test; Lachman test.
• Blood supply: Middle genicular artery (from popliteal artery).
• Common injury: Pivoting/twisting trauma; part of the unhappy triad (ACL + MCL + medial meniscus).

5. Posterior Cruciate Ligament (PCL)

• Attachments: Posterior intercondylar area of tibia → lateral surface of the medial femoral condyle (runs upward, forward, and medially).
• Fiber bundles: Anterolateral (larger/stouter) and posteromedial (more slender).
• Size: Thicker and stronger than the ACL; oriented approximately at a right angle to it.
• Function: Prevents posterior subluxation of the tibia on the femur. The primary restraint to posterior tibial displacement.
• Clinical test: Posterior drawer test; posterior sag sign.

The two cruciate ligaments cross each other, keep the articular surfaces in contact, and stabilize the knee primarily in the sagittal plane.

6. Oblique Popliteal Ligament (Posterior)

• A broad, fibrous band derived from the semimembranosus tendon.
• Runs obliquely upward and laterally across the posterior capsule.
• Reinforces the posterior capsule.

7. Arcuate Popliteal Ligament (Posterior)

• An inverted Y-shaped ligament arising from the head of the fibula.
• Arches over the popliteus muscle to attach to the posterior capsule.
• Along with the oblique popliteal ligament, forms the posterolateral corner stabilizing complex.

8. Transverse Ligament of the Knee (Intrinsic)

• Connects the anterior horns of the medial and lateral menisci.

9. Posterior Meniscofemoral Ligament (Ligament of Wrisberg) (Intrinsic)

• Runs from the posterior horn of the lateral meniscus to the lateral surface of the medial femoral condyle.

Summary Table - Clinical Correlations