Lecture on the Knee Joint

Introduction

• The knee joint is the most complex joint in the body.
• Composed of three joints surrounded by a single joint cavity.

Components of the Knee Joint

Femoro-patellar Joint

• Location: End of the femur meets the patella.
• Type: Plane joint, gliding motion.
• Movement: Patella moves along the distal ends of the femur.

Tibiofemoral Joints

• Lateral and Medial tibiofemoral joints.
• Articulation: Femoral condyles with lateral and medial menisci of the tibia.
• Type: Functionally a hinge joint.
  • Allows flexion and extension.
  • Partial extension allows some rotation.

Menisci

• Lateral and Medial Meniscus
• Vulnerable to tearing due to attachment only at terminal ends.

Structure of the Knee Joint

Joint Capsule

• Not fully enclosed, missing anteriorly.
• Contains synovial cavity and bursae.
• At least 12 bursae present.
  • Subcutaneous Prepatellar Bursae: Commonly affected by trauma.

Articular Cartilage

• Thin on both femur and tibia ends.

Tendons and Ligaments

• Reinforced by muscle tendons from quadriceps and semimembranosus muscle.
• Tendons of quadriceps muscle give rise to:
  • Patellar ligament
  • Lateral and medial patellar retinacula

Reflex Mechanism

• Patellar reflex caused by hitting patellar ligament, causing quadriceps contraction.
• Brain usually subdues this reflex; can be overridden by certain actions.

Ligaments of the Knee Joint

Capsular and Extracapsular Ligaments

• Prevent hyperextension and rotation.
• Fibular Collateral Ligament and Tibial Collateral Ligament
• Oblique Popliteal Ligament: Continuation of semimembranosus tendon.
• Arcuate Popliteal Ligament: Arcs over popliteus muscle.

Intracapsular Ligaments

• Function: Prevent anterior-posterior displacement.
• Cruciate Ligaments:
  • Anterior Cruciate Ligament (ACL): Prevents forward sliding of the femur and hyperextension.
  • Posterior Cruciate Ligament (PCL): Prevents backward displacement of the tibia.

Bone Structure and Function

• Femoral and tibial condyles act like ball bearings.
• Locking mechanism facilitates knee extension.

Knee Joint Injuries

• Knee can absorb vertical forces due to locking mechanism.
• Susceptible to injuries from horizontal blows.
• Common Injuries: Collateral ligaments, cruciate ligaments, and cartilage.
• Medial and lateral menisci are vulnerable due to limited attachment.