Lecture on the Knee Joint

Overview

• The knee joint is a complex structure consisting of:
  • Hinge synovial joint between femur and tibia
  • Plane gliding joint between the patella and femur

Bones Involved

• Femur: Condyles articulate with tibial condyles and menisci.
• Tibia: Contains concave condyles deepened by menisci, providing attachment points for ligaments.
• Patella: A sesamoid bone within the patellar ligament and quadriceps femoris tendon.

Ligaments

Capsular Ligament

• Provides stability, attaches to medial meniscus and tibial collateral ligament.
• Pierced by structures like the suprapatellar bursa and tendon of the popliteus.

Cruciate Ligaments

• Anterior Cruciate Ligament (ACL): Prevents forward displacement of tibia, weaker and more prone to injury.
• Posterior Cruciate Ligament (PCL): Prevents backward displacement of tibia, stronger than ACL.

Collateral Ligaments

• Medial (Tibial) Collateral Ligament: Resists valgus stress, often injured.
• Lateral (Fibular) Collateral Ligament: Resists varus stress, rarely injured.

Other Ligaments

• Patellar Ligament: Continuation of quadriceps femoris tendon.
• Oblique Popliteal Ligament: Strengthens posterior capsule.
• Arcuate Ligament: Y-shaped, supports the knee posteriorly.

Menisci

• Medial Meniscus: C-shaped, more frequently injured.
• Lateral Meniscus: Circular, less commonly injured.

Movements

• Extension: Beyond vertical axis by 5-10°.
• Flexion: Range 120°-140°.
• Medial/Lateral Rotation: Occurs automatically or actively.

Bursae

• Several bursae are present, providing cushioning and facilitating movement around the knee.

Innervation and Blood Supply

• Innervated by femoral, obturator, and sciatic nerves.
• Supplied by popliteal, femoral, and anterior tibial arteries.

Clinical Correlations

• Meniscal Tears: Medial meniscus is more prone to injury.
• Cruciate Ligament Ruptures: More common in ACL, tested by drawer signs.
• Unhappy Triad: Injury involving ACL, medial meniscus, and tibial collateral ligament.
• Bursitis Conditions: "Housemaid's knee" and "Clergyman's knee".

Deformities

• Genu Valgum (Knock-knee): Lateral deviation of tibia, predisposes to lateral patella dislocation.
• Genu Varum (Bowleg): Medial deviation of tibia, causes lateral side stretching.