Knee Joint Anatomy, Function, Ligaments, and Injuries

Knee Joint Anatomy and Function

This document provides a detailed look at the structure, mechanics, and common clinical aspects of the knee joint.

Type of Joint

• The knee is classified as a synovial hinge joint.
• It primarily allows flexion and extension.
• A small degree of medial/lateral rotation is possible when the knee is flexed.

Bones Involved

1. Femur (thigh bone)
2. Tibia (shin bone)
3. Patella (kneecap)

The fibula is nearby but does not participate in the primary knee joint articulation.

Articulating Surfaces

• The medial and lateral femoral condyles articulate with the tibial condyles.
• The patella articulates with the femoral trochlear groove.

Main Ligaments

1. Anterior Cruciate Ligament (ACL) – Prevents anterior displacement of the tibia relative to the femur.
2. Posterior Cruciate Ligament (PCL) – Prevents posterior displacement of the tibia relative to the femur.
3. Medial Collateral Ligament (MCL) – Stabilizes the inner (medial) aspect of the knee.
4. Lateral Collateral Ligament (LCL) – Stabilizes the outer (lateral) aspect of the knee.

Cartilage and Menisci

• Articular Cartilage: Covers the ends of the bones, providing a smooth surface for movement.
• Menisci (Medial & Lateral):
  • C-shaped pads made of fibrocartilage.
  • They improve joint congruency (fit).
  • They function as crucial shock absorbers.

Muscles Acting on the Knee

• Extension: Quadriceps femoris group (primarily the Rectus Femoris, Vastus Lateralis, Vastus Medialis, and Vastus Intermedius).
• Flexion: Hamstrings (Biceps Femoris, Semitendinosus, and Semimembranosus).
• Rotation (when flexed): Popliteus, Sartorius, and Gracilis.

Bursae (Fluid-filled sacs)

Bursae reduce friction between tendons, ligaments, and bone.

Key bursae include:

• Prepatellar bursa
• Infrapatellar bursa
• Suprapatellar bursa
• Pes Anserine bursa

Nerve Supply

• Femoral nerve
• Tibial nerve
• Common peroneal nerve
• Obturator nerve

Blood Supply

• The knee receives blood primarily from the genicular branches of the popliteal artery.

⚠ Common Knee Injuries

• ACL and PCL tears
• Meniscal tears
• Patellar dislocation
• Osteoarthritis (wear and tear)
• Ligament sprains (MCL/LCL)

Clinical Assessment Note

Further information could include a diagram of the knee joint or details on clinical assessment methods (such as specific tests for ACL integrity or meniscal damage).