Kinesiology The Knee Joint

Introduction

The knee joint is the largest and one of the most complex joints in the human body. It plays a crucial role in movement, weight-bearing, and stability, allowing activities such as walking, running, jumping, and squatting. The knee is a hinge-type synovial joint, primarily permitting flexion and extension while also allowing slight rotation.

Bones of the Knee Joint

The knee joint is formed by the articulation of three bones:

Distal End of the Femur (Thigh Bone)

  • Contains the medial and lateral condyles, which articulate with the tibia.
  • The patellar groove provides space for the kneecap.

Proximal End of the Tibia (Shin Bone)

  • Includes the tibial plateau, which articulates with the femoral condyles.
  • The tibial tuberosity serves as an attachment point for the patellar ligament.

The Patella (Kneecap)

  • A sesamoid bone embedded within the quadriceps tendon.
  • Functions to improve leverage and reduce friction at the knee.

Articulations of the Knee

The knee consists of two main joints:

Tibiofemoral Joint

  • Type: Hinge synovial joint.
  • Function: Allows flexion, extension, and slight rotation.

Patellofemoral Joint

  • Type: Plane synovial joint.
  • Function: Facilitates smooth movement of the patella over the femur.

Ligaments of the Knee

Ligaments provide stability by limiting excessive movement and preventing injuries.

Medial Collateral Ligament (MCL)

  • Prevents excessive valgus (inward) movement of the knee.

Lateral Collateral Ligament (LCL)

  • Prevents excessive varus (outward) movement of the knee.

Anterior Cruciate Ligament (ACL)

  • Prevents anterior displacement of the tibia.
  • Crucial for knee stability, especially in sports.

Posterior Cruciate Ligament (PCL)

  • Prevents posterior displacement of the tibia.

Patellar Ligament

  • Connects the patella to the tibia and assists in knee extension.

Menisci of the Knee

The medial and lateral menisci are C-shaped cartilage structures that provide shock absorption, stability, and load distribution.

Stability of the Knee

The knee relies on multiple factors for stability:

  1. Anterior-Posterior Stability:
    • Provided by the ACL and PCL.
  2. Medial-Lateral Stability:
    • Provided by the MCL and LCL.
  3. Rotational Stability:
    • Assisted by the menisci and collateral ligaments.
  4. Resistance to Hyperextension:
    • Limited by ligaments and muscle control.

Anatomical and Mechanical Axis of the Lower Limb

  • The anatomical axis refers to the alignment of the femur and tibia.
  • The mechanical axis (weight-bearing line) extends from the hip to the ankle.

Movements of the Knee Joint

The knee allows a range of movements essential for daily activities and sports.

Flexion (Bending the Knee)

  • Muscles Involved: Hamstrings, gastrocnemius.

Extension (Straightening the Knee)

  • Muscles Involved: Quadriceps femoris.

Pathological Rotation

  • Abnormal twisting movements may lead to ligament injuries.

Patellofemoral Joint

The patella plays a key role in knee mechanics.

Movements of the Patella

  • Glides superiorly during knee extension.
  • Moves inferiorly during knee flexion.

Patellar Ligament and Stability

  • The quadriceps tendon and patellar ligament help maintain knee stability.

Role of the Patella in Knee Extension

  • Enhances the mechanical efficiency of the quadriceps muscle.

Quadriceps Femoris Muscle

  • Primary Function: Knee extension.
  • Muscle Components:
    • Rectus femoris
    • Vastus medialis
    • Vastus lateralis
    • Vastus intermedius

Conclusion

The knee joint is a complex structure that balances mobility and stability. Its ligaments, menisci, and muscular support are essential for smooth and efficient movement. Proper understanding of its biomechanics is crucial for injury prevention and rehabilitation.

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