What is the function of the knee joint in the human body?

Function of the Knee Joint in the Human Body

The knee joint is a complex weight-bearing joint that accepts body weight from the femur onto the tibia while allowing a small degree of axial rotation, serving as the main lower limb motor joint essential for mobility and daily activities. 1

Anatomical Structure

The knee joint consists of two primary articulations:

• Tibiofemoral joint: Where the femur meets the tibia
• Patellofemoral joint: Where the patella articulates with the femur

Stabilizing Structures

• Passive stabilizers:
  • Cruciate ligaments (anterior and posterior)
  • Collateral ligaments (medial and lateral)
  • Menisci (medial and lateral)
• Active stabilizers:
  • Quadriceps muscles
  • Hamstring muscles
  • Gastrocnemius muscle
  • Other supporting muscles 1

Primary Functions

1. Weight-bearing: The knee joint distributes body weight during standing and movement, with approximately 70-80% of joint load passing through the medial compartment during mid-stance phase of gait 1

2. Mobility: Allows for essential movements including:

   • Flexion and extension (primary plane of movement)
   • Limited rotation when the knee is flexed
   • Slight abduction and adduction 1, 2

3. Shock absorption: The menisci and articular cartilage absorb impact forces during walking, running, and other activities 2

4. Stability: Maintains balance and supports the body during various activities through its complex system of ligaments, muscles, and joint surfaces 2

Biomechanical Importance

The knee functions as a modified hinge joint with one primary plane of movement (flexion/extension), making it susceptible to instability compared to ball-and-socket joints like the hip 1. This design allows for:

• Efficient transfer of forces between the upper and lower leg
• Controlled movement during walking, running, climbing, and squatting
• Maintenance of proper lower limb alignment 2

Role in Daily Activities

The knee joint is crucial for several daily activities:

1. Walking: Facilitates the stance and swing phases of gait
2. Running: Allows for propulsion and shock absorption
3. Stair climbing: Enables controlled ascent and descent
4. Sit-to-stand transitions: Provides stability and power for rising from seated positions 1, 2

Clinical Significance

Understanding knee function is essential because:

• It is the most vulnerable and susceptible joint in the lower limb 3
• Knee injuries significantly impact normal living ability and mental health 3
• Proper knee function is necessary for maintaining independence and quality of life 2
• Knee pain and dysfunction are common problems requiring medical attention 4

Pathological Considerations

When knee function is compromised:

• Malalignment can lead to abnormal loading patterns and accelerate osteoarthritis progression 1
• Weakness of active stabilizers (muscles) increases risk of knee osteoarthritis 1
• Injury to passive stabilizers (ligaments, menisci) can lead to joint instability and further damage 1, 2

Maintaining Knee Health

To preserve optimal knee function:

• Maintain appropriate weight to reduce joint loading 2
• Strengthen quadriceps and hamstring muscles for joint stability 2
• Use proper body mechanics during activities 2
• Avoid prolonged deep knee bending positions when possible 2
• Consider appropriate bracing for specific conditions affecting knee alignment 1

The knee's complex design balances mobility and stability, making it uniquely adapted to support human bipedal locomotion while enabling the diverse movements required for daily activities and athletic performance.