Describe the knee joint.

The knee joint is a complex hinge joint that connects the thigh bone (femur) to the shin bone (tibia). It also includes the kneecap (patella), which sits in front of the joint and helps to protect it. The knee joint allows for flexion and extension of the leg, as well as some rotation and lateral movement. It is supported by ligaments, tendons, and muscles that help to stabilize and move the joint. The knee joint is prone to injury and degeneration due to its weight-bearing function and the stresses placed on it during physical activity.

The Knee Joint (Articulatio Genus)

Bones Involved:
- Femur (thigh bone)
- Patella (kneecap)
- Tibia (shin bone)
- Fibula (smaller bone alongside the tibia)

Type of Joint:
- Modified synovial hinge joint
- Allows for flexion, extension, and very limited internal and external rotation

Joint Capsule:
- A tough, fibrous membrane that encloses the joint
- Lined with synovial membrane that secretes synovial fluid for lubrication

Ligaments:

- Medial and Lateral Collateral Ligaments: Stabilize the joint from side-to-side movement
- Anterior and Posterior Cruciate Ligaments: Cross within the joint and control anteroposterior and rotational movement

Menisci:
- Two crescent-shaped fibrocartilaginous structures that rest between the femur and tibia
- Provide stability and shock absorption

Patella and Patellar Tendon:
- The patella articulates with the femur and increases the leverage of the quadriceps muscle
- The patellar tendon attaches the patella to the tibia

Innervation:
- Femoral nerve (L2-L4)
- Sciatic nerve (L4-S3)

Range of Motion:

- Flexion: 0-140°
- Extension: 0-0° (full extension)
- Internal rotation: 5-10°
- External rotation: 10-15°

Functions:

- Supports body weight and allows for movement
- Provides stability during walking, running, and jumping
- Absorbs shock and protects the bones from damage