The knee joint is formed where the thighbone (femur) meets the shinbone (tibia). The joint has three compartments: Medical, Lateral< and the area where the kneecap meets the femur.
Four major ligaments stabilize the joint. The medial, on the inner side of the knee, the lateral, on the outer side if the knee and the cruciate, which forms a crisscross structure on the inside of the knee.
The medial collateral ligament stops the knee from gapping to the inside and the lateral collateral does the same toward the outside of the knee. The cruciates stops the knee from sliding to the front and back. The meniscus is a thick cartilage pad on the inside and outside of the knee between the femur and the tibia. The meniscus is a shock absorber and a smooth articulating surface for the motion of the knee.
The knee joint is surrounded by bursae, which are fluid filled sacs that aid tendons glide over boney surfaces.
The large muscle of the front of the thigh called the quads attaches to a tendon that is attached to the kneecap and again a tendon attached the kneecap to the shinbone. When the quads contract, they pull the knee straight into full extension. Behind the knee, the large hamstring muscles attach to the back of the shin area. When these muscles contract, they flex the knee.
The normal knee can flex to 135 degrees and extend to zero degrees.
- Rectus Femoris
- Vastus lateralis
- Vastus medialis
- Vastus intermedius
- Biceps Femoris (long/short head)