Peer Reviewed Patient Education

Bones

• The femur is the bone of the thigh. It is the largest bone in the body.
  
• The tibia is the large bone in the lower leg. The femur sits on the tibia.
  
• The fibula is the smaller bone in the lower leg. It serves as an attachment point for muscles and the lateral collateral ligament.
  
• The patella is also known as the "kneecap". It is located in front of the femur and tibia. As the knee moves, the patella slides within a groove on the femur.

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Ligaments
Four major ligaments connect the bones of the upper and lower leg. Ligaments are strong bundles of fibers that stabilize the joint, guide joint motion, and prevent excessive motion.

• Anterior Cruciate Ligament (ACL) and Posterior Cruciate Ligament (PCL)
  The cruciates are the two major ligaments inside the knee joint. The name "cruciate" means "cross" and comes from the fact that these two ligaments cross each other as they attach to the femur and the tibia.
  
• Medial Collateral Ligament (MCL) and Lateral Collateral Ligament (LCL)
  The collateral ligaments are the ligaments on either side of the knee joint. The MCL is on the inner side of the knee and the LCL is on the outer side of the knee.
  

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Muscles and Tendons

Two sets of muscles cross the knee joint to make it move.

• The quadriceps (sometimes referred to as "quads") are four muscles in the front of the thigh that straighten the knee .
  
• The hamstrings (sometimes referred to as "hams") are the muscles in the back of the thigh that work together to bend the knee.

Tendons are the connective structures that attach muscle to bones. Ligaments connect bone to bone. The four quadriceps come together to form one tendon called the quadriceps tendon. This tendon surrounds the patella and is called the patellar tendon as it attaches the muscles to the tibia.

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Cartilage