The knee joint is the junction of three major bones&mdash;the femur (the thigh bone or upper leg bone), tibia (shin bone) and patella (kneecap). 
The patella, 3 to 4 inches long and 2 to 3 inches wide, sits over the other bones at the front of the knee to provide protection. 
Other parts of the knee include: 
Menisci&mdash;pads of connective tissue between the tibia and femur that provide cushioning and absorb shock. 
Articular cartilage&mdash;tough, elastic tissue that covers the ends of all three bones in the knee joint. Cartilage absorbs shock and allows smooth motion. 
Muscles&mdash;including the quadriceps at the front of the thighs, which help straighten the leg from a bent position, and the hamstrings on the back of the thighs, which bend the leg at the knee. 
Ligaments&mdash;strong bands of tissue that connect the bones in the knee joint, provide stability and prevent the knee from moving in the wrong direction. They include the: 
<ul>
 <li>MCL (medial collateral ligament) on the inner side of the knee. </li>
 <li>LCL (lateral collateral ligament) on the outer side of the knee. </li>
 <li>ACL (anterior cruciate ligament) in the center of the knee. </li>
 <li>PCL (posterior cruciate ligament) in the back center of the knee. </li>
</ul>
Tendons&mdash;soft tissue that connects muscles to bones.
Source: <a href="https://orthoinfo.aaos.org/" target="_blank">American Academy of Orthopaedic Surgeons</a>
Reviewed 7/18/2023

Anatomy of the knee

These sophisticated joints include bones, tendons, cartilage, muscles and ligaments.