Knee:The knee is a joint composed of three components. The primary knee joint is formed where the thigh bone (femur) connects with the large shin bone (tibia). This joint is divided into inner and outer compartments. Additionally, the kneecap (patella) joins with the femur to create a third joint known as the patellofemoral joint, with the patella providing protection to the front of the knee joint.A joint capsule surrounds the knee, reinforced by ligaments on both the inside and outside (collateral ligaments) and crossing within the joint (cruciate ligaments). The collateral ligaments run along the sides of the knee, restricting lateral movement. The anterior cruciate ligament (ACL) links the tibia to the femur at the knee center, controlling the tibia's rotation and forward movement. Meanwhile, the posterior cruciate ligament (PCL), positioned just behind the ACL, limits the tibia's backward movement. These ligaments collectively ensure the knee joint's stability and strength.Between the femur and tibia lies the meniscus, a thick pad acting as a smooth surface for joint movement. Surrounding the knee joint are fluid-filled sacs called bursae, which minimize tendon friction. Below the kneecap, the patellar tendon connects to the tibia's front. Major blood vessels traverse the area behind the knee, known as the popliteal space.The thigh's large muscles facilitate knee movement. At the front, the quadriceps extend the knee joint, while the hamstring muscles at the back flex it. The knee can also rotate slightly, guided by specific thigh muscles. The knee is essential for leg movement and plays a crucial role in walking. It typically flexes up to 135 degrees and extends to 0 degrees. The bursae reduce tendon friction, serving as gliding surfaces. As a weight-bearing joint, the knee relies on the menisci to distribute load evenly and assist in joint lubrication by dispersing joint fluid.