To better understand how knee problems occur, it is important to understand some of the anatomy of the knee joint and how the parts of the knee work together to maintain normal function.
The most important nerve around the knee is the popliteal nerve in the back of the knee. This large nerve travels to the lower leg and foot, supplying sensation and muscle control. The nerve splits just above the knee to form the tibial nerve and the peroneal nerve. The tibial nerve continues down the back of the leg while the peroneal nerve travels around the outside of the knee and down the front of the leg to the foot. Both of these nerves can be damaged by injuries around the knee.
Inside the knee joint, two other important ligaments stretch between the femur and the tibia: the anterior cruciate ligament (ACL) in front, and the posterior cruciate ligament (PCL) in back.
The extensor mechanism is the motor that drives the knee joint and allows us to walk. It sits in front of the knee joint and is made up of the patella, the patellar tendon, the quadriceps tendon, and the quadriceps muscles. The four quadriceps muscles in front of the thigh are the muscles that attach to the quadriceps tendon. When these muscles contract, they straighten the knee joint, such as when you get up from a squatting position.
This guide will help you understand
Taken all together, the ligaments of the knee are the most important structures that stabilize the joint. Remember, ligaments connect bones to bones. Without strong, tight ligaments to connect the femur to the tibia, the knee joint would be too loose. Unlike other joints in the body, the knee joint lacks a stable bony configuration. The hip joint, for example, is a ball that sits inside a deep socket. The ankle joint has a shape similar to a mortise and tenon, a way of joining wood used by craftsmen for centuries.
Without the menisci, any weight on the femur will be concentrated to one point on the tibia. But with the menisci, weight is spread out across the tibial surface. Weight distribution by the menisci is important because it protects the articular cartilage on the ends of the bones from excessive forces. Without the menisci, the concentration of force into a small area on the articular cartilage can damage the surface, leading to degeneration over time.
The knee joint is a synovial joint. Synovial joints are enclosed by a ligament capsule and contain a fluid, called synovium, that lubricates the joint.
The way in which the kneecap fits into the patellofemoral groove on the front of the femur and slides as the knee bends can affect the overall function of the knee. The patella works like a fulcrum, increasing the force exerted by the quadriceps muscles as the knee straightens. When the quadriceps muscles contract, the knee straightens.