The knee joint is one of the largest joints in the body. It is subject to a lot of impact, particularly in athletes who run or jump. Here’s some information to help you understand the anatomy of the knee better.
The hinge factor
The knee is a synovial hinge joint. A synovial joint is one that has a synovial fluid filled capsule surrounding the joint. This helps lubricate the joint and therefore keeps it moving smoothly. A hinge joint is one that moves like a hinge, in only two directions – flexion and extension.
Either side of the joint are the femur and tibia bones of the upper and lower legs. On top of the joint is the patella, a floating piece of bone otherwise known as the knee cap. These bones work together to support the body. They transfer weight and impact between the hip and foot. This allows the leg to move smoothly and efficiently as we, for example, walk, run, squat and jump.
Structurally sound
Inside the knee joint are various structures to ensure that the joint is strong, smooth and secure. These are the articular cartilage, the knee meniscus, bursa and ligaments. The articular cartilage and meniscus are types of cartilage to cover the bone and take the impact of the joint. The back of the patella is also lined with thick cartilage, as this joint takes some of the highest impact in the body.
Along with cartilage understanding the anatomy of the knee includes as many as fourteen bursa, fluid filled sacs in and around the joint. If there is excessive friction on the bursa, then the bursa can become inflamed, known as knee bursitis.
The knee also has a series of ligaments. If you’ve ever experienced or seen knee injuries then you’ve probably seen (or felt) a ligament rupture. Football, tennis, almost any sport that requires athletes to run in a lateral direction puts the knee under at risk of ligament injury.
Muscle bound
The muscles that control the knee allow us to bend and straighten the knee include the;
- Quadriceps: four muscles on the front of the thigh which straighten the knee,
- Hamstrings: three muscles on the back of the thigh which bend the knee,
- Calves: two muscles on the back of the lower leg that control both the knee and ankle.
The gluteal muscles, that is, the three buttock muscles, are very important in controlling the position of the knee and how the forces transfer through the joint. They protect the knee, along with the other leg muscles and ligaments, from going in any direction that it is not supposed to.
The muscles are joined to the bone by tendons. The patella tendon is unique in the body, as the bone sits within the tendon. This joins the quadriceps to the patella, and then to the tibia.
The sum of it’s parts
The specific design of knee joint anatomy allows a number of functions, including;
- Supports the body in upright position without muscles having to work hard,
- Helps in lowering and raising body e.g. sitting, climbing and squatting,
- Allows rotation/twisting of the leg to place and position foot accurately,
- Makes walking more efficient (ever had a knee brace on or not been able to bend your knee for any length of time?),
- Acts with the ankle joint as a strong forward propeller of the body – particularly important when running
- Provides stability and proprioception of the leg
- Acts as a shock absorber
Because of the impact a knee takes in a life time, and the complexity of it’s structure, it is fraught with injuries, complications, inflammation, and pain. Hopefully this short article has given you a better understanding of the structure of the knee. And will lead you to better care for the joint and muscles around it.
