The knee is the largest joint in the body and one that everyone uses daily. It is a hinge joint, which means it is only capable of flexing, or bending, and extending, yet dancers rely on it for almost every movement they execute and should, therefore, have a thorough understanding of it and how it works.
In between the tibia and the femur are two C-shaped pads of cartilage called the lateral meniscus and the medial meniscus. Their job is to provide cushioning between the two bones and to absorb the shock that comes from the bones hitting against each other while walking, running, and jumping.
The knee joint is surrounded by ligaments that provide stability and prevent unwanted movement that could harm the joint. The collateral ligaments connect the tibia to the femur on the outside of the knee (the lateral collateral ligament) and on the inside of the knee (the medial collateral ligament). These ligaments prevent sideways movement of the femur. The anterior collateral ligament, or ACL, crosses the center of the joint, connects the tibia to the femur, and prevents the tibia from sliding forward during movement. The posterior collateral ligament, or PCL, runs directly behind the ACL and prevents the tibia from sliding backward.
The patella slides along a groove on the front of the femur and is held in place above by the quadriceps tendon which connects the thigh muscles to the joint and below by the patellar tendon which connects the patella to the tibia.
The knee contains many fluid-filled sacs called bursae that help cushion the joint and keep the bones moving smoothly against each other.
The four quadriceps muscles found on the front of the thigh – the rectus femoris, the vastus intermedius, the vastus lateralis, and the vastus medialis are responsible for extending the knee.
The hamstring muscles which are found on the back of the thigh as well as the gastrocnemius, which is the major calf muscle, and the popliteus, which runs across the back of the knee, are responsible for bending, or flexing the knee.
Next week’s post will focus on common knee injuries and concerns that dancers may have and how to prevent and care for them.