To better understand a Baker's cyst, it helps to understand the anatomy of the knee joint.
A cyst is a lined sac that contains fluid. Cysts that form around joints are due to a bulging of the joint capsule. A Baker's cyst develops from the knee joint capsule. It protrudes into the tissues in the back of the knee.
Four bones come together at the knee joint:
* Patella/Kneecap - The patella is a small, flat, round bone that articulates with the femur in front of the kneejoint. The undersurface has articular cartilage on it to allow it to glide smoothly over the femoral groove (trochlea) as the knee is flexed. The quadriceps muscle uses the the patella as a fulcrum to increase its power when extending the knee. * Femur/Thighbone – A long bone between the hip and the knee. The head of the femur articulates with the acetabulum of the hip bone * Tibia:
* Thick bone in the front of the lower leg
* Thin bone on the side of the lower leg
The tibia supports all of the body's weight below the knee joint. The tibia and femur form the major portion of the knee joint, and the patella protects the front of the knee.
Bones of the knee:
* Knee muscles and bones
* Knee bones and x-ray
The main tendons in knee include:
* Quadriceps tendon: attaches the quadriceps muscle to the kneecap * Patellar tendon: attaches the patella to the tibia
* Popliteus tendon: extends from the outer bottom surface of the femur and travels diagonally behind the knee to attach to the inner upper surface of the tibia. * Hamstring tendons: attach the hamstring muscles to the tibia * Calf tendons: attach the calf muscles to the femur
Strong fibrous bands, called ligaments, support the knee. Injuries to the knee ligaments are common.
The knee ligaments include:
* Lateral collateral ligament: stabilizes the knee from stress applied to the sides of the knee * Medial...