Stephen J. Schueler, M.D.

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Cyst Behind the Knee Anatomy

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
  • Femur:
    • Thighbone
  • Tibia:
    • Thick bone in the front of the lower leg
  • Fibula:
    • 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

Knee Ligaments
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 collateral ligament: stabilizes the knee from stress applied to the sides of the knee
  • Posterior cruciate ligament: stabilizes the knee from stress applied to the front or back of the knee
  • Anterior cruciate ligament: stabilizes the knee from stress applied to the front or back of the knee

Knee Cartilage
Cartilage is a very smooth, firm layer of tissue that lines all of the joints in the body. Two discs of cartilage, called the medial meniscus, and lateral meniscus, line the inside of the knee. Torn cartilage refers to an injury to a meniscus.

Last Updated: Dec 2, 2010 References
Authors: Stephen J. Schueler, MD; John H. Beckett, MD; D. Scott Gettings, MD
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PubMed Cyst Behind the Knee References
  1. Handy JR. Popliteal cysts in adults: a review. Semin Arthritis Rheum. 2001 Oct;31(2):108-18. [11590580]
  2. Van Rhijn LW, Jansen EJ, Pruijs HE. Long-term follow-up of conservatively treated popliteal cysts in children. J Pediatr Orthop B. 2000 Jan;9(1):62-4. [10647115]
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