Stephen J. Schueler, M.D.

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ACL Tear Anatomy

To better understand cruciate ligament knee injury, it helps to understand the anatomy of the knee joint.

Three bones come together at the knee joint:

  • Femur:
    • Thighbone
    • Articulates with hip joint above and knee joint below
    • The femur and tibia form the major portion of the knee joint,
  • Tibia:
    • Thick bone in the front of the lower leg or shin
    • The tibia supports all of the body's weight below the knee joint.
  • Patella:
    • Kneecap
    • The patella protects the front of the knee joint.
    • Connected by tendons above and below

Knee Tendons
The tendons are strong fibrous bands that connect the muscles to bone.

The knee tendons 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 smooth, firm layer of tissue that lines all of the joints in the body. There are two c-shaped discs of cartilage that line the inside of the knee. They keep the knee easy to move and also stabilize the knee during range of motion.

The knee cartilages include:
  • Medial meniscus
  • Lateral meniscus

Last Updated: Dec 8, 2010 References
Authors: Stephen J. Schueler, MD; John H. Beckett, MD; D. Scott Gettings, MD
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PubMed ACL Tear References
  1. Beynnon BD, Johnson RJ, Abate JA, Fleming BC, Nichols CE. Treatment of anterior cruciate ligament injuries, part I. Am J Sports Med. 2005 Oct;33(10):1579-602. [16199611]
  2. Boutin RD, Fritz RC. MRI of snow skiing and snowboarding injuries. Semin Musculoskelet Radiol. 2005 Dec;9(4):360-78. [16315118]
  3. Hayashi R, Kitamura N, Kondo E, Anaguchi Y, Tohyama H, Yasuda K. Simultaneous anterior and posterior cruciate ligament reconstruction in chronic knee instabilities: surgical concepts and clinical outcome. Knee Surg Sports Traumatol Arthrosc. 2008 Jun 7. [18536904]
  4. Iversen MD, Friden C. Pilot study of female high school basketball players' anterior cruciate ligament injury knowledge, attitudes, and practices. Scand J Med Sci Sports. 2008 Jun 18. [18627558]
  5. Oztekin HH, Boya H, Ozcan O, Zeren B, Pinar P. Pain and affective distress before and after ACL surgery: A comparison of amateur and professional male soccer players in the early postoperative period. Knee. 2008 Jul 15. [18635361]
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