Causes
By Mayo Clinic staffLigaments are strong bands of tissue that connect one bone to another. The ACL, one of two ligaments that cross in the middle of the knee, connects your thighbone (femur) to your shinbone (tibia) and helps stabilize your knee joint.
Most ACL injuries happen during sports and fitness activities. The ligament may tear when you slow down suddenly to change direction or pivot with your foot firmly planted, twisting or overextending your knee.
Landing awkwardly from a jump can also injure your ACL, as can falls during downhill skiing. A football tackle or motor vehicle accident also can cause an ACL injury. However, most ACL injuries occur without such contact.
- Amy E, et al. Anterior cruciate ligament tear. In: Frontera WR, et al. Essentials of Physical Medicine and Rehabilitation: Musculoskeletal Disorders, Pain, and Rehabilitation. 2nd ed. Philadelphia, Pa.: Saunders Elsevier; 2008. http://www.mdconsult.com/das/book/body/220179329-3/1059395304/1678/58.html#4-u1.0-B978-1-4160-4007-1..50057-2--cesec12_907. Accessed Sept. 24, 2010.
- Friedberg RP. Anterior cruciate ligament. http://www.uptodate.com/home/index.html. Accessed Sept 24, 2010.
- Anterior cruciate ligament (ACL) injury prevention. American Orthopaedic Society for Sports Medicine. http://www.sportsmed.org/secure/reveal/admin/uploads/documents/ST%20ACL%20Injury%2008.pdf. Accessed Sept. 24, 2010.
- The injured ACL. American Orthopaedic Society for Sports Medicine. http://www.sportsmed.org/secure/reveal/admin/uploads/documents/ST%20Injured%20ACL%2008.pdf. Accessed Sept. 24, 2010.
- Pallin DJ, et al. Knee and lower leg. In: Marx JA, et al. Rosen's Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, Pa.: Mosby Elsevier; 2010. http://www.mdconsult.com/books/page.do?sid=1060123978&eid=4-u1.0-B978-0-323-05472-0..00054-2&isbn=978-0-323-05472-0&type=bookPage§ionEid=4-u1.0-B978-0-323-05472-0..00054-2--s0415&uniqId=220363422-3. Accessed Sept. 28, 2010.
- Laskowski ER (expert opinion). Mayo Clinic, Rochester, Minn. Sept. 29, 2010.

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