Anterior Cruciate Ligament Injury

(ACL Injury)


An anterior cruciate ligament (ACL) injury is a tear in the ACL ligament. The ACL is located in the middle of the knee joint. It connects the lower leg bone to the thigh bone. It stabilizes the knee and prevents the lower leg bone from sliding too far forward at the knee.
Anterior Cruciate Ligament Injury
ACL injury
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ACL injury occurs when your knee gets twisted or during a hard landing from a jump. It can also happen with:
  • Sudden stops or changes in direction
  • Sidestepping or pivoting
  • Direct contact

Risk Factors

ACL injuries are more common in women. Other factors that increase your chance of ACL injury include:
  • Weak knee structure
  • Muscle strength imbalance between the quadriceps and hamstrings
  • Playing sports that require sudden changes of direction and deceleration
  • Use of incorrect technique for cutting, planting, pivoting, or jumping
  • Previous injury or reconstructive ACL surgery


Symptoms may include:
  • A popping sound at the time of the injury
  • Pain and swelling in the knee
  • Loss of full range of motion
  • Weakness or instability in the knee
  • Difficulty walking


You will be asked about your symptoms and how you injured your knee. A physical exam will be done.Your knee will need to be viewed. This can be done with:Ligament sprains are graded according to their severity:
  • Grade 1—Mild ligament damage.
  • Grade 2—Partial tearing of the ligament.
  • Grade 3—Complete tearing of the ligament.

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