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MusculoskeletalICD-10: S83.51Approximately 200,000-250,000 ACL injuries occur annually in the United States

Torn ACL (Anterior Cruciate Ligament Tear)

A torn ACL (anterior cruciate ligament) is one of the most common knee injuries, frequently occurring during sports that involve sudden stops, direction changes, or jumping and landing. The ACL is a key ligament that connects the thighbone (femur) to the shinbone (tibia) and provides rotational stability to the knee. ACL tears range from partial to complete ruptures and often require surgical reconstruction for individuals who wish to return to high-demand physical activities.

Symptoms

A loud 'pop' or popping sensation in the knee at the time of injury
Severe knee pain and inability to continue activity
Rapid swelling of the knee within hours of injury
Loss of range of motion in the knee
Feeling of the knee 'giving way' or buckling with weight bearing
Tenderness along the joint line

Causes

  • Sudden deceleration combined with a change of direction or pivot
  • Landing awkwardly from a jump
  • Direct blow or collision to the knee (contact injury)
  • Hyperextension of the knee beyond its normal range

Risk Factors

  • Participation in high-risk sports (soccer, basketball, football, skiing)
  • Female sex (2-8 times higher risk due to anatomical and hormonal factors)
  • Poor neuromuscular control and landing mechanics
  • Previous ACL injury in either knee
  • Playing on artificial turf surfaces
  • Inadequate strength and conditioning

Diagnosis

  • Physical examination including Lachman test, anterior drawer test, and pivot shift test
  • MRI of the knee to confirm the tear and assess associated injuries (meniscus, other ligaments)
  • X-rays to rule out fractures
  • Arthroscopy in some cases for definitive diagnosis and treatment

Treatment

  • Immediate RICE protocol (rest, ice, compression, elevation)
  • Knee bracing and crutches for initial stabilization
  • Physical therapy and rehabilitation (non-surgical approach for lower-demand patients)
  • ACL reconstruction surgery using a graft (patellar tendon, hamstring, quadriceps, or allograft)
  • Post-surgical rehabilitation program lasting 6-12 months
  • NSAIDs and pain management during recovery

Prevention

  • Neuromuscular training programs (FIFA 11+, PEP program) to improve landing and cutting mechanics
  • Strengthen quadriceps, hamstrings, hip abductors, and core muscles
  • Practice proper landing techniques—land with knees bent and aligned over toes
  • Warm up thoroughly before sports and physical activity
  • Wear appropriate footwear for the sport and playing surface

When to See a Doctor

  • You hear or feel a pop in your knee followed by swelling and instability
  • Your knee gives way or feels unstable during weight-bearing activities
  • Knee pain and swelling do not improve within 48-72 hours

Frequently Asked Questions

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