“ACL” stands for anterior cruciate ligament. You may have heard of it from watching or playing sports, since physically intensive sports like football, soccer, basketball, and skiing make ACL tears far more likely.

Many ACL tears require ACL reconstruction surgery to regain full knee function, but it’s important to weigh various factors to decide, including your injury severity and your overall activity level.




The ACL (“anterior cruciate ligament”) is in the middle of the above diagram.

As a ligament, the ACL acts like a strong rope to hold your bones together, which makes walking extremely painful once the ligament is torn.

Overall, three bones meet to form your knee joint:

  1. Your thighbone (femur)
  2. Your shinbone (tibia), and
  3. Your kneecap (patella).

Four primary ligaments connect the knee bones to keep your knee stable, even if you’re sprinting or running a long distance.

Collateral ligaments are on the sides of each knee. The lateral collateral ligament (LCL) is on the outside and the medial collateral ligament (MCL) is on the inside. Together, the LCL and MCL brace your knee against excess sideways motion.

Inside your knee joint is where the cruciate ligaments are. Your anterior cruciate ligament (ACL) crosses in front of your posterior cruciate ligament (PCL) to form an “X.” Together, the ACL and PCL regulate the back-and-forth motion of your knee. Since your ACL runs diagonally across, it prevents your tibia from sliding in front of your femur, in addition to rotationally stabilizing your knee.

You also have additional cushioning and shock absorption from articular cartilage and meniscus tissues.



Almost half of ACL injuries happen as part of damage to other knee structures, like the articular cartilage, meniscus, or other ligaments.

ACL tear


There are countless ways to injure your ACL, but here are the most common ones:

  • Stopping suddenly
  • Slowing down too fast while running
  • Changing direction sharply
  • Landing from a jump incorrectly
  • Direct contact or collision (e.g., a football tackle)


If you tear your ACL, you may hear a “popping” noise, and you may feel your knee buckle under you. Your knee will swell up within 24 hours, which may resolve on its own, but you’re likely to worsen the damage if you go back to normal activity without treatment.


ACL Reconstruction Surgery

A torn ACL won’t heal without ACL reconstruction surgery, so athletes and others who require agility need the procedure to restore stability and knee function.

ACL Reconstruction Surgery

What happens during the surgery?

Since ACL tears can’t be sutured (stitched), repairing the ACL requires the ligament must be rebuilt. Los Angeles orthopedic surgeon, Dr. Samimi, specializes in ACL reconstruction surgery using minimally invasive techniques to help you recover the fastest.

First, Dr. Samimi makes a small incision to insert a tiny camera (called an “arthroscope”) into your knee. The camera picture shows on a video monitor, so the doctor can see all tissues inside your knee joint — your cartilage, your meniscus, and your ligaments.

Once Dr. Samimi sees everything clearly, he can remove the torn ACL tissues and graft in new tissue.


A good physical therapy rehab program is critical after ACL reconstruction surgery. You’ll regain your knee strength, motion, and conditioning step by step.

ACL Reconstruction

More specifically, physical therapy focuses first on returning range of motion to your knee joint and its surrounding muscles. Then comes a strengthening program to protect the new ligament. As the strengthening increases the stress the ACL can handle, rehab can start focusing on returning function. Especially if you play sports, you may need six months or more to perform as an athlete again.

Want more detailed information about ACL Reconstruction? Go here:

AAOS Online Services Fact Sheet – ACL Injury: Does It Require Surgery?