Knee Pain due to ACL (Anterior Cruciate Ligament) Injuries

Anterior Cruciate Ligament (ACL) Tear

What is ACL Injuries?

Different Knee Ligament
Different Knee Ligament

Ligaments are tough bands of fibrous tissue that connect two bones. The anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) are inside the knee joint. These ligaments connect the thigh bone (femur) and the large bone of the lower leg (tibia) at the knee joint. The ACL and PCL form an “X” inside the knee that stabilizes the knee against front-to-back or back-to-front forces.

An ACL injury is a sprain, in which the ligament is torn or stretched beyond its normal range. In almost all cases, when the ACL is torn, it’s almost always due to at least one of the following patterns of injury:

  • A sudden stop, twist, pivot or change in direction at the knee joint. These knee movements are a routine part of football, basketball, soccer, rugby, gymnastics and skiing. For this reason, athletes who participate in these sports have an especially high risk of ACL tears.
  • Extreme hyperextension of the knee. Sometimes, during athletic jumps and landings, the knee straightens out more than it should and extends beyond its normal range of motion, causing an ACL tear. This type of ACL injury often occurs because of a missed dismount in gymnastics or an awkward landing in basketball.
  • Direct contact. The ACL may be injured during contact sports, usually during direct impact to the outside of the knee or lower leg. Examples are a sideways football tackle, a misdirected soccer kick that strikes the knee or a sliding tackle in soccer.
Anterior Cruciate Ligament (ACL) Tear
Women who play contact sports injure their ACLs about seven times more often than men who play such sports. So far, sports medicine experts have not been able to determine why women athletes have a higher risk of ACL injuries. Some researchers believe it’s related to a slight difference in the anatomy of the knee in males and females. Others blame it on the effects of female hormones on body ligaments. Still others point to differences between females and males in skill, training, conditioning or even athletic shoes.


Symptoms of an ACL injury can include:

  • Feeling a “pop” inside your knee when the ACL tears
  • Significant knee swelling and deformity within a few hours after injury
  • Severe knee pain that prevents you from continuing to participate in your sport (most common in partial tears of the ACL)
  • No knee pain, especially if the ACL has been completely torn and there is no tension across the injured ligament
  • A black and blue discoloration around the knee, due to bleeding from inside the knee joint
  • A feeling that your injured knee will buckle, “give out” or “give way” if you try to stand

Treatment for ACL Injuries

Treatment depends on your activity level. Surgery may be used for those needing to return to sports that involve pivoting and jumping. Once swelling subsides, the torn ACL may be reconstructed surgically using either a piece of your own tissue (autograft) or a piece of donor tissue (allograft). When an autograft is done, the surgeon usually replaces your torn ACL with a portion of your own patellar tendon (tendon below the kneecap) or a section of tendon taken from a large leg muscle. Currently, almost all knee reconstructions are done using arthroscopic surgery, which uses smaller incisions and causes less scarring than traditional open surgery.

Arthroscopic View of the Anterior Cruciate Ligament (ACL) Tear
Arthroscopic View of the Anterior Cruciate Ligament (ACL) Tear

When To Call Us

Call us immediately if your knee becomes swollen or deformed, even if it is not painful. This is especially important if you cannot bear weight on your injured knee or if the knee feels as if it will buckle or “give out.”

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