The ACL is one of two cross-shaped ligaments that connect the thighbone to the shinbone and help stabilize the knee.
What is an ACL injury?
An ACL injury develops when the ACL, a ligament that links the thighbone and shinbone, stretches beyond its capacity and tears.
This type of injury frequently occurs during active sports that involve a lot of jumping and rapid starts and stops. More than 70% of ACL injuriesTrusted Source occur without any contact or blow to the knee.
Along with significant pain, a key sign of an ACL injury is a “popping” sound, which occurs at the moment that the ACL is torn or stressed.
The symptoms of an ACL injury can include:
difficulty or inability to extend the knee
discomfort when walking
soreness around the knee
an inability to put weight on the leg
a feeling that the knee may give out
Although an individual of any age and fitness level can injure their ACL, these injuries usually occur during activity and in connection with:
sudden starts, stops, or changes of direction while moving
a blow to the knee, especially from the side
overstretching the knee
ACL injuries are more common during sports that involve a lot of twisting and turning, such as:
Doctors categorize ACL injuries by their severity, as follows:
Grade 1 sprains: At this level, the ACL can still keep the knee stable, but the ligament is overstretched.
Grade 2 sprains: Also called a partial tear, this involves the ACL stretching to the point that it becomes loose.
Grade 3 sprains: Also known as a complete tear of the ligament, this involves the ACL tearing in two and no longer controlling the kneecap.
A physician will assess the extent of the injury, evaluate the range of motion of the affected knee, and compare it to the other knee before making a diagnosis.
They may use X-rays to look for signs of bone damage or an MRI to conclusively identify a soft tissue injury, such as damage to the ACL.
After an ACL injury, a doctor may recommend:
elevating the foot above the level of the head
applying an ice pack (wrapped in a towel) to the knee
taking ibuprofen to reduce pain and swelling
seeing a doctor for evaluation and treatment
Approaches to treatment vary, depending on the severity of the injury and the age and fitness of the person.
For young and otherwise healthy people, a doctor may recommend surgery to ensure that the person can fully resume their activities.
Surgery for an ACL injury involves miniature cameras and small incisions. This less invasive procedure is called an arthroscopy.
Usually, a surgeon removes the damaged portion of the ACL and grafts a new ligament into place. The graft can come from the injured individual’s body, from a donor, or it may be synthetic.