The anterior cruciate ligament (ACL) is one of the four main ligaments in the knee. It runs through the middle of the knee keeping the tibia (shin bone) from slipping too far forward from underneath the femur (thigh bone) and providing stability to the knee joint.
What is an anterior cruciate ligament tear?
Anterior cruciate ligament tears are complete or partial tears that often occur while participating in sports that require sudden stopping, pivoting or jumping, such as basketball or tennis.It is common for ACL tears to happen in conjunction with other injuries, such as tears in the meniscus or other ligaments.
ACL tears range in severity and are measured in grades:
- Grade I – sprained or stretched ligament with no tearing
- Grade II – stretching of the ligament to the point some fibers tear and the ligament becomes loose
- Grade III –a severe injury where virtually all the fibers in the ACL are torn
ACL tears are more common in women, although the cause is not clear. Possible reasons are differences in training, muscle strength, body alignment, looser ligaments, and estrogen’s effect on ligaments.
Symptoms of an anterior cruciate ligament tear
Minor injuries to the anterior cruciate ligament may be subtle with weakness and knee instability the primary complaints.
Other common signs and symptoms of an ACL tear include:
- Popping at the time of injury
- Pain in the affected knee, particularly with weight-bearing
- Swelling that occurs within hours of the injury
- Limited range of motion of the joint
Causes of anterior cruciate ligament tears
Anterior cruciate ligament tears are usually the result of the following:
- Abrupt stops or turns
- Landing after a jump
- A direct blow to the side of the knee from a tackle or collision
Diagnosing an anterior cruciate ligament tear
Anterior cruciate ligament tears are diagnosed through a history of the injury and symptoms, as well as a physical examination of the injured knee – particularly as compared to the healthy knee.
Most diagnoses are based on the physical examination, but magnetic resonance imaging (MRI),x-rayand ultrasoundmaybe used to confirm the diagnosis and to check for additional injuries.
Treatment of ACL tears
Immediate treatment of anterior cruciate ligament tears includes resting with the leg in an elevated position, applying ice packs intermittently for 20 minutes at a time and wrapping the knee with a compression bandage to reduce swelling and provide support.
If the injury is not severe or the patient is only moderately active or elderly, non-surgical treatment may be recommended. This option may include:
- Crutches to reduce weight bearing
- Knee brace to stabilize and protect the injured knee
- Physical therapy or rehabilitation
Athletes, young patients and physically active adults usually require surgical intervention to repair ACL tears.When possible, surgery is often delayed until inflammation subsides and some movement returns. This reduces the risk of complications such as scarring.
In most cases the damaged ligament cannot be rejoined, making reconstruction necessary.During reconstructive surgery, the damaged tendon is replaced with a graft. The graft material may be a section of tendon harvested from another area of the knee or thigh. If necessary, donor tissue from a cadaver may also be used.
The procedure is usually done arthroscopically through a series of small incisions. The minimally invasive technique speeds healing, requires less hospital time and reduces pain. Following the surgical repair, physical therapy is needed to regain range of motion and strengthen ligaments and muscles.