ACL and MCL injuries are injuries to the ligaments of the knee that most commonly occur in sports that require cutting and pivoting with potential for collision. Learn who is at most risk for these injuries and how to prevent injury.
Knee Ligament Injuries
Learn about the 4 major ligaments of the knee, and about common injuries, symptoms, and treatment.
Our Sports Medicine specialists provide treatment and rehabilitation for sports-related injuries from recreational, amateur and professional sports. Our faculty specialize in sports injuries in athletes and non-athletes.
Knee Ligament Injuries
What are knee ligament injuries?
Knee ligaments are the short bands of tough, flexible connective tissue that hold the knee together. Knee ligament injuries can be caused by trauma, such as a car accident. Or they can be caused by sports injuries. An example is a twisting knee injury in basketball or skiing.
The knee has 4 major ligaments. Ligaments connect bones to each other. They give the joint stability and strength. The 4 knee ligaments connect the thighbone (femur) to the shin bone (tibia). They are:
Anterior cruciate ligament (ACL). This ligament is in the center of the knee. It controls rotation and forward movement of the shin bone.
Posterior cruciate ligament (PCL). This ligament is in the back of the knee. It controls backward movement of the shin bone.
Medial collateral ligament (MCL). This ligament gives stability to the inner knee.
Lateral collateral ligament (LCL). This ligament gives stability to the outer knee.
What causes knee ligament injuries?
The ACL is one of the most common ligaments to be injured. The ACL is often stretched or torn during a sudden twisting motion. This is when the feet stay planted one way, but the knees turn the other way. Slowing down while running or landing from a jump incorrectly can cause ACL injuries. Skiing, basketball, and football are sports that have a higher risk for ACL injuries.
The PCL is also a common ligament to become injured in the knee. But a PCL injury often occurs with a sudden, direct hit, such as in a car accident or during a football tackle.
The MCL is injured more often than the LCL. Stretch and tear injuries to the collateral ligaments are often caused by a blow to the outer side of the knee. This can happen when playing hockey or football.
What are the symptoms of knee ligament injuries?
A cruciate ligament injury often causes pain. Often you may hear a popping sound when the injury happens. Then your leg buckles when you try to stand on it. The knee also swells. You also aren't able to move your knee as you normally would. You may also feel pain along the joint and pain when walking.
The symptoms of a cruciate ligament injury may seem like other health conditions. Always see your healthcare provider for a diagnosis.
Collateral ligament injury
An injury to the collateral ligament also causes the knee to pop and buckle. It also causes pain and swelling. Often you will have pain at the sides of the knee and swelling over the injury site. If it is an MCL injury, the pain is on the inside of the knee. An LCL injury may cause pain on the outside of the knee. The knee will also feel unstable, like it is going to give way.
How are knee ligament injuries diagnosed?
Your healthcare provider will ask about your health history and do a physical exam. You may also need 1 or both of these tests:
X-ray. This imaging test can rule out an injury to bone instead of a ligament injury. It uses energy beams to make images of internal tissues, bones, and organs on film.
MRI. This test uses large magnets, radio waves, and a computer to make detailed images of organs and structures in the body. It can often find damage or disease in bones and a surrounding ligament, tendon, or muscle.
How are knee ligament injuries treated?
Treatment will depend on your symptoms, age, and general health. It will also depend on how severe the condition is. Treatment may include:
Pain medicine, such as ibuprofen
Protective knee brace
Ice pack to ease swelling
Key points about knee ligament injuries
Knee ligaments are the short bands of elastic tissue that holds the knee together. There are 4 main ligaments in each knee.
Knee ligament injuries can be cause by trauma, such as a car accident. Or they can by caused by sports injuries.
The anterior cruciate ligament (ACL) is one of the most common ligaments to be injured.
Treatment may include medicine, muscle-strengthening exercises, a knee brace, or surgery.
Tips to help you get the most from a visit to your healthcare provider:
Know the reason for your visit and what you want to happen.
Before your visit, write down questions you want answered.
Bring someone with you to help you ask questions and remember what your provider tells you.
At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new directions your provider gives you.
Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.
Ask if your condition can be treated in other ways.
Know why a test or procedure is recommended and what the results could mean.
Know what to expect if you do not take the medicine or have the test or procedure.
If you have a follow-up appointment, write down the date, time, and purpose for that visit.
Know how you can contact your healthcare provider if you have questions.
News & Publications
Our publication keeps health care professionals up to date on the latest research and clinical advances from Mass General.
News and notes from the largest hospital-based research program in the United States
The Patient Gateway provides secure online access to your health information whenever you need it. Check upcoming appointments, communicate with your doctor’s office, review medications and pay medical bills—all seamlessly online 24/7.