What Is It?
A knee sprain is an injury of the ligaments, tough bands of fibrous tissue that connect the bones of the upper and lower leg at the knee joint. The knee joint has four major ligaments.
Like other types of sprains, knee sprains are classified according to a grading system:
When one knee ligament suffers a serious sprain, there is a good chance that other parts of the knee may also be injured. For example, because the MCL helps to protect the ACL from certain types of extreme knee forces, the ACL can become vulnerable to injury when the MCL is torn. In more than half of moderate or severe MCL sprains, the ACL also is sprained.
Knee sprains are very common. ACL sprains tend to cause more significant symptoms compared to MCL injuries. Many MCL sprains are so mild that they don't result in a visit to a doctor.
More than any other group, competitive athletes have a very high risk of knee sprains and other types of knee problems. In U.S. high schools, the knee is the most frequently injured joint among athletes who compete in football, soccer or wrestling.
Symptoms of a knee sprain vary depending on the specific ligament that is torn:
Your doctor will want to know exactly how you hurt your knee. He or she will ask about:
The doctor will examine both your knees, comparing your injured knee with your uninjured one. During this exam, the doctor will check your injured knee for signs of swelling, deformity, tenderness, fluid inside the knee joint and discoloration. If you don't have too much pain and swelling, the doctor will evaluate your knee's range of motion and will pull against the ligaments to check their strength. During the exam, you will bend your knee and the doctor will gently pull forward or push backward on your lower leg where it meets the knee.
If the results of your physical exam suggest you have a significant knee injury, you will need diagnostic tests to further evaluate your knee. These may include standard X-rays to check for ligament separation from bone or fracture. Tests may also include a magnetic resonance imaging (MRI) scan or camera-guided knee surgery (arthroscopy).
How long a knee sprain lasts depends on the type of knee sprain, the severity of your injury, your rehabilitation program and the types of sports you play. In general, milder Grade I and Grade II MCL or LCL sprains heal within 2 to 4 weeks, but other types of knee sprains may take 4 to 12 months.
To help prevent sports-related knee injures, you can:
If you have a Grade I or Grade II knee sprain, your doctor probably will recommend that you follow the RICE rule:
Your doctor may suggest that you wear a knee brace for a short period of time and that you take a nonsteroidal anti-inflammatory drug (NSAID), such as ibuprofen (Advil, Motrin and others), to relieve pain and ease swelling. As your knee pain gradually goes away, your doctor will prescribe a rehabilitation program to strengthen the muscles around your knee. This program should help to stabilize your knee joint and prevent you from injuring it again.
If you have a Grade III knee sprain or if multiple ligaments are injured, treatment depends on the specific type of sprain:
When To Call a Professional
If you injure your knee, call your doctor to request an urgent evaluation if the knee:
About 90% of people with ACL injuries and 80% with PCL injuries can expect a full recovery after proper treatment and a good physical therapy program. Almost all MCL sprains and most LCL sprains have an excellent prognosis.
As a long-term complication, some people with ACL or PCL sprains eventually develop pain from osteoarthritis in the injured knee joint. This symptom may not start until 15 to 25 years after the initial knee injury.
National Institute of Arthritis and Musculoskeletal and Skin Diseases
National Insitutes of Health
1 AMS Circle
Bethesda, MD 20892-3675
National Rehabilitation Information Center (NARIC)
4200 Forbes Blvd.
Lanham, MD 20706
American Orthopaedic Society for Sports Medicine
6300 North River Road
Rosemont, IL 60018
American Academy of Orthopaedic Surgeons (AAOS)
6300 North River Road
Rosemont, IL 60018-4262
National Athletic Trainers' Association
2952 Stemmons Freeway
Dallas, TX 75247
American Physical Therapy Association
1111 North Fairfax St.
Alexandria, VA 22314-1488