KNEE SPRAIN

CONDITION

A knee sprain happens when ligaments within or around the knee are stretched and torn. Ligaments are strong bands of fibrous tissue that connect the bones above and below the knee.

Knee ligaments keep the knee bones aligned in the proper position so they work well together.
The knee can become unstable and “loose” when one or more ligaments are torn.
Knee ligament injuries can occur at any age, but are much less likely during childhood when bone growth plates are open. Growth plates, areas of growing tissue near the ends of the bones in youngsters, are the weakest part of the skeleton and usually give out before ligaments.

There are three degrees, or grades, of ligament sprains:

Grade I (mild) sprain: Only a few fibers of a ligament are torn, but the ligament still holds the bones together well.
Grade II (moderate) sprain: More ligament fibers are torn and stability of the joint is slightly affected.
Grade III (severe) sprain: The ligament ruptures completely or tears through and the bones it holds become “loose” and unstable.

There are four main ligaments that stabilize the knee: anterior cruciate, posterior cruciate, medial collateral and lateral collateral (Figure 1 below).

Figure 1

The anterior and posterior cruciate ligaments are inside the knee joint in the middle of the knee. They prevent the knee bones from sliding too far forward or backward on each other, from going too far in or out and from hyperextending.
The anterior cruciate ligament (ACL) is the ligament most commonly torn that will not heal without surgery.
The medial collateral ligament is located on the inner (medial) side. The lateral collateral ligament is located on the outer (lateral) side of the knee joint.
The collateral ligaments are outside the knee joint. They stabilize the knee and keep it from bending too far in or out, especially with cutting and side-to-side movements.
The medial collateral ligament is the most commonly torn knee ligament that does not usually require surgery.
Most collateral ligament injuries will heal without surgery, but injuries to the ligaments inside the knee, such as rupture or tear of the ACL, are often more serious and require surgical repair.

Causes

Knee ligaments are injured when forces acting upon them exceed ligament strength, such as may result from direct contact or indirect impact in sports like football and with athletic activities such as cutting and changing direction rapidly; slowing down, stopping and starting while running; and jumping and landing;

There are certain situations that commonly cause injury to particular ligaments:

Anterior cruciate: sudden twisting, pivoting, changing direction, over-straightening (hyperextension) or falling, or an impact to the side of the knee or lower leg in sports such as football, soccer, basketball, gymnastics, rugby and skiing.
Posterior cruciate: a blow to the front of the knee just below the kneecap, such as from a dashboard during a motor vehicle accident or from landing on the front of the knee with a fall in sports, or a severe twisting injury with a straight knee, or a sideways fall or blow to a straight knee.
Medial collateral: twisting or sideways inward fall or blow to the outside of the knee or lower leg, especially with the foot rotated outward.
Lateral collateral: twisting or sideways outward (“bow-legged”) fall or blow to the inside of the knee or lower leg, especially with foot rotated inward.

Risk factors that may increase the likelihood of an injury to the knee ligaments include:

improper sports form
poor coordination
weak knee and leg muscles
a previous knee ligament injury
smoking
participation in some athletic activities such as contact sports (football, soccer, rugby, hockey), skiing and basketball.

Symptoms and Signs

Symptoms depend on the location and severity of the knee ligament injury.
Most acute tears are associated with the symptoms listed below, but some tears may go unnoticed and cause more subtle, chronic symptoms such as a mild sense of knee buckling, swelling or general aching.
Any ligament injury can be associated with a loud pop at the time of the injury, but this is more common with anterior cruciate and medial collateral ligament injuries.
You will usually feel immediate pain in the location of the ligament torn or over the bone where the ligament attaches.
You will develop swelling and, sometimes, bruising within or around the joint immediately or soon after your injury.
You will notice stiffness and problems bending your knee, especially if you have swelling inside the joint.

Symptoms specific to the ligament injured include:

Anterior cruciate: You will often hear a loud pop; have severe, general knee pain; difficulty putting weight on your leg and delayed (by a few hours), severe swelling inside the knee with problems bending the knee. Your knee may give out or buckle. You may have a sense of your knee bones sliding too much on each other when you try to walk and you may sweat and feel dizzy, faint or nauseated.
Posterior cruciate: Symptoms are more subtle than with ACL injuries. You may develop mild swelling and you may have discomfort that is general or felt in the back of your knee. You may have a sense of knee instability or feel that your knee is giving way.
Medial collateral: You may hear a pop when you are injured, have pain and swelling over the inside of the knee and a sense of your knee giving way or collapsing inward.
Lateral collateral: There may be pain and swelling on the outside of your knee and a sense of knee giving way or collapsing outward or backward. Because other structures are often damaged with lateral collateral ligament injuries, you may also have almost any of the other symptoms listed above.

WHEN TO CALL YOUR DOCTOR

Call 911 if:

You have a knee dislocation, a condition in which the bones above and below your knee do not line up correctly.
You have had a serious knee injury and your lower leg and foot are pale and cool. You may have torn an important blood vessel that carries blood to your leg and foot.

Call your doctor right away (night or day) if:

You have severe pain, swelling, redness or warmth of your knee, especially after an injury.
You can’t bend your knee after an injury.
You can’t put weight on your knee after an injury.
You heard or felt a loud pop during an injury.
Your knee feels swollen like a balloon.
You hear crunching that occurs with pain when you try to move your knee or to walk.
Your knee gives out or buckles, gets locked or something catches in the joint when you try to walk after an injury.
You have numbness, tingling, or loss of sensation at or anywhere below your knee after an injury.
You have had a knee injury and develop a fever or flu-like symptoms.

Call your doctor during regular office hours if you have mild to moderate pain and swelling after an injury but:

You have no warmth or redness around your knee.
You can bend your knee well.
You can put weight on your knee and leg without a lot of pain.

You should also contact your doctor during regular office hours if you have not injured your knee but you notice that it sometimes buckles, gives out or locks, or something catches in the joint.

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SELF-CARE AT HOME

If you are over 15 years old, you usually do not need to see a doctor for mild knee sprains that get progressively better over a week or two and that cause little discomfort on the inside or outside of your knee, minimal swelling, no significant bruising and no locking, catching or buckling. If you are younger than 15 years old, you are at higher risk for having a fractured growth plate in the area of bone where a ligament attaches, so even mild knee pain should be evaluated by a doctor.

Once your soreness starts to get better, you may try riding a stationary bike using low resistance for 10 to 20 minutes daily or every other day.
If your knee starts to feel normal within one to two weeks, you may try functional drills to see if you are ready to start sports or regular exercise again. You may progress through a series of drills by completing each one pain-free. If you get symptoms when you do a drill, stop and try it again in a day or two.

Jog a straight, 50-yard line at about 50-percent intensity.
Run a straight, 50-yard line at 75-percent, then 100-percent intensity.
Using the same intensity progressions, run a straight line and progress through 45-degree and then 90-degree cuts to the right and to the left.
Then, run a large or “loose” figure-of-eight path. Gradually make it smaller or “tighter” and faster with repeat attempts.

When you can do all of these drills pain free, you can try sports-specific activity.When you return to specific sports or exercise activity, at first try sports-specific drills or exercise at only 50-percent intensity and in a noncompetitive setting. Progress in intensity and participation only if you can do so without pain.

All other knee ligament injuries should be evaluated by a doctor because serious injuries can be missed easily if you have more significant symptoms than those mentioned directly above.

Avoid running, jumping, twisting and kicking until your knee has been examined by a doctor or until it is completely better.
Use crutches to take all the weight off your injured knee if you have pain or a sense of buckling when you try to walk or put weight on your knee or leg.
For the first few days after injury, elevate your knee on a couch or chair as often as possible and for as long as you can. Place an ice pack or cold pack directly over the injured area of your knee or, if the pain is not localized, around your knee. You can use an elastic wrap to hold the ice pack or cold pack in place.
To minimize pain, swelling and bruising, use the cold pack for 20 minutes every one to two hours for the first 24 to 36 hours.
After the first day or two, use cold packs at least three times daily, more frequently if your symptoms require it.
If you are not using an elastic wrap directly over your skin, place a thin washcloth between the cold pack and your skin to minimize the risk of frostbite.
If you are busy, you may choose to ice during meals so as to save time and avoid interrupting other activities.
Use a snug elastic wrap or sleeve around your knee to minimize swelling.
Because most over- the-counter knee braces do not help stabilize your knee very well, don’t use them without advice from your doctor.
You may take ibuprofen (Advil®, Motrin®) or naproxen (Aleve®) for swelling and pain. (See labels for dose and risks).

PREVENTION

Keep your knee and leg strong and flexible, use proper sports form. Consider participating in a knee injury prevention program with a physical therapist or athletic trainer that focuses on strengthening and coordination with sports-specific drills in high-risk sports.

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FOR MORE INFORMATION

REFERENCES

Brown JR: Anterior and posterior cruciate ligament injuries. Primary Care: Clinics in Office Practice 31(4): 925-56, 2004.
Quarles JD: Medial and lateral collateral ligament injuries: prognosis and treatment. Primary Care: Clinics in Office Practice 31(4) 957-75, 2004.
Walsh WM, Vanicek JJ: Knee injuries. In Mellion M, Walsh WM, Madden C, et al: Team Physician’s Handbook, p 490-508, Hanley & Belfus, Philadelphia, 2002.

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Authored by Christopher Madden, M.D.

Favorably reviewed by The American Medical Society for Sports Medicine

http://amssm.org

Disclaimer: This content is reviewed periodically and is subject to change as new healthcare information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.