Knee pain is an extremely common complaint, and there are many causes. It is important to make an accurate diagnosis of the cause of your symptoms so that appropriate treatment can be directed at the cause. If you have knee pain, some common causes include:
Arthritis is among the most common causes of knee pain, and there are many treatments available.
Ligament injuries commonly occur during athletic activities and can cause discomfort and instability.
Anterior Cruciate Ligament (ACL) Injury
Posterior Cruciate Ligament (PCL) Injury
Medial Collateral Ligament (MCL) Injury
Cartilage tears are seen in young and old patients alike, and are also an extremely common cause of knee pain.
Tendonitis around the joint is most commonly of the patellar tendon, the large tendon over the front of the knee.
Chondromalacia causes knee pain under the kneecap and is due to softening of the cartilage. It is most common in younger patients (15-35 years old).
A dislocating kneecap causes acute symptoms during the dislocation, but can also lead to chronic knee pain.
A Baker's cyst is swelling in the back of the joint, and is usually a sign of another underlying problem such as a meniscus tear.
The most common bursa affected around the joint is just above the kneecap. This is most common in people who kneel for work, such as gardeners or carpetlayers.
Plica syndrome is an uncommon cause of knee pain, and can be difficult to diagnose. The diagnosis is usually made at the time of arthroscopy.
Osgood-Schlatter disease is a condition seen in adolescents and is due to irritation of the growth plate just at the front of the joint.
Osteochondritis dissecans (OCD) is another condition seen in adolescents due to the growth of the bone around the joint.
Gout is an uncommon cause of knee pain. However, in patients who have a diagnosis of gout, it must be considered as a cause for new onset knee pain.
Knee pain can be caused by injuries, mechanical problems, types of arthritis and other problems.
A knee injury can affect any of the ligaments, tendons or fluid-filled sacs (bursae) that surround your knee joint as well as the bones, cartilage and ligaments that form the joint itself. Some of the more common knee injuries include:
ACL injury. An ACL injury is the tearing of the anterior cruciate ligament (ACL) — one of four ligaments that connect your shinbone to your thighbone. An ACL injury is particularly common in people who play basketball or go downhill skiing, because it's linked to sudden changes in direction.
Torn meniscus. The meniscus is formed of tough, rubbery cartilage and acts as a shock absorber between your shinbone and thighbone. It can be torn if you suddenly twist your knee while bearing weight on it.
Knee bursitis. Some knee injuries cause inflammation in the bursae, the small sacs of fluid that cushion the outside of your knee joint so that tendons and ligaments glide smoothly over the joint.
Patellar tendinitis. Tendinitis is irritation and inflammation of one or more tendons — the thick, fibrous cords that attach muscles to bones. Runners, skiers and cyclists are prone to develop inflammation in the patellar tendon, which connects the quadriceps muscle on the front of the thigh to the shinbone.
Loose body. Sometimes injury or degeneration of bone or cartilage can cause a piece of bone or cartilage to break off and float in the joint space. This may not create any problems unless the loose body interferes with knee joint movement — the effect is something like a pencil caught in a door hinge.
Knee 'locking.' This can occur from a cartilage tear. When a portion of cartilage from the tear flips inside the knee joint, you may not be able to fully straighten your knee.
Dislocated kneecap. This occurs when the triangular bone (patella) that covers the front of your knee slips out of place, usually to the outside of your knee. You'll be able to see the dislocation, and your kneecap is likely to move excessively from side to side.
Hip or foot pain. If you have hip or foot pain, you may change the way you walk to spare these painful joints. But this altered gait can interfere with the alignment of your kneecap and place more stress on your knee joint. In some cases, problems in the hip or foot can refer pain to the knee.
Iliotibial band syndrome. This occurs when the ligament that extends from the outside of your pelvic bone to the outside of your tibia (iliotibial band) becomes so tight that it rubs against the outer portion of your femur. Distance runners are especially susceptible to iliotibial band syndrome.
Chondromalacia patellae (patellofemoral pain syndrome). This is a general term that refers to pain arising between your patella and the underlying thighbone (femur). It's common in young adults, especially those who have a slight misalignment of the kneecap; in athletes; and in older adults, who usually develop the condition as a result of arthritis of the kneecap.
Osgood-Schlatter disease. This condition affects the softer area of bone near the top of the shinbone, where bone growth occurs. It's most common in boys who play games or sports that involve running or jumping. The discomfort can last a few months and may continue to recur until the child's bones stop growing.
Osteochondritis dissecans. Caused by reduced blood flow to the end of a bone, osteochondritis dissecans is a joint condition in which a piece of cartilage, along with a thin layer of the bone beneath it, comes loose from the end of a bone. It occurs most often in young men, particularly after an injury to the knee.
Understanding what is causing your knee pain may be a simple task, or more complicated. A skilled physician can use clues to determine the cause of knee pain. Some of these clues have to do with you (how old are you? What types of activities do you do?), and some with your symptoms (has your knee pain been ongoing? Was there a recent injury?).
Here are some of the common knee pain symptoms that are experienced by patients, and what these symptoms may mean about the cause of your knee pain.
Location of Pain: Front of Knee: Pain over the front of the knee is most commonly related to the knee cap. Kneecap pain can be caused by several different problems.
Inside of Knee: Pain on the inside, or medial side, of the knee is commonly caused by medial meniscus tears, MCL injuries, and arthritis.
Outside of Knee: Pain on the outside of the knee, or lateral side, is commonly caused by lateral meniscus tears, LCL injuries, IT band tendonitis, and arthritis.
Back of Knee: Pain in the back of the knee can be due to the collection of fluid, called a Baker's Cyst.
Timing of Pain: While going down stairs: Pain while walking down steps is very commonly associated with kneecap problems, such as chondromalacia.
Morning pain: Pain after first waking in the morning that quickly resolves with gentle activity is typical of early arthritis.
Swelling: Swelling of the knee is common with several different knee problems. When there is an effusion immediately after a knee injury, a possible cause is severe injury to an internal joint structure, like the anterior cruciate ligament or a fracture of the top of the shin bone. When swelling develops gradually over hours to days after an injury, it is likely to be something less severe, like a tear of the meniscus or a ligament sprain. Swelling that occurs without the presence of a known injury can be due to osteoarthritis (common), gout (less common), inflammatory arthritis, or a joint infection (uncommon).
Mobility: Mobility of the knee can be affected by a number of common conditions. If mobility is chronically limited, often the cause is arthritis. When the surface of the joint becomes irregular as a result of the arthritis, the mobility of the joint may become limited. If the mobility is limited after an acute injury, there is likely swelling limiting the motion, or a torn structure that is limiting the mobility.
Instability/Giving Way: The stability of the knee is provided by the ligaments that connect the shin bone (tibia) to the thigh bone (femur). When the ligaments are stretched or torn, the knee may feel as though it is giving way beneath the patient. A sensation that the knee may give out from beneath you is a common symptom of ligament injury.
Popping/Clicking/Crunching/Grinding: Popping and snapping within the knee is common, and often not a symptom of any particular problem. When the pops are painless, there is usually no problem, but painful pops and snaps should be evaluated by your doctor. A pop is often heard or felt during an injury when a ligament, such as the ACL, is torn.
Grinding or crunching is a common symptom of cartilage problems. If the cartilage is damaged -- a condition called chondromalacia -- a crunching sensation is often felt by placing the hand over the kneecap and bending the knee. A similar grinding sensation may be felt with knee arthritis.
Locking: Locking is a symptom that occurs when a patient cannot bend or straighten their knee. The locking can either be due to something physically blocking motion of the knee, or by pain preventing normal knee motion.
One way to determine if there is something physically blocking knee motion is to inject the knee with a numbing medication. After the medication has taken effect, you can attempt to bend the knee to determine if pain was blocking the motion or if there is a structure, such as a torn meniscus, that is blocking normal motion.
Examining the Knee: Determining the cause of knee pain relies on a proper examination of the knee joint. Learn about how your doctor can examine your knee to determine the source of your pain, and what tests can be performed to make the diagnosis.
There is a variety of medication available for knee pain, including both oral and injectable medication, depending on the source of your pain. But most medication used by people with knee pain falls into one of two categories: anti-inflammatories and pain relievers, also known as analgesics.
Most medication that falls in the anti-inflammatory category also has analgesic effects, says William Bargar, MD, director of the Joint Replacement Center with Sutter General Hospital in Sacramento, Calif., and a spokesman for the American Academy of Orthopaedic Surgeons.
The main over-the-counter drugs are acetaminophen brands and non-steroidal anti-inflammatory drugs (or NSAIDs), including aspirin, ibuprofen and naproxen brands. These can help with simple sprains or even arthritis.
Dr. Bargar points out that even though knee pain-relieving medication is available without a prescription, you should use care when taking it. Be sure to follow the instructions for any medication and read the warnings.
"What you also have to watch for is that some of these over-the-counter drugs are sold as 'arthritis strength,' and that means they are larger doses. For example, too much arthritis-strength Tylenol can damage the liver," he says. "Ibuprofen can cause gastrointestinal damage, such as ulcers and bleeding, if you take too much. You have to be careful about overdoing it with over-the-counter drugs for knee pain."
Another option to try is glucosamine and chondroitin sulfate, which are oral supplements believed to relieve the pain of osteoarthritis. Side effects can include headache, upset stomach, and skin reactions. The American Academy of Orthopaedic Surgeons reports that these supplements might help you during the earliest stages of knee pain caused by osteoarthritis, but it can take up to two months of consecutive use to notice any relief. Be sure to tell your doctor you are taking the supplements, because they can interfere with other medication.
Prescription medication is usually a more potent pain reliever than the over-the-counter variety. These include prescription-strength NSAIDs and COX-2 inhibitors (meant to decrease gastrointestinal side effects like stomach bleeding). These drugs are typically used if your pain level is considered moderate to severe. The only COX-2 inhibitor currently on the market is celecoxib (Celebrex). Rofecoxib (Vioxx) and others were removed from the market because it was discovered that they led to an increased risk of heart complications.
Bargar also advises people with knee pain who are taking large doses of ibuprofen regularly to have blood tests every four months to check for kidney toxicity and anemia.
Injecting medication to reduce knee pain is usually the step between taking oral medication and replacing arthritic knee joints with surgery. Corticosteroids or viscosupplementation with hyaluronic acid can be injected when knee pain becomes severe.
Corticosteroids reduce inflammation and offer pain relief and are injected directly into the knee. These injections aren't permanent solutions, and you may need to return for repeat injections every few months (though not to exceed four injections in the same joint per year).
Viscosupplementation is an injection of hyaluronic acid that lubricates your joint to reduce knee pain and increase mobility. A series of three to five weekly injections is necessary to complete the therapy. These injections are helpful if you have early stage arthritis and haven't responded well to oral medication.
If you have modest knee pain caused by a simple strain, try an over-the-counter medication. If your knee pain or injury is severe, visit your physician for a prescription medication that may improve your particular condition.