By Mayo Clinic staff
If you're suffering from knee pain, you're not alone. Almost one in three Americans older than age 45 reports some type of knee pain, and it's a common reason that people visit their doctors or the emergency room.
Knee pain may be the result of an injury, such as a ruptured ligament or torn cartilage. Or, certain medical conditions, including arthritis, gout and infection, may be at the root of your knee pain.
Many relatively minor instances of knee pain respond well to self-care measures. More-serious injuries, such as a ruptured ligament or tendon, may require surgical repair.
Although every knee problem can't be prevented — especially if you're active — you can take certain steps to reduce the risk of injury or disease.
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. Because of the knee's complexity, the number of structures involved, the amount of use it gets over a lifetime, and the range of injuries and diseases that can cause knee pain, the signs and symptoms of knee problems can vary widely.
Some of the more common knee injuries and their signs and symptoms include the following:
Ligament injuries. Your knee contains four ligaments — tough bands of tissue that connect your thighbone (femur) to your lower leg bones (tibia and fibula). You have two collateral ligaments — one on the inside (medial collateral ligament) and one on the outside (lateral collateral ligament) of each knee. The other two ligaments are inside your knee and cross each other as they stretch diagonally from the bottom of your thighbone to the top of your shinbone (tibia). The posterior cruciate ligament (PCL) connects to the back of your shinbone, and the anterior cruciate ligament (ACL) connects near the front of your shinbone. A tear in one of these ligaments, which may be caused by a fall or contact trauma, is likely to cause:
§ Immediate pain that worsens when you try to walk or bend your knee
§ A popping sound
§ An inability to bear weight on the injured knee
§ A feeling that the knee might buckle or give way
Tendon injuries (tendinitis). Tendinitis is irritation and inflammation of one or more tendons — the thick, fibrous cords that attach muscles to bones. Athletes, such as especially 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 larger lower leg bone (tibia). If your knee pain is caused by tendinitis, some of the signs and symptoms include:
§ Pain, in one or both knees
§ Swelling in the front of the knee or just below the kneecap
§ Worsening pain when you jump, run, squat or climb stairs
§ An inability to completely extend or straighten your knee
Meniscus injuries. The meniscus is a C-shaped piece of cartilage that curves within your knee joint. Meniscus injuries involve tears in the cartilage, which can occur in various places and configurations. Signs and symptoms of this type of injury include:
§ Mild to moderate swelling that occurs slowly, as long as 24 to 36 hours after the injury
§ An inability to straighten the knee completely; the knee may feel locked in place
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. Bursitis can lead to:
§ Pain, even at rest
§ Aching or stiffness when you walk
§ Considerable pain when you kneel or go up and down stairs
§ Fever, pain and swelling if the bursa located over your kneecap bone (prepatellar bursa) becomes infected
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 — leading to pain and a locked joint.
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. Signs and symptoms of a dislocated kneecap include:
§ Intense pain
§ Difficulty walking or straightening your knee
Osgood-Schlatter disease. Primarily affecting athletic teens and preteens, this overuse syndrome causes:
§ Pain, usually worse with activity, especially running and jumping
§ Tenderness at the bony prominence (tibial tuberosity) just below the kneecap
The discomfort can last a few months and may continue to recur until your teen or preteen stops growing.
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, which generally causes:
§ A sharp, burning pain on the outer side of the knee that usually begins after longer distance runs
§ Pain that initially goes away with rest from running, but in time may persist when you walk or go up and down stairs
With this type of knee injury, there usually isn't swelling and you'll likely have normal range of motion.
Hyperextended knee. In this injury, your knee extends beyond its normally straightened position so that it bends back on itself. Sometimes the damage is relatively minor, with pain and swelling when you try to extend your knee. But a hyperextended knee may also lead to a partial or complete ligament tear, especially in your ACL.
Septic arthritis. Sometimes your knee joint can become infected, leading to swelling, pain and redness. There's usually no trauma before the onset of pain. Septic arthritis often occurs with a fever.
Rheumatoid arthritis. The most debilitating of the more than 100 types of arthritis, rheumatoid arthritis can affect almost any joint in your body, including your knees. Common signs and symptoms of rheumatoid arthritis include:
§ Aching and stiffness, especially when you get up in the morning or after periods of inactivity
§ Loss of motion in your knees and eventually deformity of the knee joints
§ Sometimes, a low-grade fever and a general sense of not feeling well (malaise)
Although rheumatoid arthritis is a chronic disease, it tends to vary in severity and may even come and go. Periods of increased disease activity — called flare-ups or flares — often alternate with periods of remission.
Osteoarthritis. Sometimes called degenerative arthritis, this is the most common type of arthritis. It's a wear-and-tear condition that occurs when the cartilage in your knee deteriorates with use and age. Osteoarthritis usually develops gradually and tends to cause:
§ Varying degrees of pain, especially when you stand or walk
§ Stiffness, especially in the morning and after you've been active
§ Creaking or popping sounds
§ A loss of flexibility in your knee joints
Gout and pseudogout. Gout, a type of arthritis, is likely to cause:
§ Intense knee pain that comes on suddenly — often at night — and without warning. The pain typically lasts five to 10 days and then stops. The discomfort subsides gradually over one to two weeks, leaving your knee joints apparently normal and pain-free.
Another condition, pseudogout (chondrocalcinosis), which mainly occurs in older adults, can cause:
§ Severe inflammation
§ Intermittent attacks of sudden pain and swelling in large joints, especially the knees
Chondromalacia of the patella, or patellofemoral pain. 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. Chondromalacia of the patella causes:
§ Pain and tenderness in the front of your knee that's worse when you sit for long periods, when you get up from a chair, and when you climb or descend stairs.
§ A grating or grinding sensation may be present when you extend your knee.
When to see a doctor
If you have new knee pain that isn't severe or disabling, a good rule of thumb is to try treating it yourself first. This includes resting, icing and elevating the affected knee, and sometimes using nonsteroidal anti-inflammatory drugs to reduce pain and inflammation. If you don't notice any improvement in three to seven days, see your doctor or a specialist in sports medicine or orthopedics.
Some types of knee pain require more immediate medical care. Call your doctor if you:
§ Can't bear weight on your knee
§ Have marked knee swelling
§ See an obvious deformity in your leg or knee
§ Have worrisome pain
§ Have a fever, in addition to redness, pain and swelling in your knee, which may indicate an infection
In the simplest terms, a joint occurs wherever two bones come together. But that definition doesn't begin to convey the complexity of joints, which provide your body with flexibility, support and a wide range of motion.
You have four types of joints: fixed, pivot, ball-and-socket and hinge. Your knees are hinge joints, which, as the name suggests, work much like the hinge of a door, allowing the joint to move backward and forward. Your knees are the largest and heaviest hinge joints in your body. They're also the most complex. In addition to bending and straightening, they twist and rotate. This makes them especially vulnerable to damage, which is why they sustain more injuries on average than do other joints.
A closer look at your knees
Your knee joint is essentially four bones held together by ligaments. Your thighbone (femur) makes up the top part of the joint, and two lower leg bones, the tibia and the fibula, comprise the lower part. The fourth bone, the patella, slides in a groove on the end of the femur.
Ligaments are large bands of tissue that connect bones to one another. In the knee joint, four main ligaments link the femur to the tibia and help stabilize your knee as it moves through its arc of motion. These include the collateral ligaments along the inner (medial) and outer (lateral) sides of your knee and the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL), which cross each other as they stretch diagonally from the bottom of your thighbone to the top of your shinbone.
Other structures in your knee include:
§ Tendons. These fibrous bands of tissue connect muscles to bones. Your knee has two important tendons, which make it possible for you to straighten or extend your leg: the quadriceps tendon, which connects the long quadriceps muscle on the front of your thigh to the patella, and the patellar tendon, which connects the patella to the tibia.
§ Meniscus. This C-shaped cartilage, which curves around the inside and outside of your knee, cushions your knee joint.
§ Bursae. A number of these fluid-filled sacs surround your knee. They help cushion your knee joint so that ligaments and tendons slide across it smoothly.
Normally, all of these structures work together smoothly. But injury and disease can disrupt this balance, resulting in pain, muscle weakness and decreased function.
Some common causes of knee pain and injuries include:
§ A blow to the knee, either from contact during sports, a fall or a car accident
§ Repeated stress or overuse, which may occur from playing sports or if your work or hobby requires doing the same activity over and over again
§ Sudden turning, pivoting, stopping, cutting from side to side, which happens frequently during certain sports
§ Awkward landings from a fall or from jumping during sports, such as basketball
§ Rapidly growing bones, which are especially prone to injury during sports
§ Degeneration from aging
Pinpointing the reason for knee pain can be challenging because of the wide range of possible causes. Often, a comprehensive medical history and thorough physical exam play a larger role in knee pain diagnosis than does any single test.
In addition to asking about your pain — its location, what it feels like, when it started, what makes it seem better or worse — your doctor may inquire about your exercise program, sports you play or used to play, and any previous injuries to your knee joint. During the physical exam, your doctor is likely to inspect your knee for swelling, pain, tenderness, warmth and visible bruising; check your range of motion; and perform a number of maneuvers to evaluate the integrity of the structures in your knee.
One of these maneuvers, the Lachman test, helps detect injuries to the ACL. In the Lachman test, your knee is bent at a 30-degree angle and your doctor gently moves your lower leg forward at the knee. If your lower leg moves freely without reaching a firm endpoint, you're likely to have a torn ACL. Other maneuvers assess the PCL, tendons and menisci.
These tests may not be accurate in some instances — when movement in your knee is restricted by swelling or by contracted muscles in the back of your leg, for example. In that case, your doctor may order a magnetic resonance imaging (MRI) test or another imaging test to aid in the diagnosis.
Unlike an X-ray, which isn't useful for viewing ligaments, tendons and muscles, an MRI can help identify injuries and damage to soft tissue. MRI uses a powerful magnet to create 3-D images of the inside of your knee. Generally, no special preparation is needed for this test; however, if you're bothered by confined spaces, be sure to let your doctor know. He or she may be able to send you to a facility with an open MRI machine, which allows you to see outside of the machine, or you may be prescribed a mild sedative for the test.
Depending on the type of injury, your doctor may order other imaging tests, including:
§ X-ray. Your doctor may first recommend having an X-ray, which can help detect bone fractures and degenerative joint disease.
§ Computerized tomography (CT) scan. This specialized X-ray, which creates cross-sectional images of the inside of your body, may help diagnose bone problems and detect loose bodies.
If your doctor suspects an infection, gout or pseudogout, you're likely to have blood tests and sometimes arthrocentesis, a procedure in which a small amount of fluid is removed from your injured joint with a needle and sent to a laboratory for analysis.
The key to treating many types of knee pain is to break the cycle of inflammation that begins right after an injury. Even minor trauma causes your body to release substances that lead to inflammation. The inflammation itself causes further damage, which in turn triggers more inflammation, and so on. But a few simple self-care measures can be remarkably effective in ending this cycle. For best results, start treating your injury right away.
Commonly referred to by the acronym P.R.I.C.E., self-care measures for an injured knee include:
§ Protection. The best way to protect your knee from further damage depends on the type and severity of your injury. For most minor injuries, a compression wrap is usually sufficient. More-serious injuries, such as a torn ACL or high-grade collateral ligament sprain, usually require crutches and sometimes also a brace to help stabilize the joint with weight bearing.
§ Rest. Taking a break from your normal activities reduces repetitive strain on your knee, gives the injury time to heal and helps prevent further damage. A day or two of rest may be all that's needed for minor injuries. More severe damage is likely to need a longer recovery time.
§ Ice. A staple for most acute injuries, ice reduces both pain and inflammation. Some doctors recommend applying ice to your injured knee for about 20 minutes three times a day. A bag of frozen peas works well because it covers your whole knee. You can also use an ice pack wrapped in thin fabric to protect your skin. Although ice therapy is generally safe and effective, don't leave ice on longer than recommended because of the risk of damage to your nerves and skin.
§ Compression. This helps prevent fluid buildup (edema) in damaged tissues and maintains knee alignment and stability. Look for a compression bandage that's lightweight, breathable and self-adhesive. It should be tight enough to support your knee without interfering with circulation.
§ Elevation. Because gravity drains away fluids that might otherwise accumulate after an injury, elevating your knee can help reduce swelling. Try propping your injured leg on pillows or sitting in a recliner.
Nonsteroidal anti-inflammatory drugs (NSAIDs), including aspirin, ibuprofen (Advil, Motrin, others) and naproxen (Aleve, Naprosyn), can help relieve pain. But, NSAIDs can have side effects, especially if you take them for long periods or in amounts greater than the recommended dosage.
NSAIDs also have a ceiling effect, which means there's a limit to how much pain they can control. Taking two different NSAIDs at the same time also won't provide more relief and may increase your risk of side effects.
When self-care measures aren't enough to control pain and swelling and promote healing in an injured knee, your doctor may recommend other options, including:
Normally, the goal of physical therapy is to strengthen the muscles around your knee and help you regain knee stability. Depending on your injury, training is likely to focus on the muscles in the back of your thigh (hamstrings), the muscles on the front of your thigh (quadriceps), and your calf, hip and ankle. You can do some exercises at home. Others require the use of weight machines, exercise bicycles or treadmills, which may mean visits to an athletic club, fitness center or clinic.
In the early stages of rehabilitation, you work on re-establishing full range of motion in your knee. You then progress to knee-, hip- and ankle-strengthening exercises combined with training to improve your stability and balance. Finally, you work on training specific to your sport or work activities, including exercises to help you prevent further injury.
Depending on the type of injury, you can expect to be back to your normal daily activities in as little as two to four weeks. But to maintain maximum knee stability, you'll need to follow your prescribed exercise program.
Treating underlying medical conditions. If your knee pain is caused by other medical conditions, such as rheumatoid arthritis or gout, your doctor will likely prescribe disease-modifying antirheumatic drugs (DMARDs) to help control those conditions. Commonly used DMARDs include methotrexate, hydroxychloroquine (Plaquenil), sulfasalazine (Azulfidine) and leflunomide (Arava). Other drugs, known as biologics, also may be used with DMARDs. Examples of biologics include etanercept (Enbrel), adalimumab (Humira), infliximab (Remicade) and anakinra (Kineret).
There's no single best way to treat most knee injuries. Whether surgical treatment is right for you depends on many factors, including:
§ The type of injury and amount of damage to your knee
§ The risk of future injury or damage if you don't have surgery
§ Your lifestyle, including which sports you play
§ Your willingness to modify your activities and sports
§ Your motivation to work through rehabilitation to strengthen your knee after surgery
If you have an injury that may require surgery, it's usually not necessary to have the operation immediately. In most cases, you'll do better if you wait until the swelling goes down and you regain strength and full range of motion in your knee.
Before making any decision, consider the pros and cons of both nonsurgical rehabilitation and surgical reconstruction in relation to what's most important to you. Nonsurgical treatment isn't an option if you have cartilage damage that interferes with your range of motion (locked knee) or if the blood supply to your knee is severely compromised.
If you choose to have surgery, your options may include:
§ Arthroscopic surgery. Depending on the nature of your injury, your doctor may be able to examine and repair your joint damage using an arthroscopic technique (arthroscopy) that requires just a few small incisions. Arthroscopy may be used to remove loose bodies from your knee joint, repair torn or damaged cartilage, reconstruct torn ligaments and occasionally correct damage from degenerative joint diseases such as arthritis.
The advantage of the procedure is that you're likely to recover more quickly and with less discomfort than you would with open surgery. Even so, recovery from ligament and meniscus surgery is often slow and requires a strong commitment to physical therapy.
§ Partial knee replacement surgery. If you have considerable knee damage from degenerative arthritis but still retain some healthy cartilage, and conservative measures such as lifestyle changes, medication and physical therapy fail to help your symptoms, you may be a candidate for a partial knee replacement.
In this procedure (unicompartmental arthroplasty), your surgeon replaces only the most damaged portion of your knee with a prosthesis made of metal and plastic. The surgery can usually be performed with a small incision, and your hospital stay is typically just one night. You're also likely to heal more quickly than you are with surgery to replace your entire knee. Unfortunately, many people who opt for knee replacement surgery have damage too extensive for unicompartmental arthroplasty. In addition, long-term results may not be as good as they are with a total knee replacement.
§ Total knee replacement. In this procedure (total knee arthroplasty), your surgeon cuts away damaged bone and cartilage from your thighbone, shinbone and kneecap, and replaces it with an artificial joint (prostheses) made of metal alloys, high-grade plastics and polymers. Total knee arthroplasty can improve knee problems associated with osteoarthritis, rheumatoid arthritis and other degenerative conditions such as osteonecrosis — a condition in which obstructed blood flow causes your bone tissue to die.
You may be a candidate for total knee replacement if you have a severely damaged, arthritic knee that limits your mobility and function, you're older than 60 and in generally good health, and conservative measures fail to improve your symptoms.
In recent years, a number of nonsurgical treatments for knee pain that results from arthritis have been investigated or become available. Some are in the experimental stage, and others are used fairly routinely to control pain and inflammation. They include:
§ Orthotics and bracing. Arch supports, sometimes with wedges on the inner or outer aspect of the heel, can help to shift pressure away from the side of the knee most affected by osteoarthritis. A brace called an "unloader" brace also may be used to help ease the pressure on the most arthritic side of the knee.
§ Corticosteroid injections. Injections of a corticosteroid drug into your knee joint may help reduce the symptoms of an arthritis flare and provide pain relief that lasts a few months. You usually must wait at least four months between injections. The injections aren't effective in all cases and cause some of the same side effects that oral steroid medications do, including an increased risk of infection, water retention and elevated blood sugar levels.
§ Hyaluronic acid. This thick fluid is normally found in healthy joints, and injecting it into damaged ones may ease pain and provide lubrication. Experts aren't quite sure how hyaluronic acid works, but it may reduce inflammation. Relief from a series of shots may last as long as six months to a year.
§ Topical painkillers. Applying certain ointments to your skin may help relieve the pain and stiffness of osteoarthritis. A cream called Celadrin, which contains cetylated fatty acids, may improve mobility and function in people with osteoarthritis of the knee. Another over-the-counter product, capsicum, provides temporary relief of arthritis pain. It's sold under several brand names, but many pharmacies also carry their own brands. Patches containing the analgesic lidocaine also can provide significant pain relief.