Often, knee pain is the result of an injury, such as a ruptured ligament or torn cartilage. But some medical conditions can also bring you to your knees, including arthritis, gout and infections. Depending on the type and severity of damage, knee pain can be a minor annoyance, causing an occasional twinge when you kneel down or exercise strenuously. Or knee pain can lead to severe discomfort and disability. 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 (bursa) 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.
Acute knee pain
Severe knee pain that comes on suddenly (acute pain) is often the result of injury. 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. A tear in one of these ligaments is usually the result of a fall or contact trauma, especially in sports like football, and is likely to cause immediate pain in the injured area. The discomfort, which can range from mild to severe, is usually worse when you walk or bend your knee. If the collateral ligament on the inside of your knee sprains or tears, you may feel a ripping sensation. In some cases, this ligament may become calcified after repeated injuries (Pellegrini-Stieda syndrome).
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. If you tear the ACL, either partially or completely, you’re likely to know it right away. You may feel or hear a pop in your knee and have intense pain and immediate swelling. When you try to stand and put weight on your injured leg, your knee may “buckle” or at least feel as if it might give way. In most cases, you’ll have to stop all activity, either because the pain is too severe or because your knee isn’t stable enough to support your weight.
PCL tears aren’t usually as dramatic or painful. Most often, you’ll experience pain and swelling in the space behind your knee (popliteal fossa) and a feeling of instability, as if your knee might give way.
Tendon injuries (tendinitis). Tendinitis is irritation and inflammation of one or more tendons — the thick, fibrous cords that attach muscles to bone. Athletes — 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). Tendinitis can occur in one or both knees and often causes pain and swelling at the front of your knee and just below your kneecap. The discomfort usually isn’t constant but tends to occur when you jump, run, squat or climb stairs. The quadriceps or patellar tendons may also rupture, either partially or completely. In that case, the pain is likely to be most intense when you try to extend your knee. If the tendon is completely ruptured, you won’t be able to extend or straighten your knee at all.
Meniscus injuries. The meniscus is a C-shaped cartilage that curves within your knee joint. Meniscus injuries involve tears in the cartilage, which can occur in various places and configurations. For example, the cartilage may tear lengthwise or from the inside to the outside rim of the meniscus (radial tear). Although you may not notice small tears, in most cases, you’ll have pain and mild to moderate swelling that develops over 24 to 48 hours. Occasionally, a lengthwise tear flips into the knee joint instead of staying around the joint’s edge, an injury called a bucket-handle tear. A flap of the torn cartilage can interfere with knee movement and cause your knee joint to lock so that you can’t straighten it completely. Meniscal injuries that cause locking of your knee should be surgically treated. Meniscal tears that don’t cause locking, including those of a degenerative nature, can usually be managed nonsurgically.
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 warmth, swelling and redness over the inflamed area, aching or stiffness when you walk, and considerable pain when you kneel. Sometimes the bursa located over your kneecap bone (prepatellar bursa) can become infected, leading to fever, pain and swelling. When the pes anserine bursa on the lower inner side of your knee is affected, you’re likely to have pain when you go up or down stairs.
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 that covers the front of your knee (patella) 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. You’re also likely to have intense pain and swelling in the affected area and difficulty walking or straightening your knee. Unfortunately, once you’ve had a dislocated kneecap, you’re at increased risk of having it happen again. Although you may not experience as much swelling or discomfort with subsequent episodes, repeated dislocations can lead to chronic knee pain. But good rehabilitation, with a focus on strength training of the muscles that control your kneecap, can help prevent dislocation.
Osgood-Schlatter disease. Primarily affecting athletic teens and preteens, this overuse syndrome causes pain, swelling and tenderness at the bony prominence (tibial tuberosity) just below the kneecap. The pain, which can range from mild to debilitating, is usually worse with activity, especially running and jumping, and improves with rest. Osgood-Schlatter disease frequently affects just one knee, but sometimes develops in both knees. The discomfort can last from weeks to months and may continue to recur until your child 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 in the knee that often begins 10 to 15 minutes into a run. Initially, the pain goes away with rest, but in time it may persist when you walk or go up and down stairs.
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. Septic arthritis often occurs with a fever.
Sometimes an injury can lead to ongoing (chronic) knee pain. Often, chronic pain results from a medical condition such as:
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. In addition to pain and swelling, you’re likely to have 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; and sometimes a low-grade fever and a general sense of not feeling well (malaise). Rheumatoid arthritis usually affects both knees at the same time. And although it’s 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 and swelling when you stand or walk and before a change in the weather. It also can lead to stiffness, especially in the morning and after you’ve been active, and to a loss of flexibility in your knee joints.
Gout. With this type of arthritis, you’re likely to experience redness, swelling and intense pain in your knee 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 and intermittent attacks of 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 women, 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 stairs. You may also notice a grating or grinding sensation when you extend your knee.
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 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.
Knee injuries: The hows and whys
Common knee injuries and their causes include:
Ligament injuries. You’re most likely to tear your collateral ligaments in sports that require quick stops and turns, such as soccer, basketball and skiing, or in contact sports when repeated blows to the inside or outside of your knee can cause the opposing ligament to stretch or tear. Collateral ligaments can also be damaged by repeated stress, which causes them to lose their elasticity, much like an overstretched rubber band. Most ACL injuries are sports-related. They frequently occur during activities such as football, basketball, soccer and skiing, when you slow down suddenly or cut or pivot with your foot firmly planted — movements that twist or overextend your knee. ACL tears rarely result from contact with other players, but they can develop when you land awkwardly from a jump or fall. PCL tears, on the other hand, aren’t usually associated with sports. Because the PCL is a strong ligament located deep inside your knee, tears most often result from traumatic injuries, such as those you might receive in a car accident. And because a violent impact is needed to damage the PCL, you’re almost certain to injure other ligaments at the same time.
Tendon injuries. Inflammation of the quadriceps tendon (tendinitis) can occur in people who run, bicycle or ski. It can also result from inflammatory diseases that occur throughout your body, most notably rheumatoid arthritis. Middle-age weekend warriors are more likely to rupture their quadriceps tendon than seasoned athletes are. And patellar tendon ruptures frequently occur in active younger people who have a history of tendinitis or who have had steroid injections in their knees.
Meniscus injuries. A meniscus tear can result from aggressive pivoting or sudden turns — any activity that twists or rotates your knee. Occasionally, you can tear your meniscus while lifting something heavy. Older adults sometimes tear their meniscus during repetitive movements, such as kneeling or squatting, but more often it tears because it has degenerated over time.
Bursitis. Sometimes called housemaid’s knee or carpet layer’s knee, prepatellar bursitis often occurs after an activity that requires you to kneel for long periods — scrubbing floors, gardening, or installing tile or carpet, for example. It can also result from an infection or as one of the signs of arthritis or gout.
Dislocated kneecap. Kneecap (patellar) dislocations can occur in contact sports and in activities that require you to change direction while running, such as tennis, racquetball and volleyball. If your knees tend to turn inward or your kneecaps are higher than normal, you may be more prone to this injury.
Osgood-Schlatter disease. This condition can develop in athletic young people during the years when their bones are growing rapidly — usually ages 10 to 15 for boys and 8 to 13 for girls. Osgood-Schlatter disease results from repeated tugging of the patellar tendon on a growth plate at the top of the tibia. This is most likely to occur during activities that involve running, jumping and bending, when the pull of the quadriceps muscle puts tension on the patellar tendon. In time, the tendon may begin to pull away from the tibia, resulting in a small bump you can see. In severe cases, the tendon may come away from the tibia completely.
Hyperextended knee. This usually results from an awkward landing after a jump or from a contact injury.
Iliotibial band syndrome. This is a common cause of lateral knee pain in runners. Competitive runners are especially susceptible, but amateurs aren’t exempt. You’re more likely to develop iliotibial band syndrome if you have biomechanical problems such as unequal leg length or weak hip abductors, the muscles responsible for sideways leg motion. Exercising on concrete surfaces or uneven ground, increasing the intensity or duration of your exercise too quickly, wearing worn or ill-fitting shoes, and excessive uphill or downhill running also can contribute to iliotibial band syndrome.
Weighing more than your ideal weight is one of the leading risk factors for knee pain. Excess weight increases stress on your knee joints, even during ordinary activities such as walking or going up and down stairs. It also puts you at increased risk of osteoarthritis by accelerating the breakdown of joint cartilage.
Other factors that make you more susceptible to knee pain include:
Overuse. Any repetitive activity, from cycling a few miles every morning to gardening all weekend, can fatigue the muscles around your joints and lead to excessive loading stress. This causes an inflammatory response that damages tissue. If you don’t allow your body time to recover, the cycle of inflammation and microdamage continues, putting you at increased risk of injury. It’s not repeated motion itself that’s to blame, but rather the lack of adequate recovery time. That’s why current strength training guidelines advise against working the same muscle group on consecutive days, for example.
Lack of muscle flexibility or strength. According to experts, lack of strength and flexibility are among the leading causes of knee injuries. Tight or weak muscles offer less support for your knee because they don’t absorb enough of the stress exerted on your knee joints.
Mechanical problems. Certain structural abnormalities, such as having one leg shorter than the other, misaligned knees and even flat feet, can make you more prone to knee problems.
High-risk sports and activities. Some sports and activities put greater stress on your knees than others. Alpine skiing with its sharp twists and turns and potential for falls, basketball’s jumps and pivots, and the repeated pounding your knees take when you run or jog all increase your risk of injury.
Previous injury. Having a previous knee injury makes it more likely that you’ll injure your knee again.
Age. Certain types of knee problems are more common in young people — Osgood-Schlatter disease and patellar tendinitis, for example. Others, such as osteoarthritis, gout and pseudogout, tend to affect older adults.
Sex. For reasons that aren’t entirely clear, your sex may increase your risk of some types of knee injuries. Women are more prone to ACL tears than men are, and teenage girls are more likely than boys to experience a dislocated kneecap. Boys, on the other hand, are at greater risk of Osgood-Schlatter disease and patellar tendinitis than girls are.
Often, a comprehensive medical history and thorough physical exam play a larger role in 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 test, helps detect injuries to the ACL. In the Lachman’s 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 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. Still, if your injury allows your doctor to perform a complete physical exam, this exam is likely to be accurate. 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 and continue for at least 48 hours.
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. Minor injuries may require only a day or two of rest, but 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 15 to 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. After two days, you might try switching to heat to relax your muscles and increase blood flow.
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 sodium (Aleve, Naprosyn), can help relieve pain. But if taken immediately after an injury, they may actually increase swelling. What’s more, NSAIDs can have side effects, especially if you take them for long periods or in amounts greater than the recommended dosage. Even small doses may cause nausea, stomach pain, stomach bleeding or ulcers; and large doses can lead to kidney problems and fluid retention. NSAIDs also have a ceiling effect, which means there’s a limit to how much pain they can control. If you have moderate to severe pain, exceeding the dosage limit probably won’t relieve your symptoms. 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 an exercise program for your legs two to three days a week.
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 55 and in generally good health, and conservative measures fail to improve your symptoms.
Not all knee pain is serious. But some knee injuries and medical conditions, such as osteoarthritis, can lead to increasing pain, joint damage and even disability if left untreated. And having a knee injury — even a minor one — makes it more likely that you’ll have similar injuries in the future. Repeated injuries increase your risk of arthritis in the affected joint.