Knee Pain Overview

Introduction to Knee Pain

Knee pain is the most common musculoskeletal complaint that brings people to their doctor. With today's increasingly active society, the number of knee problems is increasing. Knee pain has a wide variety of specific causes and treatments.

Anatomy of the Knee

The knee joint's main function is to bend, straighten, and bear the weight of the body, along with the ankles and hips. The knee, more than just a simple hinged joint, however, also twists and rotates. In order to perform all of these actions and to support the entire body while doing so, the knee relies on a number of structures including bones, ligaments, tendons, and cartilage.

Bones

  • The knee joint involves four bones.
  • The thighbone or femur comprises the top portion of the joint.
  • One of the bones in the lower leg (or calf area), the tibia, provides the bottom weight-bearing portion of the joint.
  • The kneecap or patella rides along the front of the femur.
  • The remaining bone in the calf, the fibula, is not involved in the weight-bearing portion of the knee joint but provides ligament attachments for stability.

Ligaments

  • Ligaments are dense fibrous bands that connect bones to each other.
  • The knee includes four important ligaments, all of which connect the femur to the tibia:
  • The anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) provide front and back (anterior and posterior) and rotational stability to the knee.
  • The medial collateral ligament (MCL) and lateral collateral ligament (LCL) located along the inner (medial) and outer (lateral) sides of the knee provide medial and lateral stability to the knee.

Tendons

  • Tendons are fibrous bands similar to ligaments.
  • Instead of connecting bones to other bones as ligaments do, tendons connect muscles to bones.
  • The two important tendons in the knee are (1) the quadriceps tendon connecting the quadriceps muscle, which lies on the front of the thigh, to the patella and (2) the patellar tendon connecting the patella to the tibia (technically, this is a ligament because it connects two bones).
  • The quadriceps and patellar tendons are sometimes called the extensor mechanism, and together with the quadriceps muscle they facilitate leg extension (straightening).

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Cartilage

  • Cartilaginous structures called menisci (singular form is "meniscus") line the top of the tibia and lie between the tibia and the 2 knuckles at the bottom of the femur (called the femoral condyles).
  • The menisci's primary job is to provide cushioning for the knee joint.

Bursae

  • Bursae (one is a bursa) are fluid-filled sacs that help to cushion the knee. The knee contains 3 important groups of bursae:
  • The prepatellar bursae lie in front of the patella.
  • The Pes anserine bursae is located on the inner side of the knee about 2 inches below the joint.
  • The infrapatellar bursae are located underneath the patella.

Home Care for Knee Pain

Inflammation is the body's physiologic response to an injury. In treating many types of knee pain, a common goal is to break the inflammatory cycle. The inflammatory cycle starts with an injury. After an injury, substances that cause inflammation invade the knee to assist in healing. However, if the injury and subsequent inflammation is not resolved, inflammation can become a chronic issue, leading to further inflammation and additional injury. This cycle of inflammation leads to continued or progressive knee pain. The cycle can be broken by controlling the substances that cause inflammation, and by limiting further injury to tissue.

Some common home care techniques for knee pain that control inflammation and help to break the inflammatory cycle are protection, rest, ice, compression, and elevation. This regimen is summarized by the memory device PRICE.

PROTECT the knee from further trauma.

  • This can be done with knee padding or splinting.
  • A pad over the kneecap, for example, helps to control the symptoms of some knee injuries (an example is a form of bursitis sometimes called housemaid's knee) by preventing further repetitive injury to the prepatellar bursae.

REST the knee.

  • Rest reduces the repetitive strain placed on the knee by activity.
  • Rest both gives the knee time to heal and helps to prevent further injury.

ICE the knee.

  • Icing the knee reduces swelling and can be used for both acute and chronic knee injuries.
  • Most authorities recommend icing the knee 2 to 3 times a day for 20-30 minutes each time.
  • Use an ice bag or a bag of frozen vegetables placed on the knee.

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COMPRESS the knee with a knee brace or wrap.

 

  • Compression reduces swelling.
  • In some knee injuries, compression can be used to keep the patella aligned and to keep joint mechanics intact.

ELEVATE the knee.

  • Elevation also helps reduce swelling.
  • Elevation works with gravity to help fluid that would otherwise accumulate in the knee flow back to the central circulation.
  • Prop your leg up when you are sitting, or use a recliner, which naturally elevates the legs. Elevation works best when the knee -- or any other injured body part -- is higher than the level of the heart.

Over-the-counter pain medicine: Commonly used pain relievers, such as nonsteroidal anti-inflammatory drugs (NSAIDs) like naproxen (Aleve or Naprosyn) and ibuprofen (Advil or Motrin), also play a role in the treatment of knee pain.

  • These drugs directly control pain and, at higher doses, act as anti-inflammatory agents, helping to break the inflammatory cycle. Like all medications, however, these drugs have side effects.
  • You should not use NSAIDs if you have a problem with bleeding or stomach ulcers or some types of kidney disease.
  • Acetaminophen (Tylenol) can also be used to control knee pain but does not have the anti-inflammatory properties of the NSAIDs. Still, this treatment is remarkably useful in many types of knee pain, such as osteoarthritis.

When to Call the Doctor for Knee Pain

When you are deciding whether to call the doctor about your knee pain, a good rule of thumb exists for most long-term knee injuries. If your symptoms have not gone away after trying a week of PRICE therapy and over-the-counter anti-inflammatory pain meds, you should set up an appointment with your doctor, physical therapist, or a sports medicine orthopaedic (bone and muscle) specialist to further evaluate the pain. This rule can also be applied to new knee injuries that are not disabling. Remember, however, that this rule should only serve as a guide. If you are concerned about the pain, you should call the doctor.

When to Go to the Hospital for Knee Pain

If you cannot put weight on your knee, feel sick, or have a fever or if your knee is red and hot, you should consider going to the ER to be evaluated by a doctor because of the possibility of a fracture or infection.

  • Many fractures may require immobilization in a specific position or surgery.
  • Infections need immediate attention. They can be managed but require prompt care.
  • Putting off seeing a doctor may hinder healing.

Other signs and symptoms that demand emergency evaluation:

  • Unbearable pain
  • Pain that does not improve with rest
  • Pain that wakes you
  • Drainage
  • Large wounds
  • Puncture wounds
  • Swelling, if you are on a blood thinner (warfarin or Coumadin) or have a bleeding disorder (such as hemophilia)

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Getting a Knee Pain Diagnosis

History: Even in today's world of technology, doctors rely on a detailed history and physical exam more than any single test.

The doctor will typically want to know the exact nature of the pain.

  • Where in the knee is your pain?
  • What does the pain feel like?
  • How long has the pain been present?
  • Has it happened before?
  • Describe any injuries to the knee.
  • What makes it better or worse?
  • Does the knee pain wake you up at night?
  • Does the knee feel unstable?
  • Have you been limping?

The doctor will also want to know a bit about you.

  • Do you have any major medical problems?
  • How active is your lifestyle?
  • What are the names of the medications you are taking?

The doctor will want to know about any related symptoms.

  • Do you still have normal sensation in your foot and lower leg?
  • Have you been having fevers?

Physical exam

  • The doctor will likely have you disrobe to completely expose the knee. If possible, wear shorts to your appointment.
  • The doctor will then inspect the knee and press around the knee to see exactly where it is tender.
  • In addition, the doctor may perform a number of maneuvers to stress the ligaments, tendons, and menisci of the knee and evaluate the integrity of each of these.

X-rays, CT scans, and other tests

  • Depending on your particular history and exam, the doctor may suggest X-rays of the knee. X-rays show fractures (broken bones) and dislocations of bones in the knee as well as arthritis and abnormally large or small joint spaces.
  • Rarely, the doctor may order a CT scan (a 3-dimensional X-ray) of the knee to precisely define a fracture or deformity.
  • Both X-rays and CT scans are excellent for diagnosing fractures. They both are also poor, however, at evaluating soft tissue structures of the knee, such as ligaments, tendons, and the menisci.

MRI

  • Magnetic resonance imaging (MRI) uses large magnets to create a 3-dimensional image of the knee.
  • In contrast to CT scans, MRIs do not image bones and fractures. However, they are excellent for evaluating ligaments and tendons.

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Fluid removal

  • The knee and all bursae of the knee are filled with fluid.
  • If your symptoms suggest infection or crystalline arthritis, such as gout, your physician may remove fluid, with a needle, from the knee.
  • This fluid will then be analyzed to better clarify the diagnosis.
  • Crystals, which suggest crystalline arthritis, often can be seen under the microscope. Infection may also be detected under a microscope by finding bacteria and pus in the fluid.
  • The doctor may also elect to perform certain blood tests to evaluate for signs of infection or diseases such as rheumatoid arthritis, lupus, and diabetes.

Arthroscopy

  • The orthopedic surgeon may elect to perform arthroscopy if you have chronic knee pain.
  • This is a surgical procedure where the doctor will place a fiber optic telescope within the knee joint. The arthroscope is attached to a camera that relays real-time images to a video monitor.
  • By doing so, the surgeon may be able to see small particles in the knee or to look more closely at damaged menisci or cartilage.
  • The doctor may also be able to treat damage by shaving down torn cartilage or removing particles from the knee while looking at the inside of your knee on a video monitor.

Types of Knee Pain

The nerves that provide sensation to the knee come from the lower back and also provide hip, leg, and ankle sensation. Pain from a deeper injury (called referred pain) can be passed along the nerve to be felt on the surface. Knee pain, therefore, can arise from the knee itself or be referred from conditions of the hip, ankle, or lower back. All of the following sources of knee pain arise from the knee joint itself.

In general, knee pain is either immediate (acute) or long-term (chronic). Acute knee pains can be caused by an acute injury or infection. Chronic knee pain is often from injuries or inflammation (such as arthritis) but can also be caused by infection.

Acute Knee Pain

Sprained and Torn Cruciate Ligaments

  • Description: An anterior cruciate ligament (ACL) injury is a common sports injury generally caused by a hard stop or a violent twisting of the knee. The posterior cruciate ligament (PCL) is stronger than the ACL and much less commonly torn. A PCL injury may happen with a serious blow, such as when the knee strikes the dashboard in a car accident; this is why a PCL injury is often associated with other ligament and bone injuries.
  • Symptoms: If you tear your ACL, you may hear a pop. You will also notice your knee give way or become unstable and feel pain that is bad enough that you might feel like vomiting. This will, almost always, be followed by marked knee swelling over the next couple of hours because the ACL bleeds briskly when torn.
  • Treatment: Surgical repair is often recommended for high-level athletes who demand optimal outcomes. Conservative treatment and knee braces may prove sufficient for those who do not demand quite so much from their knees.

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Tendon Ruptures

  • Description: Both the quadriceps and patellar tendons may rupture partially or completely. A quadriceps tendon rupture typically occurs in recreational athletes older than 40 years (this is the injury former President Clinton suffered while jogging), and a patellar tendon rupture typically occurs in younger people who have had previous tendonitis or steroid injections to the knee.
  • Symptoms: Rupture of either the quadriceps or patellar tendon causes pain (especially when trying to kick or extend the knee). Those people with complete ruptures are unable to extend the knee. The patella is also often out of place either upward (with patellar tendon rupture) or downward (with quadriceps tendon rupture).
  • Treatment: Tendon ruptures require urgent care. They typically need surgical repair, while a partial rupture may be treated with splinting alone.

Meniscal Injuries

  • Description: Injuries to the meniscus are typically traumatic injuries but can also be due to overuse. Often, a piece of the meniscus will tear off and float in the knee joint.
  • Symptoms: Meniscal injuries may cause the knee to lock in a particular position, or either click or grind through its range of motion. Meniscal injuries may also cause the knee to give way. Swelling typically accompanies these symptoms, although the swelling may be much less severe than with an ACL injury.
  • Treatment: Meniscal injuries often require arthroscopic surgical repair. A locking knee or a knee that "gives" should be evaluated for arthroscopic repair.

Knee Dislocation

  • Description: Knee dislocation is a medical emergency. Dislocation of the knee is caused by a particularly powerful blow to the knee. The lower leg becomes completely displaced with relation to the upper leg. This displacement stretches and frequently tears not only the ligaments of the knee but also arteries and nerves. Untreated arterial injuries leave the lower leg without a blood supply. If circulation is not restored, amputation may be required. Nerve injuries, on the other hand, may leave the lower leg viable but without strength or sensation.
  • Symptoms: Knee dislocations are severely painful and produce an obvious deformity of the knee. Many dislocations are reduced -- or put back into alignment -- on their own. As this occurs, many will report feeling a dull clunk.
  • Treatment: If the knee dislocation has not been put back into place on its own, the doctor will immediately reduce the dislocation. Medical treatment, however, does not stop here. Whether a dislocation reduces by itself or is put back into place in the hospital, it requires further evaluation and care. After reduction, people with these injuries are observed in the hospital where they usually do a number of tests to ensure that no arterial or nerve injury has occurred. If such an injury is found, it must be repaired immediately in the operating room.

Dislocated Kneecap (patella)

  • Description: A common injury caused by direct trauma or forceful straightening of the leg, such as an injury that happens when serving in volleyball or tennis. Kneecap dislocation is more common in women, the obese, knock-kneed people, and in those with high-riding kneecaps.
  • Symptoms: If you have this injury, you will notice the patella being out of place and may have difficulty flexing or extending your knee.
  • Treatment: The doctor will move the patella back into place (reduce the dislocation). Even if the patella goes back into place by itself, it needs to be X-rayed for a fracture. After reducing the dislocation and ensuring the absence of a fracture, the doctors will treat these injuries by splinting the knee to allow the soft tissues around the patella to heal followed by strengthening exercises to keep the patella in line. This injury often causes damage to the cartilage on the back of the patella.

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Chronic Knee Pain

Arthritis: Arthritis of the knee is an inflammatory disorder of the knee joint that is often painful. Arthritis has many causes.

Knee Osteoarthritis

  • Description: Osteoarthritis (OA) is caused by degeneration of cartilage in the knee. In its extreme form, the menisci (cartilage) will be completely eroded, and the femur will rub on the tibia, bone on bone.
  • Symptoms: Osteoarthritis causes a chronically painful knee that is often more painful with activity.
  • Treatment: Treatment is aimed at pain control with over-the-counter pain relievers. Anti-inflammatory medications, either over-the-counter or by prescription, can be helpful. Hyaluronic acid, a lubricating gel, often injected into the knee over a course of 3-6 weeks, can provide substantial relief for one year or more. Severe OA can be treated with narcotic pain medicines or a knee joint replacement in which a synthetic joint replaces your knee joint. Additionally, physical therapy to manage OA pain and knee function can be beneficial.

Rheumatoid Arthritis of the Knee

Crystalline Arthritis (gout and pseudogout)

  • Description: These severely painful forms of arthritis are caused by sharp crystals that form in the knee and other joints. These crystals can form as a result of defects in the absorption or metabolism of various natural substances such as uric acid (which produces gout) and calcium pyrophosphate (pseudogout).
  • Treatment: Treatment is aimed at controlling inflammation with anti-inflammatory medications, and at aiding the metabolism of the various chemicals that may lead to crystal formation.

Bursitis

  • Description: As a result of trauma, infection, or crystalline deposits, the various bursae of the knee may become inflamed.
  • Symptoms: Acute or chronic trauma causes a painful and often swollen knee from the inflammation of the bursae. A particularly common bursitis is prepatellar bursitis. This type of bursitis occurs in people who work on their knees. It is often referred to as housemaid's knee or carpet layer's knee. Another type of bursitis is anserine bursitis. The anserine bursa is located about 2 inches below the knee along the medial side of the knee. More commonly occurring in the overweight and in women, but also affecting athletes and others, anserine bursitis often causes pain in the region of the bursa and is often worse with bending the knee or at night with sleep.
  • Treatment: Treatment will usually include home care with PRICE therapy and NSAIDs. Severe forms, however, can be treated with periodic steroid injections.

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Infection (or infectious arthritis)

  • Description: Many organisms may infect the knee. Gonorrhea, a common sexually transmitted disease, can infect the knee, as can common organisms residing on normal skin.
  • Symptoms: Infection of the knee causes painful knee swelling. In addition, people who develop such infection typically complain of fevers and chills. Less severe infections may not have associated fevers.
  • Treatment: New swelling and pain in the knee must be evaluated for infection by a doctor. Treatment usually includes intensive antibiotic therapy. Aspiration of the joint or surgical drainage may also be recommended.

Patellofemoral Syndrome and Chondromalacia Patella

  • Description: These two conditions represent a continuum of diseases caused by patellar mistracking.
  • Symptoms: The conditions typically occur in young women, in athletes of both sexes, and in older people. In patellofemoral syndrome, the patella rubs against the inner or outer femur rather than tracking straight down the middle. As a result, the patellofemoral joint on either the inner or outer side may become inflamed, causing pain that is worse with activity or prolonged sitting. As the condition progresses, softening and roughening of the articular cartilage on the underside of the patella occurs, leading to chondromalacia patella.
  • Treatment: Home care with PRICE therapy, NSAIDs, and exercises (such as straight leg raises) that balance the muscles around the patella work for most people. Physical therapy to assess factors that may contribute to the disease process guides management to include exercise, bracing or taping of the patella, commercial arch supports (for the arch of the foot), or orthotic supports that correct foot mechanics and may reduce abnormal forces on the knee. Severe cases of patellofemoral syndrome or chondromalacia may be treated surgically through a variety of procedures.

Jumper's Knee

  • Description: Tendonitis (inflammation of the tendon) of the quadriceps tendon at the upper point of the patella, where it inserts, or tendonitis of the patellar tendon either at the lower point of the patella, or at the place where it inserts on the tibia (called the tibial tuberosity, the bump is about 2 inches below the knee on the front side). Jumper's knee is so named because it is typically seen in basketball players, volleyball players, and people doing other jumping sports.
  • Symptoms: Jumper's knee causes localized pain that is worse with activity. It usually hurts more as you jump up than when you land, because jumping puts more stress on tendons of the knee.
  • Treatment: Home therapy with the PRICE regimen, along with anti-inflammatory drugs, is the basis of treatment to manage the acute phase. Particularly important are rest, ice, and NSAID drugs, which will help stop the pain and break the cycle of inflammation. After controlling the pain, you should slowly start an exercise regimen to strengthen the quadriceps, hamstrings, hip, and calf muscles before resuming your sport of choice a few weeks down the line. Also, bracing of the extensor mechanism may help remove stress from the tendons.

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Osgood- Schlatter Disease

  • Description: Osgood-Schlatter disease occurs in adolescent athletes where repetitive extension of the knee causes inflammation and injury of the tibial tubercle (the bony protrusion at the top of the shin, just below the kneecap).
  • Symptoms: Children suffering from this syndrome report pain at the tibial tubercle. This pain is typically worse when extending the leg. The tibial tubercle is tender to touch and over time begins to protrude more because the chronic inflammation stimulates the bone to grow.
  • Treatment: Osgood-Schlatter disease is a self-limited condition that usually resolves as the the tibial tubercle stops growing with the end of adolescence (at about age 17 in males and age 15 in females). Treatment includes PRICE and NSAID therapy to minimize acute pain from activity. Physical therapy to identify limitations will reduce stress to the tibial tubercle and often includes strength training of the hip and core. In severe cases, splinting the knee for a few weeks may help reduce the pain and halt the inflammation cycle.

Iliotibial Band Syndrome

  • Description: A fibrous ligament, called the iliotibial band, extends from the outside of the pelvic bone to the outside of the tibia. When this band is tight it may rub against the bottom outer portion of the femur (the lateral femoral condyle).
  • Symptoms: Distance runners typically suffer from this condition. These runners complain of outside knee pain usually at the lateral femoral condyle. Early on, the pain will typically come on 10 minutes to 15 minutes into a run and improve with rest.
  • Treatment: The most important aspect of treating iliotibial band syndrome is to identify why it is tight. A physical therapist can evaluate mechanics and prescribe treatments, which may include stretching the iliotibial band. One way to do this is to place the right leg behind the left while standing with your left side about 2 feet to 3 feet from a wall. Then, lean toward your left for 20 to 30 seconds using the wall to help you support yourself. In addition to stretching the iliotibial band, PRICE therapy and NSAIDs may be of some help.

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Knee Pain Prevention

Knee pain has a host of causes. Many types of pain are difficult to prevent, but you can do some general things to reduce the likelihood of sustaining a knee injury.

Stay Slim

  • Staying slim reduces the forces placed on the knee during both athletics and everyday walking and may, according to some medical research, reduce osteoarthritis.
  • Keeping your weight down may also reduce the number of ligament and tendon injuries for similar reasons.

Keep Limber, Keep Fit

  • Many knee problems are caused by tight or imbalanced musculature. Stretching and strengthening, therefore, also help to prevent knee pain.
  • Stretching keeps your knee from being too tight and aids in preventing both patellofemoral syndrome and iliotibial band syndrome.
  • Strengthening exercises, particularly of the quadriceps (straight leg raises and leg extensions are among the prescribed exercises), can help prevent knee injury and are essential to reducing arthritis and associated complications.

Exercise Wisely

  • If you have chronic knee pain, consider swimming or water exercises. In water, the force of buoyancy supports some of our weight so our knees aren't burdened.
  • If you don't have access to a pool or do not enjoy water activities, at least try to limit hard pounding and twisting activities such as basketball, tennis, or jogging.
  • You may find that your aching knees will act up if you play basketball or tennis every day but will not if you limit your pounding sports to twice a week.
  • Whatever you do, respect and listen to your body. If it hurts, change what you are doing.
  • If you are fatigued, consider stopping -- many injuries occur when people are tired.

Protect the Knee

  • Wearing proper protection for the activity at hand can help avoid knee injuries.
  • When playing volleyball or when laying carpet, protecting your knees may include kneepads.
  • When driving, knee protection may include wearing a seatbelt to avoid the knee-versus-dashboard injuries as well as injuries to other parts of your body.

 

WebMD Medical Reference Reviewed by Ross Brakeville, DPT on January 21, 2017

Sources

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Hart L. "Knee Pain." Woman's Day. 2001.

Lally S. "End Knee Pain Forever." Men's Health. 1990.

Levy AM, Fuerst ML. Sports Injury Handbook: Professional Advice for Amateur Athletes. New York: John Wiley & Sons; 1993.

Roberts DM, Stallard TC.  Emerg Med Clin North Am. Feb 2000.

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