Knee pain can be an extremely common complaint. While unpleasant and frustrating, the upside is that many causes of knee pain are often very treatable.

Diagnosing your knee pain first requires a focused medical history, one that sorts out the details of the pain, such as what it feels like (e.g. aching, sharp, or burning), where it's located (e.g. front of or behind the knee), when it started (e.g., gradually or suddenly), and whether there was any recent trauma (e.g. blow to the knee).

Besides a medical history, your doctor will perform an examination of the knee joint and potentially order imaging tests to make or confirm a diagnosis.

In the end, understanding the precise cause of your knee pain is key to you and your doctor formulating an effective treatment plan—one that optimizes the relief of symptoms and return to normal function.

Illustration by Alexandra Gordon, Verywell

Causes

Your knee is a complex structure consisting of three bones—the lower part of the thighbone, the upper part of the shinbone, and the kneecap.

Then, there are strong ligaments and tendons that hold these bones together, as well as cartilage beneath the kneecap and between the bones to cushion and stabilize the knee. Damage or disease that affects any of these structures may lead to pain.

Common

If you have knee pain, some common causes include:

Knee Arthritis

There are different types of arthritis that affect the knee joint, the two most common ones being osteoarthritis and rheumatoid arthritis.

Knee osteoarthritis develops as a result of "wear and tear" of the cartilage in the knee and is more common in people over the age of 50. ﻿ ﻿ As the cartilage deteriorates, pain develops, often gradually escalating from a sharp pain that worsens with knee movement to a constant dull, aching pain.

﻿ As the cartilage deteriorates, pain develops, often gradually escalating from a sharp pain that worsens with knee movement to a constant dull, aching pain. Rheumatoid arthritis is an autoimmune disease whereby a person's immune system attacks multiple joints in the body. In addition to pain, swelling, redness, and warmth over the kneecap may develop. Unlike osteoarthritis, knee pain from rheumatoid arthritis tends to improve with activity.

Knee Ligament Injuries

There are four primary ligaments in your knee—two collateral ligaments and two cruciate ligaments.

Collateral Ligament Injury

The collateral ligaments (medial collateral and lateral collateral) are found on the side of your knee and connect your thighbone (femur) to your lower leg bone. Injury to the medial collateral ligament (MCL) often results from a direct blow to the outside of the knee, which causes pain on the inside of the knee.

A blow to the inside of the knee may cause a lateral collateral ligament (LCL) injury, which causes pain to the outside of the knee.

Cruciate Ligament Injury

The cruciate ligaments (anterior cruciate and posterior cruciate) cross each other inside the knee joint, with the anterior cruciate attaching to the shin bone in the front and the posterior cruciate attaching in the back.

Anterior cruciate ligament injuries are the most common type of knee injury, often resulting from a direct blow or a sudden change in direction or speed when running.﻿﻿ Usually, a "popping" noise is heard, along with sudden swelling, and a giving out of the knee.

Posterior cruciate ligament injuries are uncommon and are generally caused by some sort of high-energy force to the knee (for example, a bent knee colliding with the dashboard during a car accident). Besides pain at the back of the knee, knee swelling and instability are typical symptoms associated with this ligament injury.

Torn Knee Cartilage (Meniscus)

There are two "C" shaped, tough pieces of cartilage (called menisci) located between your thighbone and shinbone. Tearing of the meniscus is a common cause of knee pain and may occur in young people (often during sports) or older people, as the cartilage weakens with age, making it more prone to tear.﻿﻿

Besides pain, a person with a meniscus tear may initially hear a "pop" when the tear occurs. This is followed by a gradual development of knee stiffness and swelling, along with knee clicking, locking, or catching.

Patellar Tendonitis and Tear

Patellar tendonitis refers to inflammation of the patellar tendon—a large tendon that connects your kneecap to the top of your shinbone. Patellar tendonitis is most common in people who engage in sports or activities that require frequent running and jumping.﻿﻿ Often times, people with this condition describes a constant dull pain that becomes sharp with activity.

In some cases, the patellar tendon can weaken, making it more likely to tear. A patellar tendon tear causes severe pain, swelling over the knee, and a tearing or popping sensation. Depending on the degree of the tear, a person may notice an indentation at the bottom of the kneecap and experience walking difficulties due to the knee giving out.

Patellofemoral Pain Syndrome

Patellofemoral pain syndrome is most common in adolescents and young adults and is usually caused by vigorous activities that put stress on the knee, like running, squatting, or climbing stairs.﻿﻿

This condition causes a dull, aching pain felt underneath the kneecap and is sometimes referred to as chondromalacia patella, which means that the cartilage behind the kneecap has softened and begun to wear away. Abnormal knee alignment may also cause or contribute to this condition.

Besides pain, which worsens with activities that require frequent knee bending or sitting for long periods of time (for example, working at a desk), a person may note popping sounds in the knee when standing up from prolonged sitting or when climbing stairs. Knee swelling and locking are rarely seen with this syndrome.

Baker's Cyst

A Baker's cyst is swelling in the back of the knee joint and is sometimes a sign of another underlying problem such as a meniscus tear.﻿﻿ While not all Baker's cysts cause pain, if they do, the "tightening" pain is felt in the back of the knee and is often associated with knee stiffness and a visible bulge that worsens with activity.

Prepatellar Bursitis

Your prepatellar bursa (a fluid-filled sac) is located right over the kneecap. Prepatellar bursitis—when the bursa becomes inflamed— is most commonly caused by people who frequently kneel, like gardeners or carpet layers.﻿﻿

Less commonly, an infection, gout, rheumatoid arthritis, or a direct blow to the knee may cause bursitis. Besides a mildly aching knee pain that may only be felt with knee movement or when touching the affected area, rapid swelling over the kneecap typically occurs.

Iliotibial Band Syndrome

﻿Iliotibial band syndrome refers to inflammation of the iliotibial band—a thick collection of fibers that runs along the outside of the thigh. Iliotibial band inflammation commonly happens as a result of overuse, especially in runners, and causes an aching, burning pain on the outside of the knee joint.﻿﻿ Sometimes, the pain spreads up the thigh to the hip.

Less Common

Here are some less common causes of knee pain:

Dislocating Kneecap

A dislocating kneecap causes acute symptoms during the dislocation and occurs either from a sharp blow to the knee, such as from a car accident or fall to the ground﻿﻿ , or from a twisting event that causes the patella to disengage.

Besides pain in front of the knee, a person may notice knee buckling, slipping off to one side, or catching during movement. Knee swelling, stiffness, and cracking sounds are also common.

Gout

Gout is an inflammatory condition that occurs in people with high levels of uric acid in their bloodstream.﻿﻿ These high levels of uric acid form crystals within certain joints, like the big toe, fingers, knee, or hip.

A gout attack often affects one joint at a time, causing a severe, burning pain, as well as swelling, warmth, and redness of the affected area.

Plica Syndrome

Plica syndrome is an uncommon cause of knee pain and occurs when a plica—an embryonic remnant of the synovial capsule of the knee joint—becomes irritated.﻿﻿

People with plica syndrome often report middle and front knee pain that worsens with knee activity, like squatting, running, or kneeling, or with prolonged sitting. A popping sensation can be felt when bending the knee.

Osgood-Schlatter Disease

Osgood-Schlatter disease is a condition seen in children between the ages of 9 and 14.﻿﻿ This disease classically occurs after a recent growth spurt when irritation at the front of the knee joint develops, triggering pain and sometimes swelling just below the kneecap. The pain improves with rest and worsens with knee activity such as running and jumping.

Osteochondritis Dissecans

Osteochondritis dissecans (OCD) is another condition seen in children and adolescents that occurs as a result of a lack of blood supply to a small segment of the knee bone.﻿﻿ This causes the affected bone and the cartilage covering it to weaken and sometimes separate from the underlying bone.

Pain poorly localized to the knee that is felt with activity is the first symptom. Keep in mind that many conditions may have similar symptoms. As the condition progresses, on-and-off swelling and knee stiffness may occur.

Knee Joint Infection

An infected knee joint causes significant knee pain, along with swelling, warmth, painful movements, and oftentimes, fever. In some cases, a bacterial infection in the bloodstream is the culprit behind an infected joint.﻿﻿

Kneecap Fracture

A fracture of the kneecap may occur from a fall directly onto the knee, or from a direct blow to the knee,﻿﻿ like hitting the knee on the dashboard from a car accident. Besides significant pain and difficulty in straightening the knee, bruising and swelling over the kneecap usually occurs, sometimes with a visible deformity.

Bone Tumor

Very rarely, a bone tumor, such as an osteosarcoma, may be the source of one's knee pain.﻿﻿ Associated symptoms like fever or unintentional weight loss and pain that is particularly worse at night may also be present.

When to See a Doctor

If you are unsure of the cause of your symptoms, or if you do not know the specific treatment recommendations for your condition, you should seek medical attention. Treatment of knee pain must be directed at the specific cause of your problem.

See the Doctor If You Have: An inability to walk comfortably on the affected side

An injury that causes deformity around the joint

Knee pain that occurs at night or while resting

Knee pain that persists beyond a few days

Locking (inability to bend) in the knee

Swelling of the joint or the calf area

Signs of an infection, including fever, redness, or warmth

Any other unusual symptoms

Diagnosis

Many knee conditions can be diagnosed by a medical professional based on a medical history and physical examination alone.

Medical History

When discussing your knee pain with your doctor, try to be as detailed as possible. This is because clues like the precise location and timing of your knee pain, along with associated symptoms, can help your doctor nail down the diagnosis.

Location

Where on the knee you feel the pain can offer some clues about what type of injury or condition is causing the discomfort.

For instance, pain on the inside or medial side of the knee (the side closest to the other knee) can be caused by medial meniscus tears, MCL injuries, and arthritis, whereas pain on the outside of the knee, or lateral side, can be caused by lateral meniscus tears, LCL injuries, IT band tendonitis, and arthritis.

Likewise, pain in the back of the knee may be due to a Baker's Cyst. Pain over the front of the knee is most commonly related to the kneecap and can be caused by several different problems that affect the area, such as chondromalacia or prepatellar bursitis.

Timing

Just as the location of knee pain may indicate what's causing the problem, the time of day when the pain occurs and the activities that trigger the pain also can offer insight.

Pain while walking down steps is very commonly associated with inflammation under the kneecap. Knee pain after first waking in the morning that quickly resolves with gentle activity can sometimes be associated with early arthritis.

Associated Symptoms

Besides pain, your doctor will also ask you whether you have noticed any swelling, or experienced symptoms like fever or chills (a sign of a potential infection) or other whole-body symptoms (for example, joint aches elsewhere, fatigue, or unexplained weight loss), which could indicate a systemic disease like rheumatoid arthritis.

Physical Examination

In addition to a comprehensive medical history, a thorough physical exam is important to arrive at the correct diagnosis.﻿﻿ While examining your affected knee, your doctor will look closely for swelling of the knee, and move the knee around to assess for stability, noises, and locking.

Swelling

Swelling of the knee is common with many different types of knee problems. When there is an effusion (excess fluid build-up around the joint) immediately after a knee injury, a possible cause is an injury to an internal joint structure. When swelling develops gradually over hours to days after an injury, it can be associated with less severe problems.

When swelling develops gradually over hours to days after an injury, it can be associated with less severe problems. Swelling that occurs without a present known injury can be due to osteoarthritis, gout, inflammatory arthritis, or a joint infection.

Range of Motion

Mobility of the knee can be affected by a number of common conditions. If mobility is gradually limited, often the cause can be related to arthritis. If the mobility is limited after an acute injury, there can be swelling limiting the motion, or sometimes a torn structure that is limiting the mobility.

Stability

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, although this feeling also can occur due to swelling or muscle weakness in the knee.

Noises

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 can be heard or felt during a twisting injury to the knee when a ligament, such as the ACL, is injured.

Grinding or crunching are common symptoms of cartilage problems. If the cartilage is worn down, as in 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 the 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 have a healthcare professional inject the knee with a numbing medication. After the medication has taken effect, you can attempt to bend the knee to determine if the pain was blocking the motion or if there is a structure, such as a torn meniscus, that is blocking normal motion.

Imaging

When seen by a doctor, is important to have a comprehensive evaluation to obtain a diagnosis. This includes imaging studies.

In most cases, your doctor will start off with an X-ray, which can not only show the bones but can also show signs of soft tissue injury, arthritis, or alignment problems, and then proceed with either an ultrasound or an MRI if needed to further evaluate soft tissue injuries.

Differential Diagnoses

While it may seem obvious that knee pain originates from the knee, this is not always the case. Sometimes a problem in the lower back, sacroiliac joint, or hip can refer pain to the knee. Your doctor will suspect a referred source based on your physical exam.

For example, pain from a non-knee location will not cause knee tenderness when pressing on it. There will also be no knee swelling present and your knee will have a normal range of motion.

Treatments

Some common treatments for knee pain are listed here (although, not exhaustive) and not all of these treatments are appropriate for every condition.

Self-Care Strategies

Many initial therapies for knee pain are simple, straightforward, and can be done at home.

Rest

The first treatment for most common conditions that cause knee pain is to temporarily rest the joint, allowing the immediate inflammation to subside. Sometimes, this is the only step needed to relieve knee pain.

Ice

Besides rest, applying a cold gel pack, bag of ice, or a bag of frozen vegetables on the knee is perhaps the most commonly used treatment for knee pain. When icing your knee, be sure to not directly apply the ice to your skin and ice for only 15 to 20-minute sessions (multiple times per day).

Support

Depending on the diagnosis, your doctor may recommend knee support to ease your pain. For example, in the case of patellar tendonitis, your doctor may advise supportive taping and patellar tendon straps.

Sometimes a knee brace may be advised to maintain knee stability, as in the case of a collateral ligament injury or partial dislocation of the knee. Likewise, for some types of fractures, a cast or splint may be placed for healing.

Physical Therapy

Physical therapy is an extremely important aspect of treatment for almost all orthopedic conditions. Physical therapists use different techniques to increase strength, regain mobility, and help return patients to their pre-injury level of activity.

The American Academy of Orthopedic Surgeons (AAOS) emphasizes the importance of engaging in an exercise conditioning program (under the guidance of your doctor and physical therapist) after a knee injury or surgery. One knee conditioning program the AAOS suggests focuses on stretching and strengthening the muscles that support the knee, including the quadriceps, hamstrings, inner and outer thigh muscles, and buttocks.

Medications

Medication is often utilized not only to alleviate pain but also to help treat the underlying knee problem.

NSAIDs

Nonsteroidal anti-inflammatory medications, commonly referred to as NSAIDs, are some of the most commonly prescribed medications, especially for patients with knee pain caused by problems such as arthritis, bursitis, and tendonitis.

Injections

If your pain or swelling is persisting despite conservative therapies like rest, ice, and taking an NSAID, your doctor may inject cortisone—a powerful medication that treats inflammation—into your knee.

An example of a knee condition that may warrant a cortisone injection is knee osteoarthritis. Cortisone is a powerful medication that can have side effects, therefore injections should be used sparingly.

Other

Depending on your diagnosis, other medications, like a disease-modifying anti-rheumatic drug (DMARD) to treat rheumatoid arthritis, antibiotics to treat an infected knee joint, or an oral steroid to treat a gout flare, may be warranted.

Complementary and Alternative Therapies

A number of mind-body therapies, such as acupuncture and tai chi, may be used to treat knee pain, especially knee osteoarthritis.

While once popular, the dietary supplements glucosamine and chondroitin have fallen out of favor for treating knee osteoarthritis. This is due to their lack of benefit based on scientific studies; although, some people may obtain mild relief. Like any medication, vitamin, or supplement, be sure to talk with your doctor first before taking it to be certain it is safe for you.

Surgery

Surgery is generally reserved for specific diagnoses, such as:

Certain types of ligament injuries or knee dislocations

Certain knee fractures

Certain infected knee joints that require surgical drainage

Some advanced cases of knee osteoarthritis

Prevention

There are several things you can do to prevent knee injuries and/or prevent the progression of chronic knee conditions, like osteoarthritis:

Lose weight if overweight or obese

Strengthen and stretch your quadriceps and hamstrings muscles

Engage in low-impact aerobic exercises that strengthen the muscles while placing less stress on your knee, like swimming or cycling

Wear knee pads if you work on your knees

A Word From Verywell

Treatment of knee pain depends entirely on the cause of the problem. Therefore, it is of utmost importance that you receive a diagnosis and understand the cause of your symptoms before embarking on a treatment program. If you have not been diagnosed, you should seek medical advice before beginning any treatment plan.