Anatomy illustration of the knee.Source: MedicineNet
Facts you should know about knee pain
- Knee pain is a common problem with many causes, from acute injuries to complications of medical conditions.
- Knee pain can be localized to a specific area of the knee or be diffuse throughout the knee.
- Knee pain is often accompanied by physical restriction.
- A thorough physical examination will usually establish the diagnosis of knee pain.
- The treatment of knee pain depends on the underlying cause.
- The prognosis of knee pain, even severe knee pain, is usually good although it might require surgery or other interventions.
What is knee pain?
Pain is a common knee problem that can originate in any of the bony structures compromising the knee joint (femur, tibia, fibula), the kneecap (patella), or the ligaments, tendons, and cartilage (meniscus) of the knee.
- Knee pain can be aggravated by physical activity, as well as obesity, affected by the surrounding muscles and their movements, and be triggered by other problems (such as a foot injury).
- Knee pain can affect people of all ages, and home remedies can be helpful unless it becomes severe.
Torn ACL Symptoms and Signs
With an acute injury, the patient often describes that they heard a loud pop and then developed intense pain in the knee. The pain makes walking or weight-bearing very difficult. The knee joint will begin to swell within a few hours because of bleeding within the joint, making it difficult to straighten the knee.
A female runner helps a male runner experiencing knee pain.Source: iStock
What are knee pain symptoms and signs?
The location of the knee pain can vary depending on which structure is involved. With infection or an inflammatory process, the whole knee might be swollen and painful, while a torn meniscus or fracture of a bone gives symptoms only in one specific location. A Baker cyst will usually cause pain in the back of the knee.
The severity of the joint pain can vary, from a minor ache to severe and disabling pain.
Some of the other signs and symptoms that accompany knee pain are
- difficulty weight-bearing or walking due to instability of the knee,
- limping due to discomfort,
- difficulty walking up or down steps due to ligament damage (sprain),
- locking of the knee (unable to bend the knee),
- redness and swelling,
- inability to extend the knee, and
- shifting weight to the opposite knee and foot.
X-ray of a tibial plateau fracture.Source: "TibPlateauF" by James Heilman, MD
What causes knee pain?
Knee pain can be divided into three major categories:
Below is a list of some of the more common causes of knee pain. This is not an all-inclusive list but rather highlights a few common causes of knee pain in each of the above categories.
Acute knee injuries
Fractures: A direct blow to the bony structure can cause one of the bones in the knee to break. This is usually a very obvious and painful knee injury. Most knee fractures are not only painful but will also interfere with the proper functioning of the knee (such as kneecap fracture) or make it very painful to bear weight (such as tibial plateau fracture). All fractures need immediate medical attention. Many fractures require significant force, and a thorough examination is performed to detect other injuries.
Ligament injuries: The most common injury is the ACL (anterior cruciate ligament) injury. An ACL injury is often a sports-related injury due to a sudden stop and change in directions. The remaining ligaments (posterior cruciate ligament, lateral collateral ligament, and medial collateral ligament) are injured less frequently.
Meniscus injuries: The menisci (medial and lateral) are made of cartilage and act as shock absorbers between bones in the knee. Twisting the knee can injure the meniscus.
Dislocation: The knee joint can be dislocated, which is a medical emergency that requires immediate attention. Knee dislocation can compromise blood flow to the leg and have other related problems. This injury often occurs during a motor-vehicle accident when the knee hits the dashboard.
X-ray of a patellar tendon rupture.Source: "Patellar tendon rupture" by James Heilman, MD
What medical conditions cause knee pain?
Rheumatoid arthritis is an autoimmune condition that can affect any joint in the body. It can cause severe pain and disability, as well as swelling.
Gout is a form of arthritis that is most commonly found in the big toe, though it can also affect the knee. Gout tends to flare up and is extremely painful during acute episodes. When there is no flare-up, the knee can be pain-free.
With septic arthritis (infectious arthritis), the knee joint can become infected; this leads to pain, swelling, and fever. This condition requires antibiotics and drainage treatments as soon as possible.
Chronic use/overuse conditions
Patellar tendinitis is an inflammation of the tendons connecting the kneecap (patella) to the shinbone (the bone of the lower leg). Patellar tendinitis is a chronic condition often found in individuals repeating the same motion during exercise (such as runners and cyclists).
Patellofemoral pain syndrome is caused by degeneration or stress under the kneecap (patella) where it meets the thighbone (femur). Patellofemoral pain syndrome occurs in runners and cyclists.
Osteoarthritis: a wearing down of cartilage of the joint due to use and age
Prepatellar bursitis: Inflammation to the bursa (fluid-filled sac) in front of the kneecap may cause anterior knee pain.
Children can develop inflammation of the point of bony insertion of the patellar tendon (Osgood-Schlatter disease).
See a medical illustration of the knee's anatomy plus our entire medical gallery of human anatomy and physiology
A 3-D rendered illustration of the knee, a runner, an electrician kneeling, and an overweight woman performing squats.Source: iStock
What are risk factors for knee pain?
Biomechanics: The knee joint is complicated in its operation and is used frequently throughout the day. Any change in the movement of the joint (leg-length difference, change in walking style due to back problems) can cause subtle changes and cause pain and injuries.
Excess weight: The stress on the knee joint is increased with excess weight. Obesity also increases the risk of knee osteoarthritis as the cartilage breaks down more rapidly.
Overuse during repetitive motions as are found during certain exercises (jogging, skiing) or work conditions (long periods of kneeling) can cause the breakdown of cartilage and lead to pain.
A man with knee pain has trouble walking down the stairs.Source: iStock
When should you see a doctor for knee pain?
Any pain that does not respond to rest or disappears within a few days should be evaluated by a doctor. In addition, the following are symptoms and signs in the knee that a doctor should evaluate: swelling, inability to bend, deformity, unable to walk or discomfort while walking, significant pain, and fever.
Osteoarthritis (OA): Treatment, Symptoms, Diagnosis
A doctor examines a male patient with knee pain.Source: Getty Images
What procedures and tests diagnose knee pain?
A health care professional will begin by asking questions related to the person's general health and then specifically to the nature of the knee pain (how long, how severe, does anything make it feel better or worse, etc.).
Next, an examination of the knee will be performed. This will include bending the knee through the full range of motion, checking for the stability of the ligaments, and evaluating for any tenderness and swelling. It is often helpful to compare the results of the examination of the painful knee with the other knee. Frequently, this is all that is required to make a diagnosis and start treatment. In several research studies, it has been found that an experienced examiner is as reliable as an X-ray examination.
Sometimes the doctor might want to do further studies such as the following tests.
A plain X-ray can establish fractures and degenerative changes in the knee.
MRI is used to evaluate the soft tissues of the knee for ligament tears or cartilage and muscle injuries.
If gout, arthritis, or other medical conditions are suspected, a health care professional might order blood tests.
Removal of joint fluid (arthrocentesis)
Some conditions are best diagnosed by the removal of a small amount of fluid from the knee joint. During arthrocentesis, a small needle is placed into your joint, and fluid is withdrawn. This is done in a sterile method. The fluid is then sent to the laboratory for evaluation. This procedure is especially helpful if an infected knee joint is suspected or to distinguish between gout and different forms of arthritis. If there is a collection of blood in the joint due to a traumatic injury, removing the fluid can help relieve the pain.
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A physical therapist manipulates the knee of a female patient.Source: iStock
Which types of doctors treat knee pain?
Often knee pain can be evaluated and treated by your primary care doctor. If the knee pain requires surgery or the cause of the pain needs further evaluation, an orthopedic surgeon will usually be consulted. With arthritis, gout, or inflammatory joint problems a rheumatologist may be consulted.
What is the treatment for knee pain?
Treatments for knee pain are as varied as the conditions that can cause the pain.
Medications might be prescribed to treat an underlying medical condition or for pain relief.
If you are taking over-the-counter anti-inflammatory pain medications regularly for your knee pain, you should see your doctor be evaluated.
Sometimes physical therapy sessions to strengthen the muscles around the knee will make it more stable and help guarantee the best mechanical movements. Working with a physical therapist can help avoid injuries or further worsening of an injury.
Injecting medications directly into your knee might help in certain situations. The two most common injections are corticosteroids and lubricants. Corticosteroid injections can help arthritis and other inflammations of the knee. They usually need to be repeated every few months. Lubricants that are similar to the fluid already in your knee joint can help with movement and pain.
Model of a knee replacement with titanium hinge joint.Source: iStock
Will surgery treat and cure knee pain?
Knee operations range from arthroscopic knee surgery to total knee replacement. Arthroscopic knee surgery is a very common surgical procedure that allows the physician to look inside your knee through a few small holes and a fiberoptic camera. The surgeon can repair many of the injuries and remove small pieces of loose bones or cartilage. This is a common outpatient procedure.
Partial knee replacement: The surgeon replaces the damaged portions of the knee with plastic and metal parts. Because only part of the knee joint is replaced, this procedure has a shorter recovery than a total knee replacement.
Total knee replacement: In this procedure, the knee is replaced with an artificial joint.
Acupuncture has shown some relief of knee pain, especially in patients with osteoarthritis. Glucosamine and chondroitin supplements have shown mixed results in research studies.
A female ices her knee to relieve pain.Source: Getty Images/PhotoAlto
What natural home remedies relieve knee pain?
Over-the-counter pain medications can frequently alleviate the pain. If someone is taking these medications on a regular basis, he or she should see a health care professional to evaluate the knee pain for proper diagnosis and to avoid the potential side effects of chronic medication use.
- The RICE mnemonic is often helpful, especially for minor injuries:
- Rest: Rest the joint, and take a break from your usual activities involving the knee joint.
- Ice: Applying ice can help with pain and inflammation.
- Compress: A compression bandage can help prevent swelling and help knee alignment. It should not be tight and should be removed at night.
- Elevate: Elevation can help with swelling and resting of the knee.
What are the complications of knee pain?
Frequently, knee pain will disappear without ever finding a specific cause. Depending on the underlying cause of the pain, the condition can progress and lead to more serious injuries or complications. Usually, these complications are long-term and result in worsening pain or an increasing difficulty to walk.
Can you prevent knee pain?
There can be many reasons for knee pain. Therefore, there are different strategies to prevent the pain depending on the underlying cause. Running on soft surfaces or decreasing the amount of running can help if the pain is due to overuse. Avoiding any direct injuries to the knee including wearing a seatbelt can prevent traumatic injuries. Weight loss can be helpful for many different forms of knee pain.
Can knee pain come back after treatment?
Frequently, knee pain will occur for a short period of time and then resolve. Sometimes it can return a few weeks or months later. For chronic knee pain, it is important to get it evaluated to avoid further damage to cartilage, bones, or ligaments. Prognosis depends on the underlying causes of the pain.
With modern surgical techniques, it's possible to relieve many knee pain syndromes and return to an active lifestyle.
Medically Reviewed on 4/19/2022
American Academy of Orthopaedic Surgeons. "Knee Exercises." Feb. 2009. <https://orthoinfo.aaos.org/en/staying-healthy/knee-exercises/>.
"Knee Injuries." Temple Orthopaedics & Sports Medicine. <https://ortho.templehealth.org/content/knee_injuries.htm>.
Meding, J.B., P.M. Faris, and K.E. Davis. "Bilateral Total Hip and Knee Arthroplasties: Average 10-Year Follow-Up." J Arthroplasty May 22, 2017. Epub ahead of print.