Causes of Knee Pain

Common Types and Causes of Knee Pain


Knee pain is a common medical condition affecting people of all ages and stages of life. Most knee pain can be attributed to aging, injury, overuse, or other medical conditions. Determining the underlying causes of knee pain can be the key to effective treatment and relief from pain, inflammation, and mobility problems that interfere with daily activities.

Fortunately, with physical therapy and other noninvasive treatments, many people with knee pain are able to achieve relief without surgery. Continue reading to learn about different types and causes of knee pain, treatments to improve symptoms, and what to do after a serious knee injury.

Anatomy of the Knee

Before we dive into conditions that cause knee pain, let us look at the structures that form the knee joint.

The knee is the largest joint in the body and is comprised of three bones:

Femur: the upper leg, or thigh bone
Tibia: the lower leg, or shinbone
Patella: the kneecap, or triangular bone that sits atop the other bones in the front of the knee

Cartilage covers the ends of these bones and acts as a cushion to absorb shock and enable bones to glide against each other smoothly during movement. Tendons are the connective tissues that attach muscles to bones. Ligaments are another type of connective tissue that stabilize structures and attach bone to bone.

The hamstrings are the muscles that run from the hip to just below the knee. The quadriceps are four muscles located at the front of the thigh. These muscles work in concert to bend and straighten the knees. Problems with any of these structures in and around the knee joint can cause pain and other symptoms.

What Are The Causes of Knee Pain?

Now, let us explore the most common causes of knee pain and why you may be experiencing knee pain while standing, squatting, or walking.

Dislocated Kneecap

Also known as patellar dislocation, this injury occurs when the kneecap slides out of position, usually from sudden impact to or a forceful twisting of the knee. You might hear a “pop” when this happens and notice the patella has shifted to an odd angle.

In some cases, the kneecap will go back into position itself. It is also common for someone with a dislocated kneecap to have severe knee pain and be unable to straighten their knee or walk. Never try to reset the patella yourself. Instead, go to your local urgent care or preferred healthcare provider as soon as possible.

Patellar Tendinitis

The patellar tendon connects the patella bone (kneecap) to the tibia (shin bone.) Repeated stress on this tendon through intense physical activity, can cause microtears and pain, inflammation, and weakening as the body attempts to repair itself.

Patellar tendinitis pain often increases with movement and can make it hard to do simple tasks like get up from a seated position or walk up and down stairs. Physical therapy for knee pain helps to stretch and strengthen the muscles around the knee and is often the first line of treatment for patellar tendinitis.

Osgood-Schlatter Disease

Osgood-Schlatter disease typically affects adolescents who are experiencing growth spurts. As children grow, the knee structures experience rapid change. Sports and other physical activity put added stress on these structures, causing pain and swelling.

Someone with Osgood-Schlatter disease may have tenderness, pain, and inflammation just below the knee where the kneecap connects to the shinbone. Ice, rest, and physical therapy can reduce symptoms of Osgood-Schlatter disease.


Arthritis is inflammation of any of the joints in the body. It is not a single condition, but an umbrella term for more than 100 different conditions that cause joint pain, swelling, and stiffness. Although arthritis can involve any joint, it commonly affects the knee. People who experience pain while bending the knee may have some form of arthritis.

The most common types of arthritis that cause knee pain are:

Osteoarthritis: degenerative form of arthritis resulting from joint “wear and tear,” occurs most frequently in people in their 50s and up
Posttraumatic Arthritis: form of arthritis caused by injury to the knee like a broken bone, cartilage tear, or ligament tear
Rheumatoid Arthritis: a chronic autoimmune disease that causes the body to attack its own tissues, including the knee joints on both sides of the body

Arthritis of the knee is common, impacting 50 million adults worldwide. Although arthritis has no cure, treatment can provide pain relief and possibly slow the progression of the disease. Low-impact exercise, heat and ice, and physical therapy are beneficial for many individuals with arthritis of the knee.


Bursae are small, slippery, fluid-filled sacs that function as cushions for the muscles, ligaments, tendons, and skin as they glide over the bones. There are more than 140 bursae in the body, including those located near the knee joint.

If a bursa near the knee joint becomes irritated through overuse, injury, or infection, the knee can feel painful, warm, tender, or swollen. Knee pain when squatting is also common with bursitis. Treatment for bursitis of the knee may include medication, corticosteroid injection, physical therapy, and/or surgery.

Iliotibial Band Syndrome

Pain experienced on the outside of the knee may be a sign of iliotibial band syndrome (ITBS.) The iliotibial band, or IT band, is a long, fibrous tendon that stretches from the hip down the outside of the thigh and knee to the top of the shinbone.

If the IT band becomes too tight, it can rub against the knee and hip bones, causing hip and knee clicking, swelling, and/or pain. ITBS pain is described as an aching and burning sensation that becomes worse with activity. Knee pain when running is a common sign of IIBS.

Runners, cyclists, soccer players, basketball players, and other athletes are more prone to developing this condition. People with significant foot pronation and weakness of the hip abductors are also at risk of developing ITBS. Muscle retraining through physical therapy, medication, rest, and surgery may alleviate ITBS symptoms.

Knee Fracture

Knee fractures are breaks in the patella in the front of the knee. Physical trauma from car accidents, sports, and falls typically cause knee fractures. People with osteoarthritis, people who play high-impact sports, and those who have had a previous injury have a higher risk of a knee fracture.

A misshapen joint or limb or a bone that protrudes out of the skin are obvious signs of a knee fracture. Less severe knee fractures do not typically need surgery unless the bones are significantly displaced. Casts, splints, or braces are often used to stabilize the joint and physical therapy helps reduce stiffness and increase flexibility and range of motion as one recovers from a knee fracture.

Ligament Tear

The knee contains four major ligaments. These ligaments connect the thighbone to the shinbone and cushion and support the knee joint. The anterior crucial ligament (ACL) located at the center of the knee controls rotation and forward movement of the shinbone. The ACL is one of the most commonly-injured knee ligaments. The ACL can be overstretched or torn by sudden and forceful twisting of the knee if the feet remain planted in one direction.

ACL tears are common among athletes who play football, soccer, and basketball. Knee pain levels vary from person to person, but many describe a common “popping” sensation and sensation of the knee giving out after an ACL tear.

After an ACL tear, the leg may “buckle” when standing. Conservative treatments including rest and physical therapy. Knee braces help stabilize the knee joint to avoid further injury. Surgery is recommended for some patients who tear their ACL.

Torn Meniscus

Activities that cause you to rotate the knee, especially while putting one’s full body weight on the knee joint can tear the menisci. These are the C-shaped cartilage located between the thighbones and the shinbones.

Symptoms of a meniscus tear are not always immediate. Stiffness, swelling, pain, and difficulty straightening the knee are signs of a possible tear. It is also common have knee pain when walking or feel like the knee is going to “give out.” Someone with a torn meniscus may not have immediate symptoms. They can develop a few hours or even a day after the initial injury.

Conservative treatments are effective in some cases, while others require surgery to repair the cartilage. Physical therapy has been shown to be as beneficial as surgery to help patients recovering from a torn meniscus improve joint flexibility and strength.

Baker’s Cyst

A Baker’s cyst is a condition that causes pain behind the knee. It typically presents with other conditions like arthritis and torn cartilage that create fluid buildup in the knee joint. In addition to pain behind the knee, someone with a Baker’s cyst may notice swelling, stiffness, and difficult extending the leg.

Some Baker’s cysts will disappear on their own. Over-the-counter medications can help with pain. A physical therapist can provide exercises to strengthen the muscles around the knee and increase rand of motion for better mobility and pain relief. Sometimes a procedure called “needle aspiration’ is necessary to drain the excess fluid from the cyst.

Knee Pain Treatment

Treating knee pain involves a comprehensive approach to address pain and strengthen and stabilize the joint. Rest, nonprescription medication, and physical therapy are the first, most conservative treatments prescribed for common knee injuries and conditions. From there, surgery may be medically necessary to reconstruct, remove, or repair damage knee structures.

When to Call a Doctor for Knee Pain

This is an overview of the most common conditions that cause knee pain, but it is far from complete. It is important to see your doctor if you have knee pain, swelling, or stiffness that does not improve after a week of home treatment.

If your knee locks or buckles when you bend it or try to stand or walk, see a qualified healthcare professional as soon as possible such as a physical therapist. Call 911 if you experience a knee injury that causes visible deformation after an injury. If you are experiencing extreme pain or tingling and numbness in the knee and/or lower leg, see your physician as soon as possible.

Knee pain can often be relieved with physical therapy. To find out if you are a candidate for physical therapy, visit this link to find a clinic near you.

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