Top Causes of Knee Pain When Sitting or Bending

Knee pain when you bend or flex the joint is often caused by arthritis, tendonitis, bursitis, or patellofemoral pain. If your knees hurt when sitting, it may be from sitting in the wrong position or sitting for too long.

Most adults will experience knee pain when sitting on their heels or cross-legged. These positions put stress on the knee joints that can cause discomfort. However, if simply bending your knee or lowering yourself to sit in a chair causes pain, you should have your knee examined.

When determining the cause of pain, your healthcare provider will consider the location of your pain and the activities that exacerbate it.

This article details different reasons your knees may hurt when bending, flexing, or sitting. It also discusses ways to relieve knee pain and how to protect your knees to prevent pain.

Causes of Knee Pain Upon Bending

The knee joint is made up of several parts. The shin bone (tibia), the thigh bone (femur), and the kneecap (patella) are held together by muscles, tendons, and ligaments. These joints are cushioned by cartilage and other soft tissue structures like joint capsules, linings, and bursa. Knee pain can signal a problem with any of those structures.

Here is a look at different reasons why your knee may hurt when bending your leg or sitting.

Arthritis

Arthritis of the knee can be either osteoarthritis or inflammatory arthritis, which includes rheumatoid arthritis (RA) and psoriatic arthritis. These types of arthritis have different root causes, but both feel burning, twisting, aching, or pins-and-needles pains. Arthritis may also cause your knee to lock up when you bend it or hurt when you try to bear weight on that leg.

Osteoarthritis—the more common type of knee arthritis—occurs when the joint structures break down. Commonly known as wear-and-tear arthritis, it is usually due to past injuries or overuse that comes with aging.

In osteoarthritis, the soft tissues and cartilage that cushion your joints erode, making movement painful. Without the soft tissues to protect the bones in your knees, your knees may lock in place or be more prone to injury.

RA is an autoimmune disease that causes your immune system to attack your joint tissues. Over time, the inflammation causes the soft tissues to break down.

With RA, your knees may feel stiff (usually worse in the morning) and it may be difficult for you to rotate your legs or bend your knees. And after you sit down, it may be difficult to extend your legs so you can stand up again. In contrast to OA, pain with RA typically worsens with activity.

Runner’s Knee

Runner’s knee, also known as patellofemoral syndrome, is pain near your knee cap that occurs due to damage to the soft tissues in your knee. Runner’s knee can be caused by:

• Overexertion during exercise
• A hamstring injury that puts more strain on your knees
• Being born with an abnormally shaped kneecap
• A kneecap that doesn’t glide properly

Track and field and contact sports athletes are especially prone to runner's knees.

Symptoms of runner’s knee include:

• A dull ache when sitting down
• Pain when bending or straightening your knee
• Knee pain when standing up after sitting for too long

You may experience knee weakness or notice a rubbing or clicking sensation. You might also hear a popping or cracking noise as you bend your knee. Any of these symptoms can cause discomfort and make exercise difficult.

Runner’s knee is often temporary and can improve with rest, physical therapy, and knee support, Your healthcare provider can help you come up with an individual care plan that works for your specific condition. 

Tendonitis

Several tendons support the knee. Inflammation of any of these tendons (tendonitis) can cause knee pain upon bending the leg. The location and type of pain provide clues to the cause and include:

• Hamstring tendonitis causes pain on the back of the thigh and behind the knee when bending.
• Patellar tendonitis is felt in the front of the knee or at the base of the knee cap and causes a very sharp or burning pain when bending
• Quadriceps tendonitis causes pain above or in front of the kneecap

Iliotiobal (IT) band syndrome

The iliotibial (IT) band is a thick band of fibrous tissue that starts at the hip and runs along the outer thigh to the outer shin bone (tibia) just below the knee joint. IT band syndrome causes a burning pain on the outside of the knee that spreads to the hip or thigh.

It most commonly affects runners or cyclists and is more common when you are new to the activity. Knee pain from IT band syndrome typically occurs when exercising, but may persist after the workout is over.

Without treatment, the pain can become constant and change from a dull ache or burn to sharp, more severe pain accompanied by swelling on the outside of the knee. 

Prepatellar Bursitis

The prepatellar bursa is a thin, fluid-filled sack over the kneecap. Kneeling for extended periods can cause the bursa to become inflamed and irritated, a condition known as prepatellar bursitis or housemaid’s knee. 

Symptoms of prepatellar or knee bursitis include:

• Pain when bending or straightening the leg
• Reduced or limited range of motion
• Swelling or redness in the front of the knee

Prepatellar bursitis is common in carpet layers, plumbers, gardeners, and other professions that require a lot of kneeling. The biggest risk with knee bursitis is infection. 

Baker’s Cyst 

A Baker’s cyst is a fluid-filled sac in the back of the knee joint. Excess knee-joint fluid pushes through the back of the joint capsule, causing a cyst that protrudes into the back area of the knee (popliteal fossa). It is sometimes called a popliteal cyst and causes a visible bulge. 

Baker’s cysts cause pain and swelling in the back of the knee joint that gets worse with activity. The pain is often described as joint tightening and stiffness upon bending or straightening. 

Symptoms of a ruptured Baker's cyst are similar to deep vein thrombosis, a dangerous type of blood clot, and should be evaluated by a healthcare provider.

When to See a Healthcare Provider

Persistent knee problems should be evaluated by a healthcare provider. Talk with a healthcare provider if you have:

• New knee pain
• Your normal knee pain has changed or worsened
• Your pain has persisted for several days
• You have an injury
• You are uncertain of the cause of your knee pain

If your pain is severe, chronic, or seems to signal a serious musculoskeletal condition, your primary care provider may refer you to a specialist:

• An orthopedist is a surgeon specializing in treating joint and bone conditions, especially those that could improve with surgical intervention.
• A rheumatologist is a physician who diagnoses and treats autoimmune conditions like RA.

Diagnosing Knee Pain

Diagnosing knee pain often requires a combination of a physical exam, imaging studies, and blood work. Your healthcare provider may use the following to evaluate your knee pain.

Physical Exam

A physical exam can help your healthcare provider understand precisely where and why you are hurting. The healthcare provider may feel your knee to pinpoint swelling, irritation, or potential injuries. They may ask you to walk, stretch, sit down, or bend your knee to observe your range of motion.

Lab Tests

After you have a physical exam, your healthcare provider may request blood work. Lab tests can help differentiate between osteoarthritis and RA or other autoimmune diseases. Blood work also rules out infections, cancer, Lyme disease, or other illnesses that can cause knee pain.

Imaging

An X-ray or magnetic resonance imaging (MRI) can help your healthcare provider visualize the condition of your bones and joints. Imaging studies are usually used to identify bone fractures, arthritis, soft-tissue injuries, and other structural problems with the knee.  

Treatment

Your treatment plan will depend on the cause and severity of your knee pain. Treatment options range from basic lifestyle changes to surgery.

Lifestyle Changes

Some interventions for knee pain include changes to your lifestyle. Weight loss is commonly recommended as a first-line treatment for knee pain. Your doctor may recommend walking, swimming, and other low-impact exercises to help you burn calories without putting too much stress on your knees.

Some people find the anti-inflammatory diet helpful for relieving knee pain. In addition, turmeric, lemon water, antioxidants, and omega-3 fatty acids may help reduce the inflammation in your knee joints.

If your knees hurt when sitting down at rest, it could be a sign that you're sitting in an awkward position or simply sitting too long. To differentiate between knee pain caused by structural problems versus the way you sit, try the following:

• Stretch your legs during the day. Sitting for six to eight hours during the workday may make your knees stiff and increase your risk of other health concerns like cardiovascular disease. Get up and walk around every hour or half-hour to give your knees some gentle exercise.
• Avoid or limit certain sitting positions. Some sitting positions can cause more stress on your knees than others. For example, sitting on the floor cross-legged, kneeling, or sitting on your heels stresses the ligaments around the knee cap.
• Find a comfortable chair. When sitting, your knees should be comfortable—about the same level as your hips and at a 90-degree angle. If you’re adjusting an office chair, ensure the seat is just below your kneecaps when standing next to it. This should help ensure your feet are flat on the floor while sitting.

Check with your healthcare provider if your knees still hurt after making these adjustments. They can help you determine if a condition is causing your knee pain.

Heat or Ice

Holding a cold or hot compress to your knee may help reduce pain and joint swelling. Ice is typically recommended for new injuries and inflammation. Heat can help relieve pain associated with joint stiffness and chronic pain.

Medications

Over-the-counter (OTC) pain relievers like Tylenol (acetaminophen), Advil (ibuprofen), and Aleve (naproxen) are commonly used to relieve knee pain.

If OTC medications don't relieve your pain, your healthcare provider may prescribe a stronger non-steroidal anti-inflammatory drug (NSAID) or a steroid pain reliever, such as prednisone.

A short course of opioid pain relievers may be prescribed for severe, acute pain. However, opioids have a high risk of addiction and should only be used sparingly.

Make sure you ask your healthcare provider if it is safe to take any of these medications. Certain people, such as those with liver disease, cannot take acetaminophen, while others, such as those with coronary artery disease or chronic kidney disease, cannot take NSAIDs

Physical Therapy

Depending on the cause of your knee pain, your healthcare provider may recommend physical therapy. A physical therapist can provide exercises to strengthen the muscles that support the knee and other therapies, including electronic muscle stimulation and ultrasound.

Acupuncture

Research shows acupuncture can help to relieve chronic pain. However, the research is mixed on whether it is effective for knee pain.

One study found no benefit of acupuncture treatments on people over age 50 with knee osteoarthritis. While another study found it may be effective in reducing osteoarthritis knee pain.

Braces and Orthotics

A knee brace may be used to support the knee while working or exercising. Orthotic shoe inserts may also help to reduce knee strain.

Surgery

In some situations, your healthcare provider may recommend that you consider knee replacement surgery. This surgery can be helpful to people who have extensive tissue or bone damage from arthritis. 

As with many other surgeries and invasive procedures, a knee replacement is often considered only after more conservative measures have been tried. Nonetheless, a medical study from 2013 found promising results for knee surgery and enhanced mobility for patients with advanced osteoarthritis.

Prevention

Knee problems are more common in people who are overweight or obese. Keeping an active lifestyle and following a healthy diet can help manage your weight and prevent some knee pain. A 2013 medical study found that exercise is the first and most common form of therapy that healthcare providers recommend for managing knee pain from osteoarthritis.

Exercises like swimming and yoga can keep your knees flexible without much of the joint strain of high-intensity sports. Moderate strength-building exercises can also help you avoid knee injuries by strengthening your thighs and legs. Strong leg muscles can reduce the stress on your knees.

Coping

Knee pain can interfere with daily life and be difficult to cope with. It can hinder your ability to work, exercise, and do things you enjoy. Pain can also put you in a bad mood. It is normal to feel frustrated when pain keeps you from doing things want—or need—to do. You may find you have a shorter fuse.

Try to be patient with yourself and those around you. Work closely with your healthcare team to find the right treatment strategies to ease your pain. Follow your doctor's and physical therapist's advice and keep your appointments. If you feel like the treatment plan isn't working, speak up.