Knee Osteoarthritis

What Is Knee Osteoarthritis? 

Knee osteoarthritis occurs when cartilage tissue that cushions a knee joint wears down. Bones rub against each other, causing swelling and painful, stiff knee movements.

Osteoarthritis is the most common type of knee arthritis. An estimated 242 million people worldwide have knee or hip osteoarthritis that limits their movement. The condition can affect one or both knees. 

What does osteoarthritis in the knee feel like? 

Knee pain is the most common sign of knee osteoarthritis. You may have pain when moving, standing, sitting or applying pressure to your knee. 

Other signs of knee osteoarthritis include:

• Difficulty bending or straightening your knee 
• Feeling like your knee is buckling or giving out 
• Grinding or crackling sound (crepitus) when moving your knee
• Pain that worsens with activity
• Stiffness that worsens after inactivity

When should you see a medical professional?

You should see your primary care physician if you have knee pain or other symptoms that affect your ability to walk and enjoy life.

Your doctor may refer you to a joint specialist, such as:

• Orthopedic doctor 
• Rheumatologist

Why do you have knee osteoarthritis?

Years of wear on your knees, as well as other factors, can cause cartilage to wear down.

Cartilage is a slippery, shock-absorbing substance at the end of your bones. As cartilage becomes thinner, bones press against each other. Lumps of extra bone tissue called bone spurs (osteophytes) can form, causing more friction and pain.

What are the types of knee osteoarthritis?

Doctors classify knee osteoarthritis as primary or secondary, depending on the cause. 

• Primary knee osteoarthritis occurs when cartilage wears down due to age and use. 
• Secondary knee osteoarthritis occurs from distinct causes, such as trauma to the knee joint, limb difference or underlying inflammatory conditions like rheumatoid arthritis. 

Are you at risk for knee osteoarthritis?

Anyone can develop osteoarthritis in a knee. Certain risk factors — some of them preventable — increase your risk.

These risk factors include:

• Being a female who’s older than 45 
• Excess weight or obesity
• Family history of osteoarthritis
• Knee injuries
• Metabolic diseases, such as diabetes 
• Repetitive stress on your knees from sports, hobbies or jobs

How do doctors diagnose knee osteoarthritis?

Your doctor will perform a physical exam to check for joint tenderness, swelling and instability.

You may also get one or more of these tests:

• Blood test: A blood test can help your provider rule out other arthritic causes of knee pain, such as rheumatoid arthritis and gout.
• Imaging tests: A knee X-ray can show bone spurs and loss of cartilage between bones. Your provider may also order a CT scan, MRI or ultrasound to get a better look at the bones and soft tissues in your knee.
• Joint fluid test: Less commonly, your provider may take a sample of fluid from the knee joint. They test this fluid for signs of infection or inflammatory conditions like gout.

How do doctors treat knee osteoarthritis?

Treatments for knee osteoarthritis depend on the severity of symptoms and how the condition affects your daily life.

Your doctor will partner with you to create a personalized treatment plan that meets your unique needs. Treatments may include:

Nonsurgical treatments for knee osteoarthritis

Certain actions can ease symptoms and protect knee cartilage. You can:

• Alternate applying heat and ice to the knee
• Participate in physical therapy to improve range of motion, strength and flexibility
• Use an assistive walking device, such as a cane or walker
• Wear a knee brace to stabilize the joint

Medication treatments for knee osteoarthritis

Different medications can ease knee pain and swelling. Your doctor may recommend one or more of these treatments:

• Injectable corticosteroids 
• Injectable lubricants (hyaluronic acid)
• Oral or topical nonsteroidal anti-inflammatory drugs (NSAIDS) 
• Pain relievers

Platelet-rich plasma (PRP) therapy for knee osteoarthritis

PRP therapy concentrates a large number of platelets in a small volume of plasma. The treatment helps boost your body’s natural healing response.

During PRP therapy, a health care provider:

• Draws your blood 
• Uses a centrifuge machine to separate platelets from other blood cells
• Uses the centrifuge to concentrate the platelets within the plasma 
• Injects the platelet-rich plasma into your knee

Genicular nerve ablation for knee osteoarthritis

Genicular nerve ablation (GNA) is a minimally invasive, outpatient procedure for patients with chronic knee pain who aren’t candidates for knee replacement or don’t want surgery. GNA targets the small sensory genicular nerves that transmit pain signals from the knee.

Interventional radiologists, pain management providers and physical medicine and rehabilitation specialists (physiatrists) are among the UCLA Health experts who perform this procedure.

GNA is a two-step procedure:  

1. First, your doctor injects a local numbing agent (anesthetic) into the targeted genicular nerves (nerve block). If you experience significant pain relief, this indicates that the genicular nerves are causing your pain and GNA is a good treatment option. 
2. Then, your doctor uses image guidance to place an ablation probe near each targeted nerve. The probe directs heat energy to the nerves, creating lesions that disrupt the nerve’s ability to send pain signals.

Genicular artery embolization for knee osteoarthritis

UCLA Health was one of the first centers in the country to offer a minimally invasive procedure for knee osteoarthritis called genicular artery embolization (GAE). The procedure reduces blood flow to the knee lining (synovium), which eases pain and swelling. For patients whose symptoms don’t improve with conservative care, GAE is a nonsurgical option that may reduce pain and improve function.

An interventional radiologist performs this outpatient procedure while you're under conscious sedation (a relaxed, sleepy state). This physician uses imaging to perform nonsurgical treatments through a blood vessel and a small cut in your skin.

During GAE, your doctor:

• Threads a thin, hollow tube (catheter) into an artery in your upper thigh
• Uses imaging technology to guide the catheter to the arteries that carry blood to the knee lining 
• Injects tiny particles through the catheter into the knee arteries. These particles block blood flow to the knee lining, reducing inflammation and improving or eliminating pain.

Surgical treatments for knee osteoarthritis

If symptoms don’t improve with nonsurgical treatments and affect your quality of life, your doctor may refer you to an orthopedic surgeon. Surgical treatments for knee osteoarthritis include:

• Cartilage grafting: Your surgeon replaces damaged cartilage with healthy cartilage from another part of your knee or a donor. This treatment can help younger people who have small areas of cartilage damage.
• Knee osteotomy: Your surgeon reshapes the end of the shinbone (tibia) or thigh bone (femur) to realign the knee and take pressure off the damaged cartilage. Osteotomy can help younger, active patients with knee malalignment or early-stage osteoarthritis on only one side of the knee. 
• Partial knee resurfacing: Your surgeon uses small metal or plastic implants to cover (resurface) sections of the knee that have worn or damaged cartilage.

Knee replacement surgery

Knee replacement surgery uses metal and plastic implants to resurface one or more knee compartments, such as the inner (medial), outer (lateral) or front (patellofemoral, which is under the kneecap) part of the knee. Our experts developed the most commonly used plastic in joint replacement surgery and we have one of the region’s most trusted joint replacement programs.

We offer:

• Partial knee replacement: Your surgeon resurfaces just one knee compartment. 
• Total knee replacement: Your surgeon resurfaces all three (inner, outer and front) knee compartments.

Promising joint regeneration therapies

UCLA Health is part of a multi-institutional, federally funded research team working to develop new treatments for knee osteoarthritis. Our physician-scientists are helping to create injectable medications to help the body make new, healthy knee cartilage and repair damaged joints. These regenerative therapies will be available in clinical trials. 

Can knee osteoarthritis get better on its own?

Unfortunately, no. Knee osteoarthritis is a degenerative condition, which means the cartilage will continue to wear down over time.

Actions, such as maintaining a healthy weight and minimizing stress on your knees, can ease symptoms and help you stay active. If the condition impacts your ability to enjoy life despite conservative treatment options, your doctor may recommend a knee replacement or other surgery.

Can you prevent knee osteoarthritis?

Certain actions can help protect your knees and lower the risk of osteoarthritis.

You can:

• Achieve and maintain a healthy weight.
• Maintain healthy blood sugar levels to manage diabetes.
• Minimize activities that require repetitive knee bending, such as kneeling and squatting.
• Participate in lower-impact activities, such as walking, cycling or swimming. 
• Seek help to quit smoking. Smoking slows blood flow to your bones and affects bone formation, weakening bones throughout your body.
• Strengthen the muscles around your knees. 
• Walk or run on softer surfaces.
• Wear shoes with good arch support and shock absorption.