Knee Osteoarthritis

What is Knee Osteoarthritis? How is it diagnosed?

What is Knee Osteoarthritis?

Osteoarthritis (OA), also called degenerative joint disease (DJD), is the most common type of arthritis, a condition that translates to “joint inflammation.” Because osteoarthritis is so common, the words osteoarthritis and arthritis are often used interchangeably unless otherwise specified. 

Osteoarthritis causes inflammation to joints from the breakdown of cartilage that lines the ends of the bones that form the joints. Without adequate cartilage to cushion and absorb shock, your joints endure increased friction and irritation, resulting in pain, swelling, and stiffness. In severe cases of osteoarthritis, the cartilage wears away so much that the ends of the bones within a joint rub directly against each other, causing bone breakdown and severe pain.

The knee joint is one of the most common joints to develop osteoarthritis due to the fact that it is a large weight bearing joint that is subjected to repetitive forces and pressure from supporting your bodyweight when you stand, walk, squat, and go up and down stairs. Knee osteoarthritis develops when the cartilage that lines the ends of the femur (thighbone) and tibia (shinbone) that form the knee joint wear down, causing knee joint pain, stiffness, and swelling.

How is it diagnosed?

History & Physical Exam

A thorough history and physical examination by your healthcare provider can help determine whether you have knee osteoarthritis. Your healthcare provider will ask you questions about your symptoms and how and when your symptoms began to get a clearer picture of how your condition occurred. 

Risk factors that increase your risk of developing knee osteoarthritis include:

• Older age
• Being overweight
• Female sex, especially after menopause
• Prior knee injury, including an ACL or meniscus tear
• Altered knee joint alignment (being knock-kneed or bow-legged)
• Repeated stress to the knee joints from work or exercise that involves prolonged standing, kneeling, and running
• Inflammatory conditions like diabetes and hyperlipidemia (high cholesterol)
• Low bone mineral density (osteopenia and osteoporosis)
• Knee joint laxity
• Leg muscle weakness
• Genetic bone diseases

In addition to discussing your medical history, your healthcare provider will perform a physical examination to assess your knee for pain, swelling, and mobility. Your healthcare provider will feel the soft tissues around your knee to see if anything is tender to the touch, and bend and straighten your knee to see if your range of motion is affected or if certain motions are painful.

Your healthcare provider will also test the strength of your leg muscles and examine your ability to walk and move your knee joint. 

Imaging 

While a thorough medical history and physical examination may be able to provide information to suggest that you have knee osteoarthritis, imaging studies are needed to ultimately confirm a diagnosis of knee osteoarthritis. Different imaging methods can be used to examine the tissues and structures of your knee, which include:

• X-Ray: An x-ray is a 2-dimensional image produced by radiation that examines the structure of your bones. Your healthcare provider will order an x-ray to make sure that you do not have a broken bone and to assess the extent of your knee osteoarthritis. 
• MRI: An MRI, or magnetic resonance imaging, is a 3-dimensional imaging scan that is produced by magnetic fields. MRIs more clearly illustrate soft tissues of the body and can be used to assess the integrity of structures within your knee like ligaments, tendons, and cartilage. An MRI is not needed to diagnose knee osteoarthritis but may be used to check for injury to other parts of your knee.

Osteoarthritis is graded based on the extent of cartilage breakdown and resulting bone damage and narrowing of a joint that can be observed on an x-ray. Bone damage from osteoarthritis is characterized by both sclerosis, or abnormal thickening of bone, and the formation of bone spurs (osteophytes), or abnormal growths of jagged bone that form within a joint, from increased stress and friction within the joint.

Osteoarthritis is graded according to the following criteria:

• Grade 1 (Minor): No joint space narrowing with possible formation of bone spurs
• Grade 2 (Mild): Minimal joint space narrowing with definitive formation of bone spurs
• Grade 3 (Moderate): Definitive joint space narrowing, moderate formation of bone spurs, and mild sclerosis and damage at the ends of bones
• Grade 4 (Severe): Severe joint space narrowing, large formation of bone spurs, and significant sclerosis and damage at the ends of bones

Knee Osteoarthritis Treatment Options (Surgical vs Non-Surgical)

Surgery for knee osteoarthritis is only recommended after all other non-surgical treatment methods have been exhausted with little improvement in your symptoms. If you are unable to achieve lasting pain relief from your knee osteoarthritis, a total knee replacement may be performed to reduce your pain, restore your range of motion, improve your ability to stand, walk, and go up and down stairs, and improve your quality of life.

Whether you have surgery or not, physical therapy is extremely important for managing your knee osteoarthritis to strengthen and support your knee joint to help alleviate some of your symptoms.

Surgery – Total Knee Replacement

When non-surgical treatment methods fail to yield a lasting improvement in your symptoms, a total knee replacement, also called total knee arthroplasty, is typically performed. A total knee replacement is used to decrease pain and improve the function of your knee with walking, bending, getting in and out of a chair, and going up and down stairs. 

A total knee replacement is performed through an open surgery where an incision is made down the front of your knee to access your knee joint. During your total knee replacement, the ends of your femur and tibia bones that join to form your knee joint will be shaved down and topped with metal caps on the ends. These metal caps will serve as the new joint surfaces to replace the damaged cartilage and bone from the ends of your femur and tibia.

A total knee replacement can either be performed in the outpatient surgical setting where you will be able to go home the same day of your surgery, or might require you to stay overnight in the hospital for 1-2 nights to make sure that your pain levels are under control and that you are able to get out of bed and walk before going home.

Sometimes, only one side of the knee joint has significant osteoarthritis while the cartilage and bone on the other side of the knee joint are generally healthy and undamaged. In these instances, a partial knee replacement may be performed. Also called a unicompartmental knee replacement, a partial knee replacement is used to resurface the joint surfaces on just one side of the knee joint. The ends of the tibia and femur bones will be shaved down and topped with metal caps like a total knee replacement, but only on either the inner side or the outer side of the knee joint. Partial knee replacements are most commonly performed for knee osteoarthritis on the inner (medial) side of the knee.

Another alternative to a total knee replacement is a patellofemoral replacement in which the undersurface of the kneecap, or patella, is resurfaced. Patellofemoral replacements are performed for people who have significant knee arthritis affecting only the patella with little effect on the tibia and femur bones that form the knee joint. A plastic button is used to replace cartilage and bone that are removed from the undersurface of the patella while the groove in the end of the femur bone where the patella rests will be resurfaced with a metal implant.

Non-Surgical Management of Knee Osteoarthritis

Non-surgical management for knee osteoarthritis includes a variety of different treatment options to address your knee pain, stiffness, swelling, and leg muscle weakness. Resting, applying ice to your knee, and use of nonsteroidal antiinflammatory drugs (NSAIDs) are recommended to help decrease knee pain and inflammation. Your healthcare provider may also trial one or more rounds of injections into your knee joint to help relieve pain and inflammation. These include cortisone injections that use steroid medication to decrease inflammation or hyaluronic acid (gel) injections that aim to restore some of the natural joint fluid within the knee.

Physical therapy is also always recommended for patients with knee osteoarthritis to improve knee joint mobility and the strength and flexibility of surrounding muscles. As your knee joint becomes arthritic and inflamed over time, the irritated joint endures most of the pressure of your bodyweight when you stand, walk, and bend down. 

When you strengthen the surrounding muscles, especially your glutes and quads, to support your knee joint and overall leg alignment, your muscles can help offload your knee joint and support more of your body weight to decrease pressure within your knee joint. A physical therapist can work with you to decrease your pain and swelling, restore normal knee joint range of motion, and improve the strength of the muscles that control your hip, knee, and ankle joints to stabilize your leg. 

Many people will find relief from their symptoms of knee osteoarthritis when they strengthen their surrounding leg muscles. If you are overweight, weight loss will also significantly help decrease your knee pain by reducing pressure within your knee joint.

While severe knee osteoarthritis often requires a total knee replacement, knee osteoarthritis in its earlier stages can be effectively treated and managed with physical therapy to strengthen the muscles that support your knee joint and prevent progression of your knee osteoarthritis from getting worse. If treatment is started early enough for less severe forms of knee osteoarthritis, total knee replacement surgery may be avoided.

Total Knee Replacement FAQs

General

How common is a Total Knee Replacement?

Between 700,000 and 800,000 total knee replacements are performed each year in the United States. The number of surgeries continues to rise significantly each year, expecting to reach over one million total knee replacements in the next several years and 2.6 million total knee replacements by the year 2060.

How long do knee replacements last?

Knee replacements typically last for 15-20 years. After this period of time, the implants used to replace the knee joint surfaces start to wear out. A knee replacement revision can then be performed to remove your old knee replacement implants and replace them with new ones.

Treatment Decision

Who is not a good candidate for surgery?

People with significant comorbidities such as heart and lung problems and bleeding disorders may not be healthy enough to undergo any type of surgery and are usually not good candidates for a total knee replacement. People with significant osteoporosis, or low bone mineral density causing brittle bones, may not have strong enough bones to support a knee replacement and will likely have to improve their bone mineral density first before undergoing surgery.

People with mild to moderate forms of knee osteoarthritis also aren’t the best candidates for surgery as they are likely to benefit from physical therapy and other conservative treatment options.

Can I wait to have surgery?

A total knee replacement is performed as the last resort treatment option for knee osteoarthritis. Waiting to have surgery while trying other treatment methods like pain medications, physical therapy, and cortisone injections is recommended for at least 3-6 months. 

After Surgery

Can I shower or take a bath?

You should avoid taking a bath or submerging your leg in water during the first two to three weeks after surgery to decrease the risk of your incision reopening or becoming infected. While you will be allowed to shower, you should avoid getting your incision wet during the first two weeks of recovery and should use a plastic bag or plastic wrap secured to your leg with tape to keep your incision and bandages dry.

Will I be able to walk after surgery?

You will be able to walk after surgery for a total knee replacement and will be encouraged to do so as soon as possible by your healthcare providers. You will likely need to use a walker to help support some of your weight as you walk to decrease pressure on your knee in the first week or more after surgery. Most people use a walker or cane to assist with their balance with walking for at least the first month after surgery and gradually decrease their usage of an assistive device as they gain more knee range of motion, strength, and stability.

Can I go up and down the stairs?

You will be able to go up and down the stairs after total knee replacement surgery but will likely be able to only go up or down one step at a time until you build up more strength and stability in your knee. Your physical therapist will instruct you in the proper sequencing up and down the stairs, which will involve leading with the unoperated leg when going up the stairs and leading with the operated leg when going down the stairs.

How long will I use a walker or a cane to walk?

Use of an assistive device like a walker or cane is typically needed for at least the first month after total knee replacement surgery to help with your balance when you walk. Your physical therapist will determine if and when it is appropriate for you to progress from using a walker to using a cane, and if you can walk independently without an assistive device depending on the quality and safety of your gait pattern.

When can I return to work/?

If your job is generally sedentary, you can likely return to work 4-6 weeks after your total knee replacement. For jobs that require prolonged standing, walking, or bending, you may not return to work until 3 months or more depending on your progress with rehabilitation and how physically demanding your job duties are.

How can I minimize scarring?

You can minimize scarring by avoiding picking at your surgical incision and leaving your stitches, staples, or steri-strips in place until they naturally come off or are removed by your healthcare provider. Keeping your incision clean and dry will also help avoid infection which can delay healing and worsen scarring.

Can I dislocate my knee replacement? 

Knee dislocation after total knee replacement is very rare, and typically only occurs with forceful, direct impact to the leg, obese indiviudals, or patients with signficant knee deformities. Walking, bending down, performing exercises, and being stretched by a physical therapist are not forceful enough motions to cause a total knee replacement to dislocate.