The knee joint is a hinge joint, named for its movement that's similar to the opening and closing of a door.
The joint consists of three main bones. The areas where each of these bones meet are covered in a protective material called cartilage. Additional pieces of cartilage known as the meniscus further support the knee.
All of these protective pieces of cartilage keep the bones in the knee from rubbing together, which can be very painful.
The daily demands on the knee and its potential for injury make it a common source for arthritis damage. Different types of arthritis exist, and the type determines which treatment a physician recommends.
According to the American Academy of Orthopaedic Surgeons, more than 100 arthritis types. Some types are more common in the knee than others.
There are many different kinds of arthritis that can affect the knee. Common ones include osteoarthritis and rheumatoid arthritis.
Osteoarthritis is the most common type of knee arthritis. Osteoarthritis is the result of a wearing away of the protective cartilage over the bones.
As a result, the bones of the knee start to rub against each other. This causes bone spurs to develop on the ends of the bones. Bone spurs are painful and can limit a person's movement.
Old injuries to the knee and surrounding joints can continue to affect a person and cause post-traumatic arthritis. This condition occurs after a person has experienced an injury.
These injuries cause extra wear to the knee joint, leading to osteoarthritis. Painful swelling in the knee joint can occur as a result.
Gout is a form of arthritis that causes uric acid crystals to deposit in the joints, including the knee joints. Uric acid is a waste product that forms when body tissues break down.
The crystals are like tiny needles to the knee joint, leading to inflammation that causes pain and swelling.
Rheumatoid arthritis is an autoimmune disorder. This means the body's immune system attacks healthy cells.
The condition tricks the body into thinking healthy tissues, like protective cartilage, are harmful. As a result, the immune system destroys and damages these tissues. This can eventually destroy the joint.
Rheumatoid arthritis can also cause joint swelling and soften the knee bones.
Each type of arthritis in the knee has different causes. For example, osteoarthritis is considered a "wear-and-tear" condition. This means that use of the knee joint eventually wears out the cartilage and ligaments. Osteoarthritis usually affects those older than age 50 because it involves overuse.
Gouty arthritis may be linked to several causes. These include:
- Family history of the condition
- Gender - men more commonly have gout than women
- Obesity - overweight people have more tissue that can be broken down into uric acid
- Certain medications
Doctors don't know exactly what causes rheumatoid arthritis. However, the condition seems to have a genetic component.
Post-traumatic arthritis occurs due to a previous injury to the knee joint. According to the Cleveland Clinic, an estimated 12 percent of patients with knee, hip, or ankle osteoarthritis have post-traumatic arthritis.
The symptoms of knee arthritis tend to get worse over time.
Symptoms commonly linked to knee arthritis include:
- Crepitus, a clicking or popping of the knee joint with movement
- Pain that is worse in the morning
- Pain that seems to be weather-related and gets worse with rain
- Weakness in the knee joint that may cause it to buckle
Warmth and redness over the joint are often symptoms of gouty arthritis, but can be seen with almost any kind of arthritis depending on the degree of inflammation.
Knee arthritis symptoms typically worsen over time. Later-stage arthritis symptoms may include visible joint deformities and stiffness that makes movement nearly impossible. However, it's possible for a person to suddenly experience severe knee arthritis symptoms.
Diagnosing arthritis of the knee
Doctors diagnose knee arthritis through a physical exam, imaging studies, and lab testing.
First, a doctor will review a person's medical history. Next, they will examine the knee by looking at it, touching it, and asking the person to walk on it (if possible).
The doctor will look for signs of potential arthritis and injury. A doctor will look all over the body as some forms of arthritis often affect other areas of the body.
One consideration in diagnosing an arthritis type is where in the body a person experiences their arthritis. Some types of arthritis tend to only affect one knee while others usually affect both knees.
A doctor will also recommend imaging studies to look for changes in the knee joint. Examples could include an X-ray, computed tomography (CT) scan, or magnetic resonance imaging (MRI) scan. The last two scan options help a doctor identify damage to the soft tissues surrounding the knee bones.
Lab tests for rheumatoid factor, an antibody often found in those with rheumatoid arthritis, can help a doctor confirm a diagnosis of rheumatoid arthritis. A doctor may also order a uric acid test for diagnosing gouty arthritis.
Treatments for arthritis of the knee
Doctors often treat early signs of arthritis with at-home care to lessen pain. Ideally, these treatments will help keep arthritis from getting worse. Examples of knee arthritis care at home include:
Wearing a brace can help people with arthritis make their knees more stable.
- Losing weight if a person is overweight
- Choosing low-impact exercises over high-impact ones
- Applying heat or ice to the knee joint to reduce inflammation
- Using physical therapy exercises to strengthen the muscles around the joint and improve flexibility
- Taking over-the-counter pain relievers to reduce inflammation and pain.
- Wearing a knee brace or wrapping an elastic cloth bandage around the knee to boost stability.
Alternative therapies could also help. Although these haven't been proven to work for all people with arthritis, options like acupuncture may help some.
More significant treatment may be needed if these options do not reduce a person's pain and their symptoms get worse. For example, a doctor may prescribe medications used to reduce rheumatoid arthritis symptoms. Examples include methotrexate and sulfasalazine.
Doctors can also use corticosteroid injections to reduce inflammation in the knee joint. However, these usually offer only short-term pain relief.
Knee surgeries are typically the last-resort treatment for knee arthritis. Examples of these procedures include:
- Arthroscopy: This treatment involves inserting small instruments into the knee to look at potential areas of damage. A doctor can remove any damaged bone fragments from the knee or flush out the joint in an attempt to reduce pain. If a meniscus or ligaments are torn around the knee, a doctor may also be able to repair these areas.
- Cartilage grafting: A doctor may take cartilage from another area of the body and graft it around the knee bones.
- Total or partial knee replacements: This involves surgically removing the damaged knee joint and replacing it with a metal or plastic joint. The new joint attempts to work as the knee joint would.
Things to avoid with knee arthritis
Just as there are advised treatments, there are knee arthritis "don'ts" as well.
Don't stop all physical activity
While it can be tempting to limit the use of a painful knee joint, completely cutting out physical activity can cause stiffness, muscle weakness, and limit the range of motion in the joint.
Rest the knee during pain flare-ups and after performing physical exercises.
Don't get corticosteroid injections without discussing the side effects first
Corticosteroid injections can relieve inflammation, but they should be limited to three to four times a year at most. Injections can affect multiple organ systems and cause osteonecrosis, the death of bone tissue.
According to the Mayo Clinic (resource no longer available at www.mayoclinic.org), some doctors are also concerned that injections could weaken the protective cartilage around the knee joint. Patients should always talk to their doctor about side effects before receiving these injections.
Other causes of knee pain
Arthritis isn't the only condition that causes knee pain. Your doctor may try to rule out other conditions that can mimic arthritis.
Examples include illnesses that affect the whole body such as lupus, or sepsis, a severe infection. Inflammation of the protective areas around the joint, such as the tendons, can also cause symptoms that are like arthritis.