Osteoarthritis is the most common form of arthritis. It is a degenerative joint disease that affects the cartilage on the end of the bones. Cartilage is a slippery tissue that provides a smooth gliding surface for joint motion and acts as a cushion between the bones.
Synovium and cartilage are two parts of the joints that help them to work properly. The synovium tissue lines the joint. This tissue produces fluid that lubricates the joint and supplies nutrients and oxygen to the cartilage.
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In people who have osteoarthritis (OA), the cartilage wears away, leading to an overgrowth of bone underneath. The cartilage becomes rough and then breaks down.
When the cartilage breaks down, it causes pain, swelling, and problems with moving the joint. These symptoms can worsen over time.
The knee is one of the joints that is most often affected by osteoarthritis.
OA can affect any joint. This includes large ones such as the knee or hip, and smaller ones such as the joints of the fingers.
The knee is one of the most common joints affected by OA. Knee joints provide flexibility, support, stability, and protection.
OA can develop at any age, but it is most common in people older than 65. According to the Arthritis Foundation, 1 in every 2 adults will develop symptoms of knee OA during their lives.
There are certain risk factors that can make people more susceptible to developing OA. These include:
- Increasing age
- Previous joint injury
- Overuse of the joint
- Weak thigh muscles
What are the stages of osteoarthritis of the knee?
OA of the knee develops gradually over several years. It can be hard to treat as sometimes it is not detected until it has reached an advanced stage. At times, people only begin to experience OA symptoms when the damage done to the knee can't be reversed.
OA progresses in stages. People with knee OA should pay attention to these stages and their symptoms to keep the condition under control.
Stage 0 - normal knee health
Stage 0 is the period after an injury or a physical exam where an X-ray is taken.
X-rays can show detailed pictures of bones to help doctors determine if a patient has OA. At this stage, the X-ray will not show any damage, and the knee joints are still healthy. No signs of OA are present.
Stage 1 - minor
During this stage, small lumps of bone (called osteophytes) may grow in the knee area. The cartilage may be slightly damaged. There is no apparent narrowing of the space between the bones to indicate the cartilage is breaking down.
At stage 1, people with OA are unlikely to feel any pain or experience any discomfort. Even an X-ray of the joint would appear normal at this stage.
Stage 2 - mild
There are four stages of increasing severity for osteoarthritis, ranging from minor to severe.
During this stage, the symptoms of OA begin to get more noticeable, and doctors can see some specific signs of wear.
X-rays and scans of the knee joints will clearly show more bone lump growth, and the cartilage will begin to slightly thin.
The space in between the bones will be normal, but the contacting bone surfaces and tissues are hardening. Hardening tissue makes the bone thicker and denser. In turn, this leads to the development of a thin layer of bone beneath the cartilage in the joints.
People with OA may begin to experience symptoms such as stiffness or joint pain. The area around the knee joint may start to feel particularly stiff and uncomfortable after sitting for a long time.
Though there may be some minor damage, the bones are not rubbing or scraping against each other. Synovial fluid is still present which helps to reduce friction and increase knee movement.
Stage 3 - moderate
During this stage, the damage to the cartilage has progressed. The gap between the bones has narrowed, and cartilage loss can be seen on X-rays.
At stage 3, people with OA of the knee may begin to experience pain and discomfort while performing daily activities. Running, walking, kneeling, and bending may cause discomfort. People with OA of the knee may also start to experience joint inflammation.
As OA progresses, the cartilage continues to thin and break down. The bones react by becoming thicker. They start to grow outward and form lumps.
The tissue lining the joint becomes inflamed and may produce extra fluid that causes increased swelling. This is known commonly as "water on the knee" or medically as synovitis.
Stage 4 - severe
This stage is the most advanced stage of OA. At this stage, the symptoms of OA are very visible. The joint space between the bones is further reduced, causing the cartilage to break down further.
This advanced breakdown stiffens the joint and leads to constant inflammation and less fluid around the joint. There is more friction in the joint and greater pain and discomfort when moving.
X-rays will show bone on bone, meaning that there is either very little cartilage left or it has completely worn away.
People with OA will likely develop more bone lumps and experience intense pain frequently while doing simple tasks such as walking. In severe cases, the bones may become deformed and angulated because of asymmetric loss of cartilage.
How is osteoarthritis of the knee diagnosed?
Diagnosing OA is not always simple. As mentioned earlier, X-rays may not always pick up problems with the knee.
If someone is having knee pain, their doctor will collect information on their personal and family medical history, perform a full physical examination, and order special diagnostic tests.
The patient will be asked to describe any symptoms such as when pain is experienced. During the physical exam, the doctor will examine the joints and test their overall range of motion. They will pay close attention to any areas that are tender, painful, or swollen.
MRI (magnetic resonance imaging) scans or tests on the fluid in the joints may also be used to detect any early signs of OA. In some instances, blood tests may be helpful in diagnosis to rule out other diseases such as gout and rheumatoid arthritis.
Treatments for osteoarthritis of the knee
Treatment options vary according to the stage of OA and how quickly it is progressing.
A knee brace can relieve the symptoms of mild osteoarthritis.
During Stage 0, when the knee is considered normal, no treatment is often recommended. If there is pain, over-the-counter pain medication is prescribed.
During stage 1, symptoms may last from 6 to 8 weeks and then go away. At this point, a cautious approach is often taken. Acetaminophens or other non-prescription medication may be recommended for pain relief. Special exercises may be recommended to build strength and mobility.
It can take several months before the disease progresses to stage 2. Pain relief and physical therapy are common treatments. A special knee brace may help to relieve pressure on the joint surface.
People with knee OA may need to change their routine activities to reduce knee pain. Cortisone or lubrication injections may also offer some relief.
OA may reach stage 3 and stage 4 anywhere from 3 to 6 months after onset. At these stages, there is either very little cartilage left, or it has been destroyed. Joint replacement surgery or a similar operation is likely to be the final treatment method.
How can osteoarthritis of the knee be prevented?
OA was originally described as a disorder where the joints wore out over time. The disease was considered to be unavoidable.
It is now known that OA is not an inevitable part of aging but due to a combination of factors. Many of these can be changed or prevented, helping lower the risk of OA of the knee.
Avoiding overusing joints and maintaining a healthy weight plays a significant role in preventing OA of the knee. Being overweight puts extra pressure on the knees. Over time, this added weight wears down the cushion between the joints faster.
OA of the knee can be hard to treat if people do not seek help until it has reached advanced stages such as 3 or 4. At this point, the damage is irreversible and drastic treatment such as surgery is often the only option.
The symptoms and progression of OA can vary from person to person. People with any OA symptoms should see a doctor for tests and treatment.