OA is the most common type. It’s a progressive condition that usually appears after midlife where the cartilage in the knee joint gradually wears away.
RA is an inflammatory autoimmune disease that can occur at any age. It involves other joints and can affect a number of other body systems.
Arthritis can also develop after a knee injury. Post-traumatic arthritis can result from a torn meniscus, ligament injury, or knee fracture. Symptoms can appear several years following an injury.
OA and RA can cause similar symptoms, but there are also some key differences. Learn more here about how to recognize each type.
Gradual increase in pain
Arthritis pain usually starts slowly, although it can appear suddenly in some cases.
At first, you may notice pain in the morning or after you’ve been inactive for a while.
Your knees may hurt when you:
- climb stairs
- stand up from a sitting position
- walk on a flat surface
- sit down for a while
Knee pain that wakes you up from sleep can be a symptom of OA.
For people with RA, the symptoms often start in the smaller joints. They are also more likely to be symmetrical, affecting both sides of the body. The joint may be warm and red.
With OA, symptoms may progress rapidly or they may develop over several years, depending on the individual. Symptoms can worsen and then remain stable for a long time, and they can vary day to day.
Factors that may cause worsening of symptoms include:
- cold weather
- excessive activity
With RA, symptoms usually appear over several weeks, but they can develop or worsen in a few days. A flare can happen when disease activity increases. Triggers vary and can include changes in medication.
Swelling or tenderness
Arthritis of the knee can sometimes cause inflammation.
With OA, this can be:
- hard swelling, due to the formation of bone spurs (osteophytes)
- soft swelling, as inflammation causes extra fluid to collect around the joint
Swelling may be more noticeable after a long period of inactivity, like when you first wake up in the morning.
Joint swelling is common with RA, as it’s an inflammatory disease.
People with RA may also have other symptoms, such as:
- general feeling of being unwell
Other body organs that can be affected with inflammatory changes include the eyes, heart, and lungs.
This is because RA is a systemic disease, which means it affects the whole body. OA, meanwhile, only has a direct impact on the affected joint.
Buckling and locking
Over time, damage to the joint can cause the knee structure to become unstable. This can cause it to give way or buckle.
RA can cause damage to the tendons, which join the muscle to the bone. This damage can affect the knee’s stability.
Bone spurs can also develop as the cartilage erodes and the bones rub together. These produce a bumpy surface that can cause the joint to stick or lock up, making it hard to bend or straighten out.
Cracking or popping sounds
When you bend or straighten your knee, you may feel a grinding sensation or hear cracking or popping sounds. Doctors call this crepitus.
These symptoms can occur when you’ve lost some of the cartilage that helps with smooth range of motion. Both OA and RA can result in cartilage damage.
When cartilage is damaged, rough surfaces and bone spurs develop. As you move your joints, these irregular areas rub against each other.
Poor range of motion
The bone and cartilage changes that occur with OA of the knee or after a knee injury can make it hard for your knee joints to move smoothly. It can become hard to move the knee to walk, stand up, and carry out other everyday movements.
People with RA may find it hard to bend and flex their knee or to walk, due to pain and swelling. Damage to the joint can also affect mobility.
In time, you may need a cane or walker to help you stay balanced and mobile.
Loss of joint space
Some of the effects arthritis has on the knee are not obvious. Diagnostic tools, such as a knee X-ray, can help detect internal damage.
Cartilage normally occupies a space around the bones, where it cushions the joint. An X-ray image of the knees can detect the results of cartilage damage
Deformities of the knee
The appearance of the knee can change during a flare and as damage progresses.
In RA, swelling and redness are common during a flare. In the long term, persistent inflammation can result in permanent damage to the cartilage and the tendons. This can affect the shape and appearance of the knee.
With OA, the muscles around the knee can weaken, resulting in a sunken appearance. The knees can start to point toward each other or bend outward.
Knee deformities range from barely noticeable to severe and debilitating.
Treatment will depend on the type of arthritis a person has.
Home remedies and medical options
- weight management
- physical activity, like:
- tai chi
- water exercise
- nonsteroidal anti-inflammatory drugs (NSAIDs), like ibuprofen or aspirin, to reduce pain and inflammation
- tramadol, available by prescription for more severe pain
- corticosteroid injections to reduce inflammation
- other medications, such as disease-modifying antirheumatic drugs (DMARDs) for RA but not OA
- applying heat and cold pads to relieve pain and swelling
- topical creams, such as capsaicin
- use of a cane or walker to help you balance
- cognitive behavioral therapy
Experts say that people who play an active role in managing their OA, for example, are likely to see a more positive outcome. You can do so by learning about arthritis, becoming aware of what makes symptoms better or worse, and making decisions with your doctor.
Discover exercises to strengthen the knee muscles.
If pain and a loss of mobility are severe enough to affect your quality of life, a doctor may recommend surgery.
- partial surgery, to remove damaged tissue
- total knee replacement, which will give you an artificial knee joint
A doctor can help you decide your best option.
Treatment is available for different types of arthritis. The earlier you seek treatment, the more likely it is to be effective.
See your doctor if:
- pain or inflammation are not responding to any kind of treatment
- symptoms get worse, or you have other symptoms, such as a fever
- symptoms affect your daily life, including sleeping and walking
The doctor may:
- ask about symptoms in joints as well as other body organ involvement
- consider your medical history and other health conditions
- carry out a physical examination
- do some imaging tests to identify the cause of pain and mobility loss
- carry out blood tests for RA, lupus, or other conditions that can cause joint pain
The symptoms of knee arthritis will depend, to some extent, on the type of arthritis. Pain, swelling, and a loss of mobility are common with different types of arthritis.
There’s no cure for arthritis, but treatment can relieve symptoms, slow the progress of the disease, and reduce the risk of complications. In the case of RA, medication may help reduce the frequency and severity of flares.
Strategies, such as weight management and exercise, may help postpone or eliminate the need for surgery in the future.
Your doctor will help you make the best decisions for the type of knee arthritis you have.