Osteoarthritis (OA) is a joint disease affecting the entire joint, including the cartilage, bone, and joint lining.
Lifestyle factors, age, joint injury, and genetics can all contribute to OA and cause the breakdown of cartilage in the joints.
This can lead to inflammation and changes in the bones and joint tissues. People may experience joint pain, stiffness, and reduced range of motion.
This article looks at the changes that occur in OA and how these cause symptoms.
OA is a disease of the whole joint, which includes:
- fat pads
- lining of the joint, called the synovium
In OA, cartilage breaks down, which results in changes to the bone and joint tissues. Alongside inflammation, this can cause pain, stiffness, and loss of flexibility.
OA can occur in any joint, but it most often affects the knees, hips, lower back, neck, and hands.
The symptoms of OA may appear gradually and can include:
- joint pain
- stiffness, often first thing in the morning or following rest
- reduced range of motion, which may improve with movement
- weakness in the muscles surrounding an affected joint
- loss of balance or instability
- popping or clicking sounds when a joint moves
OA causes inflammation, changes in bone shape, and cartilage deterioration. It is primarily a disease affecting the cartilage.
OA occurs due to a combination of factors,
- physical stress on the body, such as general wear and tear
- physical changes that affect joint function, which may be present from birth or may develop due to excess weight placing pressure on the joint or an injury
- other risk factors, such as aging or genetics
People with the condition have higher levels of pro-inflammatory markers, which indicate inflammation, and proteases, which are enzymes that break down protein. These eventually cause joint deterioration.
In most cases, the first changes that occur in the body due to OA affect the articular cartilage. This is the cartilage covering the ends of the bones where they meet at the joint.
The articular cartilage may erode or become irregular, split, or frayed. If there are erosions in the cartilage, these may gradually expand down to bone level and affect more of the joint surface.
Cartilage consists of water and the matrix, which is a gel-like substance containing different types of protein:
- non-collagenous proteins
Articular cartilage contains a group of cells called chondrocytes, which produce and maintain the matrix.
Injury or damage to the cartilage
Damage to the matrix can also cause thickening of the bone underneath the cartilage and may sometimes cause fluid-filled areas in the bone called bone cysts.
Alongside these changes to the cartilage, there may be inflammation of the joint’s synovium.
These changes can occur gradually, and people may slowly start to experience symptoms of OA, such as pain, stiffness, and limited range of motion.
Certain risk factors may increase the likelihood of OA. These include:
- Age: People over 50 years of age may be more likely to have OA, as the risk increases with age.
- Joint injury: An injury to the joint area, such as a bone fracture or a cartilage or ligament tear, may lead to OA.
- Overuse: Repetitive use of the same joint, such as through a sport or an occupation, may lead to OA.
- Obesity: Excess weight puts extra stress and pressure on the joints, and fat cells can increase inflammation.
- Musculoskeletal abnormalities: Incorrect alignment of the bones or joints may increase the OA risk.
- Weak muscles: If the muscles cannot support the joints properly, this can lead to incorrect alignment and OA.
- Genetics: People with a close family member with OA are more likely to develop the condition themselves.
- Gender: OA is more likely to affect females than males.
- Environmental factors: This includes factors such as level of physical activity, occupation, diet, sex hormones, and bone density.
The complications of OA may include:
- difficulty walking
- incorrect alignment of joints
- reduced range of motion
- pinched nerves in the spine
- side effects from pain relief medications, such as dizziness
According to the Arthritis Foundation (AF), people with OA have an increased risk of falling, which, in turn, raises the risk of fractures.
This increased risk is due to the fact that OA — particularly OA of the knees or hips — can affect balance, weaken muscles, and reduce joint function.
If medications for OA cause dizziness, this may also increase the risk of falls.
The AF also states that weight gain may occur in people with OA if joint pain causes difficulty exercising. Carrying excess weight can lead to various health problems, such as:
If people have concerns about OA complications, they can talk with a healthcare professional about minimizing the risks. The healthcare professional may recommend lifestyle changes, exercise programs, and assistive devices to improve stability.
The following conditions
- Rheumatoid arthritis (RA): RA is an autoimmune condition that causes joint inflammation. It can cause pain and stiffness,
usuallyin the hands, wrists, or knees.
- Psoriatic arthritis (PsA): PsA is a type of arthritis that often affects people with psoriasis. It can cause swollen, painful joints.
- Crystalline arthritis: This occurs when deposits of crystals, such as uric acid or calcium, rub against the joints.
- Bursitis: Bursitis is the term for inflammation of the bursae, which are fluid-filled sacs that cushion the joints.
- Tendinitis: Tendinitis is inflammation of a tendon, the tissue that connects muscle to bone.
- Excess iron: If excess iron builds up in the body, it can cause joint pain,
especiallyin the hands and knees.
- Avascular necrosis: A lack of blood supply to the bone can cause bone tissue death.
- Radiculopathy: Radiculopathy is a pinched nerve in the spine, which can cause pain, weakness, tingling, or numbness.
The outlook for people with OA
Some people may find that OA has little effect on their day-to-day life, while others may have more severe symptoms that affect their ability to carry out everyday tasks.
Treatments can help people manage OA symptoms. In some cases, joint replacement surgery may provide the best long-term outcome for a person with OA.
OA occurs when the cartilage in joints breaks down, causing changes to the bone and joint tissues. The symptoms include pain, stiffness, and reduced mobility.
Various risk factors, such as age and genetics, can combine to cause production of pro-inflammatory markers and proteases, which eventually lead to joint deterioration.
Exercise, medications, and, in some cases, surgery can help manage the symptoms of OA and minimize further joint damage.