Primary vs. secondary osteoarthritis: What is the difference?

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Primary osteoarthritis occurs for no known reason. It is the most common form of arthritis that affects adults and older adults.

Most people will develop this type of primary osteoarthritis by age 65 years. It affects about 80% of people over the age of 75 years.

Though the exact cause of primary osteoarthritis is unknown and not well understood, experts attribute its development to environmental and genetic factors, as well as aging and degenerative changes.

The primary risk factor is advanced age, though other factors can also contribute to its development. These factors include menopause, issues with joint alignment, and obesity.

Primary osteoarthritis causes joint stiffness, pain, and mobility issues. It can also lead to muscle weakness and changes in gait that can affect balance.

The most commonly affected joint is the knee. Other common areas include the hips and hands.

It is a progressive condition. This means that over time, damage to the joint will slowly get worse, causing more severe symptoms.

Learn more about osteoarthritis.

Secondary osteoarthritis, unlike primary, develops from a preexisting joint abnormality due to factors such as infections or trauma. Underlying conditions, such as inflammatory arthritis, Paget’s disease, and infectious arthritis, can also lead to secondary osteoarthritis.

It shares similar occurrence rates, with about 60% of adults over the age of 65 years having symptomatic osteoarthritis and about 80% showing radiographic (X-ray or other imaging test) evidence of osteoarthritis with or without symptoms.

As with primary osteoarthritis, secondary osteoarthritis typically affects the knee but can also affect other joints. The condition presents with joint pain, stiffness, and reduced range of motion and may lead to muscle weakness or issues with balance.

Also like primary osteoarthritis, secondary osteoarthritis is progressive and will slowly cause worsening damage to the affected joints and more severe symptoms.

Read about the early symptoms of osteoarthritis.

Osteoarthritis may have no clear cause, or its cause may be apparent.

Primary

Primary osteoarthritis does not have a clear underlying cause. It is associated with advanced age.

Experts suspect that both genetic and environmental factors contribute to its development.

People assigned female at birth have a higher risk of developing primary osteoarthritis, particularly following menopause.

Secondary

Secondary osteoarthritis has a known underlying cause.

Common causes include:

• infectious arthritis
• congenital joint disorders
• trauma or injury
• osteopetrosis, a rare disorder that causes the bones to grow abnormally and become denser than usual
• avascular necrosis
• inflammatory arthritis
• metabolic disorders, such as hemochromatosis or Wilson’s disease
• Paget’s disease
• osteochondritis dissecans
• Marfan syndrome
• Ehlers-Danlos syndrome

Osteoarthritis has several potential risk factors. Living with one more risk factor does not mean a person will definitely develop a condition. Instead, it means they have an increased chance of developing it.

Risk factors may be modifiable or nonmodifiable. Modifiable means a person can take steps to reduce their risk. Nonmodifiable means a person cannot do anything to change their risk.

According to the Centers for Disease Control and Prevention (CDC), common risk factors for osteoarthritis include:

• Sex: People assigned female at birth have a higher risk, particularly past age 50 years.
• Joint injury or overuse: Both injury and overuse (repetitive motions or stress) can damage a joint and increase the risk of osteoarthritis in the joint.
• Age: Osteoarthritis is heavily associated with advanced age.
• Genetics: A person with a family history of osteoarthritis has a higher risk of developing it.
• Other joint involvement: Osteoarthritis in one joint increases the risk of developing the condition in another joint.
• Obesity: Having obesity places extra strain on the knees and hips. Metabolic effects due to obesity may also increase risk.

It may not be possible to prevent osteoarthritis, but taking some steps may help reduce a person’s risk. A 2021 study suggests that all people may benefit from a lifelong prevention strategy to help protect the joints.

Some steps the authors recommend taking include:

• avoiding sports or activities that risk knee or joint injury
• avoiding occupations that place excessive strain on the joints
• taking steps to maintain or reduce weight
• performing strength training to prevent weakness

A person can take these steps at nearly all stages of their life.

Osteoarthritis treatment involves a combination of pharmaceutical and nonpharmaceutical interventions. Typical goals for osteoarthritis include reducing pain and minimizing functional movement loss.

Nonpharmaceutical treatments include:

• performing strength exercises
• avoiding activities that increase joint load or cause pain
• losing weight, if necessary
• performing occupational therapy
• using braces, canes, splints, or crutches

Pharmaceutical treatment options for osteoarthritis include oral, topical, and injected medications.

Oral medications may include the use of nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen.

A person may apply NSAIDs topically. This can help prevent some of the potential side effects or complications associated with oral NSAID use.

In some cases, a doctor may recommend injections, such as glucocorticoid injections. However, people do not always respond well to these injections.

People who are in good physical health and not responding well to other treatments may benefit from surgical correction or joint replacement.

People who are not good candidates for surgery or who do not want to undergo a procedure may benefit from opioids.

Individuals should discuss treatment options with their healthcare professional.

The following sections provide answers to some frequently asked questions about osteoarthritis.

What is a secondary condition of osteoarthritis?

Secondary osteoarthritis occurs due to an underlying health condition or injury that causes a joint abnormality. Several factors can cause or put a person at risk of osteoarthritis, such as sports injury, metabolic disorders, or congenital joint disorders.

What is the most common cause of secondary osteoarthritis?

The knee is the most common joint osteoarthritis affects. The typical causes include wear and tear as well as loss of cartilage. Other causes may also include trauma, injury to the ligaments or tendons, and fractures.

Age is also a risk factor for osteoarthritis. The condition is common in people over age 65 years.

How bad is primary osteoarthritis?

Primary osteoarthritis is the most common type of arthritis and most often affects people over the age of 65 years. It is a progressive disease, meaning it will slowly worsen over time. Some people will develop a disability due to the condition. However, osteoarthritis affects people differently.

Primary and secondary osteoarthritis vary only in their underlying cause. Both share similar symptoms, treatments, and risk factors.

Both conditions are progressive and tend to worsen in severity over time.

A person can take steps to help reduce their risk of developing osteoarthritis, such as managing weight and doing regular strength training. However, it may not be possible to prevent its development.

Treatment can help reduce pain and maintain or restore some movement in the joint.