Osteoarthritis is the most common form of arthritis worldwide, affecting millions of people and causing joint pain, stiffness, and reduced mobility. While there is no cure for this condition, understanding its causes, symptoms, and management strategies can help people maintain their quality of life and stay active.

How Common Is Osteoarthritis?

Osteoarthritis stands as the most widespread type of arthritis affecting people around the globe. According to data from the United States, approximately 33 million adults live with this condition.^[1] When we look at older populations, the numbers become even more striking. Research suggests that more than 80% of adults older than 55 have osteoarthritis, although not all of them experience noticeable symptoms.^[2] In fact, only about 60% of people with osteoarthritis actually feel or notice their symptoms, which means many individuals have the condition without even knowing it.

Globally, the World Health Organization reports that in 2019, about 528 million people worldwide were living with osteoarthritis, representing a 113% increase since 1990.^[3] This dramatic rise reflects both aging populations and increasing rates of obesity and joint injuries. The condition doesn’t affect everyone equally. About 73% of people living with osteoarthritis are older than 55 years, and approximately 60% are female.^[3] The knee is by far the most frequently affected joint, with 365 million people experiencing knee osteoarthritis, followed by the hip and hand.

Osteoarthritis is most common among adults aged 45 and older, but it’s important to understand that it is not simply an inevitable part of aging.^[4] Younger people can also develop osteoarthritis, especially if they have experienced joint injuries or trauma. The condition typically begins to show symptoms in people’s late 40s to mid-50s, although it can affect much younger individuals, particularly athletes or those who have had previous joint injuries such as torn ligaments or cartilage damage.

What Causes Osteoarthritis?

The exact cause of osteoarthritis remains somewhat unclear to medical experts, but we know it involves a complex interaction of multiple factors. The condition occurs when the protective cartilage (the smooth, rubbery tissue that cushions the ends of bones in joints) breaks down and wears away over time.^[1] This cartilage normally acts like a shock absorber and lubricant, helping bones move smoothly past each other. When osteoarthritis develops, this protective layer deteriorates, eventually causing bones to rub directly against each other during movement.

Osteoarthritis is classified into two main categories based on its origins. Primary osteoarthritis is the most common type and develops gradually over time without any obvious preceding cause. Experts believe it results from the normal wear and tear of using joints throughout life, combined with the natural aging process.^[2] As people get older, their joints naturally experience low-level damage from everyday activities, and in most cases, the body repairs this damage without problems. However, in osteoarthritis, this repair process fails, and the cartilage progressively breaks down.

Secondary osteoarthritis occurs when something directly damages a joint before osteoarthritis develops. This type can develop much more rapidly than primary osteoarthritis, sometimes appearing within just a few years after the initial damage.^[2] Common causes include sports injuries, falls, car accidents, or any trauma that affects the joint structure. Other forms of arthritis, particularly inflammatory types like rheumatoid arthritis, gout, or psoriatic arthritis, can damage cartilage severely enough to eventually cause osteoarthritis in those joints.

Health conditions that affect joints can also lead to secondary osteoarthritis. These include genetic disorders like Ehlers-Danlos syndrome or joint hypermobility syndrome, as well as conditions like avascular necrosis (when bone tissue dies due to lack of blood supply), infectious arthritis, or metabolic disorders such as hemochromatosis or Wilson’s disease.^[5]

Who Is at Higher Risk?

Several factors can increase a person’s chances of developing osteoarthritis. Age is one of the most significant risk factors, with the likelihood of developing the condition increasing substantially in middle-aged and older adults.^[4] After age 50, osteoarthritis becomes more common in women than in men, though researchers aren’t entirely sure why this gender difference exists.

Body weight plays a crucial role in osteoarthritis risk, particularly for joints that bear weight. Being overweight or obese places extra stress and pressure on joints, especially the hips and knees.^[2] The relationship between weight and osteoarthritis goes beyond simple mechanical stress. Fat cells also produce substances that promote inflammation throughout the body, and this inflammation can contribute to joint damage. Research has shown that for every pound of weight a person carries, their knees experience an additional 3 to 6 pounds of pressure during movement.

Joint injury or overuse represents another major risk factor. People who have injured a joint in the past, whether through sports, accidents, or occupational activities, are more likely to develop osteoarthritis in that joint later in life.^[4] Jobs or sports that involve repetitive motions, such as repeated knee bending, jumping, twisting, running, or throwing, can increase risk by putting excessive stress on joints over time. Athletes who participate in high-impact sports face particular risk if they sustain injuries.

Genetics also plays a role in osteoarthritis risk. People who have family members with osteoarthritis are more likely to develop the condition themselves, suggesting that some people inherit genetic characteristics that make their joints more vulnerable.^[4] However, researchers haven’t identified a single gene responsible for this increased risk; rather, multiple genes likely contribute to a person’s susceptibility.

Certain health conditions can increase osteoarthritis risk as well. These include diabetes, high cholesterol (also called hyperlipidemia), and some autoimmune diseases that affect joints.^[3] Additionally, people with joint abnormalities present from birth or developmental problems affecting joint alignment may be more prone to developing osteoarthritis as they age.

Common Symptoms and How They Affect Daily Life

The hallmark symptom of osteoarthritis is joint pain. This pain typically worsens with activity and improves with rest, though patterns can vary from person to person.^[1] Many people notice a phenomenon sometimes called “gelling,” where their joints feel particularly stiff after periods of inactivity, such as sitting for a long time or first thing in the morning. However, unlike some other forms of arthritis, morning stiffness in osteoarthritis usually lasts less than 30 minutes.

Stiffness is another common complaint, making it difficult to move the affected joint through its full range of motion. People with osteoarthritis often find they can’t bend or straighten their joints as far as they used to, which can interfere with everyday activities like climbing stairs, opening jars, or getting dressed.^[1] This loss of flexibility develops gradually over time as the joint structures change.

When touching or applying light pressure to an affected joint, many people experience tenderness. The area around the joint may also become swollen, particularly after using it extensively.^[1] This swelling can result from inflammation in the soft tissues surrounding the joint or from the accumulation of fluid within the joint space itself. Some people notice that their joints look visibly larger or differently shaped than they used to.

A distinctive feature of osteoarthritis is a grating sensation or sound during joint movement. People often describe hearing popping, crackling, or grinding noises when they use affected joints.^[1] This sensation, called crepitus, occurs because damaged cartilage creates an uneven surface that produces these sounds as bones move against each other. While unsettling, crepitus itself isn’t necessarily painful, though it often accompanies other symptoms.

As osteoarthritis progresses, extra bits of bone called bone spurs may form around the affected joint. These feel like hard lumps and can sometimes be seen or felt under the skin, particularly in the hands and fingers.^[1] In advanced cases, joints may feel unstable or loose, as if they might give way during use. Some people notice that affected joints look noticeably different from how they appeared before, with visible deformity or changes in alignment.

The impact of these symptoms on daily life can be significant. While some people experience mild symptoms that come and go, others face continuous and severe problems that make it difficult to carry out everyday activities.^[6] Simple tasks like brushing teeth, getting dressed, or walking short distances may become challenging. The pain and limitation can affect people’s ability to work, participate in hobbies and social activities, and maintain their independence. This physical impact often leads to emotional consequences as well, with many people experiencing frustration, worry, or sadness about their changing abilities.

How to Prevent or Delay Osteoarthritis

While it’s not possible to prevent osteoarthritis completely, there are several strategies that can minimize the risk of developing the condition or delay its onset. One of the most important preventive measures is maintaining a healthy body weight through balanced nutrition and regular physical activity.^[6] Because excess weight places tremendous stress on weight-bearing joints and promotes inflammation throughout the body, keeping weight within a healthy range significantly reduces osteoarthritis risk.

Regular exercise serves multiple preventive functions. Physical activity helps maintain strong muscles that support and protect joints, keeps joints flexible and mobile, and helps control weight.^[4] Adults should aim for at least 150 minutes of moderate aerobic activity each week, such as brisk walking or cycling, plus strength training exercises. However, it’s important to choose exercises wisely. Low-impact activities like swimming, water aerobics, cycling, and walking are generally safer for joints than high-impact activities that involve a lot of jumping or jarring movements.

Protecting joints from injury is crucial for preventing secondary osteoarthritis. This means using proper techniques during sports and exercise, wearing appropriate protective equipment, and avoiding activities that place excessive or repetitive stress on joints.^[4] If a joint injury does occur, it’s important to allow adequate time for healing before returning to full activity. Rushing back to sports or strenuous activities before an injury has completely healed can increase the risk of long-term joint damage.

In occupational settings, being mindful of repetitive motions and taking steps to reduce joint stress can help prevent osteoarthritis. This might involve rotating tasks, taking regular breaks, using ergonomic tools and equipment, or modifying work techniques to reduce strain on vulnerable joints. For people whose jobs require significant physical demands, working with occupational health specialists to identify and implement protective strategies can be valuable.

Maintaining good posture and proper body mechanics during daily activities also helps protect joints from unnecessary stress. Learning correct techniques for lifting, carrying, bending, and reaching can prevent cumulative damage over time. Physical therapists can provide guidance on body mechanics and joint protection strategies for both work and home activities.

How Osteoarthritis Changes the Body

Osteoarthritis is now understood to be a disease affecting the entire joint, not just the cartilage. The condition involves changes to multiple joint structures including cartilage, bone, ligaments, fat tissue, and the synovium (the tissue lining the joint).^[2] Understanding these changes helps explain why the condition causes pain and limits movement.

The primary change in osteoarthritis is the breakdown of cartilage. This smooth, elastic tissue normally covers the ends of bones within joints, allowing them to glide smoothly past each other with minimal friction. In healthy joints, cartilage acts as both a shock absorber, cushioning impact during movement, and a lubricant, enabling effortless motion.^[3] When osteoarthritis develops, this cartilage gradually deteriorates, becoming rough, thin, and eventually wearing away completely in some areas. Without this protective cushion, bones begin rubbing directly against each other, causing pain and further damage.

As cartilage breaks down, the bone underneath undergoes changes as well. The bone may become denser in some areas and develop cysts in others. Along the edges of joints, the body often forms new bone growth called osteophytes or bone spurs.^[1] While the body may be attempting to stabilize the damaged joint through these bone changes, the spurs can actually interfere with joint movement and cause additional pain.

The synovium, which produces fluid that lubricates the joint, often becomes inflamed in osteoarthritis. This inflammation can cause the joint to swell and feel warm to the touch.^[1] The inflamed synovium may produce excess fluid, leading to joint effusion (fluid accumulation), which causes visible swelling and contributes to stiffness and discomfort.

Ligaments, the tough bands of tissue that connect bones and provide joint stability, may become lax or loose as osteoarthritis progresses. This can make joints feel unstable or as if they might give way during use. Muscles around affected joints often weaken as well, partly because pain causes people to use the joint less, leading to muscle atrophy from disuse.^[2] This muscle weakness further compromises joint stability and support, creating a cycle where reduced activity leads to weaker muscles, which in turn accelerates joint problems.

In joints like the knee, other structures may be affected too. The meniscus (cartilage pads that cushion the knee joint) can become damaged, and joint capsules may thicken. All these changes together contribute to the pain, stiffness, swelling, and reduced mobility that characterize osteoarthritis.

The inflammatory processes involved in osteoarthritis also play an important role in symptoms and disease progression. Various inflammatory chemicals are released within the joint, contributing to pain, swelling, and further cartilage breakdown. This inflammation is generally less severe than in inflammatory forms of arthritis like rheumatoid arthritis, but it still contributes significantly to symptoms and joint damage over time.