The most common type of arthritis is osteoarthritis, or age-related cartilage loss

Diagnosis and treatment of hip and knee osteoarthritis

Osteoarthritis is the most common type of arthritis, resulting from age-related degeneration of the soft cartilage lining between bones. As this layer breaks down, the normal smooth motion between bones is lost and the joint becomes painful.

Arthritis is an umbrella term for various conditions that cause joint pain

Arthritis isn’t one single disease, but rather a range of conditions that all lead back to the same outcome—joint pain. This American Academy of Orthopaedic Surgeons primer is a go-to resource for understanding what arthritis is, the most common types, and various treatment options depending on the underlying cause.

Arthritis explained, with Dr. Nick Golinvaux

Arthritis, a condition affecting millions globally, is more than just joint pain—it’s a breakdown of cartilage that cushions bones, leading to stiffness, swelling, and discomfort. While often associated with aging, arthritis can affect people of all ages, especially after injuries. Though there’s no cure yet, treatments range from medication and physical therapy to surgical interventions like joint replacements.

Arthritis affects almost 60 million Americans

Arthritis refers to a range of conditions resulting in joint pain that currently affects nearly 60 million people in the United States alone. This resource from the Centers for Disease Control and Prevention explores the basics of arthritis and provides resources for understanding its near-universal impact on our population.

Real surgical footage reveals what arthritis looks like up close

Arthritis is a painful condition of human joints that often results from the loss or breakdown of the soft cartilage padding that naturally exists between bones. This video shows footage from an actual knee surgery that beautifully demonstrates the difference between normal cartilage and the degenerative cartilage seen in osteoarthritis.

Five advancements in arthritis research

It is estimated that nearly 350 million people worldwide are currently suffering from arthritis. This resource explores five of the most promising recent advancements in arthritis research as scientists work towards improved treatments and continue the search for a cure.

There is no cure for the general condition of arthritis

While there are innumerable conditions ultimately leading to the joint pain we collectively term "arthritis," one common pathway is progressive inflammation and joint damage many years after an injury.

Anatomy of a healthy knee joint

To understand arthritis, study a normal joint. Where two bones come together, each is lined by a cartilage cap. These bones are linked together by strong ligaments. The inner juncture is lined by a joint capsule (synovial membrane) containing lubricating joint fluid between the two surfaces, allowing for near-frictionless motion.

Rheumatoid arthritis occurs when the immune system attacks cells within joints

Rheumatoid arthritis is a specific type of arthritis that occurs when the body's immune system attacks normal cells within the connective tissues of the joint and degrades them. This sets off a painful cycle of inflammation and joint destruction that often requires lifelong medication to control.

Kangaroos evolved exceptionally thick knee cartilage to absorb shock

There is significant conflict in the medical field regarding chronic arthritis. Some advocate for keeping the joint as active as possible while others argue progressive overuse leads to worsening arthritis. To settle the score, scientists have looked outside the human population, discovering kangaroos rarely suffer from arthritis in their knees.

Age-related macular degeneration is the primary cause of blindness in older Americans

Around 20 million Americans suffer from macular degeneration, and it's the leading cause of blindness in older Americans. Risk factors for age-related macular degeneration include aging, genetics, smoking, hypertension, obesity, and diet.

Age-related hearing loss, known as presbycusis, is a top cause of hearing loss

This video walks through the biology of why presbycusis (prez-buh-kyoo-sis) occurs and its etiology. This type of hearing loss is gradual and typically starts with reductions in the ability to hear high-pitched sounds.

Inflammaging is chronic low-level inflammation as we age, and it may be a key disease driver

The term refers to the idea that largely invisible but consistent low-level inflammation as humans age fuels chronic diseases and cellular aging. Inflammaging, this article says, is due to lifestyle factors like poor sleep, low levels of activity, and poor diet, acting in concert to cause cellular damage and trigger inflammation.

Why young women experience the most workplace ageism

While one might assume that older women face the most unfair treatment due to age in the workplace, some research from McKinsey & Co. suggests otherwise. The consulting firm found that while ageism impacts older women and men at similar rates, women in their 20s and 30s report much higher instances of ageism than both older women and their young, male colleagues. Learn more from the research here.

Adults may lose roughly 3% of their muscle mass each decade after 30

That muscle loss, formally referred to as sarcopenia [saar-ko-pee-nee-uh], averages 3% to 5%, depending on physical activity. These losses can progress with age, but resistance training helps combat some of this natural degradation.

Why vascular dementia develops

This type of dementia, the second most common form after Alzheimer's, develops due to microscopic bleeds and blood vessel blockages in the brain. The condition isn't curable but medications to help with blood clotting and high blood pressure are part of a suite of interventions designed to minimize damage to the brain.

Animal phobias are likely the most common type of phobias, followed by an extreme fear of heights.

'Old people' smell is real—it's a chemical buildup when fatty acids on the skin oxidize

The chemical composition of body odor seems to change with age. Later in life, we harbor higher concentrations of a chemical compound called 2-nonenal that forms when omega-7 fatty acids on the skin oxidize, and the skin's natural antioxidant defenses weaken. Commonly called "nonenal", it's the smell widely associated with aging, and it's often described as a grassy or greasy odor.

Should you give up a car in retirement?

Did you know that drivers over the age of 74 tend to pay higher car insurance rates than most other age groups? That small fortune in auto insurance payments is just one reason some people give up a car when they retire. If you're curious about the pros of getting rid of your car when you retire, read this article.

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

Animal phobias are likely the most common type of phobias, followed by an extreme fear of heights

Dr. Martin Antony, a Canadian expert on phobias and anxiety, says that fears of creepy, crawly animals like snakes, spiders, and mice are particularly common.

What is the most painful thing in the world?

Pain is famously difficult to quantify, and though our response to it may be subjective, most pain does have underlying objective causes. So what's the most painful thing of all? Many say childbirth, or a broken femur, but this article lays out one case for why, of all things, kidney stones may be the most painful experience. Prepare yourself to find out here.

Pets can experience vertigo, particularly older dogs

This type of dizziness is often caused by disorders of the vestibular system, and in dogs is often referred to as "old dog vestibular disease" because it tends to occur in older animals. The condition tends to resolve on its own in days or weeks. Vertigo is less common among cats than dogs, and in felines is typically caused by inner ear infections or other causes including a tumor.

The most common birthdays

Nine of the top 10 most common birthdays fall in September, with Sept. 9 being the most common. However, August is the most common birth month, followed by July and December. On the flip side, the least common birthdays are around major holidays, with Christmas Day being the rarest—probably due to doctors scheduling fewer inductions and C-sections on those days. Find out more birthday surprises here.

The security and privacy risks of augmented reality

One of the most serious perceived risks of augmented reality is the loss of privacy. Because AR technology can see what users are doing, user privacy is jeopardized. AR collects far more information about who users are and what they are doing than...

The most severe form of malaria is caused by the Plasmodium falciparum parasite

Multiple species of a single-celled organism called a protozoa cause malaria infection when transmitted by a mosquito bite. But Plasmodium falciparum is the most widespread in Africa, and the most deadly.

View the three types of coral reefs, categorized by where they form

Fringing reefs—the most common type—are built from coral depositing calcium carbonate onto the seafloor closest to the shoreline. Barrier reefs grow further from and parallel to the shore, while atolls are the result of mid-ocean volcanoes or seamounts eroding away and leaving a lagoon surrounded by reefs.

Bone marrow (soft tissue found inside certain bones) generates roughly 500 billion new blood cells each day

20,000 letters to the advice columnist 'Dear Abby' provide insight into prevailing sex, religion, and LGBTQ fears, anxieties, and concerns from the 1950s onward.

Poison ivy's characteristic rash is caused by an allergic response to an oily compound in the plant called urushiol.

Listen to an in-depth conversation on the links between Parkinson's disease and herbicide exposure and the challenging pace of scientific investigation.

About 2,000 US babies are born annually without some portion of their limbs, potentially leading to a lifetime of pricey prosthetics.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

US housing costs have risen by roughly 175% between 1991 and 2026—but a growing number of Gen Zers are becoming homeowners anyway. In 2025, 4% of homebuyers were Gen Z, up from 3% the year before.

See images of medical cases of firework injuries shared on this 'Instagram for doctors.' (Warning: Graphic content)

Dozens of S&P 500 stocks, including Coca-Cola and Walmart—known as the dividend aristocrats—have increased dividends every year for 25 years

The US Constitution is widely regarded as the longest-standing written national constitution still in force—see how it has influenced rights worldwide.

As of 2025, the most cited papers in science include a review of graphene, methods to improve image recognition, streamlining electron density calculations, and optimizing protein studies.

Artificial coral reefs have been 3D printed from nontoxic, biodegradable terracotta clay, which coral polyps have used as a foundation for rebuilding marine ecosystems.

Shooting stars, or meteors, are fragments of asteroids and comets that burn up as they enter Earth's atmosphere, creating streaks in the sky called meteor showers.

Art theft is the third-largest source of criminal revenues worldwide, thanks in part to the subjective nature of valuing a work of art.

The word 'jazz' evolved from 'jasm,' 19th-century American slang for 'energy'

The price of gas is a composite made up of several different factors, with the federal gas tax making up less than 20% of what drivers pay at the pump.

Volcanoes 'die' when their supply of magma runs out, if they are shifted away from their underlying magma reservoir, or if they get clogged by collapsing or their magma cooling back into rock.

Gerrymandering works through two techniques: cracking opposing voters across districts to dilute their power, and packing them into a few to waste their votes in lopsided majorities.

Take a 3D tour of the Hajj, Islam's annual pilgrimage to Mecca, undertaken by over 1.5 million Muslims.

See how each of the more than two million known species relates to each other—and to common ancestors—in this zoomable tree of life.

In 1939, baseball star Lou Gehrig delivered his inspirational 'Luckiest Man' speech after retiring due to the health condition that now bears his name.

The Russia-Ukraine conflict is the largest ground war in Europe since World War II in casualties, forces mobilized, and displacement of civilians.

An Ebola vaccine was developed during the 2018 west African Ebola outbreak, but the 2026 Ebola outbreak is with a different species of the virus, not the one that the vaccine is approved to treat.