What Is Osteoarthritis? Symptoms and Causes

Osteoarthritis — also known as OA or degenerative joint disease — is a form of arthritis that affects the cartilage cushion that sits between your bones. It’s the most common form of arthritis, affecting over 30 million adults in the United States. Most people will develop OA at some point in their lives.¹

In this article, we’ll discuss what osteoarthritis is, how it develops, and what symptoms to look out for. It’s important to understand what causes osteoarthritis and what your risk of developing it is so you can take steps to prevent joint degeneration. Roughly 80 percent of adults over the age of 55 have signs of osteoarthritis in an X-ray.¹

What Is Osteoarthritis?

Osteoarthritis is a joint condition that develops over several years as you age. It mainly affects the cartilage or flexible, rubbery tissue that covers the ends of your bones. Cartilage acts as a cushion to stop bones from rubbing together and acts as a “shock absorber.”

Osteoarthritis develops when the cartilage between your joints and bones becomes damaged and begins degrading. Your joints won’t work as well as they used to, and they’ll become stiff, inflamed, and painful. Cartilage doesn’t repair itself easily after it’s damaged. There aren’t any blood vessels that run through the cartilage to bring oxygen and nutrients to the tissue, making the healing process slow.¹

Types of Osteoarthritis

There are two types of osteoarthritis — primary and secondary.² Primary osteoarthritis is the most common type that develops from aging and general wear and tear on the joints. It mainly affects large joints in the body, including the knees, hips, spine, fingers, and big toes.

On the other hand, secondary osteoarthritis develops as a result of another injury, condition, or disease. Many people with inflammatory arthritis, such as gout, rheumatoid arthritis (RA), or psoriatic arthritis (PsA), have osteoarthritis as well. Athletes who repetitively injure or strain their large joints and those with Ehlers-Danlos syndrome also tend to have secondary osteoarthritis.

What Causes Osteoarthritis?

Your cartilage can repair itself after some damage, but your body can’t make new cartilage after a major injury. Wear and tear and inflammation over time wear down cartilage, taking away the cushion between your bones. As the cartilage changes and degrades, osteoarthritis may end up affecting the following:³

• Tendons and ligaments that connect bones, muscles, and tissues
• The bones themselves, causing them to grind against one another and change shape
• The synovium, or the fluid-filled sac that lines and cushions joints near the cartilage

Doctors and researchers believe there’s more to this condition than simple “wear and tear.” They’re also looking at how inflammation plays a role. Since osteoarthritis affects not only the joint, they believe changes in the cartilage tissue trigger inflammation and damage the entire bone and nearby structures.³

When cartilage is damaged and begins deteriorating, the bones begin to rub against one another. This creates a rough surface that makes movement painful. It also triggers bone cells to grow and divide, leading to bone spurs or osteophytes along the joint edges. These growths may break off the bone and float inside the tissues and fluid that surround the joint, leading to even more damage.

Osteoarthritis Risk Factors

Doctors and researchers have found several factors that raise your chances of developing osteoarthritis. Some of these risk factors, like body weight and cholesterol and blood sugar levels, can be managed to some extent, while others, like age and family history, can’t be changed. It’s important to note that just because you have one or more risk factors doesn’t mean you’ll go on to develop osteoarthritis.⁴

The following are risk factors for osteoarthritis:^1-4

Advanced Age

Osteoarthritis tends to develop in people ages 50 and older because as we age, we’re more likely to be injured or strain our joints; the body also has a harder time healing itself the older we get.

Joint Injuries

If you’ve injured a large joint before, you’re at a higher risk of developing osteoarthritis in that joint; examples include ligament tears, bone fractures, or cartilage injuries.

Gender

Women are more likely to develop osteoarthritis than men, especially after menopause. Doctors and researchers believe lower estrogen levels after menopause contribute to poor bone and cartilage health.

High Cholesterol Levels or Diabetes

Having high cholesterol or diabetes are associated with body-wide inflammation that increases the risk of osteoarthritis. Fat deposits can also form in cartilage, which affects blood flow into the bone tissue.

Being Overweight or Obese

Extra weight puts added strain on your joints, especially in the knees; obesity has also been associated with an increase in body-wide inflammation, which can contribute to osteoarthritis and other diseases.

Weak Muscles

Without muscle strength to support your bones and joints, you’re more likely to have misaligned joints and injuries that can lead to osteoarthritis.

Family History of Osteoarthritis

People with close relatives who have osteoarthritis are more likely to develop it themselves.

Occupation

Those whose jobs require heavy lifting or repetitive movements are at a higher risk of developing osteoarthritis due to joint overuse and damage.

If you have one or more of these risk factors, talk to your doctor about ways you can lower your chances of developing osteoarthritis. You can also learn more about steps you can take in your everyday life to help slow the development of osteoarthritis.

Osteoarthritis Symptoms and Signs

Since osteoarthritis can take several years to develop, its symptoms tend to appear slowly over time rather than suddenly. Examples of osteoarthritis symptoms to look out for as you continue to age include:⁴

• Joints aching or pain while moving or after a long day
• Swollen, tender joints
• Stiff joints, especially first thing in the morning or after taking a break and resting
• Sensation that joints are weak when performing an activity
• Popping, clicking, grinding, or crunching noises and sensations when stretching or bending joints, known as crepitus
• Weak muscles around affected joints
• Limited range of motion that improves when you move the joints

Your osteoarthritis symptoms may also change depending on which joints are affected. For example, osteoarthritis affecting the spine (known as spondylosis) can cause numbness or weakness in the arms, pain that travels from your shoulders into your arms, and neck and lower back stiffness.⁵

Other joints that are commonly affected and their symptoms include:^6-8

• Knees: Large, swollen, or puffy-looking knees that are difficult to stretch after periods of immobility such as sitting or lying down; locking or sticking knee joints; grinding or crackling noises and sensations; loss of the ability to fully bend and/or straighten out your leg.
• Hands: Swollen or bumpy nodules that form on the top (distal) joint near the fingertip (known as Heberden’s nodes) or in the middle joint (Bouchard’s nodes); weakness that makes it hard to fully close your hand and grasp things, making tasks like opening jars more difficult; misshapen or misaligned finger joints; crepitus in your knuckles or fingers.
• Hips: Aches and pain from your groin or thighs that travels into your knees or buttocks; stiff joints that make it hard to bend over or walk; worsening of pain with walking, running, or other physical activity; loss of range of motion that makes it harder to extend your legs when walking, leading to a limp; worsening of symptoms on cold or rainy days.

How Is Osteoarthritis Diagnosed?

If you’re experiencing any symptoms of osteoarthritis, you’ll want to make an appointment to talk with your doctor. They’ll use the results of your medical history, physical exam, and imaging tests to make an osteoarthritis diagnosis and develop a treatment plan for you. Your doctor may also choose to refer you to a rheumatologist or a doctor that specializes in treating arthritis and other joint conditions.

Medical History and Physical Exam

Your doctor will start by taking your medical history to learn about your risk factors. Be sure to let them know if you have a family history of osteoarthritis or are living with high cholesterol, diabetes, or another chronic disease. Your doctor may also ask about how much you exercise, what you do for a living, and whether you’ve ever injured your knees, hips, or other joints commonly affected by osteoarthritis.⁹

During your physical exam, your doctor will take your weight to note whether being overweight or obese is contributing to your osteoarthritis symptoms. They’ll also take a closer look at your affected joints for any signs of swelling, ask about your pain, and then they’ll test your range of motion. If you’re having a hard time bending or stretching your joints, or if they notice any signs of crepitus, it may point to an osteoarthritis diagnosis.

Imaging Tests

Your doctor may also order some X-rays to confirm that your joint pain isn’t due to a fracture or other injury. X-rays take pictures of bones to look for any changes in bone structure or shape, or bone growths or spurs. Cartilage doesn’t show up on X-rays — if your doctor suspects you may have any soft tissue damage, they’ll order other tests.^1,9

Magnetic resonance imaging (MRI) scans use high-powered magnets to take detailed pictures of your bones, cartilage, and muscles. MRIs aren’t typically used to diagnose osteoarthritis unless it’s a more complicated case — instead, they can be used to rule out other soft tissue injuries like a torn meniscus or anterior cruciate ligament (ACL) in the knee. A surgeon may consider an MRI before offering a joint replacement surgery in some cases.

Joint Aspiration

Joint aspiration is used to look closely at the fluid from your joints for any signs of osteoarthritis or other types of arthritis. During this procedure, your doctor will numb the area around your affected joint and insert a needle to draw out a small amount of fluid.⁴ They’ll send it to a laboratory to be looked at under a microscope. . In assessing the sample, a doctor will be looking for the number of white blood cells in the fluid and for the presence of crystals in the fluid. In some cases, a doctor may decide to look for signs of infection in the fluid and check a culture of the fluid.

Complications of Osteoarthritis

If it’s left untreated, osteoarthritis can eventually lead to mobility issues and other health complications. By working closely with your doctor and/or rheumatologist, you can lead a healthier life with osteoarthritis and prevent lasting joint damage and injuries.

Examples of complications that can develop while living with osteoarthritis include:^4,11

• Bone fractures and falls: Studies show that people with osteoarthritis are more likely to fall and injure themselves than those without osteoarthritis.
• Sleep difficulties: Joint pain and swelling can be uncomfortable, making it hard to fall asleep and/or stay asleep.

Resources for Living with Osteoarthritis

If you or a loved one is living with osteoarthritis, there are many resources available to help you better understand the condition and connect with others who understand. Browse the resources below to learn more about osteoarthritis:

• Community and Patient Resources — Osteoarthritis Action Alliance
• Osteoarthritis Resources — CreakyJoints
• Your Connect Group — Arthritis Foundation

Sources

1. Cleveland Clinic. Osteoarthritis. November 26, 2019. Accessed from: https://my.clevelandclinic.org/health/diseases/5599-osteoarthritis
2. Johns Hopkins Medicine. Osteoarthritis. Accessed from: https://www.hopkinsmedicine.org/health/conditions-and-diseases/arthritis/osteoarthritis
3. National Institute of Arthritis and Musculoskeletal and Skin Diseases. Osteoarthritis: Overview, Symptoms, & Causes. October 2019. Accessed from: https://www.niams.nih.gov/health-topics/osteoarthritis
4. Arthritis Foundation. Osteoarthritis. Accessed from: https://www.arthritis.org/diseases/osteoarthritis
5. American Association of Neurological Surgeons. Osteoarthritis. Accessed from: https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Osteoarthritis
6. Arthritis Foundation. Osteoarthritis of the Knee. Accessed from: https://www.arthritis.org/diseases/more-about/osteoarthritis-of-the-knee
7. Arthritis Foundation. Osteoarthritis of the Hands. Accessed from: https://www.arthritis.org/diseases/more-about/osteoarthritis-of-the-hands
8. OrthoInfo - American Academy of Orthopaedic Surgeons. Osteoarthritis of the Hip. February 2021. Accessed from: https://orthoinfo.aaos.org/en/diseases--conditions/osteoarthritis-of-the-hip/
9. National Institute of Arthritis and Musculoskeletal and Skin Diseases. Osteoarthritis: Diagnosis, Treatment, and Steps to Take. October 2019. Accessed from: https://www.niams.nih.gov/health-topics/osteoarthritis/diagnosis-treatment-and-steps-to-take
10. Hermansen P and Freemont T. Synovial fluid analysis in the diagnosis of joint disease. Diagnostic Histopathology. 23.5 (2017): 211-220.
11. Mayo Clinic. Osteoarthritis: Symptoms & Causes. June 16, 2021. Accessed from: https://www.mayoclinic.org/diseases-conditions/osteoarthritis/symptoms-causes/syc-20351925