What is osteoarthritis?
Osteoarthritis, also known as degenerative joint disease (DJD), is the most common type of arthritis. Osteoarthritis is more likely to develop as people age. The changes in osteoarthritis usually occur slowly over many years, though there are occasional exceptions. Inflammation and injury to the joint cause bony changes, deterioration of tendons and ligaments and a breakdown of cartilage, resulting in pain, swelling, and deformity of the joint.
There are two main types of osteoarthritis:
- Primary: Most common, generalized, primarily affects the fingers, thumbs, spine, hips, knees, and the great (big) toes.
- Secondary: Occurs with a pre-existing joint abnormality, including injury or trauma, such as repetitive or sports-related; inflammatory arthritis, such as rheumatoid, psoriatic, or gout; infectious arthritis; genetic joint disorders, such as Ehlers-Danlos (also known as hypermobility or "double-jointed; congenital joint disorders; or metabolic joint disorders.
What is cartilage?
Cartilage is a firm, rubbery, flexible connective tissue covering the ends of bones in normal joints. It is primarily made up of water and proteins whose primary function is to reduce friction in the joints and serve as a "shock absorber." The shock-absorbing quality of normal cartilage comes from its ability to change shape when compressed, because of its high water content. Although cartilage may undergo some repair when damaged, the body does not grow new cartilage after injury. Cartilage is avascular, meaning there are no blood vessels in it. Therefore, healing is a slow process.
Cartilage is made up of two main elements: cells within it known as chondrocytes and a gel-like substance called matrix, composed mostly of water and two types of proteins (collagen and proteoglycans).
- Chondrocytes, and the precursor form chondroblasts, are highly complex multifunctional cartilage cells. Functions include synthesizing and maintaining the extracellular matrix comprised of collagen and proteoglycans that help healthy cartilage grow and heal.
- Collagen is a structural protein found in many tissues such as skin, tendons and bone and is a key structural component of cartilage. Collagen provides cartilage with its strength and creates a framework for the other components.
- Proteoglycans are complex molecules composed of protein and sugar combinations that are interwoven in the matrix of cartilage. Their function is to trap large amounts of water in cartilage, which allows it to change shape when compressed thus acting as a shock absorber. At the same time, proteoglycans repel each other, allowing cartilage the ability to maintain its shape and resilience.
Who is affected by osteoarthritis?
Approximately 80% of older adults, ages 55 years and older, have evidence of osteoarthritis on X-ray. Of these, an estimated 60% experience symptoms. It is estimated that 240 million adults worldwide have symptomatic osteoarthritis, including more than 30 million U.S. adults. Post-menopausal women have an increased incidence of knee osteoarthritis compared to men.
Are there other risk factors for osteoarthritis?
In addition to age and secondary causes such as inflammatory arthritis and prior injury/ trauma, several other risk factors increase the chance of developing osteoarthritis including obesity, diabetes, elevated cholesterol, sex, and genetics.
- Obesity is a risk factor for osteoarthritis, particularly of the knee. In addition to overloading the weight-bearing mechanisms of the body, the metabolic and pro-inflammatory effects of obesity have been studied as contributory to osteoarthritis. Maintaining ideal body weight or losing extra weight is important for those at risk.
- Both diabetes and hyperlipidemia (elevated lipids/cholesterol) contribute to the inflammatory response within the body, increasing the risk of osteoarthritis. Oxidation of lipids can also create deposits in cartilage which affects affecting blood flow of subchondral bone in the same way that blood vessels are affected by atherosclerosis. Elevated blood sugars, as well as elevated cholesterol/lipids, increase free radicals within the body, this oxidative stress exceeds the resilience of cartilage on the cellular level. Controlling diabetes and hyperlipidemia is important for bone health in addition to general health.
- Decreased estrogen as experienced by post-menopausal women increases the risk of knee osteoarthritis as estrogen is protective of bone health specifically reducing oxidative stress to the cartilage.
- Heredity can play a role in osteoarthritis, as individuals born with other bone diseases or genetic traits may be more likely to develop osteoarthritis. For example, Ehlers-Danlos, which is characterized by joint laxity or hypermobility, can contribute to osteoarthritis.
Symptoms and Causes
What causes osteoarthritis?
Primary osteoarthritis is a heterogeneous disease meaning it has many different causes, it is not only “wear and tear” arthritis. Some contributing factors to OA are modifiable (can be changed) and others are non-modifiable (cannot be changed such as born with it or now permanent). Age is a contributing factor, although not all older adults develop osteoarthritis and for those who do, not all develop associated pain. As discussed above, there can also be inflammatory and metabolic risks that can increase the incidence of osteoarthritis, particularly in the setting of diabetes and/or elevated cholesterol.
Osteoarthritis can be genetic both as primary such as nodular OA of the hands as well as secondary related to other genetic disorders, such as hypermobility of joints. Inflammatory and infectious arthritis can contribute to the development of secondary osteoarthritis due to chronic inflammation and joint destruction. Previous injuries or traumas including sports-related and repetitive motions can also contribute to osteoarthritis.
Although the exact mechanisms of cartilage loss and bone changes are unknown, advancements have been made in recent years. It is suspected that complex signaling processes, during joint inflammation and defective repair mechanisms in response to injury, gradually wear down cartilage within the joints. Other changes cause the joint to lose mobility and function, resulting in joint pain with activity.
Diagnosis and Tests
How do I know if I have osteoarthritis?
Unlike other types of arthritis, the pain from osteoarthritis usually develops gradually over many months or years. Often it increases with activities that put stress on the joint, such as running or prolonged walking. Pain and joint swelling tend to increase slowly over time. Sometimes, especially in more advanced disease, a sensation of crunching or grinding may be noticed in affected joints. Prolonged morning stiffness is not a prominent symptom in OA as compared to inflammatory arthritides, such as rheumatoid or psoriatic arthritis. Osteoarthritis does not usually cause fevers, weight loss, or very hot and red joints. These features suggest some other condition or type of arthritis.
Your healthcare provider (MD, DO, NP, PA) can typically diagnose osteoarthritis by obtaining a complete history of your symptoms and examining your joints. X-rays may be helpful to make sure there is no other reason for the pain. Magnetic resonance imaging (MRI) is generally not needed except in unusual circumstances or in cases when the cartilage or surrounding ligament tear is suspected. There are no blood tests that diagnose osteoarthritis. If a joint is particularly swollen, a doctor may need to drain fluid from that joint. Tests can be performed on the fluid to look for clues for other types of arthritis, such as gout.
Management and Treatment
How is osteoarthritis treated?
There is no cure for osteoarthritis. Mild to moderate symptoms are usually well managed by a combination of pharmacologic and non-pharmacologic treatments. Medical treatments and recommendations include:
- Medications (topical pain medicines and oral analgesics including nonsteroidal anti-inflammatory medications, NSAIDs).
- Exercise (land- and water-based).
- Intermittent hot and cold packs (local modalities).
- Physical, occupational, and exercise therapy.
- Weight loss (if overweight).
- Healthy eating, managing diabetes and cholesterol.
- Supportive devices such as braces, orthotics, shoe inserts, cane, or walker.
- Intra-articular injection therapies (steroid, hyaluronic acid “gel”).
- Complementary and alternative medicine strategies, including vitamins and supplements.
Surgery may be helpful to relieve pain and restore function when other medical treatments are ineffective or have been exhausted, especially with advanced OA.
The goals of treatment are to:
- Decrease joint pain and stiffness and delay further progression.
- Improve mobility and function.
- Increase patients' quality of life.
The type of treatment regimen prescribed depends on many factors, including the patient's age, overall health, activities, occupation, and severity of the condition.
Unlike other forms of arthritis where great advances have been made in recent years, progress has been much slower in osteoarthritis. There are no medications yet available that have been shown to reverse or slow the progression of osteoarthritis. Currently, medications are focused on decreasing symptoms of the disease. Pain-relieving medications include acetaminophen and non-steroidal anti-inflammatory drugs (NSAIDs). Narcotic pain medications are not recommended due to the chronic nature of the disease and the possibility of tolerance and addiction. Topical medications in the form of analgesic patches, creams, rubs, or sprays may be applied over the skin of affected areas to relieve pain.
Although many of these medications are available in over-the-counter preparations, individuals with osteoarthritis should talk to a health care provider before taking the medications. Some medications may have dangerous or unwanted side effects and/or may interfere with other medications that are being taken. Some over the counter medications still require routine laboratory testing.
The antidepressant duloxetine hydrochloride (Cymbalta®) was approved by the FDA in 2010 to treat the pain of osteoarthritis, such as lower back pain. That has been a big help for people who can’t tolerate NSAIDs or other treatments.
Supportive or assistive devices help decrease stress on affected joints. Braces and orthotics help to support and stabilize painful, damaged joints. Medical devices should be used as instructed and under the direction of a health professional such as a physical/ occupational therapist or your licensed healthcare provider. Shoe lifts/ inserts, a cane or a walker may be helpful to take pressure off certain joints and improve body and gait mechanics.
Exercise is important to improve flexibility, joint stability and muscle strength. Regimens such as swimming, water aerobics, and low-impact strength training are recommended. These have been shown to decrease the amount of pain and disability that osteoarthritis sufferers experience. Excessively vigorous exercise programs are best avoided, as they may increase arthritis symptoms and potentially hasten the progression of the disease. Physical therapists or occupational therapists can provide appropriate and tailored exercise regimens for individuals with osteoarthritis.
Hot and cold therapies
Intermittent hot and cold treatments may provide temporary relief of pain and stiffness. Such treatments include a hot shower or bath and the careful application of heating or cooling pads or packs.
Since obesity is a known risk factor for osteoarthritis, working to better manage weight may help prevent and improve osteoarthritis. Weight loss in overweight persons who have osteoarthritis has been shown to reduce stress and the amount of pain in weight-bearing joints as well as moderate the inflammatory processes that contribute to OA.
When osteoarthritis pain cannot be controlled with medical management and it interferes with normal activities, surgery may be an option. Surgery is usually reserved for those people who have significant osteoarthritis. Several types of techniques can be employed, including minimally invasive joint replacement techniques. Although it has risks, joint surgery today can be very effective at restoring some function and reducing pain for appropriate individuals.
Supplements and alternative medicine nutraceuticals, a term derived from “nutrition” and “pharmaceutical”, are compounds that are available in pharmacies and health food stores without a prescription and are not licensed by the FDA as drugs. They include nutritional supplements, vitamins, minerals and other compounds sometimes referred to as "natural," "homeopathic," or "alternative" therapies. As this market is less regulated than the food and drug companies - many preparations exist, the actual quantity of active ingredients may vary, and there is no guarantee as to the accuracy of the label and the product.
Glucosamine and chondroitin are components of normal cartilage. As a supplement, they are most widely available as sulfate compounds. Clinical research results on glucosamine and chondroitin seem to vary, however, some trials indicate possible pain-relieving properties, particularly in osteoarthritis of the knee. Exactly how they work remains unclear and there is no strong scientific evidence supporting the claim that they build bone and cartilage. In general, glucosamine and chondroitin appear to be safe and well-tolerated however should first be discussed with your healthcare provider.
Fish oils have some anti-inflammatory activity, but these oils have been studied more extensively for rheumatoid arthritis. Supplements can potentially interact with prescription medicines and can have side effects, they should always first be reviewed with your healthcare provider.
Where can I learn more about osteoarthritis?
- American College of Rheumatology. https://www.rheumatology.org/I-Am-A/Patient-Caregiver
- The Arthritis Foundation. https://www.arthritis.org/