Osteoarthritis (OA) also known as degenerative arthritis, degenerative joint disease, or osteoarthrosis, is a type of joint disease that results from breakdown of joint cartilage and underlying bone. The most common symptoms are joint pain and stiffness. Initially this usually just occurs after exercise but over time may become constant. Other symptoms may include joint swelling, decreased range of motion, and when the back is affected weakness or numbness of the arms and legs. The most commonly involved joints are those near the ends of the fingers, at the base of the thumb, neck, lower back, knees, and hips. Joints on one side of the body are often more affected than those on the other. Usually the problems come on over years. It can affect work and normal daily activities. Unlike other types of arthritis only the joints are typically affected.
Causes include previous joint injury, abnormal joint or limb development, and inherited factors. Risk is greater in those who are overweight, have one leg of a different length, and have jobs that result in high levels of joint stress. Osteoarthritis is believed to be caused by mechanical stress on the joint and low grade inflammatory processes. It develops as cartilage is lost with eventually the underlying bone becoming affected. As pain may make it difficult to exercise, muscle loss may occur. Diagnosis is typically based on signs and symptom with medical imaging and other tests occasionally used to either support or rule out other problems. Unlike in rheumatoid arthritis, which is primarily an inflammatory condition, the joints do not typically become hot or red.
Treatment includes exercise, efforts to decrease joint stress, support groups, and pain medications. Efforts to decrease joint stress include resting, the use of a cane, and braces. Weight loss may help in those who are overweight. Pain medications may includeparacetamol (acetaminophen). If this does not work NSAIDs such as naproxen may be used but these medications are associated with greater side affects. Opioids if used are generally only recommended short term due to the risk of addiction. If pain interferes with normal life despite other treatments, joint replacement surgery may help. An artificial joint, however, only lasts a limited amount of time. Outcomes for most people with osteoarthritis are good.
OA is the most common form of arthritis with disease of the knee and hip affecting about 3.8% of people as of 2010. Among those over 60 years old about 10% of males and 18% of females are affected. It is the cause of about 2% of years lived with disability. In Australia about 1.9 million people are affected, and in the United States about 27 million people are affected. Before 45 years of age it is more common in men, while after 45 years of age it is more common in women. It becomes more common in both sexes as people become older.
The daily stresses applied to the joints, especially the weight-bearing joints (eg, ankle, knee, and hip), play an important role in the development of osteoarthritis. Most investigators believe that degenerative alterations in osteoarthritis primarily begin in the articular cartilage, as a result of either excessive loading of a healthy joint or relatively normal loading of a previously disturbed joint. External forces accelerate the catabolic effects of the chondrocytes and further disrupt the cartilaginous matrix.
Risk factors for osteoarthritis include the following:
- Genetics (significant family history)
- Reduced levels of sex hormones
- Muscle weakness
- Repetitive use (ie, jobs requiring heavy labor and bending)
- Crystal deposition
- Previous inflammatory arthritis (eg, burnt-out rheumatoid arthritis)
- Heritable metabolic causes (eg, alkaptonuria, hemochromatosis, and Wilson disease)
- Hemoglobinopathies (eg, sickle cell disease and thalassemia)
- Neuropathic disorders leading to a Charcot joint (eg, syringomyelia, tabes dorsalis, and diabetes)
- Underlying morphologic risk factors (eg, congenital hip dislocation and slipped femoral capital epiphysis)
- Disorders of bone (eg, Paget disease and avascular necrosis)
- Previous surgical procedures (eg, meniscectomy)
With advancing age come reductions in cartilage volume, proteoglycan content, cartilage vascularization, and cartilage perfusion. These changes may result in certain characteristic radiologic features, including a narrowed joint space and marginal osteophytes. However, biochemical and pathophysiologic findings support the notion that age alone is an insufficient cause of osteoarthritis.
Obesity increases the mechanical stress in a weight-bearing joint. It has been strongly linked to osteoarthritis of the knees and, to a lesser extent, of the hips. A study that evaluated the associations between body mass index (BMI) over 14 years and knee pain at year 15 in 594 women found that a higher BMI at year 1 and a significant increase in BMI over 15 years were predictors of bilateral knee pain at year 15. The association between BMI increase and knee pain was independent of radiographic changes.
In addition to its mechanical effects, obesity may be an inflammatory risk factor for osteoarthritis. Obesity is associated with increased levels (both systemic and intra-articular) of adipokines (cytokines derived from adipose tissue), which may promote chronic, low-grade inflammation in joints.
Trauma or surgery (including surgical repair of traumatic injury) involving the articular cartilage, ligaments, or menisci can lead to abnormal biomechanics in the joints and accelerate osteoarthritis. Although repairs of ligament and meniscal injuries usually restore joint function, osteoarthritis has been observed 5-15 years afterward in 50-60% of patients.
Insults to the joints may occur even in the absence of obvious trauma. Microtrauma may also cause damage, especially in individuals whose occupation or lifestyle involves frequent squatting, stair-climbing, or kneeling.
Muscle dysfunction compromises the body’s neuromuscular protective mechanisms, leading to increased joint motion and ultimately resulting in osteoarthritis. This effect underscores the need for continued muscle toning exercises as a means of preventing muscle dysfunction.
Valgus malalignment at the knee has been shown to increase the incidence and risk of radiographic progression of knee osteoarthritis involving the lateral compartment.
A hereditary component, particularly in osteoarthritis presentations involving multiple joints, has long been recognized. Several genes have been directly associated with osteoarthritis, and many more have been determined to be associated with contributing factors, such as excessive inflammation and obesity.
Osteoarthritis susceptibility genes (eg, ADAM12, CLIP, COL11A2, IL10, MMP3) have also been found to have differential methylation. Jefferies et al reports that hypomethylation of FURIN, which encodes a proprotein convertase, processes several ADAMTS molecules involved in osteoarthritic collagen degradation. Differential methylation among osteoarthritis susceptibility genes has been proposed as an alternative method for disruption of normal gene activity.
Additionally, Jefferies et al found evidence for hypermethylation and reduced expression of the type XI collagen gene COL11A2. Mutations involving COL11A2 have been associated with severe and early-onset osteoarthritis. Analysis by this goup has identified pathways enriched with “differentially methylated genes” that are effectors and upstream regulators seen in osteoarthritis linked with TGFB1 andERG.
Genes in the BMP (bone morphogenetic protein) and WNT (wingless-type) signaling cascades have been implicated in osteoarthritis. Two genes in particular,GDF5 (growth and differentiation factor 5) and FRZB (frizzled related protein), have been identified in the articular cartilage in animal studies and share a strong correlation with osteoarthritis.
Genome-wide association studies (GWAS) have identified an association between osteoarthritis of large joints and the MCF2L gene. This gene is key in neurotrophin-mediated regulation of peripheral nervous system cell motility.
Genetic factors are also important in certain heritable developmental defects and skeletal anomalies that can cause congenital misalignment of joints. These may result in damage to cartilage and the structure of the joint.
Currently, clinical genetic testing is not offered to patients who have osteoarthritis unless they also have other anomalies that could be associated with a genetic condition. In the future, testing may allow individualization of therapeutics.
During the physical exam, your doctor will closely examine your affected joint, checking for tenderness, swelling or redness, and for range of motion in the joint. Your doctor may also recommend imaging and lab tests.
Pictures of the affected joint can be obtained during imaging tests. Examples include:
- X-rays. Cartilage doesn’t show up on X-ray images, but cartilage loss is revealed by a narrowing of the space between the bones in your joint. An X-ray may also show bone spurs around a joint. Some people may have X-ray evidence of osteoarthritis before they experience any symptoms.
- Magnetic resonance imaging (MRI). MRI uses radio waves and a strong magnetic field to produce detailed images of bone and soft tissues, including cartilage. MRI isn’t commonly needed to diagnose osteoarthritis but may help provide more information in complex cases.
Analyzing your blood or joint fluid can help pinpoint the diagnosis.
- Blood tests. Blood tests may help rule out other causes of joint pain, such as rheumatoid arthritis.
- Joint fluid analysis. Your doctor may use a needle to draw fluid out of the affected joint. Examining and testing the fluid from your joint can determine if there’s inflammation and if your pain is caused by gout or an infection.
There’s no known cure for osteoarthritis, but treatments can help reduce pain and maintain joint movement.
Osteoarthritis symptoms may be helped by certain medications, including:
- Acetaminophen.Acetaminophen (Tylenol, others) can relieve pain, but it doesn’t reduce inflammation. It has been shown to be effective for people with osteoarthritis who have mild to moderate pain. Taking more than the recommended dosage of acetaminophen can cause liver damage.
- Nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDs may reduce inflammation and relieve pain. Over-the-counter NSAIDs include ibuprofen (Advil, Motrin IB, others) and naproxen (Aleve, others). Stronger NSAIDs are available by prescription. NSAIDs can cause stomach upset, ringing in your ears, cardiovascular problems, bleeding problems, and liver and kidney damage. They should not be used by people over 65 years of age and those who have stomach bleeding. Topical NSAIDS have fewer side effects and may relieve pain just as well.
Exercising and achieving a healthy weight are the best and most important ways to treat osteoarthritis. Your doctor also may suggest:
- Physical therapy. A physical therapist can work with you to create an individualized exercise program that will strengthen the muscles around your joint, increase your range of motion and reduce pain.
- Occupational therapy. An occupational therapist can help you discover ways to do everyday tasks or do your job without putting extra stress on your already painful joint. For instance, a toothbrush with a large grip could make brushing your teeth easier if you have finger osteoarthritis. A bench in your shower could help relieve the pain of standing if you have knee osteoarthritis.
- Braces or shoe inserts. Your doctor may recommend shoe inserts or other devices that can help reduce pain when you stand or walk. These devices can immobilize or support your joint to help take pressure off it.
- A chronic pain class. The Arthritis Foundation and some medical centers have classes for people with osteoarthritis and chronic pain. Ask your doctor about classes in your area or check with the Arthritis Foundation. These classes teach skills that help you manage your osteoarthritis pain. And you’ll meet other people with osteoarthritis and learn their tips and tricks for reducing and coping with joint pain.
Surgical and other procedures
If conservative treatments don’t help, you may want to consider procedures such as:
- Cortisone shots. Injections of corticosteroid medications may relieve pain in your joint. During this procedure your doctor numbs the area around your joint, then places a needle into the space within your joint and injects medication. The number of cortisone shots you can receive each year is limited, because the medication can worsen joint damage over time.
- Lubrication injections. Injections of hyaluronic acid may offer pain relief by providing some cushioning in your knee. Hyaluronic acid is similar to a component normally found in your joint fluid.
- Realigning bones. During a surgical procedure called an osteotomy, the surgeon cuts across the bone either above or below the knee to realign the leg. Osteotomy can reduce knee pain by shifting your body weight away from the worn-out part of your knee.
- Joint replacement. In joint replacement surgery (arthroplasty), your surgeon removes your damaged joint surfaces and replaces them with plastic and metal parts. The hip and knee joints are those most commonly replaced. Surgical risks include infections and blood clots. Artificial joints can wear out or come loose and may need to eventually be replaced. Repeat joint replacements are more challenging and less successful than the original surgery.
You can take steps to help prevent osteoarthritis. If you already have arthritis, these same steps may keep it from getting worse.
- Stay at a healthy weight or lose weight if you need to. Extra weight puts a lot of stress on the large, weight-bearing joints such as the knees, the hips, and the balls of the feet. Experts estimate that every 1 lb (0.5 kg) of body weight adds about4 lb (1.8 kg) of stress to the knee.This means that if you lost just 5 lb (2.3 kg), you could take 20 lb (9.1 kg)of stress off your knees.
- Be active. A lack of exercise can cause your muscles and joints to become weak. But light to moderate exercise can help keep your muscles strong and reduce joint pain and stiffness. For example, if your quadriceps (the muscles in the front of your thigh) are weak, you may be more likely to get arthritis of the knee.
- Protect your joints. Try not to do tasks that cause pain or swelling in joints. And try to use the largest joints or strongest muscles to do things. A single major injury to a joint or several minor injuries can damage cartilage over time.
Lifestyle changes and home treatments also can help reduce osteoarthritis symptoms. You might want to try some of the following tips:
- Exercise. Exercise can increase your endurance and strengthen the muscles around your joint, making your joint more stable. Try walking, biking or swimming. If you feel new joint pain, stop. New pain that lasts for hours after you exercise probably means you’ve overdone it but doesn’t mean you should stop exercising altogether.
- Lose weight. Being overweight or obese increases the stress on your weight-bearing joints, such as your knees and your hips. Even a small amount of weight loss can relieve some pressure and reduce your pain. Talk to your doctor about healthy ways to lose weight. Most people combine changes in their diet with increased exercise.
- Use heat and cold to manage pain. Both heat and cold can relieve pain in your joint. Heat also relieves stiffness, and cold can relieve muscle spasms and pain.
- Apply over-the-counter pain creams. Creams and gels available at drugstores may provide temporary relief from osteoarthritis pain. Some creams numb the pain by creating a hot or cool sensation. Other creams contain medications, such as aspirin-like compounds, that are absorbed into your skin. Pain creams work best on joints that are close to the surface of your skin, such as your knees and fingers.
- Use assistive devices. Assistive devices can make it easier to go about your day without stressing your painful joint. A cane may take weight off your knee or hip as you walk. Carry the cane in the hand opposite the leg that hurts. Gripping and grabbing tools may make it easier to work in the kitchen if you have osteoarthritis in your fingers. Your doctor or occupational therapist may have ideas about what sorts of assistive devices may be helpful to you. Catalogs and medical supply stores also may be places to look for ideas.
The prognosis in patients with osteoarthritis depends on the joints involved and on the severity of the condition. No proven disease- or structure-modifying drugs for osteoarthritis are currently known; consequently, pharmacologic treatment is directed at symptom relief.
A systematic review found the following clinical features to be associated with more rapid progression of knee osteoarthritis:
- Older age
- Higher BMI
- Varus deformity
- Multiple involved joints
Patients with osteoarthritis who have undergone joint replacement have a good prognosis, with success rates for hip and knee arthroplasty generally exceeding 90%. However, a joint prosthesis may have to be revised 10-15 years after its placement, depending on the patient’s activity level. Younger and more active patients are more likely to require revisions, whereas the majority of older patients will not
Osteoarthritis is a degenerative disease that worsens over time. Joint pain and stiffness may become severe enough to make daily tasks difficult. Some people are no longer able to work. When joint pain is this severe, doctors may suggest joint replacement surgery.