Osteoarthritis

Introduction

Osteoarthritis, also called degenerative joint disease, is the most common form of arthritis, affecting as many as 27 million Americans. A combination of joint destruction and joint pain, Osteoarthritis, affects structures of the joint at specific points and then progresses gradually to involve larger regions within the joint. While almost all joints in the body can be affected by Osteoarthritis, pain is most common at the knees, hips, and specific joints within the hand, especially the base of thumb and joints nearest the nails.

Joints form at the meeting of two bones which move relative to one another. The movement of one bone against another is lubricated by viscous synovial fluid and the pressure between the bones is lessened by compressible tissue, called cartilage. In osteoarthritis, this smooth articular cartilage develops surface erosions; the bone underneath this cartilage then changes its shape and new outgrowths of bone at the edges of the joint form, called osteophytes. With the release into the joint of degraded cartilage, the synovial tissue that secretes the lubricating fluid can become inflamed causing it to secrete more fluid. In response, the joint swells, the fibrous and ligamentous capsule which encloses the joint can thicken and stretch, and muscles surrounding the joint can become weak. (See figure 1).

Figure 1. Drawing showing the pathologic features of osteoarthritis (on the right) contrasted with a normal joint on the left

Osteoarthritis affects middle-aged and older people, but sometimes those who have had severe athletic injuries can develop osteoarthritis in their injured joints at a young age. There is no cure for osteoarthritis other than replacement of the affected joint, and most treatments target the pain that patients experience.

What causes osteoarthritis?

Since osteoarthritis is a consequence of repeated injury to parts of a joint, there are many potential causes. Typically, our bodies protect our joints from injury in a variety of ways. Muscles smooth the impact of joint "loading" - such as occurs with walking or running - by distributing the load across the joint surface. The capsule of the joint provides limits beyond which the joint can be injured. Ligaments within the joint hold it in place during movement. Nerves present in joint structures provide instantaneous feedback about whether our joints are bent or straight, what direction they are moving, and how fast. Nerves traveling to muscles also orchestrate muscle contraction to smooth joint movement and avoid injury. Viscous synovial fluid within the joint reduces the friction of movement to near zero. If any one of those protective systems (or several at once) does not work properly, the joint is vulnerable to injury.

Cartilage is often the victim of this failure of joint protection. Cartilage is a tissue without blood vessels or nerves, which replaces itself very slowly, but whose cells both synthesize and later break down the protective cartilage matrix that they form. Early in disease it is likely that cartilage synthesis fails to keep up with its breakdown, accelerating the disease process. In some persons with osteoarthritis, the failure of cartilage synthesis to produce a tissue that functions normally to withstand joint loading may be the primary cause of osteoarthritis.

However, for most persons, the cause of the disease is a combination of the failure of joint protectors leading to cartilage injury and subsequent joint breakdown. Acute joint injuries can create the earliest lesions of osteoarthritis and impair the successful functioning of joint protectors, making the joint more vulnerable to subsequent injury. For example, the meniscus serves as a spacer within the knee joint that acts to distribute load during weight bearing. When the meniscus is damaged (an example is shown in figure 2), it no longer functions normally to protect the rest of the joint. Thus, patients with meniscal injuries or who have had surgery on their meniscus are at higher risk of later osteoarthritis.

Figure 2. Tear of medial meniscus (meniscus on inside of knee), looking down from above onto the tibia and cartilage covering it. (courtesy of Dr. Martin Englund)

Similarly, during knee motion, the anterior cruciate ligament (ACL) prevents the tibia (the bone below the knee) from moving too far forward on the femur (the bone above the knee). When the ACL is torn, motion changes and parts of the knee can get damaged. Even repair of this ACL tear does not fully normalize the function of the ACL, leaving joints vulnerable to later damage and placing them at risk of osteoarthritis.

Risk Factors For Osteoarthritis

The risk factors for osteoarthritis vary by the joint affected. In knees, a history of injury plays a major role. In hip osteoarthritis, childhood developmental abnormalities play a critical role, and there are a variety of such problems, including dysplasia occurring in infancy, and Legg Perthes disease in childhood. Each of these produces a mildly deformed hip, which functions normally until a person reaches adulthood. The deformity increases loading across the hip in focal regions, and these focal regions become overwhelmed with stress and eventually break down. For hand osteoarthritis, there is probably a large inherited and, perhaps, metabolic set of causes.

More generally, osteoarthritis can be inherited, but it is unusual for a person to inherit the predilection to get osteoarthritis everywhere in their body. Usually the inheritance of osteoarthritis is joint-specific: if your mother had it in her hands, you get it in your hands, but not in your knees or hips. Similarly, if your father had hip osteoarthritis, you are at high risk of getting osteoarthritis there, perhaps because you both share a mild deformity that alters loading across the hip.

Being overweight increases the risk of osteoarthritis, especially in knees and hips. Every pound of increased weight increases the load across the knee by three to six pounds. Weight loss can prevent the development of symptomatic knee osteoarthritis. Persons with knee and hip osteoarthritis tend to be overweight or obese much more often than persons without disease.

While it is likely that nutritional factors will be found to affect the risk of osteoarthritis, none has been consistently identified yet as a cause of disease. Vitamin deficiencies that are most likely to increase the risk of osteoarthritis are vitamins C, E, D, and K. In each case, deficiency of the vitamin has potentially adverse biological effects on joint cartilage or bone. However, studies in people have not consistently suggested that supplementation with any of these vitamins has any effect on osteoarthritis.

Recreational runners are not at high risk of osteoarthritis of the knee or hip. However, those who run on Olympic teams or as professional marathon runners are at high risk of disease, perhaps because their level of long term joint overuse and loading is beyond what knees and hips can withstand. Although knees that have not previously sustained any major injuries show no increased risk of disease with running, runners who have previously had ACL tears or meniscal injuries should not run marathons or long distances, because their risk of disease is substantially increased. In such persons major joint protectors, such as the meniscus, do not function optimally, and their joints are easily injured with running.

Lastly, osteoarthritis affects primarily middle-aged and older persons and very rarely occurs in young persons. Although some people develop disease before age 50, most cases begin to appear when a person reaches their fifties. Prevalence almost doubles with every 10 years of age thereafter. The high rate of osteoarthritis in older people is probably due to the gradual failure of major joint protectors as we get older. For example, muscles get weaker, ligaments stretch, and the nervous system's response to the excursion of the joint slows down, so that instantaneous feedback on where the joint is in space may not be adequate for the joint to protect itself. All of these changes combine to make the joint more vulnerable to injury with age. In addition, the cartilage becomes less resilient and loses its ability to respond to load with age. The net effect is an older joint that is much more vulnerable than a younger one. Some of these age-related changes can be reversed by muscle conditioning; and weight loss may help prevent disease in the knees and hips.

What types of symptoms are typical of osteoarthritis?

Patients with osteoarthritis have joint pain of stiffness that is almost always worse with activity. For example, persons with knee osteoarthritis have pain going up and down stairs, pain after they sit for a long time, or pain getting up out of a chair. Patients can also have knee pain while walking on level ground, be it walking down the block or around the mall.

Hip osteoarthritis pain tends to affect the groin and occurs with walking and with getting out of a deep chair or toilet. Putting on socks and shoes or tying shoes tends to be especially painful in persons with hip osteoarthritis. Hand osteoarthritis pain is usually less intense, but affected persons often have pain with hand use like cooking, knitting or sewing.

Osteoarthritis pain does not usually occur in bed at night. If stiffness in the morning occurs, it is brief, lasting only a few minutes. While pain with osteoarthritis occurs after activity, and is relieved usually by stopping the activity, the pain relief sometimes is not immediate.

Those with knee pain also may have episodes of buckling, where their knee gives way. As a consequence they are at risk of falling. The buckling can be caused by an injury to a ligament inside the knee, but it is most often due to weakness of the muscles that support the knee, and can be addressed by strengthening, especially of the quadriceps muscle.

Figure 3. Knee x-ray showing osteoarthritis. The bones are closer together than they should be (joint space narrowing) on the left (medial) side of the knee but not the right. On the same side of the knee, there are boney protrusions (osteophytes). Reprinted from the New England Journal of Medicine 354: 841-848 , 2006. 2006 Massachusetts Medical Society. All rights reserved

How do you make the diagnosis of osteoarthritis?

An older person with knee pain or hip pain who has pain with activity usually has osteoarthritis, especially if that pain is chronic and is invariably triggered by particular activities. Diagnosis is often made with an x-ray (see Figure 2 for a typical x-ray of osteoarthritis of the knee. Sometimes the x-ray is normal, because joint damage can be limited to internal structures, such as the cartilage and meniscus that are not visualized at all on the x-ray. The severity of disease seen on x-ray correlates poorly with the severity of symptoms; a mildly osteoarthritic knee on x-ray may be severely symptomatic and vice versa. A patient should not use information about the x-ray to make any decisions about the treatment they need.

Examining fluid inside the joint may help diagnose osteoarthritis. Since osteoarthritis can be confused with other types of arthritis which cause inflammation within the joint, this fluid often can help differentiate the non-inflammatory fluid of osteoarthritis from the inflammatory fluid of other joint disorders.

An MRI is not needed to make the diagnosis of osteoarthritis and is not indicated unless there is reason to believe the patient might have an operable meniscal tear.

X-rays of the hands or hips are valuable to make the diagnosis of osteoarthritis there. In these joints, synovial fluid is less easily obtained than in the knee.

In trying to determine whether you have osteoarthritis, you doctor will consider two different categories of problems (see Table 1) other than osteoarthritis as a cause of your knee, hip, or hand pain. First, there may be other types of arthritis. In most cases, these are not disorders like osteoarthritis which affect only one or two joints, but these types of arthritis, such as rheumatoid arthritis or gout, affect multiple joints in the body. Synovial fluid assessment may be especially helpful to determine which kind of arthritis you have.

The second category of problem that can cause joint pain is a local problem where just one joint is affected, for example, just one knee. Aside from osteoarthritis, the possible causes of the pain include a tear of a structure inside the knee, tendonitis, or bursitis around the knee. Careful examination by your physician of the location of tenderness and questions about particular symptoms such as locking or buckling may help them differentiate your problem from that of osteoarthritis. In meniscal tears, your knee can lock with movement; for ACL tears, there may be buckling or giving way. Many patients with osteoarthritis also have coexistent meniscal tears and even ACL tears. These are usually part of the osteoarthritis process and do not mean that the patient needs meniscal surgery or ACL graft surgery.

Table 1. Conditions other than Osteoarthritis that cause chronic knee or hip pain

Condition	Features Distinguishing this diagnosis From Knee OA
Inflammatory Arthritis Including Rheumatoid Arthritis	Prominent morning stiffness Other joints affected
Gout or Pseudogout	Other joints affected (especially gout); sometimes acute episodes followed by time when there is no pain
Hip arthritis	Pain with hip motion; groin is tender
Chondromalacia Patellae	Person too young to be likely to have OA; symptoms in front of knee with stair climbing or getting out of a chair predominate
Anserine Bursitis	Tender below the knee on the inner side
Trochanteric Bursitis	Hip pain outside the hip; hurts when lie on that side in bed
Iliotibial Band Syndrome (ITB)	Pain near but outside of the knee.
Joint Tumors	Nocturnal or continuous pain
Meniscal tear	Prominent locking or catching of the knee; history of acute injury usually with twisting MRI shows mensical tear
Anterior Cruciate Ligament Tear	Prominent buckling; history of acute injury MRI shows ACL tear

Non-surgical treatments

1. Pain medicines and anti-inflammatories

Pain pills and anti-inflammatories can help relieve pain. Although they can have side effects, for most patients the benefits to pain relief outweigh the risks. The first medication to try is acetaminophen (Tylenol) as needed for pain relief. While not an anti-inflammatory, Tylenol can relieve pain, and has few side effects. If pain is not fully relieved by acetaminophen, a patient can take it (up to four times a day.

If that does not work, then an occasional non-steroidal anti-inflammatory medication (NSAID) can help. Though these medications have more side effects than acetaminophen, they also are more effective for osteoarthritis. Non-prescription NSAIDs include over the counter brands of ibuprofen (e.g., Advil) and naproxen (e.g., Aleve). There also is a large group of prescription NSAIDs that can provide pain relief in osteoarthritis, both by acting as pain relievers, and by alleviating the inflammation inside the joint that often causes pain. These medications are not dangerous to the joint and do not "mask pain" as many patients worry, but they can damage the stomach and need to be taken only after a person has eaten something. If there is a previous history of ulcer disease or bleeding from the stomach or upper GI tract, then a person should avoid these medications or take them only with other medications used to protect the stomach. Anti-inflammatory medications can be started intermittently once or twice a day, and if that is not sufficient, a full prescription dose can help. For ibuprofen, for example, over the counter medications contain 200 milligrams and the patient should try 2 pills after food. A full dose of ibuprofen per day is roughly 2400 milligrams (or 12 over the counter ibuprofens per day). This higher dose should be taken only under a doctor's supervision. Recently, a special class of prescription NSAID-type medications with few stomach side effects called COX2 inhibitors was found to heighten the risk of heart attack. One of these -- rofecoxib (Vioxx) - was withdrawn from the market because of its danger. The American Heart Association has warned against the use of some NSAIDs because of their potential to cause heart disease. The ones that may increase risk include celecoxib (Celebrex) and diclofenac (Voltaren) and possibly others. Naproxen does not increase heart disease risk.

Creams and ointments to rub onto painful joints can also relieve pain. Recently, the FDA approved a cream that contains an anti-inflammatory diclofenac. While this cream does not penetrate the skin well, it does so well enough that it helps relieve joint pain, especially if the joint is close to the skin surface (e.g., hands and knees). It has fewer side effects than pills, causing few stomach problems. Another rub, this one available without a prescription, is capsaicin, which contains the active ingredient of hot peppers. This can relieve pain too, especially in the hands and the knees, but because it contains hot peppers, patients should wash their hands after they rub in the cream so as not to get it in their mouth or eyes.

Shots into the joint can also help relieve pain and sometimes diminish the inflammation that causes the pain. Among the most widely used are cortisone injections (called steroids) and injections of hyaluronic acid (HA). Cortisone injections into the joint generally help relieve inflammation locally and do not cause body wide side effects, and they tend to be safe. They relieve pain for most patients with knee, hip, and hand osteoarthritis, but often do not help for very long, only a week or two. However, for some patients, their effect lasts much longer.

Hyaluronic acid (HA) injections are a controversial treatment for osteoarthritis. Some studies examining the effectiveness of HA suggest it is no better than placebo and, in fact, the HA injected does not remain in the joint for more than a day or two. Despite a paucity of compelling data showing its efficacy versus placebo injection, HA injections have become moderately popular.

Lastly, glucosamine and chondroitin also are widely sold as a treatment for the symptoms of osteoarthritis, but large studies in Canada and the United States have suggested that they are no more effective than placebo. This, however, is a controversial area as one industry source armed with evidence from its own non-FDA regulated trials strongly pushes the notion that industry sponsored trials without regulatory oversight have proven glucosamine's efficacy. Articles back and forth have disputed the credibility of each group's findings. While the likelihood that they are efficacious is negligible, there may be individuals who experience benefit from glucosamine and chondroitin, and they are safe and have become relatively inexpensive.

2. Braces and orthotics

Braces can stabilize knee or hand joints affected by osteoarthritis and when a brace or orthotic restricts joint movement, affected joints sometimes become less painful. There are a wide range of braces available for the knees, starting with a simple elastic sleeve that can be purchased at many pharmacies and can provide the patient both with pain relief and a perception of stability. Splints and braces are available also for painful hand joints, especially at the thumb base. Often these splints just restrict motion of the painful joint and can be worn without limiting hand use.

For knees, an almost infinite complexity of braces is available, including expensive ones that are custom fitted and can push a bowlegged knee into a more neutral position. Since malalignment across the knee (either in a bowlegged or knock-kneed position) can increase focal loading across the knee, it can increase the risk of pain and disability and can accelerate disease progression. Using braces and orthotics to help realign the knee can alleviate pain, improve functioning, and may preserve the knee.

Orthotics are shoe inserts that are often custom made to alleviate pressure on certain parts of the foot, and in some cases to alter the way a person walks. Braces and orthotics tend to be underused, but often relieve pain and allow patients to engage in activities they have avoided because of pain. There is currently little evidence, however, on the effectiveness of shoe orthotics for treatment of knee pain

Unloading weight bearing joints often provides effective relief. The most common strategy to unload painful knees and hips is to use a cane. Canes or walking sticks should be held in the hand on the other side of the most painful joint. So for example, if you have pain in your left knee, hold the cane in your right hand, with the hand at about the level of the outside of your hip.

3. Exercise

Exercise is a mainstay of osteoarthritis treatment; in studies of patients with knee and hip osteoarthritis, exercise substantially improves pain and function. Because muscle weakness is such a key element of the disease and because weakness makes performing activities more difficult and more painful, strengthening muscles around osteoarthritic joints can effectively decrease pain. The trick to exercise is to not make joint pain worse when exercise is carried out and to identify exercises that you enjoy doing. Exercises that strengthen muscles that cross a painful joint can often be done when the joint is in a position where it is not painful, such as lying down, or even slowly and gently doing weight bearing activities that require use of painful joints. For hip osteoarthritis, exercise of the muscles in the buttocks can often be effective. Among the major reasons for failure of exercise to be effective are that 1) patients don't do their exercises, and 2) that they do not progress in terms of exercise training, so that they do only a mild exercise and never go beyond that.

You can find examples of exercises you might try at the following websites:

http://www.arthritis.org/exercise-intro.php (the website for the Arthritis Foundation

http://www.mayoclinic.com/health/arthritis/AR00009

http://www.orthop.washington.edu/uw/livingwith/tabID__3376/ItemID__82/Articles/Default.aspx (this site has movies showing exercise in action)

For patients with knee and hip osteoarthritis, weight loss can help too. In a major trial, a combination of weight loss and exercise was found to be especially effective for patients with knee osteoarthritis.

Considering surgery

Knee and hip replacement surgeries are extremely effective, and often patients successfully return to a state where they have little pain and excellent function. While both operations represent major surgery and require many weeks of rehabilitation, most patients are gratified that they have had the surgery and are in far less pain than before the operation. You should consider surgery if you have tried the medical treatments listed above, and if after trying them still have bothersome pain in your knee or hip and limitation in activities you cherish; in other words, consider surgery when you feel your quality of life is limited in a major way by your osteoarthritis. Whether or not your x-ray shows severe disease, your choice is best determined by how much pain you are having and how disabled you are.

Short of knee and hip replacements, other surgeries are available. When only part of the knee is affected by osteoarthritis, patients can benefit from a partial replacement. A realignment operation, called an osteotomy, can also help in this circumstance. Many surgeons will try an arthroscopic "debridement and lavage, " in which they cut away strands of degraded cartilage and meniscus and remove debris from the joint. Unfortunately, there is no evidence that arthroscopy is effective for osteoarthritis, except if you are having symptoms from a meniscal or ACL tear in your knee.

When seeking a surgeon, look for orthopedists who do these surgeries all the time, not ones whose practices consist of many different kinds of surgeries. Surgeons who have specialized practices doing knee or hip replacements have better surgical outcomes, including fewer complications.

What exciting new treatments are on the horizon?

While cartilage replacement offers an exciting treatment, it is not likely to be useful or effective for patients with established knee or hip osteoarthritis because so many other tissues are already abnormal when osteoarthritis has developed. It is early in disease that cartilage only is affected, and this is usually true in younger patients and in ones who have had specific joint injuries which left cartilage damaged before other tissues also changed. By the time a person is in their fifties, sixties or seventies and has osteoarthritis, bone has probably changed, the joint has likely narrowed, and the other features of osteoarthritis described above have developed. In this setting cartilage transplant is not an option.

New types of joint replacement surgeries including minimally invasive surgeries and implants that last for many years are changing the face of knee and hip replacement and making it likely that persons can have these operations at a younger age than ever before. Even so, patients should wait until their pain and disability are substantial and should try medical treatment first.

While promising, drug treatment for osteoarthritis has never delivered on its promise. That is probably because so much of the joint has already deteriorated by the time the patient develops symptoms. Therefore, medications targeted toward cartilage or even inflammation are not enough to solve the osteoarthritis problem. New treatments targeting inflammation and offering the hope of cartilage preservation are likely to emerge in the next several years, but it is unlikely that these will cure osteoarthritis medically, especially for those with severe disease. For those with milder disease, medication may alleviate symptoms. Like the present, the future of non-surgical treatment for osteoarthritis involves a combination of pills, creams and rubs, orthotics, braces, and exercises. Experiments currently focus on optimizing and improving each of these types of therapies so that a patient with osteoarthritis can have many options to address their particular joint problem.