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Deciphering the telltale signs of osteoarthritis

Physicians need to distinguish this common condition from other joint disorders

From the July-August ACP Observer, copyright 2005 by the American College of Physicians.

By Phyllis Maguire

SAN FRANCISCO—A patient with established knee osteoarthritis—who rarely needs pain medication—arrives at your office hobbled by crushing knee pain. Her mobility is so limited that she shows up in a wheelchair, with pain so intense she hasn't been able to lie down in bed for three days.

If you think the patient is probably having just a severe flare-up of her underlying osteoarthritis (OA), you're not alone. Osteoarthritis is, after all, the most common form of arthritis, affecting as many as two-thirds of Americans over age 60.

However, according to Allan C. Gelber, ACP Member, associate professor of medicine and director of the rheumatology fellowship program at Baltimore's Johns Hopkins University School of Medicine, physicians need to recognize clues that distinguish osteoarthritis from other arthropathies, as well as from disease mimics that can affect the joints—and exacerbate an underlying diagnosis of osteoarthritis.

"There are several common scenarios," he said at an Annual Session presentation on osteoarthritis, "even in patients with established disease."

Here's an overview of the three most common sites of osteoarthritis, and a look at some telltale signs that can help you diagnose other conditions. (Also see "Classic symptoms of osteoarthritis" and "Steroids and NSAIDs: treating the pain.")

Hand OA

According to Dr. Gelber, the most common site of osteoarthritis in the peripheral skeleton—the hand—is also one of the most challenging.

To start, you need to know the three locations where hand osteoarthritis is typically found: the distal interphalangeal joint, the proximal interphalangeal joint and the base of the thumb.

Common arthridities of the hand

Fingers with osteoarthritis.

Hands with rheumatoid arthritis.

Hands with gouty tophi.

Dr. Gelber said that the more patients report classic osteoarthritis symptoms—pain that is activity-related and not too prevalent at night—the stronger the case that the patient is suffering from osteoarthritis. The challenge, however, is when patients report symptoms that last not 20 minutes but for two-and-a-half hours after they get up in the morning and that interfere with their ability to sleep.

"That may be more indicative of rheumatoid arthritis," said Dr. Gelber, adding that both osteoarthritis and rheumatoid arthritis have a predilection for the proximal interphalangeal joints.

Radiographic evidence can help with the diagnosis. Look for the following classic features of osteoarthritis on X-rays:

  • heterogeneous narrowing of the joint space;
  • development of a spur or osteophyte; and
  • subchondral cysts. "You can observe some lucencies [of bone]," Dr. Gelber said, "but they're away from the cortical margin."

If you're looking at early rheumatoid arthritis, on the other hand, you'll likely see thinning of bone around both sides of the joint and uniform narrowing of the joint space, he said, with lucencies at the cortical margin. Regarding lab tests, Dr. Gelber said he uses two serum markers to help diagnose rheumatoid arthritis: rheumatoid factor and cyclic citrullinated peptide.

For patients with osteoarthritis that causes bony prominences at the thumb's base, he recommended referring them to the physical therapist most frequently used by local hand orthopedic specialists. "Patients will have a better resolution if they can be fitted with a splint for the base of their thumb," he said. "The splint helps the process settle down."

Knee OA

When a patient presents with knee pain, Dr. Gelber said, "I'm interested, just like with a patient with chest pain or dyspnea, in the quality of the pain. How long does it last and how constant is it? What makes it better and what makes it worse?"

Typically, patients with knee OA find that their pain gets worse with activity. Patients with inflammatory arthritis, on the other hand, find that pain and stiffness abate if they stand up and move around.

And patients with knee OA typically don't find that pain interferes with their ability to sleep. When patients say they can't sleep, that may be a clue that something else may be at play.

What complicates matters, however, is that patients with moderate to severe OA can be uncomfortable at night. "I need to interpret nocturnal symptoms in the entire context of their physical exam and lab data," he said.

Patients with mild or even moderate forms of the disease have brief, self-limited pain. The classic presentation of knee osteoarthritis is the patient who complains of knee pain for up to 30 minutes when they wake up, Dr. Gelber said. "If a patient comes to you and says, 'I hurt from 7 a.m. to noon,' you have to suspect something else."

Another red flag? The tempo of a patient's osteoarthritis course dramatically changes, with a sharp crescendo in loss of mobility and discomfort.

That was the case with his female patient who had to be wheeled into his office after spending three days trying to sleep on a recliner. When the patient—who'd had an established diagnosis of osteoarthritis for several years—came to see him, her left knee was twice the size of her right one.

"The left knee was warm; the right knee was cool," he explained. "The landmarks of the left knee were clearly obscured, while on the right knee, they were still relatively well demarcated. I was impressed by what was clearly a synovial effusion."

For Dr. Gelber, the first step is arthrocentesis, a procedure that about half the internists attending the session said they performed about once a week. While normal synovial fluid is clear, abnormal fluid exhibits color and appears opaque.

"There are three pieces of information I want to know with [lab tests of] someone with a joint effusion: cell count, crystal analysis, and gram stain and culture," he said.

For patients whose synovial fluid is compatible with osteoarthritis alone, their white blood cell count will be in the range of 200 to 2,000 per cubic millimeter. The white cell count of normal synovial fluid is less than 200; the range of 200 to 2,000 is abnormal, but noninflammatory.

White blood cell counts above 2,000 are abnormal and indicate an inflammatory arthritis, while the higher the cell count goes—to 40,000, even 80,000—"you're increasing the specificity for septic [arthritis]," he said.

In the case of his female patient, her white blood cell count of 40,000 led Dr. Gelber to suspect a crystal arthropathy, which he found when he looked at the fluid for crystals under a polarized microscope: The rhomboid-shaped crystals were blue when their long axis was parallel to the axis of polarized light, and yellow when perpendicular. In addition to underlying osteoarthritis, Dr, Gelber realized, the patient also had pseudogout.

"By taking out approximately 60 cc of joint fluid and injecting her knee with steroids, there was dramatic improvement in comfort," said Dr. Gelber, who typically uses 40 mgs. of triamcinolone, along with 1 cc of 1% lidocaine. "The more you suspect crystal arthropathy, the more you can feel comfortable injecting patients with steroids at one setting." The more you suspect a septic process, however, the more you want to hold off and have patients come back another time for a steroid injection, after first confirming that culture of synovial fluid is negative.

Another common diagnosis to consider when there is an acute decline in knee symptoms is a Baker's cyst. In these patients, the swollen joint fluid extends posteriorly into the popliteal space.

"Frontline therapy for an inflamed Baker's cyst is to inject the patient," Dr. Gelber said, "but I'd like to have an ultrasound as well to either rule it in or exclude deep venous thrombosis."

And when it comes to distinguishing knee osteoarthritis from a torn meniscus, history is key. Typically, patients with a torn meniscus will report some type of trauma that brought on an abrupt change in symptoms and mobility, or another telltale sign: a knee that is locking or giving way.

Hip OA

As with other forms of osteoarthritis, patients with hip OA complain of morning stiffness and pain that is self-limiting. Dr. Gelber said that according to his own observations, about 80% of patients who report hip pain point to the buttock region as their source of pain. A large number also complain of either lateral pain or pain in the groin.

You can be most confident you're dealing with hip OA, however, when patients complain of anterior groin line pain. "I'm most comfortable diagnosing OA of the hip when the person has pain putting on his pant leg and his shoes and socks," Dr. Gelber said. "On exam, I'm most interested in hip flexion, and internal and external rotation."

There are, however, other common reasons why patients complain of hip pain. "When the pain is clearly lateral," he said, "the No. 1 concern is trochanteric bursitis." This is a relatively easy diagnosis to make when patients identify the lateral hip region as the site of their pain when you press on the greater trochanter. "Injecting 40 mgs of triamcinolone in a fanlike distribution can bring about substantial symptomatic relief," he said.

As for patients who complain of posterior pain? "I'm worried about radiculopathy and spinal disease," he said.

The information included herein should never be used as a substitute for clinical judgment and does not represent an official position of ACP.

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Steroids and NSAIDs: treating the pain

How many times a year can physicians feel comfortable injecting steroids into patients to relieve the pain associated with osteoarthritis and other joint disorders?

A patient with an inflamed joint or trochanteric bursitis may on occasion need steroid injections every three or four months, while those with knee osteoarthritis can be injected two or three times a year, said Allan C. Gelber, ACP Member, associate professor of medicine and director of the rheumatology fellowship program at Baltimore's Johns Hopkins University School of Medicine.

"That's for patients with the most advanced disease. Surgery is an option patients prefer to avoid because of their age," Dr. Gelber said, "as long as there is symptomatic relief."

While he routinely adds lidocaine to steroid injections to give patients immediate relief, he uses the drug alone only rarely and then in only one of two situations: when he is not positive what the disorder is, and the lidocaine injection is a therapeutic trial; and when a patient lives close enough to return within 36 hours when the effect of the lidocaine wears off. He will then give them a steroid injection that will likely achieve more sustained symptomatic benefit.

Although he said he is increasingly uncomfortable using nonsteroidal anti-inflammatory drugs (NSAIDs) in patients with renal insufficiency, gastrointestinal dysfunction or central nervous disease, Dr. Gelber said he nonetheless regularly prescribes NSAIDs. "There is no such thing as a risk-free medication," he said. "I try to individualize treatment to each patient's risks and benefits."

He also said he's much less skeptical now about the therapeutic benefits of glucosamine and chondroitin than he was five years ago, thanks to recent findings from well designed placebo-controlled randomized clinical trials. At the same time, he said, osteoarthritis now is where rheumatoid arthritis was 10 years ago before the development of biologic agents.

"It's clear that, as measured in synovial fluid and serum, degradative enzymes are higher in osteoarthritis patients than in controls," he said. New drugs are now being developed that may be able to interfere with those degradative processes—or stimulate or repopulate normal cartilage to improve joint structure and function.

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Classic symptoms of osteoarthritis

  • Pain usually lasts only a short period of time.
  • Pain is exacerbated by activity.
  • Pain does not keep patients awake at night.

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