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Rheumatology - Osteoarthritis - Fast Facts | NEJM Resident 360

Osteoarthritis (OA) is the most common joint disorder in the United States and most often affects the knees, hips, hands, and the metatarsophalangeal joints of the great toes. Patients typically present with chronic pain that is worsened with activity and improves with rest. Stiffness of the affected joint is common and usually lasts for a short duration (<30 minutes), unlike inflammatory arthritis, in which prolonged stiffness (>1 hour) is typical, especially in the morning. Exacerbations of pain are frequently described but occur with a variable pattern.

OA can occur as a primary disease (e.g., genetic predisposition) or secondary to damage from prior or coexisting conditions (e.g., inflammatory arthritis or trauma to the affected joint(s). A helpful mnemonic to remember causes of secondary OA is THE CHARMIN: trauma, hemarthrosis, endocrinopathy, crystal hypermobility, rheumatic disease, metabolic disease (especially iron overload), infection, neonatal/congenital. In this section, we focus on primary OA.

Diagnosis

• History and physical examination are the keys to diagnosis; often no further workup is needed.

  • Characteristics of OA include activity-related pain, insidious onset, brief morning stiffness (e.g., <30 minutes), and no systemic symptoms.

  • View a video review of how to perform a clinical knee examination here and examination of the hand and wrist here.

• Laboratory tests are not routinely required unless there is suspicion of other causes of joint pain such as infection or inflammatory arthritis.

  • Complete blood count (CBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) testing may be helpful to evaluate other possible diagnoses, but abnormalities in these tests will not rule out or rule in OA.

• Synovial fluid examination (see Undifferentiated Inflammatory Arthritis for more details) is not routinely required unless there is suspicion of other articular processes, such as infection, crystal disease, hemarthrosis, or inflammatory arthritis.

  • Synovial fluid white blood cell (WBC) counts between 200–2000 cells/mm ³ with <70% (typically<25%) polymorphonuclear leukocytes are consistent with OA or another noninflammatory joint disease.

• Radiography: Plain films are not routinely indicated, as the radiographic changes do not correlate well with the symptoms experienced by patients. Plain films may be useful to document the presence and severity of OA, to differentiate OA from other conditions (e.g., inflammatory arthritis with erosive changes, fracture, osteonecrosis, bone tumors/metastases, fracture), or in the planning for total joint replacement.

  • Radiographic features of OA include joint-space narrowing, osteophytes, sclerosis, and subchondral cysts.

The following table lists features that distinguish OA from other joint disorders:

(Source: Psoriatic Arthritis. N Engl J Med 2017.)

See these Clinical Practice cases for tables that summarize differentiating OA from hip and knee arthritis.

Treatment

The treatment of OA starts with maximizing nonpharmacologic measures. If improvement is not adequate, pharmacologic measures should then be considered.

Nonpharmacologic therapies:

• Land- or water-based exercises or physical therapy (PT) may produce lessening of pain and improvement of function; on average, improvement attributable to PT is modest.

• In those with BMI in overweight and obese range, significant loss of excess weight (at least 10% of total body weight) demonstrated benefit in knee OA.

• Biomechanical realignment can be provided with braces or shoe inserts (for knee OA).

• For hand OA, a hand therapist should conduct assessment with the aim of providing PT, devices for activities of daily living assistance, joint protection, and splinting.

Pharmacologic therapies:

• acetaminophen

• topical capsaicin

• topical nonsteroidal anti-inflammatory drugs (NSAIDs; preferred in patients aged ≥75)

• oral NSAIDs (see this study on cardiovascular safety of NSAIDs)

• duloxetine

Treatments with uncertain or unfavorable balance of risks and benefits:

• tramadol

• • Stronger opioids should be reserved for use after failure of other therapy, or avoided all together.

  • The risks associated with use of these medications were outlined in this recent study.

• glucosamine, chondroitin

• fish oil

• acupuncture

• disease-modifying antirheumatic drugs (such as methotrexate, hydroxychloroquine, sulfasalazine)

• oral glucocorticoids

• intra-articular therapy such as glucocorticoids and, in certain cases, hyaluronic acid and platelet-rich plasma

Surgical interventions:

Total knee replacement (TKR) and total hip replacement (THR):

• Indications for elective (nonemergency) knee and hip surgery include failure of conservative treatments, significantly impaired function and quality of life, radiographic evidence of significant OA deemed responsible for symptoms, lack of comorbidities that would make surgery unacceptably risky, and patient preference and willingness to accept the risks of surgery.

• Timing of surgery can be tricky, but the general principle is to avoid performing surgery too soon (when symptoms are mild and revision surgery may be necessary in the future) or too late (when the patient may no longer be a good surgical candidate and years of suffering have been endured).

• Arthroscopic surgery is not beneficial for knee OA.

Read about a randomized controlled trial comparing PT and total knee replacement for knee OA in this blog post, or watch the NEJM Quick Take video summary.

Read the Osteoarthritis Research Society International (OARSI) guidelines for nonsurgical management of knee OA here.

See a NEJM Knowledge+ algorithm on the diagnosis and treatment of osteoarthritis.

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