Osteoarthritis (OA) of the Knee

Background

• Osteoarthritis (OA) of the knee is characterized by articular cartilage loss, bone remodeling, and periarticular muscle weakness resulting in knee joint pain, swelling, deformity, and instability.
• The causes of OA can be idiopathic or a consequence of chronic repetitive trauma or joint infection, congenital or developmental disease, crystalline deposition diseases, or autoimmune arthritis.
• Risk factors for OA include age > 50 years, female sex, increasing body mass index (BMI), prior knee injury, joint laxity, occupational or recreational overuse, and family history.

Evaluation

• The patient typically presents with a gradual onset of activity-related knee pain and instability, which may progress to lower extremity weakness and functional limitations.
• Common physical exam findings include crepitus, bony tenderness, bony enlargement, restricted joint movement, and joint effusion without palpable warmth.
• There is no universally applicable reference standard for diagnosing knee OA but a diagnosis can often be made based on risk factors, symptoms, and a physical examination.
  • Patients > 40 years old with usage-related knee pain, short-lived morning stiffness, functional stiffness, and ≥ 1 typical sign on exam (crepitus, restricted movement, bony enlargement) can be diagnosed clinically with OA without radiographic imaging.
  • The severity and progression of OA pain can be assessed using the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index.
• Plain radiography is considered the ‘gold standard’ for morphological assessment of knee OA, with typical findings of focal joint space narrowing, osteophytes, and subchondral bone sclerosis and subchondral cysts.
• If a palpable effusion is present, synovial fluid should be aspirated and analyzed to exclude inflammatory or infectious disease (usually < 2,000 leukocytes/mm³ in OA), or to exclude the presence of urate and calcium pyrophosphate crystals.
• Lab testing is not routinely indicated unless another cause such as inflammatory arthritis or a systemic condition is suspected.

Management

• Exercise therapy (including physical therapy) and weight loss (if indicated) are the mainstays of nonsurgical management of symptomatic knee OA.
  • Self-management programs are recommended for patients with knee OA (Strong recommendation); primary components of self-management programs include patient education, weight management, exercise, use of assistive/adaptive devices, and appropriate footwear.
    • Weight loss is recommended for patients with BMI ≥ 25 kg/m² (Strong recommendation).
    • Patients should participate in a regular (daily) exercise program (matching his or her ability) (Strong recommendation).
    • Consider the use of walking aids, assistive technology, and adaptations at home and/or work to reduce pain and increase participation in daily activities (Weak recommendation).
    • A walking cane should be used on the contralateral side.
  • Primary goals of physical therapy are improved pain, function, and joint stability.
    • Consider adjunctive rehabilitation components, including:
      • physical modalities
      • non-elastic therapeutic knee taping (also called Leukotaping, McConnell taping, and patellar taping) (in patients with patellofemoral OA)
      • valgus knee braces (in patients with medial knee OA)
    • Do not prescribe wedge insoles for patients with symptomatic unicompartmental knee OA (Strong recommendation).
• Pharmacologic agents
  • For initial management of OA of the knee, recommended options include
    • topical and/or oral nonsteroidal anti-inflammatory drugs (NSAIDs) (Strong recommendation).
    • acetaminophen (Weak recommendation)
  • In patients with inadequate response to first-line pharmacologic agents, consider duloxetine (Weak recommendation). The use of opioid analgesics is usually discouraged, but may be considered when all other options have failed, in which case tramadol is preferred over other options (Weak recommendation).
  • In patients with a knee OA flare (joint inflammation and effusion), consider intra-articular corticosteroid injection (Weak recommendation).
  • Guideline groups disagree regarding the usefulness of hyaluronic acid, and so shared decision making is appropriate taking into account patient values.
• Alternative/complementary approaches may be considered in patients with persistent symptoms and dysfunction.
  • Dietary and herbal therapies to consider (Weak recommendation) include:
    • curcumin (turmeric extract)
    • ginger
    • glucosamaine and/or chondroitin sulfate
      • evidence for efficacy is inconsistent and the benefit is uncertain
      • glucosamine and/or chondroitin sulfate appear safe and have not been associated with significant adverse effects
  • Consider enrollment in a Tai Chi program as part of nonpharmacologic management of OA of the knee (Weak recommendation).
  • Other alternative therapies to consider include:
    • yoga
    • massage therapy
    • balneotherapy (spa therapy/mineral baths)
    • magnet therapy
    • whole body vibration
    • mud pack therapy
    • leech therapy
  • Acupuncture
    • Acupuncture is not recommended for most patients with symptomatic knee OA (Strong recommendation), but acupuncture may be considered if chronic moderate-to-severe pain is present and the patient is a candidate for total knee arthroplasty (TKA) but is unwilling to have the procedure, has comorbid conditions, or is taking concomitant medication that contraindicates surgery (Weak recommendation).
    • Moxibustion, a type of acupuncture with higher-quality evidence of efficacy, may be considered in the management of knee OA.
• Nonarthroscopic surgery (such as a partial or total knee replacement) should be reserved for cases where symptoms are persistent, and are refractory to both pharmacological and nonpharmacological treatment modalities.
  • Base the type and timing of surgery on the patient's symptoms and degree of suffering (impact on quality of life and activities of daily living), stage of knee OA, age, physical activity level, and comorbidities.
  • Joint-preserving surgery:
    • Consider high tibial osteotomy (HTO) only in active patients with symptomatic medial knee OA and varus knee alignment (Weak recommendation).
    • Consider distal femoral osteotomy (DFO) only in patients with substantial knee valgus (> 10-15 degrees between anatomic and mechanical axes) and lateral compartment knee OA.
    • Arthroscopy with lavage and/or debridement is not recommended for patients with a primary diagnosis of knee OA (Strong recommendation); however, it may be considered for short-term symptom relief in some patients who have failed physical therapy and want to delay more invasive procedures such as total knee arthroplasty. Patients need to be informed that arthroscopy has not been shown to have significant improvement in overall function or long term benefit.
  • Joint-replacing surgery:
    • Consider unicompartmental knee arthroplasty (UKA) in younger patients with less severe knee OA which is limited to 1 compartment.
    • Consider total knee arthroplasty (TKA) in patients with knee OA not achieving adequate pain relief and functional improvement from both nonpharmacologic and pharmacologic treatment (Weak recommendation).