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Updated: Aug 31 2024

Knee Osteoarthritis

Images
https://upload.orthobullets.com/topic/12287/images/xray6_bilateral_knee-lg.jpg
https://upload.orthobullets.com/topic/12287/images/sunrise.jpg
https://upload.orthobullets.com/topic/12287/images/arthritis.jpg
https://upload.orthobullets.com/topic/12287/images/kellgren_3.jpg
https://upload.orthobullets.com/topic/12287/images/kellgren_4.jpg
  • summary
    • Knee osteoarthritis is degenerative disease of the knee joint that causes progressive loss of articular cartilage.
    • Diagnosis can be made with plain radiographs of the knee.
    • Treatment is observation, NSAIDs, tramadol and corticosteroids for minimally symptomatic patients. Knee arthroplasty is indicated for progressive symptoms with severe degenerative disease.
  • Epidemiology
    • Incidence
      • hip OA (symptomatic)
        • 88 per 100,000 per year
      • knee OA (symptomatic)
        • 240 per 100,000 per year
    • Risk factors
      • modifiable
        • articular trauma
        • occupation, repetitive knee bending
        • muscle weakness
        • large body mass
        • metabolic syndrome
          • central (abdominal) obesity, dyslipidemia (high triglycerides and low-density lipoproteins), high blood pressure, and elevated fasting glucose levels.
      • non-modifiable
        • gender
          • females >males
        • increased age
        • genetics
        • race
          • African American males are the least likely to receive total joint replacement when compared to whites and Hispanics
  • Etiology
    • Pathophysiology
      • pathoanatomy
        • articular cartilage
          • increased water content
          • alterations in proteoglycans
            • eventual decrease in amount of proteoglycans
          • collagen abnormalities
            • organization and orientation are lost
          • binding of proteoglycans to hyaluronic acid
        • synovium and capsule
          • early phase of OA
            • mild inflammatory changes in synovium
          • middle phase of OA
            • moderate inflammatory changes of synovium
            • synovium becomes hypervascular
          • late phases of OA
            • synovium becomes increasingly thick and vascular
        • bone
          • subchondral bone attempts to remodel
            • forming lytic lesion with sclerotic edges (different than bone cysts in RA)
          • bone cysts form in late stages
          • osteophytes form through the pathologic activation of endochondral ossification mediated by the Indian hedgehog (Ihh) signaling molecule
    • Cell biology
      • proteolytic enzymes
        • matrix metalloproteases (MMPs)
          • responsible for cartilage matrix digestion
            • examples
              • stromelysin
              • plasmin
              • aggrecanase-1 (ADAMTS-4)
        • tissue inhibitors of MMPS (TIMPs)
          • control MMP activity preventing excessive degradation
          • imbalance between MMPs and TIMPs has been demonstrated in OA tissues
        • inflammatory cytokines
          • secreted by synoviocytes and increase MMP synthesis
            • examples
              • IL-1
              • IL-6
              • TNF-alpha
    • Genetics
      • inheritance
        • non-mendilian
      • genes potentially linked to OA
        • vitamin D receptor
        • estrogen receptor 1
        • inflammatory cytokines
          • IL-1
            • leads to catabolic effect
          • IL-4
          • matrilin-3
          • BMP-2, BMP-5
  • Classification
      • Kellgren & Lawrence
      • (based on AP weightbearing XRs)
      • Grade 0
      • No joint space narrowing (JSN) or reactive changes
      • Grade 1
      • Possible osteophytic lipping + doubtful JSN
      • Grade 2
      • Definite osteophytes + possible JSN
      • Grade 3
      • Moderate osteophytes + definite JSN + some sclerosis + possible bone end deformity
      • Grade 4
      • Large osteophytes + marked JSN + severe sclerosis + definite bone end deformity
  • Presentation
    • History
      • identify age, functional activity, pattern of arthritic involvement, overall health and duration of symptoms
    • Symptoms
      • function-limiting knee pain
        • effect on walking distances
      • pain at night or rest
      • activity induced swelling
      • knee stiffness
      • mechanical
        • instability, locking, catching sensation
    • Physical exam
      • inspection
        • body habitus
        • gait
          • often an increased adductor moment to the limb during gait
          • antalgic gait associated with knee arthritis
          • knee is maintained in flexion
          • shortened stride length
          • compensatory toe walking
        • limb alignment
        • effusion
        • skin (e.g. scars)
      • range of motion
        • lack of full extension (>5 degrees flexion contracture)
        • lack of full flexion (flexion <110 degrees)
      • ligament integrity
  • Imaging
    • Radiographs
      • recommended views
        • weight-bearing views of affected joint
      • optional views
        • knee
          • sunrise view
          • PA view in 30 degrees of flexion
      • findings
        • pattern of arthritic involvement
          • medial and/or lateral tibiofemoral, and/or patellofemoral
        • characteristics
          • joint space narrowing
          • osteophytes
          • eburnation of bone
          • subchondral sclerosis
          • subchondral cysts
  • Studies
    • Histology
      • loss of superficial chondrocytes
      • replication and breakdown of the tidemark
      • fissuring
      • cartilage destruction with eburnation of subchondral bone
  • Treatment
    • Nonoperative
      • non-steroidal anti-inflammatory drugs
        • indications
          • first line treatment for all patients with symptomatic arthritis
        • technique
          • Non-steroidal anti-inflammatory drugs (first choice)
            • topical and oral NSAIDS recommended
            • selection should be based on physician preference, patient acceptability and cost
            • duration of treatment based on effectiveness, side-effects and past medical history
        • outcomes
          • AAOS guidelines: strong evidence for
      • tramadol
        • indications
          • treatment option for patients with symptomatic arthritis
        • technique
          • weak opioid mu receptor agonist
            • good evidence for mid term (8-13 weeks) improvement in pain and stiffness over placebo
        • outcomes
          • Prior AAOS guidelines recommended its use, but newer guidelines do NOT recommend its routine use
      • rehabilitation, education and wellness activity
        • indications
          • first line treatment for all patients with symptomatic arthritis
        • technique
          • self-management and education programs
          • combination of supervised exercises and home program have shown the best results
            • these benefits lost after 6 months if exercises are stopped
        • outcomes
          • AAOS guidelines strong evidence for
      • weight loss programs
        • indications
          • patients with symptomatic arthritis and BMI > 25
        • technique
          • diet and low-impact aerobic exercise
        • outcomes
          • AAOS guidelines: moderate evidence for
      • bracing
        • medial unloader for isolated medial compartment OA
        • AAOS guidelines: moderate evidence for
      • controversial treatments
        • acupuncture
          • AAOS guidelines: strong evidence against
        • viscoelastic joint injections
          • AAOS guidelines: strong evidence against
        • glucosamine and chondroitin
          • AAOS guidelines: strong evidence against
        • needle lavage
          • AAOS guidelines: moderate evidence against
        • lateral wedge insoles
          • AAOS guidelines: moderate evidence against
        • Orthobiologics (BMAC, PRP, etc.)
          • Bone marrow aspirate concentrate has higher concentration of IL-1ra than both leukocyte poor and rich PRP
          • PRP has better outcomes than Hyaluronic Acid
    • Operative
      • high-tibial osteotomy
        • indications
          • younger patients with medial unicompartmental OA
        • technique
          • valgus producing proximal tibial oseotomy
        • outcomes
          • AAOS guidelines: limited evidence for
      • unicompartmental arthroplasty (knee)
        • indications
          • isolated unicompartmental disease
        • outcomes
          • TKA have lower revision rates than UKA in the setting of unicompartmental OA
      • total knee arthroplasty
        • indications
          • symptomatic knee osteoarthritis
          • failed non-operative treatments
        • techniques
          • cruciate retaining vs. crucitate sacrificing implants show no difference in outcomes
          • patellar resurfacing
            • no difference in pain or function with or without patella resurfacing
            • lower reoperation rates with resurfacing
          • drains are not recommended
      • controversial treatments
        • arthroscopic debridement or lavage
          • AAOS guidelines: strong evidence against
        • arthroscopic meniscal debridement
          • AAOS guidelines: inconclusive evidence
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