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Hip Arthritis

  • Osteoarthritis (OA) of the hip (coxarthrosis) is a degenerative joint disease
  • Characterised by loss of articular cartilage – leads to friction between bones

Epidemiology

  • 2nd most common joint affected in OA after the knee
  • More common in people over 65 years

Etiology/Risk factors

  • Increasing age
  • Female sex
  • Obesity
  • Genetics
  • Hip deformities – hip dysplasia, SCFE , Perthes Disease
  • Articular trauma
  • Strenuous physical occupation

Pathoanatomy

  • Abnormalities in the articular cartilage
    • Increased water content
    • Decreased level of proteoglycans
    • Loss in collagen organisation
  • Synovium and capsule
    • Early phase of OA – mild inflammation in the synovium
    • Intermediate phase of OA – moderate inflammation and hypervascularity of the synovium
    • Late phase of OA – increased thickness and vascularity of synovium
  • Bone              
    • Remodelling of subchondral bone – forms lytic lesions with sclerotic edges
    • Bone cysts

Pathophysiology

  • Basic mechanism – imbalance between matrix metalloproteases (MMPs) and tissue inhibitors of MMPs (TIMPs)
  • MMPs are proteolytic enzymes – responsible for degradation of extracellular matrix proteins
    • Examples of MMPs – stromelysin, plasmin, aggrecanase-1
    • MMP synthesis is stimulated by cytokines released by the synovium – IL-1, IL-6, TNF-alpha
  • TIMPs inhibit MMP activity and prevent excessive degradation

Classification – Tonnis Classification

  • Grade 0 – no changes
  • Grade 1 (mild) –  osteosclerosis, minor joint space narrowing
  • Grade 2  (moderate) – small bone cysts, moderate joint space narrowing
  • Grade 3 (severe) – large bone cysts, severe joint space narrowing/obliteration

Clinical features

  • Pain in the hip – aggravated by weight-bearing, improved with rest
  • Hip stiffness
  • Sensation of locking and/or crunching of joint
  • Decreased range of motion

Diagnosis

X-ray
  • Joint space narrowing
  • Osteophytes (bone spurs)
  • Subchondral sclerosis and cysts
  • Acetabular retroversion

MRI

  • If nerve root compression/spinal stenosis is suspected

Synovial fluid aspirate

  • Viscous with low cell count

Differential diagnosis

  • Trochanteric bursitis – lateral hip pain radiating down lateral leg
  • Gluteus medius tendinopathy – lateral hip pain
  • Sciatica – low back and buttock pain

Treatment

  • NSAIDs – first line
  • Walking stick
  • Lifestyle modifications – weight loss, physiotherapy
  • Intra-articular corticosteroid injections

Operative

  • Periacetabular osteotomy
  • Femoral head resection
  • Hip resurfacing – indicated for young, active males
  • Total hip replacement
    • For end-stage, severe OA in older patients
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