Arthritis

Differential by number of joints

• Monoarthritis
  • 85% of non-gonococcal septic arthritis (therefore 15% >1 joint)
  • Gout/pseudogout
  • Gonococcal septic arthritis
  • Trauma-induced arthritis
  • Osteoarthritis
  • Lyme disease
  • AVN
  • Tumor
  • Haemarthrosis
  • TB
  • Viral

Differential by number of joints

• Oligoarthritis (2-3)
  • 15% of non-gonococcal septic arthritis (more commonly Staph or Strep)
    • More likely if RA, immunocompromised, gout, diabetes and/or renal disease
    • Mortality 30% vs. 11% for monoarticular non-gonococcal septic arthritis
  • Lyme disease
  • Reactive arthritis (Reiter’s syndrome)
  • Gonococcal arthritis
  • Rheumatic fever

Differential by number of joints

• Polyarthritis
  • Rheumatoid arthritis
  • SLE
  • Viral arthritis
  • Osteoarthritis
  • Serum sickness

Polyarthritis

• Autoimmune
  • Rheumatoid
  • SLE
  • Seronegative spondyloarthropathy – Psoriatic/IBD/AS
  • Reiter’s syndrome
  • Amyloid
  • Sarcoidosis
  • Serum sickness
  • Dermatomyositis
  • Polymyalgia rheumatica

Polyarthritis

• Infective
  • Gonococcal septic arthritis
  • Viral – Parvovirus, Rubella, HepB, HepC, Ross River, Dengue
  • Endocarditis
  • Lyme disease
  • Yersinia
  • Typhus

Migratory arthralgias

• Gonococcal arthritis
• Acute rheumatic fever
• Lyme disease
• Viral arthritis
• SLE

Synovial fluid analysis

• Send for cell count and MCS + crystals
• Glucose, protein, LDH and lactate do not direct treatment at this stage
• Positive gram stain with acute joint swelling and pain
  • Empirical treatment for septic arthritis
  • Gram stain positive in <50% of patients with septic arthritis
• Classically
  • Normal – Clear/straw coloured, <200 WCC/uL
  • Inflammatory – Turbid, 2000 – 50 000 WCC/uL, >50% polymorphs
  • Infected – Opaque, WCC >50 000, >85% polymorphs

Synovial fluid analysis

• >50 000 WCC/mm3 and >75% PMN’s
  • 73% sensitive and 77% specific for septic arthritis
  • Start empirical treatment
• >25 000 WCC/mm3 or >90% PMN’s
  • Lower threshold used in those at risk or systemic signs of infection
  • Consider IV antibiotics or admission and observation while culture pending
• >200 WCC/mm3 or >25% PMN’s
  • Even lower threshold if immunocompromised with joint swelling or systemic signs of infection
  • Consider empirical antibiotics or admission for observation while culture pending

Synovial fluid analysis

• 10 000 – 80 000 WCC/mm3
  • Threshold for gonococcal arthritis if suspicion exists
  • <50% have positive culture from joint aspirate
  • Need urogenital cultures, pharynx and rectum cultures as indicated by hx
  • Empiric IV antibiotics and admit
• 2000 – 120 000 WCC/mm3
  • Threshold for rheumatoid arthritis with possible co-existing septic arthrits
  • Look for infected rheumatoid nodules or ulcerated foot calluses (source in 76% of cases)
  • Often don’t have impressive examination findings
  • Consider empirical IV antibiotics or admission and observation

Risk factors

• Non-gonococcal septic arthritis
  • IVDU
  • Immunosuppression (especially HIV)
  • Diabetes mellitus
  • Rheumatoid arthritis
  • Prosthetic joint (knee or hip mostly)
  • Age >80
  • Skin ulceration and/or infection
  • Haemophilia
  • Hypogammaglobulinaemia
  • Malignancy
  • Haemodialysis
  • Liver disease
  • Alcoholism
  • Steroid therapy

Risk factors

• Gonococcal septic arthritis
  • HIV
  • IVDU
  • Pregnancy
  • Menses
  • SLE
  • Complement deficiency

Other tests

• WCC and CRP cannot be used to rule out septic arthritis but can guide response to therapy and be used as a criterion for aspiration a prosthetic joint
• BC should be taken before empiric therapy initiated, however, sensitivity for identifying causative organism is only 23-36%

Arthrocentesis

• 1/10 000 infection rate
• Defer if INR >4 but not if on NOAC’s or antiplatelets
• Cleanse large area of skin with povidone-iodine solution then clear away with alcohol wipe to prevent introduction into joint (irritating) and sterilisation of aspiration sample
• Anaesthetise skin and soft tissues with 25G needle (avoid intra-articular injection as can inhibit bacterial growth in aspiration sample)
• Use 18G needle for aspiration of large joints (up to 22G for smaller joints)
• Remove as much synovial fluid as possible for higher yield and reduced pain
• Send for culture, gram stain, cell count and crystals

Joint aspiration

• Shoulder anterior approach
  • Externally rotate humerus and insert needle just lateral to coracoid process directed posteriorly
• Elbow
  • Elbow 90 degrees flexion on table with hand prone
  • Centre of anconeus triangle between lateral epicondyle, radial head and lateral aspect of olecranon tip
  • Sulcus just proximal to radial head
  • Direct needle medially and perpendicular to radius
• Wrist
  • Dorsal aspect of wrist, perpendicular to skin, ulnar to the radial tubercle and anatomic snuffbox, between EPL and common extensor tendons

Joint aspiration

• Hip joint
  • Get ortho involved
• Knee joint aspiration
  • Medial or lateral to patella with knee fully extended
  • 1cm inferior to the patellar edge (when supine)
  • Direct needle posterior to patella and horizontally towards joint space
  • Suprapatellar bursa also possible
• Ankle joint
  • Tibiotalar joint (medial) preferred with needle inserted into sulcus lateral to medial malleolus and medial to tibialis anterior and EHL tendons
  • Planar flex foot and insert needle angled cephalad

Septic arthritis

• Non-gonococcal 
  • Joint pain (85%), joint swelling (78%), fever (57%) are the only findings that occur in >50% of patients with bacterial nongonococcal arthritis
  • Sweats and rigors are less common
  • Knee in 50% of adults
  • Resistance to passive or active joint movement with limited ROM are notable but common with gout without infection and may be absent in the immunosuppressed patient

Septic arthritis

• Non-gonococcal
  • Sensitivity of WCC >50 000 is only 56% in all-comers
  • Sensitivity of ESR >30 is 76-96% but is non-specific
  • If septic arthritis cannot be reliably excluded after aspiration, admit patient for empirical antibiotics and observation until synovial fluid culture results obtained
    • Flucloxacillin 2g q6h + BenPen 1.2g q6h
    • + Gent if <6yo or IVDU
    • Consider vancomycin

Septic arthritis

• Gonococcal
  • Most common cause in sexually-active young adults
  • Typically prodromal migratory arthritis and tenosynovitis before pain and swelling settle on one or two joints
  • Vesiculopustular lesions on fingers may be seen
  • Synovial fluid cultures positive in only 25-50%

Septic arthritis

• Gonococcal
  • Cultures of posterior pharynx, urethra, cervix and rectum increase the culture yield
  • If clinically suspected, should be empirically treated
  • Daily joint aspiration is typical until resolution
  • Third-generation cephalosporins are effective, however, early on treat as for non-gonoccal septic arthritis

Gout and pseudogout

• Gout is the most common form of inflammatory arthritis in men >40
• Risk factors: Post-chemo, psoriasis, renal Tx, ciclosporin, alcohol, diuretics, renal disease, tacrolimus, levodopa, Indigenous
• Typically great toe or knee monoarthritis in man >40 (monoarticular in 90%)
• Clinical features
  • Joint pain over hours often following trauma, surgery, significant illness or change in medications (maximal within 6-12 hours)
  • Predilection for foot and knee

Gout and pseudogout

• Diagnosis
  • Uric acid crystals (negatively bifringent) and calcium pyrophosphate (positively bifringent)
  • 30% of patients will have normal serum uric acid levels
  • Presence of crystals, absence of gram stain or culture and dramatic response to NSAID’s confirms diagnosis
  • If initially cannot rule out septic arthritis, admit until cultures and/or clinical response clarify the diagnosis
  • Serum urate <450umol/L in untreated patients almost excludes gout

Gout and pseudogout

• Treatment
  • NSAID’s for 5-7 days (not for renal patients though)
    • Indomethacin 50mg TDS
  • Colchicine 1mg then 500mcg 1 hour later (do not repeat within 3 days)
  • If renal insufficiency, narcotics indicated + prednisone 10mg BD or 30mg daily for 3-5 days then taper over 2 weeks if not diabetic
  • Once acute symptoms resolved, prophylatic allopurinol/probenacid and elimination of diuretics, aspirin or cyclosporine therapy

Pseudogout

• Knee joint in 50%
• Polyarticular in 5%
• Ix – X-ray always shows calcification of intra-articular cartilage
• NSAID’s and colchicine effective

Viral arthritis

• Parvovirus arthritis
  • Erythema infectiosum in children
  • <50% of adults get rash but do get polyarticular arthralgia, morning stiffness, swelling, erythema
• Hepatitis virus arthritis
  • Hep B most often causes knee arthritis
  • Fever, lymphadenopathy, joint pain then jaundice
  • Immune complex deposition is the cause
  • HepC can cause polyarticular arthritis that may become chronic
• Rubella arthritis
  • Occurs in 50% of adult females with acute rubella after classic rash

Viral arthritis

• Alpha viruses
  • Barmah forest virus
  • Chikungunya
  • Ross river virus

Haemarthrosis

• Traumatic
  • High association with ligamentous injury and intra-articular fracture
  • Aspiration of large traumatic effusions provides pain relief for approximately 1 weeks and increased ROM but no long-term benefit
  • Treatment 
    • Immobilisation, ice, elevation
    • Follow-up with LMO
• Spontaneous
  • Usually indicates systemic illness
  • Haemophiliacs
  • Joint aspiration is controversial but is recommended for large haemarthroses that can be aspirated within 12 hours of onset
  • Joint aspiration should only be performed after factor replacement

Reactive arthritis

• Reiter’s syndrome
• Seronegative spondyloarthropathy characterised by acute, asymmetric oligoarthritis occurring 2-6 weeks after infectious illness
• Classic triad is arthritis, urethritis and conjunctivitis
  • Do not need all three for diagnosis
• Post-venereal – Follows chlamydia, Ureaplasma
• Post-dysenteric – Salmonella, Shigella, Yersinia, Campylobacter, E. coli and C. difficile
• Conjunctivitis occurs in 1/3 of post-venereal and >50% of post-dysentery cases
• Typically lower extremity joint involvement, especially feet
• Long-term combination antibiotics now used for Chlamydia-induced post-venereal reactive arthritis using rifampicin + doxy/azithromycin

Bursitis

• Non-septic
  • Mostly elbow or knee
  • Repetitive trauma, gout, pseudogout or RA
  • Affected bursa easily palpated but not tender or erythematous
  • If bursitis is acute – consider infectious cause
  • Treatment – NSAID’s, avoidance of activities that produce symptoms
  • Aspiration only if infection considered likely

• Infectious
  • Likely from skin contiguous spread to injured or inflamed bursa
  • Acute pain, tenderness, erythema, overlying warmth
  • Prepatellar (50%), olecranon (40%)
  • Fever in <50%
  • Aspirate for diagnosis and therapy

• Infectious
  • Diagnosis confirmed by one of the following:
    • Positive gram stain (in 2/3)
    • WCC >3000/mm3
    • >50% PMN
    • Glucose <1.7mmol/L
    • Bursal to serum glucose ratio <50%
    • WCC >1000 suggestive of infection, RA or gout
    • WCC > 50 000 = septic
  • Organisms – S. aureus, S. epidermidis, Strep
  • Generally responds well to oral antibiotics
  • Admit for incision and debridement, IV antibiotics (if unwell, extensive purulent bursitis, extensive surrounding cellulitis, suspected joint involvement, immunocompromise or failure to improve on oral therapy)

Osteomyelitis

• In adults, mostly contiguous spread from joints or skin infections e.g. diabetic foot infection
  • Commonly suffer spinal osteomyelitis
• In children, mostly haematogenous to metaphysis of long bones
  • If metaphysis is intracapsular (proximal radius, humerus or femur) risk of spread to septic arthritis
• All mostly S. aureus
• In the elderly, spinal osteomyelitis often due to Gram-negative enteric bacteria

Last Updated on November 4, 2020 by Andrew Crofton