1. Septic arthritis
Inflammatory joint disease caused by bacterial, viral or fungal infection.

2. Route of infection
dissemination of pathogens via
Blood (most common)
Direct from adjacent site
Acute osteomylitic focus
Adjacent soft tissue infection
Penetrating trauma
Iatrogenic means
Etiology
S. aureus
H. influenzae (children < 3 y.)
G-ve bacilli (E. coli)
Streptococci

4. Pathology Acute synovitis with a purulent joint effusion
Synovial membrane becomes edematous, swollen, hyperemic & produces increase amount of cloudy exudates contains leukocytes and bacteria
As infection spread through the joint, articular cartilage is destroyed by bacterial and cellular enzymes.
If the infection is not arrested the cartilage may be completely destroyed.
Pus may burst out of the joint to form abscesses and sinuses.
The joint may be become pathologically dislocated.

5. With healing there will be:
Complete resolution and return to normal.
Partial loss of cartilage and fibrosis.
Bone ankylosis
Bone destruction and permanent deformity.

6. Clinical presentation
Acute pain and swelling in a single large joint
Commonly the hip in children and the knee in adults.
The most commonly involved joint
Knee (50%)
Hip (20%)
Shoulder (8%)
Ankle & wrists (7%)
Interphalangeal, sternoclavicular & sacroiliac joints (1-4%)

7. Newborns or infants
The emphasis is on septicemia rather than joint pain.
Irritability, Fever, refuses to feed, rapid pulse.
Pseudoparalysis (unable to move the limb with the infected joint).
Cries when infected joint is moved (diaper changing)
Infection is usually suspected, but it could be anywhere so the joints should be carefully felt and moved to elicit the local signs of warmth, tenderness and resistance to movement.
Umbilical cord or the site of injection should be examined for possible source of infection.
If the baby is distressed and wont move his/her leg think of hip infection.

8. Children: Adult: Fever Acute pain in single large joint.
The joint is swollen, warm and tender.
Pseudoparesis (all movements are restricted due to muscle spasm).
Adult:
Low-grade fever
Intense joint pain
Joint swelling, redness
Unable to move the limb with the infected joint

9. Physical examination
Signs of inflammation: joint swelling, warmth, tenderness and erythema.
Decreased or absent rang of motion.
Joint orientation as to minimize pain (position of comfort):
Hip: abducted, flexed and externally rotated.
Knee, ankle and elbow: partially flexed.
Shoulder: abducted and internally rotated.

10. Investigation Lab studies:
The diagnosis can usually be confirmed by joint aspiration and immediate microbiological investigation of the fluid.
Leucocytosis, elevated ESR & CRP (suggestive but not diagnostic).
Ask for: gram stain, culture, leukocyte count with differential, and crystal examination
Leukocyte count generally >75,000/µL, with a predominance of neutrophils >75% in synovial fluid aspiration.
Gram stain are positive in approximately 75% of patients with staphylococcal infections; however, results are positive in only 50% of patients with gram-negative infections.
Crystal examination to exclude crystal-induced arthritis (may coexist)
Synovial fluid glucose, protein, & lactic acid concentration not specific.

11. RA <50,000 wbc count

12. Imaging studies X-ray US
Detecting joint effusions generated by septic arthritis.
Define the extent of septic arthritis & guide treatment.
Differentiate septic arthritis from other conditions (soft tissue abscesses, tenosynovitis)
Radio-isotope bone scan
Increase uptake (help in difficult site as sacroiliac & sternoclavicular joints)
CT scan (sternoclavicular or sacroiliac joint infections)
MRI, most useful in assessing the presence of periarticular osteomyelitis as a causative mechanism.

13. Plain x-ray
The appearance of significant x-ray findings depends upon the duration and virulence of infection.
Findings are generally nonspecific:
Soft tissue swelling
Widening of the joint space (effusion)
Periarticular osteoporosis during the 1st 2 w.
Later, when the articular cartilage is attacked
Narrowed joint space (persistent subluxation, destructive arthritis).

14. Septic arthritis of the hip following group B strep psoas abscess

16. Septic arthritis of the ankle

18. Differential diagnosis
Osteomyelitis: near a joint may be indistinguishable from septic arthritis ;the safest is to assume that both are present.
Acute haemarthrosis: either post-traumatic or due to a haemophilic bleed ,can closely resemble infection. The history is helpful and joint aspiration will resolve any doubt.
Transient synovitis (irritable joint) in children: symptoms & signs are less acute.
Gout and pseudogout in adults: aspirated fluid may look turbid but the presence of urate or pyrophosphate crystals will confirm the diagnosis.
Rheumatic fever

19. Complication Dislocation: a tense effusion may cause dislocation
Epiphyseal destruction: in neglected infants the largely cartilaginous epiphysis may be destroyed ,leaving an unstable pseudarthrosis.
Growth disturbance: physeal damage may result in shortening or deformity
Ankylosis: if articular cartilage is eroded healing may lead to ankylosis
Secondary osteoarthritis
Osteomyleitis/abcess/sinus

20. Treatment Aspirate the joint and examine the fluid, then treat.
Analgesics and splinting of the involved joint in the position of maximal comfort alleviate pain.
Fluid replacement and nutritional support may be required.
Treat any infection or coexisting medical conditions.
Blood sample & culture
IV antibiotics
Flucloxacillin (G+ve)
3rd generation cephalosporin (G+ve & G-ve).
Ampicillin: children <4y. (suspicion of H.Infl)

21. Drainage Indication of Surgical Drainage:
Joints that do not respond to antimicrobial therapy and daily arthrocentesis.
Any joint with limited accessibility, including the sternoclavicular or the hip joint.
Patients with underlying disease, including diabetes, RA, immunosuppression, or other systemic symptoms, should be treated more aggressively with earlier surgical intervention.

22. Thank you