• Fever

• Feeling unwell

• Pain and swelling of the affected joint

• The joint is warm and tender on palpation

• Inability to move the joint (pseudo-paralysis)

The attending physician should thoroughly examine the other parts of the body to find the infection focus.

• Recent joint operationO

• steomyelitis in adjacent bones. In children, younger than 3 years, the transphyseal blood supply allows easy transmission of bacteria from metaphyseal osteomyelitis to the joint to the joint to cause septic arthritis.

• IV drug users

• History of crystal arthropathy

• Medical conditions like diabetes, HIV, lever cirrhosis

• Male gender

• Punctured wound

• Upper respiratory infections

Routes of organisms getting into the joint causing infection include:

• Direct inoculation: This can occur following joint operation or procedure or trauma including punctured wound in which an organism is introduced into the joint.

• Haematogenous spread: Bacteria dissemination from other foci in the body into the joint.

• Extension from adjacent bone with osteomyelitis as found in children less than 3 years old.

Arthrocentesis: This is a diagnostic procedure that could be done bedside. It is very important to follow a strict aseptic technique. Ultrasound guidance could be needed in large joints especially the hip joint. It involves inserting a needle into the synovial cavity to aspirate the joint fluid. Presence of pus/turbid appearance confirms septic arthritis. The aspirate should be sent for cell count, gram stain, culture, glucose level and crystal analysis. WBC count: >50,000/ml or >75% polymorph neutrophils confirm septic arthritis. Glucose level in the aspirate <60% of serum level is also suggestive. This is because the bacteria use up the glucose in the joint.

• C-reactive protein is elevated

• ESR high especially >40mmol/hour

• Full blood count: WBC >12,000/ml

• Ultrasound scan: This is important in paediatric patients where joint effusion is detected as an early sign.

• X-ray and CT-scan are alternatives with ambiguity in the clinical presentation.

• Magnetic resonance imaging visualises soft tissues well where available could be used for diagnosis of septic arthritis.

This has 4 criteria. Presence of 4 criteria in a patient has a 97% probability of having septic arthritis. This was devised for hip septic arthritis in children. This used by surgeons in other joints also

The following are the criteria:

• Fever >38.5ﹾC

• ESR >40mm/hr

• WBC >12,000/ml

• Pseudo-paralysis/ inability to bear weight

• Blood culture may grow the organism in septic patients

• Modified Kocher Criteria is specific where Caird added elevated CRP which differentiates between transient synovitis and septic arthritis in children.

• Osteoarthritis patients are not septic

• Crystal arthropathy: Fever is absent even if there are other signs of inflammation. Crystal analysis would help to confirm the diagnosis.

• Reiter’s Syndrome: A classic triad od conjunctivitis, urethritis and arthritis confirm the diagnosis

• Trauma with haemathrosis

• Reactive synovitis

• Pathological dislocation: This occurs due to joint effusion leading to dislocation. This typically affect the hip joints if there is no immediate treatment.

• Avascular necrosis of femoral head due to destruction of blood supply to the femoral head due to joint effusion

• Arthritis

• Chronic osteomyelitis especially in children.

• Arthroscopic lavage of the joint is minimally invasive. This is to remove the pus and wash out the joints. This may be done repeatedly if the patient has reaccumulating of fluid in the joint.

• Arthrotomy: This is a form of incision and drainage of the joint abscess (septic arthritis). It is more extensive compared to arthroscopic washout. The joint pus is drained, washout and closure of the wounds. A drain is rarely needed after a thorough drainage and washout of the joint

• Antibiotics: Empirical antibiotics should be commenced based on local guidelines and change to sensitivity result once it is available. Antibiotics is given intravenously, change to oral based on patient’s clinical condition and given for a total of 4-6 weeks.

• Analgesics to relieve pain.

• Joint immobilization with splint or traction to prevent further cartilage damage by rubbing of the articular surfaces

• Physiotherapy to exercise the joint and prevent stiffness.

Septic arthritis is an orthopaedic emergency. Arthrocentesis is diagnostic in some patients. Prompt treatment is important to prevent destruction of the joint. High index of suspicion is thus needed by the attending physician. Delay in treatment lead to increased in morbidity and mortality.