Septic arthritis is an infection of a joint that is caused by germs that travel through the bloodstream from another part of the body, such as a urinary tract infection.
The patient experiences severe pain with swelling of sudden onset. Septic arthritis is a medical emergency. Timely diagnosis and treatment are very essential, as mismanagement can lead to serious consequences, including systemic sepsis, avascular necrosis, growth plate damage, and cartilage destruction
The symptoms include pain, fever, and the child being unable to bear weight on the affected joint as well the restricted movement of the involved joint.
Due to extremely severe pain in the septic joint, range of motion is not tolerated by most children. This results in pseudoparalysis. If the knee or hip joint is involved, the child who had been mobile refuses to walk and bear weight on the affected limb.
There are a number of conditions that mimic septic arthritis. Hence arriving at the diagnosis of septic arthritis is very difficult.
Transient synovitisof the hips is a condition which mimics Septic arthritis.The symptoms are very similar to septic arthritis and hence can be confused. Also transient synovitis is a more common condition than septic arthritis, but it is better to consider the diagnosis of septic arthritis unless proved otherwise due to the serious nature of septic arthritis.
Osteomyelitis is another condition that can mimic septic arthritis in presentation. Both these conditions manifest with symptoms of fever, limping, and pain. Ultrasound is recommended to rule out joint effusion, which would suggest septic arthritis. A bone scan is performed to confirm the diagnosis of osteomyelitis.
Other diagnoses such as trauma and tumor are ruled out after performing an x-ray.
Children with septic arthritis present with fever, severe pain in the joint, limited movement, swelling and warmth. A few studies suggest that temperature greater than 38.5?C/101.3?F and non-weightbearing are the most reliable clinical signs that differentiates septic arthritis from transient synovitis.
Immediate action needs to be taken if any child presents with symptoms consistent with septic arthritis. Also it is important to collect the fluid from the joint (synovial fluid) and send for analysis before starting the child on any antibiotics.
Blood tests are also performed for WBC count (white blood cell count) differential count, ESR (erythrocyte sedimentation rate), CRP (C-reactive protein) and synovial fluid cultures. In case of infection, the WBC count will be elevated as will be ESR and CRP. X-rays of the affected joints and the adjacent bones are also recommended to exclude other pathologies, such as fracture, osteomyelitis, or tumor. Also MRI may be recommended as it provides clearer images of the joint and helps in arriving at a more accurate diagnosis.
The treatment involves joint fluid aspiration and empiric antibiotics intravenously. The drainage of the fluids is done arthroscopically in case of knee and shoulder joints and via an open arthrotomy in case of hip and ankle joints. In case of very young children, since arthroscopic instruments are very large, arthrotomy is performed. The synovial fluid is also sent for analysis.
Upon obtaining the synovial fluid, antibiotics are started intravenously. Once culture and sensitivity results are obtained, antibiotics are adjusted. In most cases, in two days’ time the child is switched to oral antibiotics.
A repeat clinical examination and repeat inflammatory markers in a week’s time as well as a week after stopping the antibiotics is recommended to ensure complete recovery. In a clear case of septic arthritis in a child, 3-week course of oral antibiotics is sufficient. Regular follow-ups for at least two years is recommended for long-term corollary of septic arthritis.