Understanding Septic Arthritis: Causes and Risk Factors

Septic arthritis happens when harmful microbes invade a joint and trigger intense inflammation. Normally, joints are protected and free from infection. Most commonly, bacteria or fungi reach the joint through the bloodstream — a process known as haematogenous spread. Sometimes, infections enter directly via injuries, surgical procedures, injections, or spread from nearby infected tissues. The main culprit in the UK is Staphylococcus aureus, a bacterium that can cause particularly aggressive infections. Other germs often involved include Neisseria gonorrhoeae—especially in younger adults—and certain Gram-negative bacteria, which are more common in older people or those with weaker immune systems. The development of septic arthritis depends on a complex interplay between the invading pathogens and the person’s immune system, including how bacteria evade defences and cling to joint tissues (Shirtliff & Mader, 2002). In older adults, studies show that while Staphylococcus aureus is the commonest cause, enteric gram-negative bacteria also play a significant role (McGuire & Kauffman, 1985). Risk factors that increase the likelihood of developing septic arthritis include advanced age, existing joint conditions like osteoarthritis or rheumatoid arthritis, recent joint surgery or injections, diabetes, and a weakened immune system caused by diseases or medications. NICE guidelines highlight the importance of recognising these risks for early vigilance and prevention.

Recognising the Symptoms: Early Signs and Presentation

Recognising septic arthritis symptoms early is crucial to stop permanent joint damage. Typically, a single joint becomes swollen, warm, red, and very painful, with movement severely limited. The knee is the joint most commonly affected, followed by the hip, shoulder, and smaller joints in the fingers or toes. Patients often report intense pain, worsened by any attempt to move the joint. Fever, chills, and a general feeling of being unwell usually accompany the joint symptoms. However, in older people or those with weakened immune systems, these systemic signs may be mild or altogether absent. Children display slightly different patterns—often refusing to use the affected limb and showing irritability alongside fever. Prosthetic joint infections can be trickier to detect, sometimes presenting with more subtle symptoms. This makes maintaining a high degree of suspicion essential, particularly in vulnerable patients, so they can be evaluated quickly (NICE clinical summaries). Notably, research confirms that in older patients, the knee is the most commonly infected joint (McGuire & Kauffman, 1985).

Diagnosis and Treatment: Evidence-Based Approach

Timely diagnosis is the cornerstone of successful septic arthritis treatment. As Abbod et al. (2018) remind us, “Early diagnosis may prevent complications that may otherwise lead to the patient's disability.” Diagnosis primarily involves taking a sample of the joint fluid (synovial fluid) via aspiration. Testing this fluid in the lab helps identify the infecting organism and guides treatment. Alongside this, blood tests measuring inflammation and blood cultures help confirm the diagnosis. Imaging tools such as ultrasound can detect fluid build-up and assist with fluid sampling, while X-rays and MRI scans highlight complications or alternative causes. Treatment has two main components: antibiotics and sometimes surgery. UK guidelines recommend starting intravenous antibiotics promptly, typically targeting Staphylococcus aureus. Flucloxacillin is commonly used as first-line treatment, but alternatives like vancomycin may be necessary if resistant bacteria are suspected. Where infection persists despite antibiotics, surgical drainage by arthroscopy or open washout is required to clear the joint of infectious material (Shirtliff & Mader, 2002). An effective response to septic arthritis involves a team approach, including orthopaedic surgeons, infectious disease specialists, and physiotherapists. Delays or inadequate treatment increase risks of severe joint damage and spread of infection, making adherence to protocols and local policies essential.

Complications, Outlook, and Long-Term Impact

If septic arthritis isn’t treated properly or quickly, it can cause serious complications like permanent cartilage loss, joint deformity, and even sepsis. In elderly patients, nearly half of survivors may develop bone infections near the joint, and recovery of joint function often takes a long time (McGuire & Kauffman, 1985). Despite modern treatments, septic arthritis still carries a notable risk of death, especially among older adults and those with other health issues (Shirtliff & Mader, 2002). The question often arises: “Can septic arthritis kill you?” Sadly, it can. Up to 20% of high-risk patients may die from complications linked to the infection or related hospital-acquired infections. This underlines the critical importance of aggressive, timely medical and surgical care. Long-term problems may include chronic joint pain, recurrent infections, and limited mobility. Physical therapy and ongoing monitoring are vital for rehabilitation and preventing recurrence. Patient education about symptoms and treatment adherence plays a key role in ensuring full recovery and reducing complications.

Conclusion

Septic arthritis is a potentially serious condition but one that can be effectively treated with prompt diagnosis and care grounded in evidence-based guidelines. Recognising the symptoms early, seeking immediate medical attention, and adhering to recommended treatments are crucial to preserving joint health and improving outcomes. By maintaining awareness and acting quickly, both patients and healthcare professionals can help prevent long-term damage and support full recovery. For further information and support, patients and healthcare providers in the UK should consult NICE guidelines and local clinical resources.

References

• Abbod, H., Al‐Otaibi, L., & Alshamiri, K. (2018). Septic arthritis. International Journal of Pediatrics and Adolescent Medicine, 5(4), 152–154. https://doi.org/10.1016/j.ijpam.2018.12.005
• Shirtliff, M. E., & Mader, J. T. (2002). Acute Septic Arthritis. Clinical Microbiology Reviews, 15(4), 527–544. https://doi.org/10.1128/cmr.15.4.527-544.2002
• McGuire, N. M., & Kauffman, C. A. (1985). Septic Arthritis in the Elderly. Journal of the American Geriatrics Society, 33(3), 170–174. https://doi.org/10.1111/j.1532-5415.1985.tb04887.x