Septic arthritis is acute onset of monoarticular inflammation of a joint due to an infectious etiology. It is usually bacterial but can be viral or fungal. Septic arthritis causes significant morbidity and mortality and requires prompt diagnosis and treatment. Risk factors include age older than 80 years, smoking, comorbid conditions (eg, diabetes, rheumatoid arthritis, skin infection, HIV infection, osteoarthritis), and other factors (eg, recent joint surgery, joint prosthesis, previous intra-articular injection). The clinical presentation of septic arthritis can overlap with those of many other joint conditions, which can make diagnosis challenging. Poor functional outcomes, such as amputation, arthrodesis, prosthetic surgery, and severe functional deterioration, occur in approximately 24% to 33% of patients with septic arthritis. Due to the significant sequelae associated with septic arthritis, it is critical for physicians to maintain a high index of suspicion for this condition. Management involves a combination of medical and surgical treatments tailored to infection severity, causative pathogens, and overall patient condition. Medical treatment is not inferior to surgical treatment. However, 30% of patients with septic arthritis ultimately require surgical treatment. The 90-day mortality rate of knee septic arthritis is 7% in patients 79 years and younger and from 22% to 69% in patients older than 79 years.
Case 3. OL is an 80-year-old patient with a history of diet- and exercise-controlled type 2 diabetes and hypertension. She presents to the office with worsening right knee pain and swelling that started 4 days ago. OL says the pain is different from that of previous flare-ups of knee osteoarthritis. She has received four previous intra-articular corticosteroid injections, the last of which was 5 months ago. Since yesterday, OL has noticed redness in her knee, difficulty bearing weight, and no similar symptoms in other joints.
Vital signs for OL include a temperature of 105°F (40.7°C), blood pressure of 98/65 mm Hg, pulse of 82 beats/min, respiratory rate of 16 breaths/min, and an oxygen saturation level of 98% on room air. OL appears alert and oriented but uncomfortable, with an abnormal gait, slight flexion of the right knee, and limited weight-bearing ability. The right knee has moderate effusion and erythema with diffuse tenderness. OL shows guarding of the knee with minimal flexion and extension due to pain. She is able to lift the affected leg off the table but is reluctant to test knee strength. You perform no further knee tests.
Presenting Features and Most Affected Joints
Septic arthritis is acute onset of monoarticular inflammation of a joint due to an infectious etiology. Patients typically present with local symptoms but can also have systemic symptoms (Table 11–9). The most common presenting symptoms include joint swelling, joint pain, and fever, with diaphoresis and rigor occurring less commonly.1
Table 1 Septic Arthritis Risk Factors, Symptoms, Complications, and Sequelae
| Risk Factors | ||
| Local | Systemic | Other |
| Skin infection or cutaneous ulcerations Previous intra-articular injection(s) Joint prosthesis (within 2 years) Recent joint surgery Osteoarthritis | Diabetes Rheumatoid arthritis HIV infection Sexual activity Immunosuppression/immunosuppressive medication use Intravenous illicit drug use | Age older than 80 years Smoking |
| Symptoms | ||
| Local | Systemic | |
| Swelling of a single joint Pain +/− difficulty bearing weight Limited range of motion Pseudoparalysis (refusal to move or use the affected joint) Erythema Joint warm to touch | Ill appearance Fever Tachycardia Lethargy Irritability or fussiness Sweats or rigor | |
| Complications | ||
| Systemic infection | ||
| Septic arthritis can lead to systemic infection, including bacteremia or sepsis. Systemic infections can result in organ dysfunction and septic shock if not promptly treated. | ||
| Joint destruction | ||
| Untreated or inadequately treated septic arthritis can lead to irreversible damage to the affected joint, resulting in joint destruction. This can cause chronic pain, loss of joint function, and disability. | ||
| Chronic arthritis | ||
| Even with appropriate treatment, some patients may develop chronic arthritis following septic arthritis. Chronic arthritis can lead to persistent joint pain, swelling, and stiffness and negatively affect quality of life. | ||
| Joint deformity | ||
| Severe cases of septic arthritis may lead to joint deformity due to destruction of joint structures. Deformity can result in functional impairment and may necessitate surgical intervention for reconstruction or replacement. | ||
| Osteomyelitis | ||
| In some cases, infection can spread from the joint into the surrounding bone, leading to osteomyelitis, which is a serious bone infection requiring aggressive treatment that can lead to bone destruction or amputation. | ||
| Sequelae | ||
| Joint damage and dysfunction | ||
| Primary sequelae of septic arthritis are joint damage and dysfunction. Even with timely treatment, joint destruction can occur due to the inflammatory response and enzymatic degradation caused by the infection. | ||
| Recurrent infections | ||
| Residual joint damage and altered immune responses can increase susceptibility to subsequent episodes of infection. Additionally, prosthetic joint replacements, if required, can be prone to infection, leading to further complications. | ||
| Chronic pain and disability | ||
| Some patients may experience chronic pain and disability following septic arthritis. Residual effects of joint damage, such as osteoarthritis, can contribute to persistent symptoms and functional limitations, affecting quality of life. | ||
| Psychological effects | ||
| Experiencing septic arthritis and its sequelae can have psychological effects on patients, including anxiety, depression, and decreased emotional well-being. Chronic pain, disability, and uncertainty of recurrent infections can significantly affect mental health and overall psychological functioning. | ||
Information from references 1-9.
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