OVERVIEW

What is acute infectious arthritis?

Infectious arthritis is an infection caused by pathogenic microorganisms such as bacteria, viruses, or spirochetes invading the joint. Microorganisms typically invade the joint in cases of sepsis, joint trauma, joint surgery, or infection of nearby tissues. People of all ages can develop infectious arthritis.
Infectious arthritis can be classified into acute and chronic types. Acute infectious arthritis has a sudden onset, developing within hours to days, and manifests as joint redness, swelling, warmth, pain, joint effusion, limited mobility, and systemic fever. Treatment primarily involves antibiotics, drainage of pus from the joint, and symptomatic supportive care. With timely and proper treatment, it can usually be cured.
Chronic infectious arthritis develops over weeks, mainly presenting as gradual joint swelling and warmth, with milder pain and less noticeable skin redness.

Is acute infectious arthritis common?

The incidence of infectious arthritis varies significantly worldwide: in the U.S., it is < 200 per 100,000, while European countries report lower rates, such as Switzerland with < 5 per 100,000. However, developing regions like Africa, Latin America, and Asia have higher incidences. China currently lacks specific statistical data on its incidence.
Among all cases of infectious arthritis, acute infectious arthritis accounts for over 90%, whereas chronic infectious arthritis is relatively rare.

SYMPTOMS

What are the manifestations of acute infectious arthritis?

Patients develop symptoms within hours to days, mainly presenting with joint pain in a single joint, increased skin temperature, redness, limited joint mobility, and may be accompanied by systemic fever. Infants and children may also exhibit limb pseudoparalysis, irritability, and feeding difficulties. Some acute infectious arthritis caused by specific pathogens has its own characteristic manifestations. For example, gonococcal arthritis may present with rashes, migratory joint pain (i.e., pain alternating between multiple joints), and tenosynovitis, commonly affecting small joints in the hands, wrists, elbows, knees, and ankles. However, gonococcal infections rarely damage the normal structure of the joint.

What complications can acute infectious arthritis cause?

It can lead to the destruction of periarticular structures, joint deformities, and impair normal limb movement.

CAUSES

What are the causes of acute infectious arthritis?

The cause of acute infectious arthritis is the invasion of joints by various pathogenic microorganisms such as bacteria, viruses, and spirochetes.

• Common bacteria include streptococci, Staphylococcus aureus, Escherichia coli, Neisseria gonorrhoeae, and Pseudomonas aeruginosa. Among these, sexually active young adults are more likely to be infected with Neisseria gonorrhoeae.

• Common viruses include parvovirus B19, hepatitis B virus, hepatitis C virus, rubella virus, varicella-zoster virus, adenovirus, coxsackievirus, and Epstein-Barr virus.

• Spirochete infections mainly occur in individuals bitten by ticks or rodents.

Pathogenic microorganisms can invade joints through various routes, including:

• Direct invasion: Commonly seen in joint trauma, joint surgery, joint aspiration, or bites.

• Spread from adjacent infections: Often occurs with osteomyelitis, soft tissue abscesses, or infected wounds.

• Hematogenous infection: Typically associated with sepsis.

Who is more susceptible to acute infectious arthritis?

• Individuals with weakened immunity: Such as children under 2 years old, elderly over 60, cancer patients, those with chronic diseases (diabetes, lung disease, liver disease, uremia), HIV-infected individuals, or patients on long-term immunosuppressive therapy (e.g., corticosteroids).

• Patients undergoing joint aspiration or joint replacement surgery: Infection may occur due to non-sterile procedures, postoperative immune suppression, or lack of prophylactic antibiotics.

• Patients with joint trauma: Untreated joint injuries may lead to soft tissue infections around the joint, which can spread into the joint cavity and cause infectious arthritis.

• Individuals with a history of unprotected sex: Such as those with multiple sexual partners or who do not use condoms.

Is acute infectious arthritis contagious? How is it transmitted?

Most cases of acute infectious arthritis involve localized joint inflammation and are not contagious. However, Neisseria gonorrhoeae, which causes gonococcal arthritis, can be transmitted through sexual contact.

DIAGNOSIS

What medical history is important for doctors to diagnose after acute infectious arthritis occurs?

Whether there are the aforementioned high-risk factors for acute infectious arthritis, such as malignant tumors, diabetes, uremia, HIV infection, immunosuppressant use, history of joint surgery, history of joint trauma, history of unprotected sexual activity, etc.

What tests are needed when acute infectious arthritis is suspected?

• Routine infection tests: such as complete blood count, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). Patients with acute infectious arthritis typically exhibit increased white blood cell count, elevated ESR, and raised CRP levels.

• Joint aspiration: If necessary, joint fluid analysis and culture should be performed to identify the causative microorganism and its drug sensitivity.

• Blood culture: If there is significant fever, blood culture can be conducted simultaneously to determine the causative microorganism and its drug sensitivity.

• Imaging studies: Including X-rays, CT scans, MRI, and bone scans, which can aid in diagnosis and disease assessment.

Is joint aspiration painful for acute infectious arthritis? What precautions should be taken?

Joint aspiration may cause mild pain, but most people can tolerate it after local anesthesia at the puncture site.
When acute infectious arthritis is suspected, and there is significant joint swelling, substantial joint effusion, or an unidentified pathogen, joint aspiration should be performed. This procedure allows analysis of joint fluid to identify the pathogen. Additionally, draining an appropriate amount of joint effusion can reduce swelling and pain, promoting recovery.

Which diseases is acute infectious arthritis easily confused with?

• Rheumatoid arthritis: Acute infectious arthritis has a sudden onset, usually affects a single joint, causes more severe pain, and presents with obvious systemic symptoms. Pus can be aspirated from the joint cavity, and cultures may identify the pathogen. Rheumatoid factor is typically negative. Rheumatoid arthritis often involves multiple finger joints, and rheumatoid factor is positive.

• Acute hematogenous osteomyelitis: This is an inflammation of bone tissue, primarily located in the medullary cavity, with most joints remaining normal.

• Joint tuberculosis: Joint tuberculosis often has a history of tuberculosis, and Mycobacterium tuberculosis can be detected.

• Osteoarthritis: A chronic degenerative condition that may involve bone spurs. Blood tests show no abnormalities.

TREATMENT

Which department should I visit for acute infectious arthritis?

Orthopedic outpatient clinic or infectious disease department. If there is significant joint redness, swelling, pain, limited function, or fever, hospitalization for anti-infection treatment may be required.

How is acute infectious arthritis treated?

• Anti-infection therapy: Before identifying the specific pathogen but suspecting bacterial infection, broad-spectrum antibiotic combination therapy should be administered under medical guidance. Once the pathogen is confirmed, sensitive antibiotics should be selected based on drug sensitivity test results.

• Local joint treatment: Includes joint puncture to drain effusion, reduce swelling, saline irrigation of the joint cavity, intra-articular antibiotic injection, and continuous negative-pressure drainage of pus. For severe infections, arthroscopic or open joint surgery may be performed to remove purulent material and thoroughly irrigate the joint cavity. Additionally, infrared therapy on swollen and painful areas can help alleviate symptoms.

• Supportive treatment: Restrict joint movement to reduce pain and prevent deformities. Fever should be managed with antipyretics.

• Joint deformity correction surgery: If joint function is limited or significant deformity develops later, surgical correction may be performed to restore function.

Does acute infectious arthritis require surgery? When is surgery needed?

If symptoms are mild, with minimal joint redness/swelling and largely unaffected function, surgery is usually unnecessary.
For severe cases with significant joint effusion, limited function, or obvious deformity, joint puncture may be required.
If joint puncture fails to control the condition, arthroscopic or open joint surgery may be needed to completely remove the infected tissue.

Can acute infectious arthritis be completely cured?

Early treatment usually leads to a full recovery. If the condition persists, it may progress to chronic infectious arthritis with recurrent episodes.

Can acute infectious arthritis cause death?

It generally does not lead to death.

DIET & LIFESTYLE

What should be paid attention to in the diet of acute infectious arthritis?

Pay attention to supplementing protein-rich foods such as eggs, milk, and meat, and prepare them into light, easily digestible meals to aid in body recovery.

What should patients with acute infectious arthritis pay attention to in daily life?

During the illness, prioritize rest and avoid joint weight-bearing and exercise to prevent further joint damage and deformity.
During the recovery period, it is recommended to engage in exercise and functional training under the guidance of a rehabilitation doctor to avoid joint stiffness caused by delayed exercise, as well as joint deformity or further damage caused by premature exercise.

PREVENTION

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Timely vaccination of children with Haemophilus influenzae type B vaccine (Hib vaccine) and pneumococcal vaccine (PCV13 or PPV23) can effectively reduce acute infectious arthritis during childhood.