OVERVIEW

What is reactive arthritis?

Reactive arthritis refers to a condition where the affected joint is not directly infected by microorganisms, but rather develops inflammation in distant joints following microbial infections in other parts of the body. Simply put, the arthritis appears unrelated to the primary infection site, occurring as a "reaction" within our body.

For example, after a streptococcal (a pathogenic bacteria) infection in a child's lungs, symptoms like knee swelling, pain, warmth in the knee skin, and limited mobility may occur, presenting as knee arthritis. First reported by Reiter in 1916, this condition was later identified as a specific clinical type of reactive arthritis. Currently, when occurring in children, it is also called Reiter syndrome.

SYMPTOMS

What are the manifestations of reactive arthritis?

• Systemic manifestations: Reactive arthritis often has a history of preceding infection, such as a cold, and typically develops 1–4 weeks after infection. Patients frequently experience fever, especially high fever, which can reach 39°C or higher, and sometimes persistent fever. In most cases, symptoms affect only a few joints, usually the knees, ankles, or foot joints.
• Joint manifestations: Swelling is often visible at the joints, with increased skin temperature compared to normal, and a fluid-like fluctuation can be felt upon touch, accompanied by pain and discomfort. Some patients may notice that their joints are no longer as straight as before, possibly bending inward or outward, leading to deformity. Pressing on the joints may cause severe pain. Additionally, the affected joints may lose flexibility, making it difficult to squat, cross legs, etc.
• Extra-articular manifestations: Conjunctivitis, anterior uveitis, occasionally scleritis and corneal ulcers; genitourinary symptoms such as dysuria, pelvic pain, urethritis, cervicitis, prostatitis, salpingo-oophoritis, or cystitis; oral mucosal ulcers; rashes, including erythema nodosum; genital lesions such as circinate balanitis.

What are the common manifestations of Reiter's syndrome (the main type of reactive arthritis) in children?

Children with Reiter's syndrome may exhibit the classic triad of symptoms (local arthritis + ocular inflammation + urethral inflammation) or a combination of two symptoms (local arthritis + ocular inflammation, arthritis + urethritis, or ocular inflammation + urethritis). Some may initially present with only arthritis, ocular inflammation, urethritis, or isolated joint pain.

Diagnosis is relatively straightforward when a child exhibits the classic triad. However, if symptoms are atypical and the child cannot articulate their condition clearly, the condition may be overlooked. Close monitoring of symptom progression is essential.

CAUSES

Which groups are commonly affected by reactive arthritis?

There are two main groups:

• Children: especially school-aged children;
• Young adults: most commonly seen between 20-50 years old.

What are the causes of reactive arthritis?

The main known causes include:

• Bacterial infections: such as Streptococcus pneumoniae (a common bacteria causing pneumonia), Staphylococcus aureus (a bacteria often causing purulent infections), syphilis, etc.;
• Non-bacterial inflammation: such as ankylosing spondylitis (a specific disease mainly characterized by progressively worsening discomfort in the lower back and hips, and difficulty in spinal movement), reactive arthritis following treatment for rheumatoid arthritis (rheumatoid arthritis itself is not reactive arthritis);
• Unknown causes: autoimmune diseases combined with neoplastic diseases, such as Sjögren's syndrome combined with lung cancer, leading to reactive arthritis after treatment.

What are the common causes of reactive arthritis in children?

• The most common cause is bacterial infections, especially streptococcal pneumonia, with distant joint manifestations appearing about 4 weeks after treatment;
• Next are autoimmune diseases, such as Kawasaki disease in children (often presenting with acute fever, early redness of the skin on the palms and soles, later peeling, rashes on other parts of the body, oral mucosal congestion, strawberry-like tongue, and palpable enlarged lymph nodes in the neck), rheumatoid arthritis, etc.;
• Lastly, a small portion of cases have unknown causes.

What are the common causes of reactive arthritis in adults?

The primary cause of reactive arthritis in adults is bacterial infections, such as Staphylococcus aureus or streptococcal infections, leading to distant joint infections like hip or knee arthritis after some time. The second most common cause is autoimmune diseases, such as ankylosing spondylitis and systemic lupus erythematosus.

DIAGNOSIS

What tests are needed for reactive arthritis?

• Blood-related tests: such as complete blood count, liver and kidney function, rheumatoid factor, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), HLA-B27, PPD test (tuberculin test, auxiliary diagnosis of tuberculosis infection), and other immune-related indicators;
• Imaging examinations: X-ray of the affected joints, and if necessary, CT or MRI scans;
• Invasive tests: such as joint puncture to extract synovial fluid for examination.

What abnormal findings might blood tests show in reactive arthritis?

• Complete blood count may show elevated white blood cells, with no significant increase in neutrophils;
• Markedly elevated erythrocyte sedimentation rate (ESR);
• Significantly increased C-reactive protein (CRP) levels;
• Bacteria may be cultured from blood samples;
• Bacteria may also be cultured from synovial fluid;
• Some patients may test positive for HLA-B27;
• Some patients may exhibit liver or kidney function impairment.

What are the common imaging findings in reactive arthritis?

• Imaging mainly focuses on the affected joints. For example, X-rays of the knee (anteroposterior and lateral views) may show joint swelling, cartilage destruction, sclerosis (bright sclerotic bone visible in the knee joint), and uneven joint space;
• Some patients may exhibit ossification of the posterior longitudinal ligament on spinal X-rays (continuous bony strips visible along the spinous processes).

Is reactive arthritis difficult to diagnose?

Yes, diagnosis is relatively challenging.

Reactive arthritis is a secondary aseptic arthritis. Due to its diverse manifestations, prolonged disease course, uncertain etiology, and limited clinical awareness, there are no specific clinical features. Its symptoms also resemble other types of arthritis, making misdiagnosis or missed diagnosis common. In some cases, what appears to be reactive arthritis may actually be a tumor-related condition.

How is reactive arthritis diagnosed?

Due to its subtle manifestations and prolonged course in some patients, diagnosis is relatively difficult.
Diagnosis is primarily based on:

• A history of infection or extra-articular infection from open trauma within the past few weeks (usually within 4 weeks): such as pneumonia caused by streptococcal infection, syphilis infection, or trauma-related injuries like cuts, blast wounds, or stab wounds to the arms, thighs, or calves;
• Arthritis manifestations: typically involving large joints such as the knee or hip, with symptoms like joint swelling, pain, increased skin temperature, joint effusion, and limited mobility;
• Extra-articular manifestations: classic triad of arthritis + eye inflammation + urethritis, or a dual presentation of eye inflammation + urethritis. Urethritis in males may manifest as balanitis, while in females, it may present as gynecological inflammation. Some reported cases involve only heel or toe pain, later confirmed as reactive arthritis.

What is the difference between reactive arthritis and acute joint infection?

Acute joint infection: Usually affects a single joint, often accompanied by systemic high fever (over 39°C) and chills. The infected joint typically shows swelling, elevated skin temperature, severe pain limiting movement, and in some cases, skin ulceration with pus discharge. Bacterial cultures from blood or synovial fluid usually confirm the presence of bacteria.

Additionally, patients often have weakened immunity or significant trauma, such as lung cancer, tuberculosis, or injuries from accidents or workplace accidents leading to skin breaks or exposed muscles/bones. Some cases involve infections originating from dental caries (tooth decay).

How does reactive arthritis differ from bone tumors?

Bone tumor patients usually do not develop high fever, often presenting only with low-grade fever (mostly below 38°C). Some experience localized pain, and imaging may reveal masses or bone destruction. For example, pediatric osteosarcoma often occurs near the knee (distal femur or proximal tibia) and may cause nighttime pain. Some patients only seek medical attention after pathological fractures due to tumor erosion.

Adults can also develop bone tumors, such as sarcomas (malignant tumors) in the thigh near the knee, which may mimic arthritis symptoms. However, X-rays, CT, or MRI can differentiate these from reactive arthritis.

TREATMENT

Which department should I visit for reactive arthritis?

Children often go to pediatrics or orthopedics; adults often go to orthopedics.

Patients with concurrent autoimmune diseases are advised to visit rheumatology and immunology, with orthopedics assisting in diagnosis and treatment. For example, patients with Sjögren's syndrome or systemic lupus erythematosus should receive standardized treatment in rheumatology and immunology.

Does reactive arthritis require hospitalization?

Hospitalization is recommended.

Since arthritis is difficult to diagnose, multiple blood tests and necessary imaging examinations are required, such as joint X-rays, complete blood count, liver and kidney function tests, rheumatoid factor, and other immune markers. Therefore, hospitalization is recommended for comprehensive testing to clarify the diagnosis and ensure standardized treatment.

Is the treatment for reactive arthritis expensive?

Reactive arthritis usually involves higher costs for diagnosis and testing, while symptomatic treatment is relatively inexpensive overall.

What are the common treatments for reactive arthritis in children?

Common treatments for reactive arthritis in children include:

• Symptomatic treatment: Immobilization of the affected joint (e.g., traction, cast, or brace for the knee) to transition acute inflammation to chronic and reduce tissue irritation.
• Antibiotics: Use sensitive antibiotics to target specific bacteria, such as sulfasalazine (an oral medication).
• Corticosteroid therapy: Use hormones or immunosuppressants like methylprednisolone or methotrexate if necessary.
• Blood monitoring: Track indicators like complete blood count, liver/kidney function, ESR, and C-reactive protein.
• Surgery: Joint aspiration or arthroscopic synovectomy (minimally invasive) may be performed based on condition assessment.

What are the treatments for reactive arthritis in adults?

Treatments for reactive arthritis in adults include:

• For confirmed infections:
  • Use sensitive antibiotics aggressively.
  • Protect joints by immobilization (e.g., braces, casts, or skin traction).
  • Short-term corticosteroids or immunosuppressants (e.g., methylprednisolone, methotrexate) may be used after assessing risks like infection spread or superinfection.
  • Surgery (e.g., arthroscopic procedures) for severe joint swelling or effusion, involving minimal incisions (e.g., 1 cm for knee arthroscopy) to clean synovial tissue.
• For suspected autoimmune cases: Treat the underlying autoimmune disease first to improve arthritis outcomes.

Can reactive arthritis recur after treatment? Are there sequelae?

Reactive arthritis is often self-limiting, meaning joints usually recover without sequelae. Recurrence rates are below 20%, indicating a favorable prognosis.

DIET & LIFESTYLE

What are the key nursing considerations for children with reactive arthritis?

Children differ from adults in the care of reactive arthritis. Key points include:

• Psychological care: Minimize the disease's impact on the child and encourage a positive, optimistic attitude.
• Monitor skin around joints: Immobilization may lead to pressure sores (tissue breakdown due to prolonged pressure), commonly on the buttocks or heels. Prevent this by repositioning regularly, warm-water cleansing, using breathable cushions, and gentle massage to improve circulation.
• During joint traction: Daily check the weight, direction, and positioning of traction.
• Parental involvement: Children rely heavily on parents, so increased companionship aids treatment adherence.
• Positioning and exercises: Preoperatively, maintain supine positioning with ankle/knee/quadriceps contraction exercises to boost circulation and prevent venous thrombosis. Postoperative exercises depend on surgical specifics.

What should adult patients with reactive arthritis focus on during rehabilitation and care?

• Rehabilitation education: Learn bed-based exercises during hospitalization to prevent venous thrombosis and muscle atrophy. Gradual joint mobilization and assistive devices (e.g., walkers) may be needed. Follow the principle of "balancing rest/activity, progressing stepwise from simple to complex."
• Psychological support: Understand the disease course and favorable prognosis. Family should foster optimism, confidence, and treatment compliance.
• Disease awareness: Educate patients to recognize disease progression and maintain realistic expectations.

What dietary precautions apply to reactive arthritis patients?

Prioritize light, high-protein, easily digestible foods. Limit oily, sugary, large-chunk, or spicy items. Fiber-rich foods (e.g., celery, bamboo shoots) aid digestion and bowel regularity.

PREVENTION

How to Prevent Reactive Arthritis?

Prevention mainly focuses on the following aspects:

• Strengthen physical exercise in daily life to actively improve immunity;
• Avoid trauma as much as possible, especially local infections caused by open wounds, such as falls from heights or machinery injuries leading to open fractures in the thighs or calves, where fractures penetrate muscles and cause infections;
• For patients with a family history of conditions like ankylosing spondylitis, monitor disease progression closely. Seek medical attention promptly if discomfort occurs to rule out other illnesses and actively treat underlying conditions;
• For children, due to their weaker immunity, ensure proper nutrition while administering age-appropriate vaccinations to enhance disease resistance, such as timely flu shots;
• Tertiary prevention: From a medical perspective, patients who have already developed the disease or experienced a relapse should undergo comprehensive examinations and receive standardized treatment throughout the course to achieve favorable outcomes. This also counts as a form of disease prevention, aiming to avoid complications.