Arthritis

# Overview
Arthritis (from Greek arthro-, joint + -itis, inflammation; plural: arthritides) could be defined as painful joint damage. It might be as part of a systemic disorder or a single joint involvement. Arthritis may present as joint pain (arthralgia), swelling, erythema, warmness, and limitation of movement. It could be classified according to the number of involved joints, presence of inflammation, or duration of symptoms. Osteoarthritis (also known as degenerative joint disease) is the most common form of arthritis in the United States which involves up to 10% of population older than 60 years. Inflammatory arthritis is common in systemic autoimmune disorders, such as rheumatoid arthritis and systemic lupus erythematosus (SLE) and is part of diagnostic criteria for this spectrum of diseases. Disease course in systemic disorders is usually chronic and multiple joints (polyarticular) are involved. In the other hand, infectious conditions like septic arthritis are acute in nature and they usually involve single joints (monoarticular). Crystal induced arthropathies may result in inflammatory joint(s) involvement, mainly are due to uric acid crystal deposition (gout) in articular space. Although, disease course and presence of other systemic manifestations are important for diagnosis but the gold standard method for diagnosis is joint aspiration, fluid analysis, and microscopic evaluation. Imaging might be helpful in certain condition to find the disease chronicity and structural changes in articular and periarticular structures. Prompt treatment is necessary specially for septic and inflammatory conditions to prevent structural joint damage and deformities.

# Classification

## Primary Forms of Arthritis:
- Osteoarthritis
- Rheumatoid arthritis
- Septic arthritis
- Gout and pseudogout
- Juvenile idiopathic arthritis
- Still's disease
- Ankylosing spondylitis

# Differential Diagnosis

## Differential Diagnosis of Monoarthritis
To review the differential diagnosis of monoarthritis with joint swelling, click here.
To review the differential diagnosis of monoarthritis with fever, click here.
To review the differential diagnosis of monoarthritis with weight loss, click here.
To review the differential diagnosis of monoarthritis with claudication, click here.
To review the differential diagnosis of monoarthritis with morning stiffness, click here.
To review the differential diagnosis of monoarthritis with local erythema, click here.
To review the differential diagnosis of monoarthritis with joint swelling and fever, click here.
To review the differential diagnosis of monoarthritis with joint swelling, fever, and weight loss, click here.

## Differential Diagnosis of Diseases That Cause Polyarthritis

### Differentiating the diseases that can cause polyarthritis:
To review the differential diagnosis of polyarthritis with joint swelling, click here.
To review the differential diagnosis of polyarthritis with fever, click here.
To review the differential diagnosis of polyarthritis with weight loss, click here.
To review the differential diagnosis of polyarthritis with claudication, click here.
To review the differential diagnosis of polyarthritis with morning stiffness, click here.
To review the differential diagnosis of polyarthritis with local erythema, click here.
To review the differential diagnosis of polyarthritis with joint swelling and fever, click here.
To review the differential diagnosis of polyarthritis with joint swelling, fever, and weight loss, click here.