Write a short note on the clinical approach to monoarthritis and polyarthritis.
Definitions
- Monoarthritis — one joint involved.
- Oligoarthritis (pauciarticular) — two to four joints.
- Polyarthritis — five or more joints.
- Acute — under 6 weeks; chronic — beyond 6 weeks.
The first task is always to confirm that the problem is articular (pain on both active and passive movement, with swelling and effusion) rather than periarticular (bursitis, tendonitis, cellulitis — pain on active movement with preserved passive movement), and to establish whether it is inflammatory or mechanical.
| Feature | Inflammatory | Mechanical / degenerative |
|---|---|---|
| Morning stiffness | > 30–60 minutes | < 30 minutes |
| Effect of activity | Improves | Worsens |
| Effect of rest | Worsens | Improves |
| Swelling | Soft tissue, warm | Bony, cool |
| Systemic features | Fever, weight loss, fatigue | Absent |
| ESR/CRP | Raised | Normal |
Acute Monoarthritis — Septic Until Proved Otherwise
Causes:
- Septic arthritis — *Staphylococcus aureus* (commonest), streptococci, gonococcus in young sexually active adults, Gram-negatives in the elderly and immunosuppressed, and tuberculosis (chronic monoarthritis, particularly of hip or knee — important in India).
- Crystal arthritis — gout, pseudogout (CPPD).
- Trauma and haemarthrosis — fracture, internal derangement, haemophilia, anticoagulation.
- Monoarticular presentation of a polyarthritis — early RA, psoriatic or reactive arthritis, spondyloarthritis.
- Avascular necrosis, tumour (pigmented villonodular synovitis, osteoid osteoma).
Every acute hot swollen joint requires urgent joint aspiration before antibiotics. Septic arthritis destroys cartilage within days and carries significant mortality. Risk factors include pre-existing joint disease (especially RA), prosthetic joints, diabetes, immunosuppression, intravenous drug use and skin sepsis. Crystals in the fluid do not exclude infection — the two can coexist. If in doubt, treat as septic while cultures are pending.
Synovial Fluid Analysis — the Key Investigation
| Type | Appearance | WBC/µL | Neutrophils | Interpretation |
|---|---|---|---|---|
| Normal | Clear, viscous | < 200 | < 25% | — |
| Non-inflammatory | Clear, yellow | 200–2 000 | < 25% | Osteoarthritis, trauma |
| Inflammatory | Cloudy, yellow | 2 000–50 000 | > 50% | RA, crystal arthritis, spondyloarthritis |
| Septic | Purulent, opaque | > 50 000 (often > 100 000) | > 75% | Infection |
| Haemorrhagic | Blood-stained | — | — | Trauma, haemophilia, anticoagulation, PVNS |
Send fluid for cell count and differential, Gram stain and culture, polarised light microscopy for crystals, and, where tuberculosis is suspected, AFB stain, CBNAAT and mycobacterial culture.
Polyarthritis — Pattern Recognition
Analyse by symmetry, joint distribution, and acute versus chronic:
| Pattern | Likely Diagnoses |
|---|---|
| Symmetrical, small joints of hands and feet, chronic | Rheumatoid arthritis, SLE, viral arthritis |
| Asymmetrical, large joints, lower limb | Seronegative spondyloarthritis — reactive, psoriatic, enteropathic |
| DIP joint involvement | Psoriatic arthritis, osteoarthritis (not RA) |
| Migratory | Acute rheumatic fever, gonococcal arthritis, viral arthritis, SLE |
| Additive, progressive | RA, psoriatic arthritis |
| Acute polyarthritis with fever and rash | Viral (chikungunya, dengue, parvovirus B19, rubella, hepatitis B), adult Still's disease, SLE, ARF |
| With back pain and sacroiliitis | Ankylosing spondylitis and related spondyloarthritis |
In India, acute symmetrical polyarthritis with fever and rash in an epidemic setting is chikungunya until proved otherwise. The arthritis is severe, often symmetrical and small-joint, and may persist for months to years after the acute illness, closely mimicking rheumatoid arthritis — but it is seronegative and non-erosive. Take a travel, epidemic and mosquito-exposure history in every acute polyarthritis.
Clinical Assessment
History: onset and speed, pattern and sequence of joint involvement, morning stiffness, systemic features, preceding infection (throat, gastrointestinal, genitourinary), sexual history, tick or travel exposure, rash, photosensitivity, oral ulcers, dry eyes and mouth, bowel symptoms, psoriasis, back pain, drug history and family history.
Examination:
- examine every joint including the spine
- assess for warmth, effusion, tenderness, deformity and range of movement
- then look for extra-articular clues — nails and skin (psoriasis), rheumatoid nodules, tophi, rash, eyes (uveitis, scleritis), murmurs, lungs, lymph nodes and neurology.
Investigations:
- CBC, ESR, CRP, renal and liver function, urate, urinalysis
- RF, anti-CCP, ANA (interpreted with clinical probability)
- ASO, viral and chlamydial serology as directed
- HLA-B27 where spondyloarthritis is suspected
- X-rays of affected joints
- ultrasound or MRI for early synovitis and sacroiliitis
- joint aspiration whenever an effusion is accessible.
All questions in Immunology & Rheumatology
- Q1Discuss the aetiopathogenesis, clinical features, investigations and management of rheumatoid arthritis. ★
- SN1Write a short note on systemic lupus erythematosus — clinical features, diagnosis and management.
- SN2Write a short note on anaphylaxis.
- SN3Write a short note on acute rheumatic fever — pathogenesis, Jones criteria and management.
- SN4Write a short note on gout.
- SN5Write a short note on antiphospholipid antibody syndrome.
- SN6Write a short note on seronegative spondyloarthritis, including ankylosing spondylitis and reactive arthritis.
- SN7Write a short note on osteoarthritis.
- SN8Write a short note on idiopathic inflammatory myopathies (polymyositis and dermatomyositis).
- SN9Write a short note on the vasculitides, with emphasis on granulomatosis with polyangiitis.
- SN10Write a short note on systemic sclerosis (scleroderma).
- SN11Write a short note on the clinical approach to monoarthritis and polyarthritis.
- SN12Write a short note on autoantibodies in rheumatology, including antinuclear antibodies.