Acute monoarthritis
This term is used to describe sudden pain and swelling in a single joint. The most important causes
are crystal arthritis, sepsis and reactive arthritis. Other potential causes are shown in Box 25.12.
Clinical assessment
The clinical history, pattern of joint involvement, speed of onset, and age and gender of the patient all
give clues to the most likely diagnosis. Reactive arthritis (p. 1107) is the most common cause in young
men, gout in middle-aged men and pseudogout in older women. Gout classically affects the first
metatarsophalangeal (MTP) joint, whereas the wrist and shoulder are typical sites for pseudogout. A
very rapid onset (6-12 hours) is suggestive of gout or pseudogout; joint sepsis develops more slowly
and continues to progress until treated. Haemarthrosis typically causes a large effusion, in the
absence of periarticular swelling or skin change, in a patient who has suffered an injury. Pigmented
villonodular synovitis
(p. 1134) also presents with synovial swelling and a large effusion, although the onset is gradual. A
previous diarrhoeal illness or recent sexual contact suggests reactive arthritis, whereas intercurrent
illness, dehydration or surgery may act as a trigger for crystal-induced arthritis. Rheumatoid arthritis
seldom presents with monoarthritis and a sudden increase in pain and swelling involving a single joint
in a patient with pre-existing RA is strongly suggestive of sepsis. Osteoarthritis can present with pain
and stiffness affecting a single joint, but the onset is gradual and there is seldom evidence of
significant joint swelling.
Investigations
Aspiration of the affected joint is mandatory. The fluid should be sent for culture and Gram stain to
seek the presence of organisms, and should be checked by microscopy for crystals. Blood cultures
should also be taken in patients suspected of having septic arthritis. CRP levels and ESR are raised in
sepsis, crystal arthritis and reactive arthritis, and this can be useful in assessing the response to
treatment. Serum uric acid measurements may be raised in gout but a normal level does not exclude
the diagnosis.
Causes of acute monoarthritis
Common :
Septic arthritis, Gout, Pseudogout, Reactive arthritis, Trauma, Haemarthrosis Seronegative
spondyloarthritis ( Psoriatic arthritis, Ankylosing spondylitis, Enteropathic arthritis)
Less common :
Erythema nodosum, Rheumatoid arthritis, juvenile idiopathic arthritis, Pigmented villonodular synovitis,
Foreign body reaction, Other infection(Gonococcal ,Tuberculosis), Leukaemia, Osteomyelitis.
Management
If there is any suspicion of sepsis, intravenous antibiotics (Box 25.52, p. 1095) should be given
promptly, pending the results of cultures. Otherwise, management should be directed towards the
underlying cause.
PoIyarthritis
This term is used to describe pain and swelling affecting five or more joints or joint groups.
Causes
Common causes:
1) Rheumatoid arthritis (Symmetrical, small and large joints, upper and lower limbs)
2) Viral arthritis (Symmetrical, small joints; may be associated with rash and prodromal illness; self-limiting )
3) Osteoarthritis (Symmetrical, targets PIP, DIP and first cmc joints in hands, knees, hips, back and neck; associated
with Heberden's and Bouchard's nodes)
4) Psoriatic arthritis (Asymmetrical, targets PIP and DIP joints of hands and feet
“sausage appearance on
examination
”, nail pitting, large joints also affected)
5) Ankylosing spondylitis and enteropathic arthritis (Tends to affect large joints, lower more than upper limbs, possible
history of inflammatory back pain)
6) SLE (Symmetrical, typically affecting small joints, clinical evidence of synovitis unusual ).
Less common
:
1) Juvenile idiopathic arthritis (Symmetrical, small and large joints, upper and lower limbs)
2) Chronic gout (Affects distal more than proximal joints, history of acute attacks)
3) Chronic sarcoidosis (Symmetrical, small and large joints)
4) Polymyalgia rheumatica (Symmetrical, small and large joints)
Rare:
1) Systemic sclerosis and polymyositis (Small and large joints)
2) Hypertrophic osteoarthropathy (Small joints, clubbing)
3) Haemochromatosis (Small and large joints)
4) Acromegaly (Mainly large joints and spine)
Clinical assessment
The hallmarks of inflammatory arthritis are early morning stiffness and worsening of symptoms with
inactivity, along with synovial swelling and tenderness on examination. Clinical features in other
systems can be helpful in determining the underlying cause (Box 25.14).
The most important diagnosis to consider is rheumatoid arthritis, which is characterised by
symmetrical involvement of the small joints of the hands and feet, often in association with other
joints. Viral arthritis should also be considered. This presents with an acute symmetrical
inflammatory polyarthritis affecting small and large joints of upper and lower limbs, often with a
rash.
The pattern of involvement can be helpful in reaching a diagnosis (Fig. 25.9). Asymmetry, lower
limb predominance and greater involvement of large joints are characteristic of seronegative
spondyloarthritis. Other extra-articular features may also be present, giving a clue to the diagnosis.
In psoriatic arthritis, the small joints of the hand and feet are often affected, but with involvement of
the proximal and distal interphalangeal (PIP and DIP) joints, as opposed to the
metacarpophalangeal (MCI') and PIP joints in ra. The pattern of involvement also tends to be
asymmetrical in psoriatic arthritis, and other clues such as nail pitting and a rash may be present.
SLE can be associated with polyarthritis but more usually causes polyarthralgia and tenosynovitis
(p. 1110).
Extra-articular features of inflammatory arthritis
• Skin, nails and mucous membranes
a) Psoriasis, nail pitting and dystrophy (Psoriatic arthritis)
b) Raynaud's phenomenon (SLE, systemic sclerosis)
c) Photosensitivity (SLE)
d) Livedo reticularis (SLE)
e) Splinter haemorrhages, nail-fold infarcts (Vasculitis)
f) Oral ulcers (SLE, reactive arthritis, BehCet's syndrome)
g) Large nodules mainly extensor surfaces (RA, gout)
h) Clubbing (Enteropathic arthritis, metastatic lung cancer, endocarditis)
• Eyes
a) Uveitis (Seronegative spondyloarthritis)
b) Conjunctivitis (Reactive arthritis)
c) Episcleritis, scleritis (RA, vasculitis)
• Heart, lungs
a) Pleuro-pericarditis (SLE, RA)
b) Fibrosing alveolitis (RA, SLE, other connective tissue disease)
• Abdominal organs
a) Hepatosplenomegaly (RA, SLE)
b) Haematuria, proteinuria (SLE, vasculitis, systemic sclerosis)
c) Urethritis (Reactive arthritis)
• Fever, Iymphadenopathy (Infection, systemic juvenile idiopathic arthritis)
Investigations
Blood samples should be taken for routine haematology, biochemistry, ESR, CRP, viral serology
and an immunological screen, including ANA, RF and ACPA. Ultrasound examination or MRI may
be required to confirm the presence of synovitis if this is not obvious clinically.
Management
Management should be directed at the underlying condition, but treatment with non-steroidal anti-
inflammatory drugs (NSAIDs) and analgesics may be required for symptom control until a
diagnosis has been made.