Differentials
Osteoarthritis (for de Quervain's, flexor carpi radialis tenosynovitis)
SIGNS / SYMPTOMS
Direct tenderness over corresponding joint. No tenderness over the suspected tendon.
INVESTIGATIONS
Plain x-rays of affected hand, wrist, and thumb base: arthritic changes including sclerosis, joint space narrowing, osteophytes, and/or cystic changes.
Occult fracture (e.g., scaphoid)
SIGNS / SYMPTOMS
Direct tenderness over corresponding region of bone - at the scaphoid waist in the anatomic snuffbox, or at the volar margin of the scaphoid for tubercle fractures. No tenderness over the suspected tendon.
INVESTIGATIONS
Plain x-ray of affected hand and wrist: occult fracture lines.
CT scan and/or MRI if plain x-ray is negative: occult fracture lines.
Cellulitis
SIGNS / SYMPTOMS
Open wound may be present; acute development of signs. Macular erythema with indistinct borders, warmth, tenderness, and oedema.
Diagnosis is clinical in most cases.
INVESTIGATIONS
ESR: elevated.
CRP: elevated.
Fluid Gram stain/culture: may be positive for causative bacteria.
Septic tenosynovitis
SIGNS / SYMPTOMS
Signs of infection, such as erythema, fusiform swelling, and fluctuance, may be present locally.
INVESTIGATIONS
FBC with differential: elevated WBC.
ESR: elevated.
CRP: elevated.
Fluid cell count: elevated.
Fluid Gram stain/culture: may be positive for causative bacteria.
Septic arthritis
SIGNS / SYMPTOMS
Open wound; acute development of signs of joint infection (e.g., pain with passive motion, effusion).
INVESTIGATIONS
FBC with differential: elevated WBC.
ESR: elevated.
CRP: elevated.
Fluid cell count: elevated.
Fluid Gram stain/culture: may be positive for causative bacteria.
MRI: will show a fluid collection or effusion in the joint with possible corresponding bone changes, if chronic.[44]
Rheumatoid arthritis
SIGNS / SYMPTOMS
Systemic signs and symptoms; other joint involvement; history of bilateral, symmetric pain and swelling of the small joints of the hands and feet that has lasted for >6 weeks; morning stiffness; rheumatoid nodules over the extensor surfaces of tendons, or vasculitic skin involvement.
INVESTIGATIONS
ESR: elevated.
CRP: elevated.
Fluid cell count: elevated.
Rheumatoid factor: positive in 70%.
Gout
SIGNS / SYMPTOMS
Swelling, effusion, warmth, erythema, and/or tenderness of the involved joint(s).
INVESTIGATIONS
Plain x-ray: degenerative changes.
Uric acid: elevated.
Joint aspirate: needle-shaped crystals strongly negative for birefringence under polarised light.
Dupuytren's contracture
SIGNS / SYMPTOMS
Painless nodules in palm and digits; insidious development over months or years. Mild cases easily confused with locked trigger digit.
INVESTIGATIONS
No specific test; clinically palpable cord in palm.
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