Radiographic Features of Psoriatic Arthritis on X-ray

Key Radiographic Features to Look For

The American Academy of Dermatology notes that the characteristic radiographic features of psoriatic arthritis (PsA) on X-ray include erosions with accompanying bone proliferation, asymmetric joint involvement with predilection for distal interphalangeal joints, pencil-in-cup deformities, periostitis, and ankylosis 1, 2
Most frequently involved joints are hands and wrists, followed by feet, ankles, knees, and shoulders, according to the American Academy of Dermatology 1
Asymmetric pattern of joint involvement is characteristic of PsA, as stated by the American Academy of Dermatology 1
Distal interphalangeal (DIP) joint involvement is a distinctive feature compared to rheumatoid arthritis, notes the American Academy of Dermatology 1

Erosions typically start at joint margins and progress toward the center, as described by the American Academy of Dermatology 1
Erosions may become extensive, giving the appearance of widened rather than narrowed joint spaces, according to the American Academy of Dermatology 2
Marked osteolysis in severely destroyed joints can lead to complete destruction of phalanges, as reported by the American Academy of Dermatology 2

Erosions with accompanying increased bone production (a distinguishing feature from rheumatoid arthritis) are noted by the American Academy of Dermatology 1
Juxta-articular new bone formation (included in CASPAR diagnostic criteria) is described by the American Academy of Dermatology 3

"Pencil-in-cup" phenomenon: blunt osseous surface on proximal bone protruding into expanded surface of distal bone, as defined by the American Academy of Dermatology 1
Arthritis mutilans (severe form with osteolysis) may be observed, according to the American Academy of Dermatology 3, 2

Joint space narrowing may be present but is less prominent than in rheumatoid arthritis, notes the American Academy of Dermatology 2
Ankylosis (fusion) of joints may occur in advanced disease, as reported by the American Academy of Dermatology 2

Several scoring methods have been developed for assessing structural damage in PsA, including the Sharp-van der Heijde modified scoring method, which evaluates erosions, joint space narrowing, subluxation, ankylosis, gross osteolysis, and "pencil-in-cup" phenomena, as described by the American Academy of Dermatology 1

Radiographic findings may not correlate with the severity of skin disease, according to the American Academy of Dermatology 4
Structural damage on radiographs is an important outcome measure in judging treatment efficacy, as stated by the American Academy of Dermatology 1

When X-rays are negative but PsA is still suspected, more sensitive imaging modalities like MRI or ultrasound may be needed, as recommended by the American College of Radiology 5, 6
MRI can detect early inflammatory changes including synovitis, enthesitis, and bone marrow edema, according to the American College of Radiology 7
Ultrasound can identify synovial hypertrophy and increased blood flow on color Doppler imaging, as noted by the American College of Radiology 6