Sonographic Diagnosis of Knuckle Pads

FIGURES 4 & 5: Palmar longitudinal and transverse B-mode ultrasound views of the Dupuytren’s contracture. An ill-defined hypoechoic lesion superficial to the flexor tendon proximal to the metacarpophalangeal joint can be seen (dotted line). Key: MC: metacarpal; PP: proximal phalanx; MP: Middle phalanx; FT: flexor tendon. (Click to enlarge.)

Ganglion cysts are usually soft, non-tender cystic to firm swellings and can be present, rarely, on the dorsal aspect of the PIP joints. On musculoskeletal ultrasound, they are anechoic to hypoechoic with increased posterior acoustic enhancement.¹³ Ganglion cysts are usually seen in proximity to underlying tendons and can originate from the tenosynovium of the tendon. Power Doppler does not usually reveal hypervascularity, and the joint underneath is normal.¹⁰

Bouchard nodes are firm to hard, non-tender nodules seen on the dorsal aspect of the PIP joints in osteoarthritis. Ultrasound usually reveals underlying osteophytes and can reveal joint effusion. Erosions can be detected by musculoskeletal ultrasound in erosive osteoarthritis.¹⁴

In Sum

Knuckle pads are benign, subcutaneous, soft-tissue nodules. Musculoskeletal ultrasound can be a useful tool in diagnosing knuckle pads and ruling out other etiologies.

Pankaj Bansal, MD, RhMSUS, serves in the Department of Rheumatology, Mayo Clinic Health System, Eau Claire, Wis.

Eugene Kissin, MD, RhMSUS, is a clinical professor in the Division of Rheumatology, Boston University School of Medicine.

Fawad Aslam, MBBS, RhMSUS, RMSK, is a rheumatologist at the Mayo Clinic in Scottsdale, Ariz.

References

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