A 53-year-old female complained about an abrupt onset of localized deep pain and aching discomfort in the sole of the left great toe for 2 weeks since she held her daughter’s wedding party and had to stand for 4 hours with high-heeled shoes. The pain was aggravated by walking and standing with the foot on the ground. There were no neurological deficits, previous pain, trauma, rheumatic diseases, fever, or other constitutional symptoms. The physical examination of the left foot revealed that the visual analogue scale was 6, antalgic gait and pain during the stance phase of gait with pes cavus and equinus (Figure 1). There was no open wound, hallux valgus or callus, swelling around the plantar aspect of the first metatarsal head, pain after deep palpation and passive dorsifl exion of the great toe, Mulder’s sign and clinical signs of infection and neurological defi cits. Radiologic fi ndings showed no bony abnormalities. Slightly increased erythrocyte sedimentation rate and C-reactive protein were noticed from blood analysis.

Ultrasound (US) scanning was performed along the longitudinal and transverse view of the left first metatarsal head. The patient was positioned prone with slight ankle dorsiflexion on a supporter under the ankle joint (Figure 2). US imaging revealed a fl attened compressible superfi cial focal lesion with a well-defined wall and complex fluid with mixed internal echotexture (containing effusion and synovial hypertrophy) in both scanning view (Figure 3). The lesion could be distinguished from the fl exor hallucis longus tendon and was superficial to the sesamoid bone. We did not identify enhanced power Doppler signals, joint effusion, or tenosynovitis. The diagnosis of adventitial bursitis was thus made.

Adventitial bursitis is inflammation of the adventitious bursae. The adventitious bursae is not permanent bursae, typically observed in areas of chronic frictional irritation, usually superficial to the bony prominences. The adventitious bursae could be found at the foot and ankle region such as the medial plantar aspect of the fi rst metatarsal head or overlying of the amputation stumps [1,2]. Clinical presentation of adventitial bursitis in the plantar aspect of the fi rst metatarsal heads is an abrupt onset of localized deep pain and aching discomfort in the plantar aspect of the fi rst metatarsal head aggravated by walking. The diagnosis of adventitial bursitis is diffi cult based solely on clinical findings. Radiography does not allow the diagnosis of soft-tissue disorders [1,3,4]. Musculoskeletal US is a useful imaging modality adjuvant to clinical presentation in the diagnosis of soft tissue disorders such as bursitis [3,4].

Figure 1. Patient in Standing Position Viewed From the Anterior (A) and Posterior (B) Demonstrating Pes Cavus and Equinus of Left Foot

Figure 2. Ultrasound Imaging of the Plantar Aspect of the Left First Metatarsal Head

The patient was positioned prone with slight ankle dorsiflexion and a folded towel under the ankle joint. The probe was placed on the most painful area over the metatarsal head for the longitudinal (A) and transverse (B) scan.

Figure 3. Ultrasound Imaging of Adventitial Bursitis in the Plantar Aspect of the First Metatarsal Head

(A) The longitudinal ultrasound scan of the plantar aspect of the left first metatarsal head (Met) show a flattened compressible superficial lesion (arrow) with a well-defined wall and complex fluid with mixed internal echotexture, representing fluid and synovial tissue separated from the flexor hallucis longus tendon (fhl). (B) The transverse scan shows the same lesion separated from the fhl.
Abbreviations: LS, lateral sesamoid; MS, medial sesamoid.

The author declare no confl ict of interest.