Ultrasound Clinical Case Study with Stephen Bird

Acute tendonosis - hydroxyapatite deposition

Stephen Bird

Sonographer – Benson Radiology
AMS, AMS (Vascular), DMU, DMU (Vascular), MMedSon

A general sonographer with 25 years clinical experience, Stephen has a strong commitment to advancing ultrasound education. In 2002 Stephen received the ASA Pru Pratten Memorial Sonographer Achievement Award and in 2008 he was made an Honorary Fellow of ASUM.

Learn more about Stephen Bird's online courses and webinars.


Deposits of basic calcium phosphate (BCP) crystals are associated with two types of musculoskeletal conditions. Calcific periarthritis results from crystal deposition in structures such as tendons, intervertebral discs and other soft tissues surrounding joints (1). Whereas BCP-associated arthritis can manifest as osteoarthritis or an aggressively destructive arthropathy known as Milwaukee Shoulder Syndrome (MSS). The most common BCP crystal species encountered is hydroxyapatite (HA) (2).

Deposits of BCP in tendons and bursae most commonly occur in the shoulder but can also occur in the small joints of the body, such as the ankle. Calcific tendonitis can result in acute attacks of inflammation and can be linked with calcific periarthritis. When the crystals migrate from the tendon into the soft tissue surrounding the joint it can result in sudden onset of painful and swollen joints, restricted movement and overlying redness.
A faint line of crystal deposition corresponding to the sonographic findings was seen on dorsi-plantar foot and anterior-posterior ankle radiographs (Figure 1, 2). 

The clinical presentation combined with sonographic and radiographic findings are characteristic of calcific tendinosis (HA deposition). Hydroxyapatite is a bone salt and requires an enthesis to migrate from bone to tendon. In this case, the enthesis is the large accessory os tibiale externum ossicle. The radiographic density of the crystal deposition suggests a diagnosis of hydroxyapatite over gout and the clinical presentation is consistent with an acute tendinosis event.
Figure 1, 2: DP foot and AP ankle radiographs demonstrate a faint line of crystal deposition, corresponding to the sonographic findings.


Canon Medical’s Aplio a550 systems provide clinicians with high-quality B-mode imaging, which enables users to differentiate between similar density structures and better visualise abnormalities such as crystal deposition. 

Advanced Dynamic Flow (ADF), available on all Aplio ultrasound systems, offers high-resolution colour flow that enables physicians to identify small complex vascularity. It offers superior spatial resolution to easily reveal minute blood flow patterns and provides high frame rates while maintaining the full B-mode image quality to accurately depict flow with directional information, even in tiny vessels. 

The use of ADF in this clinical case clearly demonstrated hypervascularity within the tendon as well as confirming the presence of crystal deposition by twinkle artifact.


1. Basic calcium phosphate crystal-associated musculoskeletal syndromes: an update
Ann K. Rosenthal [Read here]

2. Detection of calcium phosphate crystals in the joint fluid of patients with osteoarthritis – analytical approaches and challenges
Alexander Yavorskyy,a,* Aaron Hernandez-Santana,a Geraldine McCarthy,b and Gillian McMahon [Read here]

Contact Us