Fibrous dysplasia is one of the most common skeletal lesions. The wide spectrum of clinical manifestations ranges from asymptomatic conditions (typical of monostotic forms) to severe skeletal diseases with deformity and fractures for polyostotic fibrous dysplasia. The classical radiological features include: an osteolytic geographic pattern, ground-glass bone matrix, cortical thinning/cortical scalloping, bone deformities and enlargement, concavity of margins (evaluated with MRI), and cystic areas (MRI). All the bones can be affected, and the proximal femur is the most common one (about 30% of cases). Nonetheless, the disease can also affect cranio-facial bones, leading to compression of neural structures, as well as deformation and enlargement of facial bones, leading to the so-called “leontiasis ossea” or “facies leonine”. The polyostotic forms of fibrous dysplasia can be associated with multiple soft-tissue myomas (Mazabraud syndrome) or several endocrine diseases (McCune–Albright syndrome). In every diagnostic step of the disease, as well as in different fibrous dysplasia forms, imaging plays a key role. Indeed, radiology is fundamental to assess the suspicion of fibrous dysplasia in classical monostotic forms, representing the sole diagnostic tool needed in many cases. Imaging is also fundamental to staging and following up on more severe polyostotic forms, as well as for detecting complications. In this comprehensive updated review article, we examine every aspect of the disease, with a main focus on imaging presentation. The indications for biopsy are discussed as well. Most importantly, the article details the potential risk of malignant transformation (osteosarcoma, fibrosarcoma, chondrosarcoma, and other rarer sarcomas, all accounting for <1% of cases) underlying the radiological patterns of these conditions. The occurrence of aneurysmal bone cyst-like changes on fibrous dysplasia is also analyzed in the article. This review article aims to be a comprehensive guide for radiologists and clinicians involved in the care of patients affected by various forms of fibrous dysplasia, and a starting point for future research. Many classical and atypical cases are collected as an iconographic comprehensive representation.

Background: This narrative review discusses de Quervain’s tenosynovitis, a stenosing inflammatory condition affecting the first extensor compartment of the wrist that results in radial styloid pain during thumb and wrist activities. The diagnosis is primarily clinical. Conservative management includes rest, nonsteroidal anti-inflammatory drugs and corticosteroid tendon sheath injections. Main body: Inaccurate clinically guided injections and anatomical variations may lead to treatment failure. Ultrasound facilitates precise needle placement and detailed characterization of the first extensor compartment, allowing for a tailored infiltrative approach to optimize clinical outcomes. Several studies show the benefits of ultrasound-guided injections, with a good safety profile. Additionally, it may prevent the injection of corticosteroids outside the tendon sheath and inside the tendon. While complete subcompartmentalization traditionally warrants dual injections when both tendons are involved, the primary pathology in de Quervain’s tenosynovitis typically resides within the extensor pollicis brevis tendon. Notably, recent evidence suggests that a targeted single injection into the EPB sheath provides pain relief comparable to separate subcompartmental injections, regardless of abductor pollicis longus involvement. Emerging therapies, such as platelet-rich plasma injections and US-guided percutaneous release, offer durable results with minimal adverse effects, establishing them as viable contemporary treatment options. Short conclusion: Use of ultrasound is essential to determine extensor compartment anatomy and guide intervention.