Sesamoids and accessory ossicles seen in the foot vary widely in their prevalence and appearance. Occasionally, these bones may be associated with painful syndromes, due to various pathologies, including trauma, infection, inflammation, degeneration and others. However, symptomatic accessory and sesamoid bones are rare, and search for additional pathology should be performed. Although the clinical significance of these osseous structures is probably minor, clinicians very commonly ask about these bones, which may originate an unnecessary work-up. Therefore, knowledge of their presence and morphological variations is important to prevent misinterpreting them as fractures—a common error. Finally, it may be very difficult to distinguish between incidental variants and truly symptomatic ones. Radiological studies provide insight regarding the presence and pathology involving these bones. This review describes an overview of the anatomy of sesamoids and accessory ossicles in the foot, and provides a pictorial review of their pathological conditions, including trauma, sesamoiditis, osteomyelitis, osteoarthritis and pain syndromes. Radiological studies including radiography, ultrasound, scintigraphy, computed tomography (CT) and magnetic resonance imaging (MRI) provide useful information which should be used in concert with clinical findings to guide patient management.Teaching points• Sesamoids and accessory ossicles seen in the foot vary widely in their prevalence and appearance.• Pathology of these bones includes trauma, sesamoiditis, infection, osteoarthritis and pain syndromes.• Radiography, ultrasound, scintigraphy, CT and MRI provide information regarding the pathology of these bones.

Teaching Points• SLAC is the most common cause of osteoarthritis involving the wrist.• Arthritic changes of SLAC occur in a predictable progressive pathological and radiographic pattern.• Imaging is key for diagnosing, monitoring progression and assessing post-treatment changes of SLAC.

No abstract

Peripatellar fat pads are intracapsular extrasynovial adipose cushions that accommodate the changing shape and volume of articular spaces during movement. Variations in bone geometry, passive and active stabilization mechanisms and/or functional demands may lead to peripatellar fat pad abnormalities. While peripatellar fat pads may be affected a variety of conditions such as synovial inflammation, tumor and fibrosis, a mechanical origin should also be considered. Commonly, the clinical term “impingement” is used synonymously in the radiological literature to refer to three distinct entities of structural peripatellar fat pad abnormalities: superolateral the infrapatellar fat pad (Hoffa fat pad) edema, suprapatellar fat pad edema, and prepatellar fat pad edema, implying a mechanical origin of these conditions. The aim of this pictorial review is to describe the normal anatomy of the extensor mechanism of the knee, and discuss the relation of patellofemoral maltracking to the above-mentioned peripatellar fat pad conditions based on current evidence.

Patellar fractures account for approximately 1% of all skeletal fractures and may result from direct, indirect, or combined trauma. Because of the importance of patellar integrity for knee extension and the risk of associated injury to the extensor mechanism, accurate reporting and description of fracture type is paramount for appropriate management. This pictorial essay aims to review the normal anatomy of the patella, the mechanisms of injury and different types of patellar fractures, with a brief introduction to therapeutic management. Teaching Points • Patellar fractures are classified according to their morphology and degree of displacement.• Direct trauma results in stellate fractures.• Indirect trauma results in transverse fractures.• Displacement should raise suspicion for retinacular injury.