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Background
The clavicle marks the beginning and end of skeletal maturity, as it is the first bone to ossify, between 5 and 7 weeks of gestation, and one of the last growth plates to close in the body, between age 20-25 years. It is also one of the most commonly imaged bones in the body, owing largly to it's inclusion on the ubiquitous chest radiograph. We present a systematic review of clavicle anatomy and pathology, including normal variants, congenital anomalies, role in thoracic outlet syndrome, injuries, infections, rheumatologic conditions, and tumors. The target audience includes all practicing radiologists and trainees.

Educational Goals / Teaching Points
All radiologists must be familiar with normal variants of the clavicle, particularly those that may mimic pathology, to maximize accuracy of reporting. Trauma involving the clavicle is reviewed, including fractures as well as injuries of the sternoclavicular, and acromioclavicular joints. The costoclavicular subtype of thoracic outlet syndrome is reviewed, including percutaneous and surgical treatment options. Lastly, we present a spectrum of less commonly encountered cases of infections, rheumatologic and metabolic diseases, as well as tumors involving the clavicle.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Normal variants and pitfalls: forked clavicle (bifid medial head), coracoclavicular joint/coronoid tubercle, supraclavicular foramen, rhomboid fossa. Congenital anomalies: hypoplasia (cleidocranial dysostosis, Ehlers-Danlos, triple X syndrome). Impingement/overuse: costoclavicular thoracic outlet syndrome (cervical ribs, subclavius injection, rib resection); weightlifter osteolysis. Trauma: fractures, sternoclavicular injury, acromioclavicular injury, "floating clavicle." Infection: sternoclavicular septic arthritis, chronic recurrent multifocal osteomyelitis (CRMO). Tumors: enchondroma, eosinophilic granuloma, osteochondroma, metastases, multiple myeloma. Rheumatologic and metabolic conditions: eheumatoid arthritis, calcinosis of renal failure, amyloid arthropathy, calcium pyrophosphate deposition, gout (role of dual energy CT). Miscellaneous: Gorham-Stout disease, Paget's disease.

Conclusion
Knowledge of normal variants and pathology affecting the clavicle is relevant to all radiologists, as it is one of the most commonly imaged bones, being included on the standard chest radiograph. We hope this comprehensive review is helpful to all, from trainee to attending radiologist, as well as general radiologists and musculoskeletal radiology colleagues alike.