Sprains of the first metacarpo-phalangeal joint (MCPJ) are a common form of hand injury that mainly affects the ulnar collateral ligament. Although the diagnosis is made on the physical findings, radiographs must be obtained and ultrasonography or magnetic resonance imaging (MRI) is necessary in some cases. If the joint is unstable or a bony fragment is displaced, surgery must be performed within 4 weeks after the injury. Beyond this interval, ligament reconstruction is the preferred treatment. The objective of this article is to provide evidence, from both older and recent studies, that guides the choice of the best treatment in clinical practice. To this end, we will address the following questions: (1) What is a Stener lesion? (history and pathophysiology); (2) In addition to the physical examination, what other investigations are appropriate in doubtful cases? (with special attention to the indications of ultrasonography and MRI); (3) What are the clinical and radiological criteria for performing surgery in patients with acute first MCPJ sprains? (4) What reconstruction procedures are appropriate in patients with acute or chronic MCPJ sprains?