Background: Flatfoot is an alteration of the normal structure of the foot, characterized by a partial or total reduction of the medial longitudinal plantar arch, valgus deformity of the heel, and abduction of the forefoot. While treatments often include strengthening of the intrinsic foot muscles, evidence of its efficacy in adults with flatfoot remains limited. Objectives: The main objective of this review was to evaluate the effects of strengthening the plantar intrinsic muscles in adults with flatfoot. Methods: Searches were conducted in PubMed, Embase, Cochrane, PEDro, and Web of Science databases up to October 2023. The review protocol was developed and followed according to the PRISMA Extension for Scoping Reviews (PRISMA-ScR) guidelines. Studies included were those published on intrinsic muscle strengthening in adult populations. A qualitative synthesis of all included articles was performed, along with a quantitative sub-analysis of randomized controlled trials and a critical methodological assessment. Results: Eleven studies involving a total of 374 participants were selected. Most studies identified the “short foot exercise” as the optimal exercise for isolating and training the plantar intrinsic foot muscles. The most commonly analyzed variables were the Foot Posture Index and the Navicular Drop Test. Conclusions: Strengthening the plantar intrinsic muscles enhances the height of the medial longitudinal arch, improves hindfoot posture and balance, and increases hallux abductor muscle activity. This strengthening, whether achieved through short foot exercises alone or in combination with other techniques, is effective in treating adult flatfoot. Current literature suggests that a duration of 4–6 weeks may be sufficient to achieve beneficial outcomes.

Background: The origin of hallux abducto valgus (HAV) is considered to be multifactorial; however, evidence regarding the factors involved in its development is scattered and often contradictory. Understanding the factors that contribute to the onset of HAV is crucial for informing both prevention and clinical management strategies. This review aims to explore the etiological factors associated with the development of HAV. Methods: A literature search was conducted in PubMed, Embase, Web of Science and Scopus. The search included observational studies that investigated etiological or risk factors related to the development of HAV. Methodological quality was assessed using the Joanna Briggs Institute (JBI) checklists, and the level of evidence was classified according to the Oxford Centre for Evidence-Based Medicine (OCEBM). Results: A total of 36 observational studies (20 cross-sectional and 16 case–control) were included, involving 14,500 participants, predominantly females. Genetic evidence indicated strong familial aggregation and variants in collagen- and extracellular matrix-related genes as potential hereditary determinants. The most consistent biomechanical factors were first-ray hypermobility, abnormal foot pronation and reduced activity of the abductor hallucis muscle. Additionally, female sex, older age and prolonged use of narrow or inadequate footwear were identified as recurring predictive variables. Overall, the findings support a complex etiological model based on the interaction of intrinsic and extrinsic factors. Conclusions: The development of HAV appears to be determined by the interaction of genetic, structural and biomechanical factors that alter first-ray stability and forefoot function. Current evidence supports a multifactorial etiological model with a strong hereditary component and higher susceptibility in women. Longitudinal studies employing standardized methods are needed to establish causal relationships and quantify the relative contribution of each factor.