What Is the Issue? The subtalar joint enables the inversion and eversion of the feet. Excessive movement of the subtalar joint can lead to painful foot conditions that may require surgical treatment in severe cases. Subtalar joint arthroereisis involves the insertion of an implant that limits excessive movement of the subtalar joint. It is considered a minimally invasive surgical procedure with a relatively fast healing period compared to alternative surgical procedures. While this procedure is commonly used for children with pes planus, it is becoming a more common treatment for adults with foot conditions. There is uncertainty as to whether subtalar joint arthroereisis can be effective for adults. What Did We Do? We conducted a rapid review to identify, summarize, and critically appraise evidence regarding the clinical effectiveness and cost-effectiveness of subtalar joint arthroereisis for adults with pes planus (i.e., flatfoot), plantar fasciitis, and other foot conditions. Additionally, we aimed to identify, summarize, and critically appraise evidence-based guidelines regarding the use of subtalar joint arthroereisis for adults. An information specialist conducted a customized literature search, balancing comprehensiveness with relevancy, of multiple sources and grey literature on November 20, 2024. What Did We Find? We identified 8 relevant studies (1 systematic review and 7 nonrandomized studies) that evaluated the clinical effectiveness of subtalar joint arthroereisis for adults with pes planus. Compared to baseline, the literature suggests that subtalar joint arthroereisis improves key clinical outcomes, such as overall foot and ankle condition, health-related quality of life, and pain relief (1 systematic review and 4 nonrandomized studies). One nonrandomized study found mixed results when comparing subtalar joint arthroereisis to lateral column lengthening for adults living with stage IIb adult-acquired flatfoot deformity. We also found 2 relevant nonrandomized studies regarding the clinical effectiveness of subtalar joint arthroereisis for adults with other foot conditions (i.e., reducible talotarsal joint dislocation and partial talotarsal joint instability). Compared to baseline, the literature suggests that subtalar joint arthroereisis improves the function of the foot and ankle, pain relief, and ability to perform activities of daily living in the long term for adults with partial talotarsal joint issues (1 nonrandomized study). For the studies in this report, sinus tarsi pain was the most reported adverse event and the cause of implant removal. Other adverse events included implant revision, surgical infection, stress fractures, insufficient deformity correction, reoccurrence of foot deformity, wound healing issues, and muscle and tendon complications (10 studies). Overall, there is uncertainty in the identified evidence due to risk of bias and methodological limitations. We did not identify relevant studies regarding the clinical effectiveness of subtalar joint arthroereisis for adults with plantar fasciitis. We also did not find any relevant cost-effectiveness studies or evidence-based guidelines regarding the use of subtalar joint arthroereisis for adults. What Does This Mean? These results should be interpreted with caution. Most studies included in this report were of low-quality and limited to comparing before-after outcomes. Additionally, most studies did not account for the impact of confounding variables (e.g., obesity) and heterogeneity within and between treatment arms (e.g., implant sizes, adjunct procedures, and implant type). Comparative evidence from robust studies is needed before definitive conclusions regarding the clinical effectiveness of subtalar joint arthroereisis can be made. Future studies could consider evaluating the cost-effectiveness of subtalar joint arthroereisis with considerations of the implications of implant removals, as well as the clinical effectiveness of subtalar joint arthroereisis for individuals with plantar fasciitis. Given that subtalar joint arthroereisis is commonly provided in combination with other procedures, future research may also consider evaluating best practices with adjunctive treatments for adults with foot conditions.