Three decades of research on knee isokinetic strength: A bibliometric and visual exploration of global trends and emerging frontiers.

Background: Isokinetic muscle strength of the knee joint plays a pivotal role in sports performance, injury prevention, and post-surgical rehabilitation, particularly in anterior cruciate ligament recovery. Despite a growing body of literature, a systematic evaluation of the global research landscape remains lacking. This study aims to quantitatively analyze global publication trends, identify research hotspots, and highlight potential future directions in this field over the past 30 years. Methods: A comprehensive literature search was conducted using the Web of Science Core Collection for articles published between 1994 and 2024. Bibliometric indicators-including annual publication volume, prolific journals, authors, institutions, and countries-were analyzed. Visualization and keyword co-occurrence analysis were performed using VOSviewer and CiteSpace to detect thematic evolution and research frontiers. Results: A total of 1013 publications on knee joint isokinetic muscle strength were identified, with an upward trend in annual output. These articles appeared in 221 peer-reviewed journals, with Isokinetics and Exercise Science, Journal of Strength and Conditioning Research, and International Journal of Sports Medicine being the most prolific. The United States, the United Kingdom, and Brazil emerged as the leading contributors. Early research emphasized muscle strength assessment and knee stability, while recent studies have shifted toward optimizing sports performance, neuromuscular imbalance correction, and rehabilitation strategies post-ACL reconstruction. Notably, emerging keywords such as "anterior cruciate ligament reconstruction," "asymmetry," "risk," and "quadriceps strength" demonstrated high burst strength and centrality, indicating emerging research foci. Conclusions: Research on knee isokinetic strength has expanded considerably, with increasing focus on rehabilitation efficacy and performance enhancement. While global output and interdisciplinary collaboration have grown, key limitations persist-including the lack of standardized assessment protocols, ambiguous thresholds for strength asymmetry, and insufficient population-specific evidence. Future research should prioritize methodological standardization, integration with biomechanical and neuromuscular modeling, and the establishment of clinically validated criteria to inform individualized rehabilitation and return-to-sport decision-making.