Polarisation and online radicalisation pose significant threats in the modern world. YouTube, particularly its recommendation system - which drives approximately 70% of the platform's audience - has become a focal point of concern. This study presents a systematic literature review of 56 papers, addressing three core research questions to examine the extent, data collection methods, and quantification of problematic content. Our analysis identifies politics as the most polarised domain, revealing a notable convergence of polarisation and disinformation themes. We further emphasise the influential role of other social networks in spreading problematic content. The findings underscore the necessity of distinguishing between polarisation and misinformation in research methodologies, offering a comprehensive overview of the field's current state.