Despite the considerable number of papers addressing knowledge management (KM) aspects in supply chains, many research issues in the area are still neglected. One of the main research gaps in this field concerns the maturity level of KM practices adoption by small and medium enterprises (SMEs). This paper addresses this research gap by developing a framework to support the analysis of the maturity level of KM adoption in an SME context. The framework is applied in a multiple case study developed to investigate the extent to which SMEs operating in the food sector are deploying KM practices to support more sustainable initiatives. By relating KM maturity levels, perspectives and processes to sustainable practices concerning food waste and by-product synergies, the paper makes an original contribution to advance theory and practice in the area. The paper also points out potential barriers that companies face to implement sustainability-related KM practices.