We studied the relationship between Knowledge Management (KM) and Organisational Commitment (OC) based on ASH-ICI Questionnaire of Quijano, Navarro and Cornejo (2000) and the KM Questionnaire of Cardoso (2003). In an empirical study carried out in 9 Private Social Solidarity Institutions with a sample of 217 collaborators, we tried to empirically sustain the prediction capability of OC and organisational variables (length of time in the institution and post-held) in relation to KM. We conducted a statistical analysis of three models, which make up a general model of multiple hierarchic regressions with moderation of discrete variables. We concluded that only the instrumental commitment of exchange was statistically significant in all KM dimensions. The affective and values commitment showed a predictive capability in cultural orientation to knowledge and KM practices. However, instrumental commitment of necessity showed a negative impact on knowledge management practices. Lastly, we considered the post-held variable, which appears as a predictor of two knowledge management dimensions to group 1 (directors, professionals, teachers, animators, therapists and others): social and discursive knowledge and KM practices. The theoretical and practical implications of these results are analysed and discussed.