We will attempt to answer our research question by means of a randomised trial as there have been no trials to date that have proposed to clarify this clinical question. The reason for choosing a randomised trial is that it will take the quality of our research findings to a higher level than already exists in the literature. PRP will be compared with HA as these are two products with similar objectives. HA has been used for longer and has a more proven clinically successful track record. Selected participants will be randomised to receive either HA or PRP intra-articular injections.