High life expectancy and an ageing population worldwide have resulted in an ever-increasing need for bone replacements. There is great interest in biodegradable composites as these materials not only offer the potential of exhibiting desired properties but also avoid the need for additional surgery. The study presented investigates one such composite of hydroxyapatite (HA) and poly (D, L lactide-co-glycolide (50:50)) (PLGA). This book highlights the effect of silanisation and calcination of HA on the properties of PLGA/HA composites. The study shows for the first time the importance of competing effects of particle-mediated water sorption and buffering on the degradation of resorbable composites. Also described is the fact that silanisation significantly influences the plastic rather than elastic mechanical properties of the composites.