Cartilage regeneration requires a balance of anabolic and catabolic processes. This study examined the susceptibility of fibromodulin (FMOD) and lumican (LUM) to degradation by MMP-13, ADAMTS-4 and ADAMTS-5, the three major degradative proteinases in articular cartilage in osteoarthritis (OA). Immunolocalisation of FMOD and LUM in foot sections of developmental cartilages demonstrated prominent localisations in metatarsal and phalangeal foetal rudiment cartilages and growth plate. An MMP-13 neoepitope antibody (TsYG11) demonstrated localisation of MMP-13 cleaved FMOD in the hypertrophic chondrocytes of the metatarsal growth plate. FMOD was more prominently localised in the superficial cartilage of normal and fibrillated zones in OA cartilage, TsYG11 positive FMOD was located deeper in the cartilage samples. Ab TsYG11 also identified FMOD fragmentation in Western blots of extracts of normal and fibrillated cartilage and total knee replacement OA cartilage. The C-terminal anti-FMOD used in this study (PR-184) failed to identify FMOD fragmentation due to C terminal processing, an equivalent Ab to the C-terminus of LUM (pAb PR-353) identified 3 prominent LUM fragments in OA human knee cartilages. In-vitro digestion of human knee cartilage with MMP-13, ADAMTS-4 and ADAMTS-5 generated equivalently sized FMOD fragments of 54, 45 and 32kDa to those in blots of OA cartilage, LUM was not less susceptible to fragmention in in-vitro digestions however Ab PR-353 detected N-terminally processed LUM fragments of 39, 38 and 22 kDa in 65-80 year old OA knee cartilage. FMOD and LUM were differentially processed during in-vitro digestions with MMP-13, ADAMTS-4 and ADAMTS-5 with FMOD susceptible to degradation by MMP-13, ADAMTS-4 and to a lesser extent ADAMTS-5 however LUM was less susceptible to fragmentation. FMOD was processed by MMP-13 in metatarsal and phalangeal foetal rudiment developmental cartilages and growth plate indicating a role in skeletogenesis.