Enzymes from the matrix metalloproteinase (MMP) family play a crucial role in growth-plate vascularization and ossification via proteolytic cleavage and remodeling of the extracellular matrix. Their regulation in the growth plate is crucial for normal matrix assembly. Endochondral ossification, which takes place at the growth plates, is influenced by mechanical loading. Using an in-vivo avian model for mechanical loading, we have found increased blood penetration into the growth plates of loaded chicks. The purpose of this work was to study the involvement of MMP-2, 3, 9, 13, and 16 in the growth plate's response to loading and in the catch-up growth resulting from load release. We found that mechanical loading as well as release from load upregulated MMP-2, 9, and 13 expressions. In contrast, MMP-3, associated with cartilage injuries, and its associated protein connective tissue growth factor (CTGF), were downregulated by the load. However after release from load MMP-3 was upregulated and CTGF levels were elevated and caught-up with the control. MMP-3 and CTGF were also downregulated after 60 min. of mechanical stretching in-vitro. These results demonstrate the central role of MMPs in the growth plate's response to mechanical loading, as well as, in the catch-up growth followed load release.