Label-free multimodal nonlinear optical microscopy has emerged as powerful nondestructive imaging concept that has high potential to perform advanced structural, functional, and molecular characterization of intact articular cartilage. It can monitor the health status and therapy. Cartilage has only limited capacity for repair. Joint injuries cause loss of chondrocyte viability and extracellular matrix components. Since these processes are mostly irreversible, osteoarthritis prevention, understanding of disease onset, mechanism, and progression, as well as articular surface preservation pose important research questions. Until now the mechanisms are only poorly understood and few intertwined factors have been identified. Nonlinear optical microscopy provides morphological and metabolic contrast with molecular selectivity in a label-free manner, which overcomes the limitations induced by exogenous fluorescent probes. With advantages of the 3D-sectioning capability, large penetration depth, high spatial resolution, and high imaging speed, label-free nonlinear optical microscopy is suitable to promote our understanding of osteoarthritis. This chapter provides the basic theory, technical principles, the current status, opportunities, and challenges of nonlinear optical microscopy for the use in cartilage evaluation. A novel perspective is being addressed that includes the reason, need, and the importance of these techniques in the assessment of articular cartilage. Special emphasis is given to second harmonic generation and two-photon excitation fluorescence imaging. The integration of collagen specificity and intrinsic contrast from chondrocyte cell viability at cellular resolution allows for the detection of subtle structural and functional changes in early-stage cartilage damage, which are often imperceptible with standard clinical imaging techniques such as radiography and arthroscopy. The current status of nonlinear optical microscopy for articular cartilage analysis, tissue engineering, and regeneration and the major advances are briefly described. The challenges that need to be overcome are summarized before advancing toward clinical applications of nonlinear optical microscopy in the context of cartilage evaluation.