Patient-specific guides for a tibial tubercle osteotomy are provided. The guides include a guide body defining a portion with a bone-engaging surface that conforms as a negative surface to a corresponding surface of a specific patient's tibia, and a guide portion that guides a surgical instrument to a specific location on the specific patient's tibia, wherein the bone-engaging surface and guide portion are configured during a pre-operative planning stage. Methods for performing a tibial tubercle osteotomy with the patient-specific guides are also provided.