The primary objective of this study is to determine if treatment of the femoral head with core decompression and cell grafting increases the survivorship of the hip when compared to core decompression alone. The secondary objectives are to determine which factors may contribute to the success or failure of these procedures. We will define which patient demographics - including sex, age, comorbidities, osteonecrosis risk factors (e.g., corticosteroids, alcohol), radiographic features (e.g., lesion size) - are associated with favorable results. There are two co-primary outcomes: 1) evidence of and 2) time to radiological progression of osteonecrosis of their osteonecrotic femoral head (ONFH) to ARCO Stage III or IV, or pain requiring surgical intervention. Success is based on survivorship of the femoral head over the course of the study. Failure of the procedure is based upon evidence of radiographic progression to ARCO Stage III or pain requiring a surgical intervention. Radiographic progression (MRI, radiographs) will be determined, using MRIs (without contrast) and radiographs, by the presence of subchondral collapse or the degree of depression of the dome of the femoral head. Unremitting pain will be determined using a physical examination of the participant, pain as ranked using the VAS scale (10 range), and the Pain subscore of the Hip disability and Osteoarthritis Outcome Score. Secondary outcomes are listed in Table 1. Outcomes of pain will be evaluated is based upon the VAS Pain instrument and the sub-scores of the HOOS (Hip disability and Osteoarthritis Outcome Score). Second surgery may include a second core decompression, grafting, or arthroplasty procedure. Radiological progression (change in osteonecrosis stage) from baseline indicates progression to a more advanced ARCO stage of ONFH (i.e., ARCO Stage I hips may progress to II, IIIA, IIIB, or IV). Change in Hip disability and Osteoarthritis Outcome Survey (HOOS), PROMIS-10, and UCLA Activity Level are Patient Reported Outcomes (PROs) that are also secondary outcome measures