Project Summary/Abstract Lateral patellar dislocation is a common traumatic injury for young, active subjects. Approximately 50% of patients progress to symptomatic patellofemoral post-traumatic osteoarthritis (PTOA) by 25 years after dislocation. Reconstruction of the medial patellofemoral ligament (MPFL) is currently the most popular approach for surgical patellar stabilization. Stabilizing the patella to prevent additional dislocations is generally considered preventative for progressive cartilage degradation that can initiate post-traumatic OA, but preliminary data indicates ongoing patellofemoral cartilage degradation out to multiple years following MPFL reconstruction. Preliminary data indicates over constraint of the patella following MPFL reconstruction adversely influences cartilage. Aim 1 will characterize cartilage degradation for fifty patients following MPFL reconstruction for comparison to twenty-five healthy controls. The MPFL reconstruction patients will be recruited at least five years following surgery. All subjects will be evaluated at two time points, separated by two years. MRI-based T1ρ/T2 relaxation time mapping will quantify cartilage properties. Long T1ρ/T2 relaxation times indicate cartilage degradation. The hypothesis for Aim 1 is that cartilage T1ρ/T2 relaxation times for the MPFL reconstruction group will be longer than the control group and increase more dramatically over two years. Also, long T1ρ/T2 relaxation times will be significantly correlated with morphological progression toward OA as well as pain and poor function based on patient reported outcome measures (PROMs). Morphological grading will be based on comparisons between post-operative MRI and previously acquired pre-operative MRI. PROMs will be quantified at each evaluation and compared to an existing database of PROMs one year following MPFL reconstruction. Aim 2 will correlate cartilage properties vs. patellofemoral constraint to determine if over constraint of the patella following MPFL reconstruction contributes to progressive cartilage degradation. Measurements of knee alignment and anatomy will characterize patellofemoral constraint. Changes in alignment from pre-operative to post-operative MRI scans will be quantified. Weight-bearing cone beam CT will provide assessment of loaded alignment. The hypothesis of Aim 2 is that measures indicating patellofemoral constraint will be significantly correlated with long cartilage T1ρ/T2 relaxation times at least five years following MPFL reconstruction and progression of T1ρ/T2 relaxation times over the next two years. The data generated will immediately help guide patient selection and surgical parameters for MPFL reconstruction to limit the risk of progressive cartilage degradation. The data will also be used to design future clinical studies and trials focused on comparing MPFL reconstruction to other treatment options and comparing between surgical parameters within MPFL reconstruction for patients at hig...