T2* mapping of the patellofemoral joint at 3 T MRI: a repeatability and reproducibility study

BackgroundT2* mapping provides objective data on chondromalacia. However, its reliability in evaluating both patellar and trochlear cartilages has not yet been established.PurposeTo evaluate the repeatability and reproducibility of T2* mapping of patellar and trochlear cartilage in patients with patellofemoral maltracking, and to compare the reliability of axial and sagittal imaging planes for early detection of chondromalacia.Material and MethodsThis retrospective study included 106 knees from patients aged 18-40 years presenting with anterior knee pain and MRI evidence of patellofemoral malalignment between January 2023 and August 2025. T2* mapping was performed on a 3 T MRI scanner using standardized protocols. Patellar and trochlear cartilage were manually divided into 12 compartments in axial and sagittal planes. Regions of interest were placed manually, and T2* relaxation times were measured independently by a musculoskeletal radiologist and an orthopedic surgeon. Intra- and inter-observer reliability were assessed using intraclass correlation coefficients (ICCs).ResultsMost compartments demonstrated good-to-excellent intra- and inter-observer agreement (ICC ≥0.75), particularly in the upper and mid patellar cartilage zones. Axial-plane measurements consistently showed higher ICC values than sagittal-plane measurements. The lowest reliability was observed in lower cartilage zones and in sagittal-plane measurements. All results were statistically significant (P <0.001).ConclusionT2* mapping of the patellofemoral joint provides reliable measurements, with superior performance in the axial plane and in mid-upper zones. Routine use of axial-plane T2* mapping may facilitate early detection of chondromalacia in young adults with anterior knee pain, potentially improving clinical decision-making and preventing irreversible cartilage damage.