OBJECTIVE. The objective of our study was to assess correlation between patellofemoral incongruency and injury mechanism, recurrence, bilaterality, and cartilage damage in patients with patellofemoral instability (PFI). MATERIALS AND METHODS. Ninetyfour knee MRI examinations (10 bilateral) of 84 patients with PFI (47 female and 37 male patients; mean age ± SD, 15.0 ± 2.5 years) who had patella dislocation and medial patellofemoral ligament reconstruction (MPFLR) and 66 examinations of age and sexmatched control subjects were reviewed. The PFI group was subclassified on the basis of injury, recurrence, and bilaterality. Patellofemoral congruence was assessed in both groups with the following MRI measurements: lateral femoral trochlear inclination angle, femoral sulcus depth, medialtolateral facet ratio, distance between tibial tuberosity (TT) and trochlear groove (TG), and patellar tendon ratio. Patella cartilage damage was assessed in the PFI group using conventional MRI (International Cartilage Repair Society grade 0–4) and T2 relaxation time mapping at three locations. MRI measurements were compared between groups and subgroups (Wilcoxon rank sum test) and were correlated with cartilage damage (Spearman correlation). RESULTS. All MRI measurements were significantly different between the group with PFI and the group without PFI (p < 0.0001). The bilateral PFI group had significantly increased TTTG distance (mean, 15.9 vs 13.1 mm, p < 0.05) and patellar tendon ratio (mean, 1.6 vs 1.4, p < 0.05) compared with the unilateral PFI group. The TTTG distance positively correlated with T2 values of medial and lateral patella cartilage. There were no differences between other subgroups and no correlation between other MRI measurements and the severity of cartilage damage. CONCLUSION. In patients with PFI, the severity of patellofemoral incongruence was not associated with injury mechanism or cartilage damage. However, increased lateralization of the patellar tendon (TTTG distance) and patella alta (patellar tendon ratio) correlated with injury to the contralateral knee requiring bilateral MPFLR.
- Cartilage damage
- Patellofemoral instability
- Young adult
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging