MRI Characteristics and Alterations in Patellar Height in Patients with Patellar Tendinopathy—A Retrospective Study

Abstract

(1) Background: Patellar tendinopathy (PT) is an overuse condition of the knee extensor mechanism characterized by ventral knee pain at the lower pole of the patella and limited functionality. (2) Methods: In this retrospective study, a group of patients with PT (n = 41) was compared with a control group (n = 50) in terms of patient-related data and magnetic resonance imaging (MRI) characteristics. (3) Results: Patellar height was higher in the PT patient group and there was a significant difference in Caton–Deschamps index (CD) compared to the control group (p = 0.021). Patients with PT showed a lower patella–patellar tendon angle (PPTA) (p = 0.011). The patellar tendon thickness (PTT) in the proximal (PTTprox), middle (PTTmid) and distal (PTTdistal) part of the tendon was significantly thickened (p < 0.001). Increased signal intensity in MRI was detected in symptomatic tendons over 6 months compared to a duration of less than 6 months (p = 0.025). A significant relationship between the PTTprox and an increased signal intensity was observed (p < 0.001). (4) Conclusions: Patients with PT showed a significant difference in the patellar height and PPTA. With persistence of symptoms over 6 months, MRI seems suitable to detect the morphologic tendon changes and further identify patients suitable for surgical procedures.

Using the Blackburne-Peel index to measure the patellar height on magnetic resonance images

“…Loose et al studied the alterations for patellar height in patients with and without patellar tendinopathies (PT). The mean BPI values of patients with PT (n = 38) was 1.14 ± 0.18, and patients without PT were 1.07 ± 0.16 on MR images 6 . In Yue et al’s research, the BPI values of the study group (n = 112) consisting of patients with lateral patellar dislocation (LPD) were compared control group consisting of patients without patellofemoral instability (n = 129).…”

“…There are papers applying the measurement techniques of these indexes on MR images 6 ; however, the measurement values on MR images may reflect different results compared to radiographs 3 . In this current study, the adaptation of this method to MR images was discussed, and the normal values of the BPI index with gender and age group comparisons were presented.…”

Common radiographic indices used to measure patellar height do not consistently identify patella alta and lack interchangeability between measurements

“…Biomechanical studies have shown that a high-riding patella exhibits greater contact forces between the patella and femoral trochlea throughout all degrees of flexion, thus providing a potential contributing factor to anterior knee pain and the development of pathology [14]. The literature suggests that pathological states, such as patellofemoral instability, tibial tubercle apophysitis, patellar tendinosis and patellofemoral pain syndrome, are related to patellar height [4,7,[10][11][12][13]15]. To date, numerous methods have been utilised to quantify and describe patellar height in the literature, all using different anatomic landmarks on lateral radiographs, with the three most common being the Blackburne-Peel Index (BPI), Caton-Deschamps Index (CDI) and the Insall-Salvati Ratio (ISR).…”

“…Agreement between converted indices and their respective measured counterparts.Converted Index (n)Number of patella alta in agreement with measured index CDI to BPI(11) …”