Patellar tendinopathy with intratendinous alteration on MRI may be related to patellofemoral dysplasia.

Patellar tendinopathy (PT) is a frequent overuse injury of the extensor knee apparatus, whereas as up to 30% of the athletes might suffer from persisting symptoms during their entire career. In the present case-control study, 47 patients (30.8 ± 11.4 years) with PT with intratendinous alteration (PTita) of a minimum of ≥25% of the axial surface on MRI and minimum Blazina score of II (pain during without limiting sports activity) were included; MR images were analyzed for trochlear geometry, patellar height/tilt, and tibial tubercle-trochlear groove distance (TT-TG). The control group (CG) comprised 87 age- and gender-matched patients without history of anterior knee pain or lateral patellar instability. It was hypothesized that patients with PT might be related to patellofemoral dysplasia. It was found that the patella was significantly higher in patients with PT compared to the CG (patellotrochlear index [PT-I]: 0.33 vs 0.37, P = .014; Insall-Salvati index [InSa]: 1.18 vs 1.07, P = .004). PT-I was above the cut-off value in 10.6% of PT knees (CG 5.7%, P = .27), and InSa in 42.6% (CG 21.8%, P = .012). TT-TG was significantly higher in patients with PT compared to CG (12.0 mm vs 9.9 mm, P = .002); however, TT-TG was only pathologic (>20 mm) in one patient. The trochlear facet ratio was above the cut-off value in 55.3% of PT patients and 23% of CG (P < .001), and was significantly greater in patients with PT (0.39 ± 0.09) than CG (0.48 ± 0.1, P < .001). Knees with PT have significantly more morphological characteristics of patellofemoral instability, which needs to be considered especially in recurrent or treatment-refractive cases.