Introduction Patellar tendinopathy (jumper's knee) is a common injury in those sports causing high-torque forces on the patella. Several investigations have tried to elucidate its aetiology, being structural changes in the tendon insertion at the inferior patellar pole the most studied finding. Although the overload at the pole seems to be the cause of the formation of the entesophyte, its role in jumper's knee remains unclear.
Methods Study design retrospective cohort study with two groups:
– Jumper's knee group (JKG): 12 elite athletes (18 pathologic knees, mean age 29.6±7.09) from different sport specialities, with a clinical diagnosis of patellar tendinopathy from 2007 to 2010.
– Control group (CG): 18 elite athletes (mean age 28.1±5.4) without any previous clinical history of patellar tendon injury.
Anthropometrical measurements, evolution time of symptoms, and grade of tendinopathy (Blazina scale 1–4) were determined, and by means of color Doppler ultrasound examination (Voluson 730 General Electric SP6-12. Multi-frequency linear transducer) structural changes and neovascularisation (Hoksrud criteria) were classified, and tendon thickness (6 mm from the apex) and entesophyte length (if present) were measured.
Results The average evolution time of symptoms was 22.9 months, and the average Blazina scale grade for JKG was 2.7±1. No statistically significative data were found between anthropometry and symptoms. Ultrasound examination revealed that the entesophyte was present in 16 of 18 pathological tendons (JKG=89%, CG=27%), with a medium length of 6.1±3.6 mm (CG=2.1±0.4mm). Neovascularisation was present in 13 of 18 pathological tendons (JKG=72%, CG=5%), and the average tendon thickness was 69.8% higher in JKG than in CG (JK=8.68 mm/CG=5.11 mm). A direct relationship among entesophyte length, tendon thickness and evolution time of symptoms was found.
Conclusions Presence and size of a distal enthesophyte in the inferior patellar pole influence the perpetuation of symptoms, and determine tendon degeneration and chronicity.