Impaired hemodynamics of the patella in patients with patellofemoral pain: A case-control study.

PURPOSE: According to the homeostasis model, patellofemoral pain (PFP) arises as a consequence of disturbed homeostasis of anterior structures of the knee due to vascular insufficiency. Near-infrared spectroscopy (NIRS) allows to measure changes of concentrations (µmol/cm2 ) of (de)-oxygenated hemoglobine (HHb and O2 Hb). The aim was to study differences in patellar hemodynamics between patients and healthy controls.

METHODS: Hemodynamics of patients ( n  = 30 [female = 20, age = 21.5, BMI = 22.9]) and controls ( n  = 30 (female = 18, age = 21.4, BMI = 22.4]) were evaluated for two activities ('Prolonged Sitting' and 'Stair Descent'). Blinding for health status was implemented.

RESULTS: During 'Prolonged Sitting', PFP patients exhibited smaller decreases in mean changes for HHb (PFP [ M  = -1.5 to -1.9], healthy controls [ M  = -2.0 to -2.3]) and O2 Hb (PFP [ M  = -2.0 to -3.2], healthy controls [ M  = -3.4 to -4.1]). However, these differences were statistically non-significant ( p  = 0.14-0.82 and p  = 0.056-0.18, respectively). Conversely, for 'Stair Descent', PFP patients showed statistically significant smaller decreases in mean changes for HHb (PFP [ M  = -1.9, SD = 1.8], healthy controls [ M  = -2.5, SD = 1.7], p  = 0.043) and O2 Hb (PFP [ M  = -3.2, SD = 3.2], healthy controls [ M  = -4.9, SD = 2.7], p  = 0.004).

CONCLUSIONS: The differences suggest potential impairment in patellar hemodynamics in PFP patients, providing support for the homeostasis model. Evidence-based treatment strategies targeting patellar hemodynamics should be further refined and subjected to evaluation in clinical trials.

LEVEL OF EVIDENCE: Level III.