Intraosseous hypertension and venous congestion in osteonecrosis of the knee

To determine whether an angiogenic factor affects the pathogenesis of the i diopathic osteonecrosis of the medial femoral condyle, intraosseous pressur e and venogram in 11 knees with osteonecrosis were compared with intraosseo us pressure and venogram in 11 knees with the medial type of osteoarthritis . Patients were matched by age, gender, obesity index, blood pressure, tibi ofemoral angle, and clinical evaluation. The intraosseous pressure of the m edial condyle of the knees with osteonecrosis (62.8 +/- 27.3 mm Hg) was sig nificantly higher than that in the lateral condyle of the knees with osteon ecrosis (25.4 +/- 18.9 mm Hg) and those of both condyles of the knees with osteoarthritis (medial, 31.6 +/- 17.4 mm Hg; lateral, 29.5 +/- 11.0 mm Hg). In contrast, there was no significant difference in the pressure between t he medial and lateral condyles of the knees with osteoarthritis, Venography showed a marked disturbance of venous drainage in all patients with osteon ecrosis, In addition, the average clearance time of the medium in the media l femoral condyle was significantly more prolonged in patients with osteone crosis (17.7 +/- 6.1 minutes) than in patients with osteoarthritis (5.5 +/- 1.6 minutes). These data support the hypothesis that venous stasis within the medullar canal in the condyle increases intraosseous pressure and decre ases arteriovenous pressure difference, leading to osteonecrosis.