Popliteal artery-tibial plateau relationship before and after total knee replacement: a prospective ultrasound study

It seems to be a general belief that knee flexion releases the tension on the popliteal artery (PA) and displaces it posteriorly. Furthermore, there are opinions suggesting that previous surgery may result in fibrosis and rigidity of the vessels in the posterior knee region, which can lead to tethering of the PA, bringing it closer to the posterior tibia and making it more vulnerable during revision knee surgery. The aim of this study was to assess the distance between the PA and the tibial plateau in extension and flexion of the knee before and after surgery with total knee replacement (TKR). We studied 40 consecutive patients who were about to undergo TKR. The distance between the PA and tibial plateau was measured by ultrasound bilaterally in full knee extension without quadriceps contraction and in 90 degrees knee flexion, both preoperatively and 15 weeks postoperatively. The mean preoperative distances in flexion and in extension were 7 mm (3-12) and 8 mm (4-13), respectively (p < 0.05). Postoperatively, the distances were significantly increased both in flexion, 9 mm (4-14) (p < 0.001) and in extension 9 mm (3-15) (p < 0.01). Assessment of the contralateral legs where 14 previously had been operated with TKR showed no significant difference either between flexion and extension or between pre- and postoperative measurements. In conclusions, knee flexion does not increase the distance between the artery and the proximal tibia in this osteoarthritis patient group. At 15 weeks post-TKR, there was an increased distance from the PA to the posterior tibia and assessment of the contralateral knee where previous TKR had been performed showed equal distance to the ipsi-lateral preoperative knee, suggesting that the postoperative changes at 15 weeks were due to capsular swelling.