Introduction: Patellar alignment and tracking are very important to a successful surgical outcome in total knee arthroplasty (TKR) and difficult to assess in arthroscopies of the knee. The need for and use of a tourniquet in TKR’s and knee arthroscopies are debatable. One factor against its use is the possible alteration in the extensor mechanism dynamics making intraoperative assessment of patellofemoral (PF) tracking unreliable.

Aim: To assess whether an inflated tourniquet affects patellofemoral tracking.

Method: 10 Healthy male subjects, between 25 to 30 years of age, with no history of anterior knee pain; lower limb trauma, deformities or previous operations; or systemic disorders were admitted to the study. Dynamic sequence (Fast Field Echo scans) MRI scans over 57secs (flexed and extending against resistance to full extension), were performed without a tourniquet, on both knees, on all subjects as a control. A tourniquet, placed around the thigh, inflated to 300mmHg. Dynamic MRI scans were then obtained of each PF joint. PF tracking was then compared statistically.

Results: Of the 20 knees compared, sulcus and congruence angles were within normal limits. There was no significant difference in patellar tilt angle or patellar displacement. A trend of increased femoral external rotation was seen.

Conclusion: An inflated tourniquet placed around the upper thigh with the leg in extension does not alter patellofemoral kinematics in normal subjects. We believe the femoral external rotation seen is a mechanical adaptation of the tourniquet in the groin.