how do you measure oedema?

Does anyone know the correct procedure to measure oedema of the knee?
I'd be grateful if someone knows. Thank You

I think you can use usual girth measurment method ,in addition to ballotablepatella & milking tests

Hi

Here is a good reference for the reliability and validation of the girth measure for oedema and mm wasting in a knee surgery patients:

Ross, M., Worrell, T. W., Ross, M., & Worrell, T. W. (1998). Thigh and calf girth following knee injury and surgery. Journal of Orthopaedic & Sports Physical Therapy, 27(1), 9-15.

They got a good result. I have quoted the procedure they used in the study so if you followed this - you might get a robust measure:

Girth Measurement Procedure
For the thigh girth measurements, subjects were placed in a supine position with their knees extended and lower extremity musculature relaxed. Girth measurements were taken at 10 and 20 cm proximal to the superior patellar pole after this distance was measured and marked on the skin of the anterior thigh with an ink pen. Girth measurement of the calf took place with subjects positioned prone, with their knees extended and lower extremity musculature relaxed. Prior to formally measuring calf girth, it was necessary to determine the region of the calf that was greatest in circumference on the noninvolved extremity, as this point would serve as the landmark for each of the calf measurements. After identification of the calf region that was largest in girth on the noninvolved extremity, a mark was placed at this point on the skin of the lateral aspect of the calf with an ink pen. The distance from this point to the distal aspect of the fibular head was measured. Then, on the involved extremity, this distance from the fibular head was measured and marked. The distance from the fibular head was documented during the presurgery measurement and used as a landmark during the postsurgery measurement.
All measurements were taken with a nonelastic tape measure. Two girth measurements were taken at each of the three sites on the involved and noninvolved extremity prior to and following surgery. Care was taken to remove the slack from the tape measure without significantly compressing the limb musculature.