The kneeling view: evaluation of the forces involved and side-to-side difference.

The kneeling view is a method to objectively measure posterior knee laxity. However, the actual amount of load applied and the reliability of this method in term of side to side difference are not known. We studies these issues in a group a 25 healthy volunteers who underwent measurements of posterior knee laxity in both knees. A standard digital scale was positioned under both kneeling supports to measure the actual amounts of posterior displacement forces applied. We measured the mass of the subject, the side-to-side difference of the weight applied into anterior aspect of the tibia, and the ratio weight of the subject/ amount of posterior displacement load applied. The average amount of forces applied was at least 75% of the body weight of each subject, with a side-to-side variability of 3.3% of the weight applied. The kneeling view can be considered, in terms of forces applied, a reliable and reproducible alternative method for the routine radiographic evaluation of the posterior knee laxity.