Daniel et al. validated the KT-2000 arthrometer for objective measurement of anterior knee laxity. The study tested 33 cadaver specimens, 338 normal subjects, and 89 patients with confirmed unilateral ACL rupture. The goal was to establish diagnostic thresholds that distinguish intact from disrupted ACLs using instrumented side-to-side comparison.
Before instrumented arthrometry, ACL laxity assessment depended entirely on the examiner's hands — the Lachman test is accurate in experienced hands, but "soft end-point" is not a number you can track over time or compare across surgeons.
This paper established the two thresholds that still anchor KT-1000/KT-2000 use today: a side-to-side difference greater than 2 mm is your primary ACL tear indicator, and a compliance index difference greater than 0.5 mm is your secondary check when the picture is unclear.
In practice: when you order arthrometry postoperatively after ACL reconstruction, a side-to-side difference returning to 2 mm or less is the objective target. A value creeping above 3 mm warrants concern for graft failure or laxity.
One nuance worth knowing: the contralateral "normal" knee in ACL-injured patients already averaged 7.4 mm of anterior displacement versus 5.7 mm in true normals. Constitutional ligament laxity likely contributes to injury risk and means you cannot always treat the contralateral knee as a perfect reference standard.
Daniel et al. validated the KT-2000 arthrometer for objective measurement of anterior knee laxity. The study tested 33 cadaver specimens, 338 normal subjects, and 89 patients with confirmed unilateral ACL rupture. The goal was to establish diagnostic thresholds that distinguish intact from disrupted ACLs using instrumented side-to-side comparison.
Before instrumented arthrometry, ACL laxity assessment depended entirely on the examiner's hands — the Lachman test is accurate in experienced hands, but "soft end-point" is not a number you can track over time or compare across surgeons.
This paper established the two thresholds that still anchor KT-1000/KT-2000 use today: a side-to-side difference greater than 2 mm is your primary ACL tear indicator, and a compliance index difference greater than 0.5 mm is your secondary check when the picture is unclear.
In practice: when you order arthrometry postoperatively after ACL reconstruction, a side-to-side difference returning to 2 mm or less is the objective target. A value creeping above 3 mm warrants concern for graft failure or laxity.
One nuance worth knowing: the contralateral "normal" knee in ACL-injured patients already averaged 7.4 mm of anterior displacement versus 5.7 mm in true normals. Constitutional ligament laxity likely contributes to injury risk and means you cannot always treat the contralateral knee as a perfect reference standard.