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A new approach to evaluate anterior knee joint laxity
  1. C Mouton1,
  2. R Krecke2,
  3. D Theisen1
  1. 1Sports Medicine Research Laboratory, Public Research Centre for Health, Luxembourg, Luxembourg
  2. 2Centre de l Appareil Locomoteur, de Médecine du Sport et de Prévention du Centre Hospitalier de Luxembourg, Luxembourg, Luxembourg


Background Knee instability after Anterior Cruciate Ligament (ACL) reconstructive surgery may lead to osteoarthritis.

Objective To complete current evaluation of anterior knee laxity.

Design Cross-sectional pilot study.

Setting Physical therapy unit of the Clinique d'Eich, Centre Hospitalier de Luxembourg.

Patients 14 patients were examined 197±25 days following arthroscopic ACL reconstructive surgery (11 men and 3 women, age: 28±9 years) using the GNRB, a new knee arthrometer measuring anterior tibial displacement (ATD) when applying a standardised, progressive anterior tibial force. Inclusion criteria were: isolated ACL rupture; no prior injury in the controlateral knee.

Interventions Both knees were tested using three trials with a progressive force up to 200 N, starting with the controlateral leg. The average ATD-force curve of trials 2 and 3 were used for further calculations.

Main outcomes ATD at 134 and 200 N, and new variables: primary energy dissipation (PED: area under the ATD-force curve from 0 to 100 N), secondary energy dissipation (SED: area under the ATD-force curve from 100 to 200 N), primary compliance (PC: slope of the ATD-force curve between 30 and 50 N) and secondary compliance (SC: slope of the ATD-force curve between 100 and 200 N) were used as indicators of knee laxity.

Results The results found for the operated and the controlateral knee, respectively, were: ATD at 134 N=5.6±1.6 and 4.0±0.9 mm (difference: 42%); ATD at 200 N=7.2±1.8 and 5.3±1.0 mm (difference: 34%); PED=230±80 and 146±46 N/mm; SED=622±167 and 445±96 N/mm (difference of area between both curves at 134 N: 52%, at 200 N: 44%); PC=63±22 and 40±13 μm/N; SC=25±6 and 22±4 μm/N. Results were significantly different (p<0.05) for all indicators except SC (Student t-test).

Conclusion Anterior knee joint laxity 5 to 10 months after ACL reconstructive surgery remains greater than the non-injured contralateral knee. A complete evaluation of anterior knee laxity could help the prognostic of osteoarthritis after ACL reconstructive surgery.

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