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Knee Ligament Injury

EIGHT

Knee Ligament Injury

THE KT1000

TM

ARTHROMETER

The KT1000

TM

arthrometer (MEDmetric

Corporation, San Diego, California) was

first introduced in clinical practice in 1982,

following research and development led

by Dr Dale M Daniel MD at University

of California. It is the most used and

most accurate portable knee ligament

assessment system manufactured and l

purchased my first arthrometer in 1992,

which is still being used in my NHS clinic at

King’s College Hospital. I upgraded to the

London Bridge Hospital model in 2005.

While there are other knee laxity

systems, these can be complex to set

up and use, especially in clinical practice,

and two such systems can only be used

effectively by knee kinematicians in

research environments. The KT1000

TM

arthrometer avoids radiographic technique

and exposure and can be used as part

of the routine clinical knee evaluation. I

attended the first special seminar on knee

arthrometry, which was included in the

European Society of Sports Traumatology,

Knee Surgery and Arthroscopy (ESSKA)

Congress in Oslo in June 2010 and

provided data for discussion.

The KT1000

TM

measures anterior and

posterior tibial translation while controlling

rotation forces and can therefore assess

Anterior Cruciate Ligament (ACL) and

Posterior Cruciate Ligament (PCL) injuries.

Its portability has enabled me to use this

in professional soccer and rugby, and over

19 years l have established reliable and

reproducible testing techniques while

understanding the intricacies of knee

biomechanics. The arthrometer is easily

applied with 5-10min exam time. An

audible tone defines the designated force

applied in tibio-femoral displacement. The

knee flexion angle is noted and re-used

for subsequent exams. A PCL Pro device

allows varying flexion angles to measure

PCL laxity.

Knee kinematics is important to appreciate.

At shallow flexion angles, typically 20-30°,

an active quadriceps contraction (AQD

= displacement) will produce an anterior

tibial translation 1-2mm in an ACL-intact

knee. At deep flexion angles, typically

90°, an active quadriceps contraction

will produce a posterior tibial translation

1-2mm in a PCL-intact knee. I determine

the angle at which there is neither anterior

nor posterior translation and this is

termed the ‘quadriceps neutral angle’. The

two bands of the ACL can be assessed at

20-30° flexion, although the posterolateral

band controls more rotation and the

anteromedial band more translation. The

two bands of the PCL also have different

functions. At 90° the anterolateral band

is assessed and injury results in the

classic ‘tibial drop back’. However, the

posteromedial band is tight at 15° flexion

and partial or interstitial injury can only

be assessed at this relative shallow flexion

angle. Failure to do so can result in missing

these important injuries and I presented

an award-winning paper at the EFOST

meeting in Madrid 2004 on this subject.

HOW DO I USETHE KT1000

TM

ARTHROMETER?

In ACL injury, l use it in the sub-acute

and chronic setting. It is possible to

differentiate a partial from complete tear

and we now know that up to 63% of

partial tears heal. I can confirm a stable

knee in presence of meniscal tear providing

there isn’t a bucket-handle component

blocking potential knee motion. Serial

assessment is possible in conservative care

setting and measurements pre and post

ACL reconstruction provide important

outcome measures and used as part of

Dr Daniel Baron

MB DSportMed FFSEM (UK)

Sports Medicine Consultant

Dr Daniel Baron is a Sports Medicine Consultant at London Bridge Hospital and

Associate Sports Medicine Specialist in the Department of Trauma & Orthopaedics

at King’s College NHS Foundation Trust.

The London Bridge Hospital clinic is on 1st Floor, Emblem House. Clinic

information is available from Deanna Lee, PA, on:

T: 020 8852 4679