The Quadriceps Active Test

Background
 
 

In the 90 degree drawer position,                  The patellar tendon is orientated posterior as it passes
the tibia is supported by the PCL.                  from the tibia to the patella in the 90 degree drawer
                                                                     position.

Disruption or elongation of the PCL                 
results in subluxation of the tibia.        
 
 

At 90 degrees of Flexion, the Effect of a Quadriceps Contraction

      Resting Position                                                                      Tibia movies posterior

Posterior Cruciate Ligament Injured Knee

                   Resting position                                                    tibia moves anterior

The 90 degree quadriceps active test to diagnose posterior cruciate ligament disruption.

1. Place knee in the 90 degree drawer position.

2. The examiner sits beside the examining table with her/hiss eyes at knee level.

3. The examiner rests her/his elbow on the table and supports the patients thigh.   The examiner's hand monitors thigh muscle tone.

4. The foot is stabilized by the examiners other hand.

5. The patient is requested to "gently try to slide your foot down the table."

6. Thigh muscle tone is monitored to confirm that the quadriceps muscles contract and the hamstring muscles remain relaxed.

7. The posterior cruciate ligament injured knee will move anterior. The normal knee will move posterior 1 to 2 millimeters.
 
 

At the angle of flexion in the normal knee where the patellar tendon is normal to the joint surface, tension in the patellar tendon is normal to the joint surface, tension in the patellar tendon does not result in anterior or posterior tibial translation
 

Sectioning either cruciate ligament in this position will not result in a change in joint position in the quadriceps stabilized knee.  The position of the knee with a quadriceps contraction is termed the Quadriceps Active Position. The quadriceps active position at the quadriceps neutral angle will be altered by changes in the extensor mechanism anatomy (e.g. patellectomy or tibial tubercle elevation) but is not dependent on cruciate ligament integrity.  Establishment of the quadriceps active position at the quadriceps neutral angle may be used to separate anterior and posterior joint laxity.

Measurement Method

An Arthrometer® is used to measure the anterior/posterior laxity at the quadriceps neutral angle.

1. Apply the Arthrometer® to the normal knee.  An assistant sits beside the patient and supports the leg to obtain the desired relaxation. (The PCL Pro is to be used in place of assistant)

2.  Determine the Quadriceps Neutral Angle, the flexion angle at which there is no tibial anterior/posterior translation with contraction of the quadriceps (mean = 70°, range 55° to 80°).

3. Passive anterior and posterior laxity is measured with a push pull force.

4. Place the injured knee at the Quadriceps Neutral Angle (determined on the normal knee)

5. Measure passive anterior and posterior laxity from the resting position (sag position).

6. Measure the tibial displacement on the Quadriceps Active Test. This equals the distance between the resting position and the quadriceps active position.

7. Calculate the anterior and posterior laxity using the Quadriceps Active Position as the neutral position.  This is done by adding the quadriceps active displacement to the measured posterior laxity and subtracting the quadriceps active displacement from the measured anterior laxity.  The resulting numbers are termed the corrected anterior and posterior laxity measurements.
 
 

Determination of Pathologic Laxity

The injured knee laxity should be compared to the patient's normal knee laxity.  A difference of greater then 2 millimeters usually indicates a pathologic condition. Measurements performed at the Quadriceps Neutral Angle from the knee resting position.  Measurements are corrected using the Quadriceps Active Position as the neutral position.
 
 
 

Corrected Side to Side Difference
 
 

Summary

1. The quadriceps active test at 90 degrees of flexion will result in anterior tibial displacement of a knee with posterior cruciate ligament disruption.

2. In a normal knee there is a knee flexion position where the quadriceps tendon is normal to the joint surface and contraction of the quadriceps does not result in tibia displacement.  This position is known as the quadriceps neutral angle. (QNA)

3. Measurements of anterior/posterior laxity in the injured knee may be compared to the normal knee 
 
 

Ask the patient to lie supine
Rest thighs on support - the superior pole of the patella should be even with the distal edge of the thigh support
Take knee flexion angle measurement. Elevate or lower thigh support to obtain 20 to 30
Heel rotation is equal for both feet - check malleoli to ensure that are clear of the support
Realize joint line position while affixing ARTHROMETER^®
Oscillate calf to relax limb muscles while maintaining a firm, constant pressure on patellar pad.
Master the zero position with repeated 20 lb. posterior pushes - remember to continuously maintain patellar pad pressure.
Every anterior pull is followed by a 20 lb posterior push. - zero Arthrometer^®
Take posterior 20 lb., and anterior 15 lb., 20 lb., and 30 lb. measurements. - zero Arthrometer®
Energize and go for the manual maximum - place hand on calf below the joint line and lift the tibia forward ( DO NOT USE FORCE HANDLE) heel should not lift nor flexion angle change.
Record all measurements
Keep firm pressure on the patellar pad and ask the patient to "slowly lift your heel"
This measurement is the quadriceps active drawer test
1000 happy beeps to all!
 
 

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