Knee instability tests – Two tests Slocum test, Dial tests or Tibial external rotation test. With the positive and negative clinical findings.
In the knee instability test, we have discussed mainly two tests :
- Slocum test
- Dial test
I. Slocum test :
1. Purpose :
Slocum’s test is a tweaked version of the Anterior Drawer test. Anterolateral rotational instability (ALRI) and anteromedial rotary instability (AMRI) of the knee are assessed.
2. Procedure :
- The patient is kept at sideline position on the unaffected side.
- The unaffected leg is slightly flexed at the hip and knee for stability.
- The pelvis is rotated approximately 30 degree posteriorly.
- In this position, the ankle of the affected leg should be resting on the table or bed.
- The involved knee is is flexed to 10 degree, incase of torn ACL. And the tibia will internally rotate and subluxate anteriorly due to the pull of the gravity.
- The we have to place one hand above and one hand below the knee. and have to apply a valves force to the knee, while the knee is brought into flexion.
3. Clinical findings :
Positive findings :
The test will be positive if the tibia will suddenly reduce at around 40 degree of the knee flexion.
II. Dial test/Tibial external rotation test :
1. Purpose :
The Dial Test is used to identify Posterolateral Knee Instability and to distinguish between isolated Posterolateral Corner (PLC) injuries and injuries involving both the PLC and the Posterior Cruciate Ligament (PCL)
2. Procedure :
- The patient is said to lie-down in prone position.
- Then we have to flex the patient’s knee to 30 degree.
- Then we have to bring the ankle into maximal dorsiflexion to limit the rotation at the ankle.
- Then, we have to place both of our hand on the feet of the patient, and make cup to the heels and placing the fingers and thumbs alongside the talocalcaneal coalition.
- then we have to rotate the heels at maximally externally to measure the thigh angle. And we have to compare both the sides.
- In second part of the test, we have to flex the knees into 90 degree and repeating the same process.
3. Clinical findings :
Positive findings :
- An isolated PCL injury is diagnosed if there is at 10 degree of external rotation versus the contralateral side 30 degree of flexion. But nor at 90 degree as an intact posterior cruciate ligament, will restrain the rotation in 90 degree.
- If an external rotation greater than 10 degree is found in both 30 & 90 degree of knee flexion, then both the PCL and PLC injury is suspected.