Lachman Test
This test is indicated in the case of:
- Substantial fluid accumulation (and/or hemarthrosis).
- Acute ‘traumas’ (limited flexion possibilities).
- Chronic instability. This test has proven to be more specific than the drawer sign at 90°.
Procedure
- The patient lies in supine position with both knees flexed at about 15°.
- Stand on the side of the leg to be tested.
- Take hold of the distal femur with one hand and the proximal tibia with the other [Figure 80].
- Now examine the forwards and backwards mobility of the tibia on the femur.
- Note:
- Abnormal mobility in the forwards or backwards direction.
- Pain.
- Muscular defence.
- Left/right differences.
Drawer Sign
Procedure
- The patient lies in supine position, with the knees in 90° flexion and the feet flat on the examination table.
- Stand on the side of the knee to be tested.
- Place the fingers of both hands in the back of the knee, with the index fingers registering the tension of the hamstrings and the thumbs lying vertically on the joint space (next to the patellar ligament).
- Stabilise the patient’s foot by sitting on it with your thigh.
- Slowly pull the proximal tibia ventrally with respect to the femur (anterior drawer test) [Figure 81].
Figure 81
- Note:
- Abnormal mobility forwards.
- Pain.
- Muscular defence.
- Left /right differences.
If abnormal forwards mobility is observed, the anterior drawer test is positive.
- Repeat the anterior drawer test with the lower leg stabilised in maximum exorotation [Figure 82].
- Note the points listed above.
- Normally, if the capsule is intact, any instability established in the neutral position should decrease during exorotation and/or endorotation.
- If not, the instability will remain the same or even increase.
- A positive anterior drawer test in this position means that in addition to a disorder of the anterior cruciate ligament, a condition involving the postero-medial capsule and/or the ligament structures is likely.
Figure 82
- Repeat the anterior drawer test with the lower leg stabilised in maximum endorotation [Figure 83].
- Note the points listed above.
- A positive anterior drawer test in this position means that a condition involving the postero-lateral capsule and/or the ligament structures is likely.
Figure 83
- Bring the lower leg into the middle position once again and slowly push the proximal tibia dorsally with respect to the femur (‘posterior drawer test’).
- Note the previously-listed points.
- If there is any abnormal mobility in the posterior direction, it is referred to as a positive posterior drawer test.
- In that case, a condition involving the posterior cruciate ligament is likely.
- A positive posterior drawer test may not be observed in the case of an injury to the posterior cruciate ligament if the tibia is located too far dorsally.
- This gives a false-negative posterior drawer test and a false-positive anterior drawer test.
Posterior Sag Sign (Gravity Drawer Test)
This test is indicated in the case of:
- A positive posterior drawer test.
- A positive anterior drawer test.
If there is a posterior cruciate ligament rupture, the tibia might drop down slightly and a false-positive anterior drawer test may be found.
Procedure
- The patient lies in supine position.
- Bring both hips and knees into 90° flexion while supporting both lower legs.
- Stand at the foot end [Figure 84a] and/or the side [Figure 84b] of the knee concerned and, with the eyes at knee height, inspect the contours of the tibial tuberosities of both knees.
- If the tibial tuberosity of the knee concerned sinks dorsally in this position, there is an injury to the posterior cruciate ligament.
Figure 84a
Figure 84b