Monday, November 21, 2011

Diagnosis of knee instability



According to Rossi et al, for knee; clinicians should have own series of exams with whom he is more confident and on whom he relies on for diagnosis. Usually, three sets of series are used:

1. One for patello-femoral/extensor mechanism pathologies
2. Another for meniscal and chondral (articular) lesions
3. The other one for instability evaluation

Among the above said to assess the 3rd category is difficult to diagnose. Often the diagnosis becomes more difficult because there are more than one tissue involved.

Following are clues to diagnose them:

1. Anerior medial instability (AMI):

AMI occurs due to: ACL + MCL + medial meniscus injury.

Test series to diagnose it are: valgus stress, anterior drawer, Lachman tests

2. Anterior lateral instability (ALI):

ALI occurs due to: ACL + lateral capsule + lateral meniscus injury.

Test series to diagnose it are: valgus stress, anterior drawer, Lachman, pivot shift tests

3. Posterior lateral instability (PLI):

PLI occurs due to: Injury to posterior lateral corner of the knee.

Test series to diagnose it are: external rotation, dial, recurvatum, posterolateral drawer tests

4. Posterior medial instability (PMI):

PMI occurs due to: MCL + ACL + Posterior medial corner.

Test series to diagnose it are: valgus stress, posterior drawer, Lachman tests

5. AMI + ALI instability:

Occurs due to: ACL + MCL + lateral capsule ( But PCL is intact)

Test series to diagnose it are: anterior drawer, Lachman, pivot shift, valgus stress
6. PMI + PLI instability:

Occurs due to: ACL + MCL + lateral capsule (But PCL is intact)

Test series to diagnose it are: anterior drawer, Lachman, pivot shift, valgus stress, varus stress tests

Reference:

Rossi et al. Sports Medicine, Arthroscopy, Rehabilitation, Therapy & Technology 2011, 3:25 (http://www.smarttjournal.com/content/3/1/25)

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