Diagnosis of Knee Dislocation

• H.Mousavi,MD• Deprtment of Orthopaedic Surgery• Esfahan University of Medical Sciences• May 2015,Esfahan

Knee Dislocation

• Physical examination of patients with knee dislocations is not always reliable because of pain and guarding, spontaneous reduction, or ipsilateral fractures

If any of the following present R/O (Spontaneous reduction UNDERDIAGNOSED)

• Hyperextension• Popliteal ecchymosis• Vascular insufficiency• Peroneal nerve deficit• Diffuse tenderness but Absence of

hemartrosis (capsular disruption)• Obese pt low energy fall

Neurovascular examination

Neurovascular examination are mandatory at the time of initial evaluation,before reduction, and after reduction. The extremity distal to the involved knee should be examined thoroughly for color, temperature, and capillary refill. Posterior tibial and dorsalis pedis pulses are palpated and are compared with the contralateral side.

Vascular Status

• The presence of distal pulses with a warm foot is not a guarantee that an arterial injury is not present. There are multiple reports of vascular occlusion or intimal tears with normal distal pulses; the incidence is reported to be 5% to 15%. • hypotension in the acutely

traumatized patient .• Intimal lesions that may initially

present with normal pulses.

ABI Index

• Even if pulses are present, the ankle-brachial index (ABI) should be calculated and rechecked several times.• If the ABI is more than 0.90,

close observation is warranted.• If the ABI is less than 0.85,

arteriography is indicated.

ANKLE BRACHIAL INDEX

Femoral arteriography

• Questionable circulation or absent peripheral pulses either before or after reduction of a dislocated knee.• An extremity that originally has

no pulses, even though satisfactory pulses are restored after reduction.

Vascular status of the extremity

• CT angiography• MR angiography• Arterial duplex ultrasonography

Algorithm for vascular injury in knee dislocation

NERVE DAMAGE

• Peroneal Nerve• Motor: EHL, Tib. Anterior, Peroneals• Sensory: dorsum of the foot and 1st

web space

• Tibial Nerve• Motor: FHL, Gastrosoleus, Tib

Posterior• Sensory: Plantar surface and lateral

border of the foot

Collateral ligaments

• Varus/valgus stress to the knee joint both in full extension and at 30 degrees of flexion

Lachman Test

• The gold standard for testing of the ACL is the Lachman test, which is performed with the knee in 30 degrees of flexi

Posterior Drawer test

• The PCL is tested with the posterior drawer and sag tests.

Dial test

• Dial test (at 30° and 90°) (positive if 10-15° difference)

Radiographic evaluation

• Direction of dislocation and the presence of any concomitant bony injuries • Anteroposterior, lateral, and

oblique views should be obtained before and after reduction

MRI

• Evaluation of soft tissue injuries,• the actual site of cruciate and

collateral ligament injury• meniscal disorders or injuries• Status of the popliteal tendon in

posterolateral corner injury

Thanks