Anterior Cruciate Ligament Tear: The Daily PANCE Blueprint
An 18-year-old collegiate soccer player is evaluated after an injury during a match. She planted her right foot and pivoted sharply, with no contact from another player, felt a “pop” in the knee, and was unable to continue playing. The knee swelled within two hours. She reports that it feels unstable and “gives way” when she tries to turn on it. Radiographs of the knee show no fracture. Which of the following findings would you most expect on examination?
A. A palpable defect in the patellar tendon with inability to extend the knee
B. Medial joint-line tenderness with valgus laxity at 30 degrees of flexion
C. Pain and a click with the Thessaly test at 20 degrees of flexion
D. Anterior translation of the tibia with a soft endpoint on the Lachman test
E. Posterior sag of the tibia with the knee flexed to 90 degrees
Answer and topic summary
The answer is D. Anterior translation of the tibia with a soft endpoint on the Lachman test
Every element of this history points the same way — a torn anterior cruciate ligament: a non-contact pivoting or deceleration injury, an audible or felt “pop”, inability to continue play, swelling within the first few hours, and instability or giving way on turning. That early swelling is a hemarthrosis: the ACL is intra-articular and bleeds briskly, which is why the knee fills in hours rather than overnight.
The expected finding is therefore increased anterior tibial translation with a soft or absent endpoint on the Lachman test, performed at 20 to 30 degrees of flexion. Lachman is the most sensitive physical examination maneuver for an ACL tear and outperforms the anterior drawer, which is done at 90 degrees where hamstring spasm splints the knee and masks laxity. The pivot-shift test is the most specific but is difficult to elicit in an acutely painful knee.
Each distractor belongs to a different structure. A patellar tendon rupture gives a palpable defect and loss of active extension. Medial joint-line tenderness with valgus laxity is an MCL injury, typically from a blow to the outside of the knee. A positive Thessaly test suggests a meniscal tear — which commonly accompanies an ACL tear, but on its own produces slower, smaller effusions over 24 to 48 hours and mechanical catching rather than instability. A posterior tibial sag indicates a PCL injury, usually from a dashboard-type blow to the flexed knee. Confirm with MRI, the imaging study of choice.
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