Which finding best indicates an MCL or LCL tear?

Which finding best indicates an MCL or LCL tear?

• A. Valgus laxity indicates lateral tear
• B. Laxity > 1 cm without a firm end point indicates medial tear
• C. Laxity > 1 cm with a firm end point indicates MCL tear
• D. Varus laxity indicates medial tear

Answer: (B)

In knee collateral injuries, valgus stress tests evaluate the medial structures, especially the MCL. When the medial joint opens more than about 1 cm under a valgus stress and there is no firm endpoint to stop the movement, this pattern best fits a complete tear of the MCL. The lack of a firm end point means there’s not enough intact ligament to arrest the opening, which points to a full rupture rather than just a partial stretch. Understanding end point helps distinguish severity: a firm end point suggests some residual restraint and a partial tear or sprain, not a complete rupture. Conversely, if there were a varus stress with similar findings, that would implicate the LCL rather than the MCL. So the finding described as laxity greater than 1 cm without a firm end point aligns most closely with a complete MCL tear.

In knee collateral injuries, valgus stress tests evaluate the medial structures, especially the MCL. When the medial joint opens more than about 1 cm under a valgus stress and there is no firm endpoint to stop the movement, this pattern best fits a complete tear of the MCL. The lack of a firm end point means there’s not enough intact ligament to arrest the opening, which points to a full rupture rather than just a partial stretch.

Understanding end point helps distinguish severity: a firm end point suggests some residual restraint and a partial tear or sprain, not a complete rupture. Conversely, if there were a varus stress with similar findings, that would implicate the LCL rather than the MCL.

So the finding described as laxity greater than 1 cm without a firm end point aligns most closely with a complete MCL tear.