ACL Injuries and Ski Jumping

Peak ACL force during jump landing in downhill skiing is less sensitive to landing height than landing position
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Anatomy:
Anterior Cruciate Ligament (ACL)
The ACL is a tough band of tissue joining the thigh bone to the shin bone at the knee joint.
It runs diagonally through the inside of the knee and gives the knee joint stability. It also helps to control the back-and-forth movement of the lower leg.

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Methods:

• A 25-degree-of-freedom sagittal plane musculoskeletal model of an alpine skier, accompanied by a dynamic optimisation framework, was used to simulate jump landing manoeuvres in downhill skiing.
• First, a reference simulation was computed tracking experimental data of competitive downhill skier performing a jump landing manoeuvre. Second, sensitivity studies were performed computing 441 landing manoeuvres with perturbed landing height and trunk lean of the skier, and the corresponding effects on peak ACL force were determined.

Results:

• The studies revealed that peak ACL force increased with jump height and backward lean of the skier as expected.
• However, peak ACL was about eight times more sensitive to the trunk lean of the skier compared with landing height.
• The decreased sensitivity of the landing height was based on the lower effects on the knee muscle forces and the shear component of the knee joint reaction force.

Conclusion:

• Preventive measures are suggested to focus primarily on avoiding trunk backward lean of the skier, and consequently on proper jump preparation and technique, and secondarily on strategies to reduce landing height during jumps.

​References: Heinrich D, van den Bogert AJ, Nachbauer WPeak ACL force during jump landing in downhill skiing is less sensitive to landing height than landing position Br J Sports Med Published Online First: 28 June 2018. doi: 10.1136/bjsports-2017-098964