Sex differences in valgus knee angle during a single-leg drop jump

Area of Science:

• Biomechanics
• Sports Medicine
• Orthopedics

Background:

• Female athletes have higher anterior cruciate ligament (ACL) injury rates.
• Valgus knee alignment increases ACL strain.
• Gluteus medius (GM) activation may stabilize the leg and limit valgus during landing.

Purpose of the Study:

• Compare frontal-plane knee angle and GM activation between sexes during single-leg drop landing.
• Investigate sex differences at initial contact and maximal knee flexion.

Main Methods:

• Between-groups design with 32 healthy adults (18-30 years).
• Motion analysis laboratory.
• Measured frontal-plane knee angle and GM activation (aRMS) at initial contact and maximal knee flexion.

Main Results:

• Women landed in knee valgus, men in knee varus at initial contact.
• Both sexes showed knee varus at maximal flexion, less in women.
• GM activation increased at maximal flexion but did not differ between sexes.

Conclusions:

• Women demonstrate greater knee valgus during landing than men.
• GM activation does not explain sex differences in knee valgus.
• Increased knee valgus in women may contribute to higher ACL injury rates.