Quantifying the motion of Kager's fat pad

Area of Science:

• Biomechanics
• Anatomy
• Musculoskeletal System

Background:

• Kager's fat pad, located in Kager's triangle, has hypothesized biomechanical functions.
• Its retrocalcaneal protruding wedge may aid Achilles tendon lubrication, stress distribution, and debris removal.

Purpose of the Study:

• To investigate the influence of flexor hallucis longus (FHL) activity and Achilles tendon load on the protruding wedge's sliding distance.
• To elucidate the biomechanical roles of Kager's fat pad.

Main Methods:

• Dynamic ultrasound imaging was employed to measure the protruding wedge sliding distance.
• Surface electromyography assessed flexor hallucis longus (FHL) activity.
• Intervolunteer comparisons were made between loaded and unloaded Achilles tendon conditions.

Main Results:

• Protruding wedge sliding distance was independent of flexor hallucis longus (FHL) activity.
• The wedge slid significantly further into the retrocalcaneal bursa (average 60% increase) when the Achilles tendon was loaded versus unloaded.
• Sliding distance correlated with changes in the Achilles tendon insertion angle.

Conclusions:

• The protruding wedge's increased sliding with Achilles tendon load supports its role in lubricating the subtendinous region.
• Findings suggest the wedge helps reduce pressure changes at the Achilles tendon enthesis.
• The study supports the hypothesis that the wedge aids in clearing debris from the retrocalcaneal bursa.