title: Quantifying the motion of Kager's fat pad.
abstract: Kager's fat pad is located in Kager's triangle between the Achilles tendon, the superior cortex of the calcaneus, and flexor hallucis longus (FHL) muscle and tendon. Its biomechanical functions are not yet established, but recent studies suggest it performs important biomechanical roles as it is lined by a synovial membrane and its retrocalcaneal protruding wedge can be observed moving into the bursal space during ankle plantarflexion. Such features have prompted hypotheses that the protruding wedge assists in the lubrication of the Achilles tendon subtendinous area, distributes stress at the Achilles enthesis, and removes debris from within the retrocalcaneal bursa. This study examined the influence of FHL activity and Achilles tendon load on the protruding wedge sliding distance, using both dynamic ultrasound imaging and surface electromyogram. Intervolunteer results showed sliding distance was independent of FHL activity. This study has shown the protruding wedge to slide on average 60% further into the retrocalcaneal bursa when comparing the Achilles tendon loaded versus unloaded, consistently reaching the distal extremity. Sliding distance was dependent on a change in the Achilles tendon insertion angle. Our results support a number of hypothesized biomechanical functions of the protruding wedge including: lubrication of the subtendinous region; reduction of pressure change within the Achilles tendon enthesis organ; and removal of debris from within the retrocalcaneal bursa.
authors.affiliation: Institute of Medical Engineering and Medical Physics, School of Engineering, Cardiff University, The Parade, Cardiff, South Glamorgan CF24 3AA, United Kingdom. ghazzawiaa@cardiff.ac.uk
authors.forename: Ahmad
authors.initials: A
authors.lastname: Ghazzawi
authors.forename: Peter
authors.initials: P
authors.lastname: Theobald
authors.forename: Neil
authors.initials: N
authors.lastname: Pugh
authors.forename: Carl
authors.initials: C
authors.lastname: Byrne
authors.forename: Len
authors.initials: L
authors.lastname: Nokes
mesh_terms: D000125:Achilles Tendon / Q000502:physiology*; D000273:Adipose Tissue / Q000502:physiology*; D000328:Adult; D000843:Ankle Joint / Q000502:physiology*; D001696:Biomechanical Phenomena; D002111:Calcaneus; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement