Is real-time ultrasound reliably able to determine Kager's fat pad motion during walking?

The distal calcaneal wedge of the Kager's fat pad (KFP) has the mechanical role of lubricating the region between the Achilles tendon and calcaneus during ankle movements. The purpose of this study was to determine the reliability of real-time ultrasound (RTUS) in visualizing the motion of the KFP during walking in adults. Recordings obtained using RTUS (13-MHz linear array transducer, IOE 323, MyLab 70, Esoate, Genoa, Italy) of the Achilles enthesis region (N = 52) of 47 participants (ranging from 21–79 years in age) while walking on a motorised treadmill at their preferred speed were analysed by three blinded assessors. Motion of the KFP was rated on a 4-point Likert scale (normal to absent). There was good agreement (κ [95% confidence interval] = 0.646 [0.643–0.649]) among the three examiners, with very good agreement (0.823 [0.818–0.828]) when classifying the motion as normal. There was a poor correlation between the motion of the calcaneal wedge and participants’ age (0.23–0.32). RTUS provides an adjunct to routine clinical examination to determine if there is normal motion of the calcaneal wedge during walking. This may be of benefit in patients with posterior heel pain for whom abnormal KFP motion is implicated.