Transfer of movement between calcaneus and tibia in vitro

Area of Science:

• Biomechanics
• Orthopedics
• Kinesiology

Background:

• Knee injuries are often linked to excessive foot eversion and abnormal tibial rotation.
• The mechanical connection between the foot and lower leg, crucial for understanding knee injury causes, remains poorly understood.

Purpose of the Study:

• To investigate the in vitro movement transfer between calcaneal eversion-inversion and tibial rotation within the ankle-joint complex.
• To analyze how loading conditions and foot flexion influence this biomechanical coupling.

Main Methods:

• Utilized a 6-degree-of-freedom lower leg holding and loading device.
• Tested fourteen fresh-frozen human foot-leg specimens under controlled laboratory conditions.

Main Results:

• Significant inter-specimen variability was observed in the calcaneus-tibia movement transfer.
• Calcaneal eversion consistently induced internal tibial rotation, but the reverse was not observed.
• Vertical tibial loading and foot flexion angle significantly modulated the transferred movements.

Conclusions:

• The degree of calcaneal eversion transferred to tibial rotation is highly individual, depending on ankle joint complex mechanics.
• Excessive pronation poses a risk for knee loading only when combined with substantial ankle-driven tibial rotation.
• Inter-individual differences highlight challenges in designing total ankle replacements and custom orthotics.