biostudies-literatureSpear JKUniversity of ChicagoNational Science Foundationjeb251088https://www.ebi.ac.uk/biostudies/studies/S-EPMC12450464biostudies-literatureUnknown228(17)Movement at complex joints, such as the ankle, can be challenging to quantify from external kinematics alone. We compared X-ray reconstruction of moving morphology (XROMM) and angles derived from high-speed video footage to study dorsiflexion in the ankle of a rhesus macaque (Macaca mulatta) during stance phase. We found inconsistent correspondence between angles measured on standard videos using five approaches and those measured directly on the talocrural joint using XROMM, indicating that different measurement methods capture different kinematic processes. Many externally measured angles indicate a range of motion of 30 deg during stance phase. The XROMM data, however, demonstrate that the talocrural joint itself only dorsiflexes about 15 deg through stance phase, with much greater mobility during swing phase. This suggests that other parts of the foot, likely the midfoot, contribute substantially to dorsiflexion in stance phase, while the talocrural joint is actively held in place.The Journal of experimental biologyComparison of ankle dorsiflexion using XROMM and external angular kinematics in a quadrupedally walking macaque.PMC12450464MRI 1626552MRI 1338036Granatosky MCLaird MFRoss CFGidmark NJSpear JKTsegai ZJKuo SWard CVfalseComparison of ankle dorsiflexion using XROMM and external angular kinematics in a quadrupedally walking macaque.Movement at complex joints, such as the ankle, can be challenging to quantify from external kinematics alone. We compared X-ray reconstruction of moving morphology (XROMM) and angles derived from high-speed video footage to study dorsiflexion in the ankle of a rhesus macaque (Macaca mulatta) during stance phase. We found inconsistent correspondence between angles measured on standard videos using five approaches and those measured directly on the talocrural joint using XROMM, indicating that different measurement methods capture different kinematic processes. Many externally measured angles indicate a range of motion of 30 deg during stance phase. The XROMM data, however, demonstrate that the talocrural joint itself only dorsiflexes about 15 deg through stance phase, with much greater mobility during swing phase. This suggests that other parts of the foot, likely the midfoot, contribute substantially to dorsiflexion in stance phase, while the talocrural joint is actively held in place.2025-01-01T00:00:00Z2025 Sep2026-06-03T16:59:10.6Z2026-04-29T03:12:52.696ZS-EPMC124504644076117010.1242/jeb.251088