Effects of prolonged load carriage on angular jerk of frontal and sagittal knee motion

•Prolonged walking with body borne load increased jerky knee motion.•Load increased jerky sagittal and frontal plane knee motion up to 51 % and 110 %.•Duration of loaded walking increased jerky frontal plane knee motion up to 31 %.•Knee motion during prolonged load carriage may increase musculoskeletal injury risk. During training, service members routinely walk with heavy body borne loads for long periods of time. These loads alter knee biomechanics and may produce jerky knee motions that reportedly increase joint loading and risk of musculoskeletal injury. Yet, it is unknown if service members use jerky knee motions during prolong walking with body borne load. To quantify the effects of body borne load and duration of walking on the jerkiness of sagittal and frontal plane knee motion. Eighteen participants had angular jerk of knee motion quantified while they walked (1.3 m/s) for 60-min with three body borne loads (0, 15, and 30 kg). Peak and cost of angular jerk for sagittal and frontal plane knee motion was quantified and submitted to a repeated measures linear model to test the main effects and interaction of load (0, 15, and 30 kg) and time (0, 15, 30, 45, and 60 min). Body borne load increased peak and cost of angular jerk for sagittal plane knee motion up to 35 % and 110 %, respectively, and frontal plane knee motion up to 20 % and 51 %, respectively (all p