Date on Master's Thesis/Doctoral Dissertation

5-2011

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Mechanical Engineering

Committee Chair

Quesada, Peter M.

Author's Keywords

Anterior cruciate ligament; Simulation; Knee valgus; Forward dynamics; Drop jump activity; OpenSim

Subject

Ligaments--Wounds and injuries; Knee--Wounds and injuries; Women athletes--Wounds and injuries

Abstract

Anterior Cruciate Ligament (ACL) injuries are among the most common injuries incurred by both recreational and professional athletes. ACL injuries often occur during popular contact sports like basketball, football, volleyball and baseball, and non-contact activities like aerobics, jogging and running. Non-contact actions like jumping, sprinting and sidecutting that involve sudden or rapid changes in motion may lead to ACL injuries. At the instance of an injury, the knee joint muscles and ligaments typically undergo extremely high loads. The ACL, which is an integral part of the knee joint undergo high strain rates and rapid energy absorption, and consequently get injured. As has been shown by others, ACL injury is related to a number of dynamic variables of the knee joint. An important observation made in recent years is that recreational (also professional) female athletes have higher incidences of noncontact ACL injuries than males 33, 35. The primary focus of this study was to determine effects of several dynamic variables, associated with both knee and ACL, during normal recreational drop-jump activities performed by young female athletes. Subjects recruited were eleven young adult female recreational athletes who felt comfortable participating in the drop-jump activities, from heights of 30, 40 and 50 cm. Using a simulation environment to recreate the trials, changes in ACL load and strain were observed along with several dynamic variables related to ACL load and strain, among which the three most important were, 1. knee flexion, 2. knee valgus (abduction) which may be accompanied by increased internal rotation, and, 3. flexor to extensor muscle recruitment ratios, i.e., the co-contraction of flexor and extensor muscles. Observations from the above simulations formed the basis of the final step involving forward dynamic simulation, where the knee joint was subject to higher valgus by decreasing the distance between the knees (medial translation). Significant changes to ACL load and strain were seen in the added medial translation simulations compared to the simulations from the original jumps. Mean fiber strain for the additional valgus simulation increased from 8.82 ± 0.08 % to 11.82 ± 0.04 % for the right ACL and from 8.18 ± 0.08 % to 11.34 ± 0.06 % for the left. Mean ACL tensile force increased from 1058.19 ± 2.04 N to 1102.19 ± 1.86 N for the right ACL and from 1056.77 ± 12.36 N to 1099.99 ± 2.02 N for the left. Average peak (from eleven subjects) ACL tensile force increased from 1165.36 ± 123.83 N to 1197.07 ± 129.11 N for the right ACL and from 1160.64 ± 121.32 N to 1193.11 ± 130.16 N for the left.

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