Effect of unpredictable timing on the hip, knee, and ankle kinematics and center of mass during deceleration tasks.

BACKGROUND: Unpredictable stopping or deceleration tasks are crucial to prevent ACL injury. The purpose of this study was to reveal differences and relationships in kinematics during different deceleration tasks with and without anticipation. METHODS: Twenty-four collegiate athletes were recruited. Three commercial video cameras were used to capture frontal and sagittal lower-extremity kinematics. Participants were instructed to perform three deceleration tasks: 1) anticipated stopping and running backward at a point indicated previously (SRB-P); 2) anticipated stopping and running backward in front of a badminton net (SRB-N); and 3) unanticipated stopping and running backward upon random flashing of a light (SRB-U). Differences and relationships between hip, knee, and ankle kinematics at stopping (SS) and deceleration steps (DS) and the height of the great trochanter (HGT) at SS were analyzed. RESULTS: For all tasks, the knee flexion angle was less than 25° at SS. There were no significant differences in hip, knee, and ankle kinematics between tasks. HGT during SRB-U was higher than that in the other tasks at DS. Hip flexion angle at SS and DS was significantly correlated with HGT at SS. During SRB_P and SRB_N, only knee flexion angle at DS was significantly correlated with HGT at SS. CONCLUSIONS: The deceleration task in this study, SRB, causes a low knee-flexion angle at SS. The COM remained higher during unanticipated stopping, which is related only to hip flexion angle during the task. Knee flexion movement does not contribute to lowering COM during an unpredictable deceleration task.

Anatomical analysis of ligaments surrounding calcaneocuboid joint; implications for role in foot stability.

PURPOSE: The calcaneocuboid joint is located in the lateral part of the foot and acts as a major stabilizer for the foot. Injuries to this joint often occur in association with ankle or foot injuries and are frequently overlooked, subsequently causing chronic pain or osteoarthritis. However, the relationship between ligaments surrounding the joint and joint instability remains unclear. Therefore, this study aimed to clarify the morphology and position of the ligaments surrounding the calcaneocuboid joint, and to reveal the relationship between the ligament structure. METHODS: The position and morphology of the bifurcate ligament (subdivided into calcaneonavicular and calcaneocuboid ligaments), dorsal calcaneocuboid ligament, lateral calcaneocuboid ligament, long plantar ligament, and short plantar ligament were measured (N = 11 feet in 6 Japanese cadavers). The circumference of the joint was quartered, while the ligament-uncovered area and the estimated cross-sectional area of each ligament were compared between the four sides. Furthermore, the estimated cross-sectional area of each ligament was calculated as an index for the ligament strength. RESULTS: The inferolateral side of the calcaneocuboid joint had the most uncovered area (54.63%) by the ligaments. In addition, the cross-sectional area of the ligaments on the lateral side was considerably smaller than that on the medial side. CONCLUSION: Our results suggest that ligament weakness on the inferolateral side may cause instability of the calcaneocuboid joint, especially after an inversion sprain injury, and may decrease the lateral longitudinal arch function, which results in chronic foot pain.

Detection of knee wobbling as a screen to identify athletes who may be at high risk for ACL injury.

This study developed a method to detect knee wobbling (KW) at low knee flexion. KW consists of quick uncontrollable medio-lateral knee movements without knee flexion, which may indicate a risk of ACL injury. Ten female athletes were recorded while performing slow, single-leg squats. Using motion capture data, the ratio of the frontal angular velocity to sagittal angular velocity (F/S) was calculated. An 'F/S spike' was defined when the F/S ratio exceeded 100%. The number of F/S spikes was counted before and after low-pass filtering at different cut-off frequencies. Intraclass correlation coefficients for KW and filtered F/S spike were analysed. KWs per squat cycle showed a median (range) of 3 (2-8) times. F/S spikes before and after low-pass filtering at 3-, 6-, 10-, and 15-Hz were 51 (12-108), 2 (0-6), 3 (1-12), 5 (2-21), and 9 (3-33) times, respectively. KWs and F/S spikes on motion capture with 6-Hz, low-pass filtering were well correlated (r = 0 .76). Median percentages of valgus and varus F/S spikes were 71% and 29%, respectively. After 6Hz, low-pass filtering, the number of F/S spikes was strongly correlated with observed KWs. An F/S spike assessment may be used to objectively detect KW, including flexion and varus/valgus angular velocity.

Anterior Tibial Post Impingement During Stair Climbing: A Kinematic Analysis and Clinical Outcomes.

BACKGROUND: Anterior tibial post impingement during gait and stair ambulation was reported in knees with posterior-stabilized prostheses. However, the link between anterior post impingement and knee kinematics and between anterior post impingement and the clinical outcome has not been well investigated. Therefore, the purpose of this study was to assess the anterior impingement to clarify the relevant kinematics and clinical results including patient-reported outcomes. METHODS: We analyzed 40 well-functioning knees in 20 patients with a posterior-stabilized prosthesis due to osteoarthritis and who were followed up for 2 years or more. Dynamic lateral radiographs during stair-climbing activity were analyzed using a shape-matching technique, and anterior post impingement and the clinical outcome were assessed. RESULTS: Anterior impingement of the tibial post was observed in 13 knees (33%) during the latter half of the stance phase and at the beginning of the swing phase with the average implant flexion angle of -2.4°. Implant flexion was significantly smaller, while the femoral component was located more posterior in the impingement knees. The posterior tibial slope was significantly greater in the impingement group (6.7° ± 2.0°, 5.3° ± 1.9°, respectively; P = .041); however, no significant differences were demonstrated in anteroposterior laxity and patient-derived assessments. CONCLUSION: To avoid anterior post impingement, the posterior tibial slope should be made at 5° or less. Femoral notch-anterior post articulation should be designed to have good congruency in order to act as an anterior stabilizer in the case of impingement at knee extension.