At? (2) Does FAI decrease maximal normalized squat depth? We measured the effect of cam FAI on the 3-D motion of the hip and pelvis during a maximal depth squat as compared with a healthy control group. Fifteen participants diagnosed with cam FAI and 11 matched control participants performed unloaded squats while 3-D motion analysis was collected. Patients with FAI had no differences in hip motion during squatting but had decreased sagittal pelvic range of motion compared to the control group (14.7 ± 8.4° versus 24.2 ± 6.8°, respectively). The FAI group also could not squat as low as the control group (41.5 ± 12.5% versus 32.3 ± 6.8% of leg length, respectively), indicating the maximal depth squat may be useful as a diagnostic exercise. Limited sagittal pelvic ROM in FAI patients may contribute to their decreased squatting depth, and could represent a factor amongst others in the pathomechanics of FAI. Level of Evidence: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence....

Most musculoskeletal models (MSKM) are designed to evaluate gait and running, which have limited range of motion (ROM). The purpose of this study was to examine the effect of wrapping surfaces (WS) at the knee and hip joints in a MSKM, on the muscle moment arms (MA) and activations during squatting. The MSKM was then customized by changing parameters of the original WS and by implementing additional WS. The WS prevent muscles from crossing into the bones, providing realistic muscle MA for large ROM. The modified MSKM is suitable for analysis up to 138° hip and 145° knee flexions.

Background: Understanding how the function of the lower extremity joints during everyday movements following surgery to treat cam femoro-acetabular impingement is essential to assess whether surgical intervention effectively restores the normal biomechanics of the hip. The purpose of this study was to compare preoperative and postoperative lower-extremity joint and pelvic angular displacements during maximal depth squatting of patients with unilateral symptomatic cam femoro-acetabular impingement. Methods: Ten participants were compared with respect to their preoperative and postoperative test results. The participants were between eighteen and fifty years of age and had a positive impingement test and visible cam deformity on anteroposterior and Dunn view radiographs. Postoperative testing for each participant occurred between eight and thirty-two months following surgical intervention. Three-dimensional lower-limb joint and pelvic kinematics of participants were collected during maximal depth squats. Results: Postoperatively, participants squatted to a greater mean maximal depth than they did preoperatively. Postoperative knee flexion and ankle dorsiflexion angles of the affected extremity at maximal depth were significantly greater than preoperative values. The postoperative sum of all joint angles of the affected limb at maximal squat depth was significantly larger than the preoperative sum. No significant differences were detected between the preoperative and postoperative measurements of the patients with cam impingement with respect to the kinematics of the affected hip at maximal squat depth, the pelvic angular displacements at maximal squat depth, or the overall pelvic range of motion during maximal deep squatting (p > 0.05). Conclusions: The squat performance improved postoperatively, likely because of the combined effects of increased knee and ankle angles as well as a greater acetabular opening and thus reduced anterior femoral head coverage, allowing increased posterior pelvic pitch during the descent phase of the squat. Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

The choice of marker set is a source of variability in motion analysis. Studies exist which assess the performance of marker sets when direct kinematics is used, but these results cannot be extrapolated to the inverse kinematic framework. Therefore, the purpose of this study was to examine the sensitivity of kinematic outcomes to inter-marker set variability in an inverse kinematic framework. The compared marker sets were plug-in-gait, University of Ottawa motion analysis model and a three-marker-cluster marker set. Walking trials of 12 participants were processed in opensim. The coefficient of multiple correlations was very good for sagittal (>0.99) and transverse (>0.92) plane angles, but worsened for the transverse plane (0.72). Absolute reliability indices are also provided for comparison among studies: minimum detectable change values ranged from 3 deg for the hip sagittal range of motion to 16.6 deg of the hip transverse range of motion. Ranges of motion of hip and knee abduction/adduction angles and hip and ankle rotations were significantly different among the three marker configurations (P < 0.001), with plug-in-gait producing larger ranges of motion. Although the same model was used for all the marker sets, the resulting minimum detectable changes were high and clinically relevant, which warns for caution when comparing studies that use different marker configurations, especially if they differ in the joint-defining markers.

Cam-type femoroacetabular impingement (FAI) is a causative factor for hip pain and early hip osteoarthritis. Although cam FAI can alter hip joint biomechanics, it is unclear what role muscle forces play and how they affect the hip joint loading. The purpose was to examine the muscle contributions and hip contact forces in individuals with symptomatic cam FAI during level walking. Patients with symptomatic cam FAI would demonstrate different muscle and hip contact forces during gait. Controlled laboratory study. Eighteen patients with symptomatic cam FAI were matched for age and body mass index with 18 control participants. Each participant’s walking kinematics and kinetics were recorded throughout a gait cycle (ipsilateral foot-strike to ipsilateral foot-off) by use of a motion capture system and force plates. Muscle and hip contact forces were subsequently computed by use of a musculoskeletal modeling program and static optimization methods. The FAI group walked slower and with shorter steps, demonstrating reduced joint motions and moments during contralateral foot-strike, compared with the control group. The FAI group showed reduced psoas major (median, 1.1 newtons per bodyweight [N/BW]; interquartile range [IQR], 1.0-1.5 N/BW) and iliacus forces (median, 1.2 N/BW; IQR, 1.0-1.6 N/BW), during contralateral foot-strike, compared with the control group (median, 1.6 N/BW; IQR, 1.3-1.6 N/BW, P = .004; and median, 1.5 N/BW; IQR, 1.3-1.6 N/BW, P = .03, respectively), which resulted in lower hip contact forces in the anterior (P = .026), superior (P = .02), and medial directions (P = .038). The 3 vectors produced a resultant peak force at the anterosuperior aspect of the acetabulum for both groups, with the FAI group demonstrating a substantially lower magnitude. FAI participants altered their walking kinematics and kinetics, especially during contralateral foot-strike, as a protective mechanism, which resulted in reduced psoas major and iliacus muscle force and anterosuperior hip contact force estimations. Limited hip mobility not only is attributed to bone-on-bone impingement, caused by cam morphology, but could be attributed to musculature as well. Not only would the psoas major and iliacus be able to protect the hip joint during flexion-extension, athletic conditioning could further strengthen core muscles for improved hip mobility and pelvic balance.