Sagittal movement of the medial longitudinal arch is unchanged in plantar fasciitis

Background: Although a lowered medial longitudinal arch has been cited as a causal factor in plantar fasciitis, there is little experimental evidence linking arch motion to the pathogenesis of the condition. This study investigated the sagittal movement of the arch in subjects with and without plantar fasciitis during gait. Methods: Digital fluoroscopy was used to acquire dynamic lateral radiographs from 10 subjects with unilateral plantar fasciitis and 10 matched control subjects. The arch angle and the first metatarsophalangeal joint angle were digitized and their respective maxima recorded. Sagittal movement of the arch was defined as the angular change between heel strike and the maximum arch angle observed during the stance phase of gait. The-thickness of the proximal plantar fascia was determined from sagittal sonograms of both feet. ANOVA models were used to identify differences between limbs with respect to each dependent variable. Relationships between arch movement and fascial thickness were investigated using correlations. Results: There was no significant difference in either the movement or maximum arch angle between limbs. However, subjects with plantar fasciitis were found to have a larger metatarsophalangeal joint angle than controls (P < 0.05). Whereas the symptomatic and asymptomatic plantar fascia were thicker than those of control feet (P < 0.05), significant correlations were noted between fascial thickness and peak arch and metatarsophalangeal joint angles (P < 0.05) in the symptomatic limb only. Conclusions: Neither abnormal shape nor movement of the arch are associated with chronic plantar fasciitis. However, arch mechanics may influence the severity of plantar fasciitis once the condition is present. Digital flexion, in contrast, has a protective role in what might be a bilateral disease process.

Changes in head and neck position have a greater effect on elbow joint position sense in people with whiplash-associated disorders

Background: It has been shown that perception of elbow joint position is affected by changes in head and neck position. Further, people with whiplash-associated disorders (WAD) present with deficits in upper limb coordination and movement. Objectives: This study is aimed to determine whether the effect of changes in head position on elbow joint position error (JPE) is more pronounced in people with WAD, and to determine whether this is related to the participant's pain and anxiety levels. Methods: Nine people with chronic and disabling WAD and 11 healthy people participated in this experiment. The ability to reproduce a position at the elbow joint was assessed after changes in the position of the head and neck to 30 degrees, and with the head in the midline. Pain was monitored in WAD participants. Results: Absolute elbow JPE with the head in neutral was not different between WAD and control participants (P = 0.5). Changes in the head and neck position increased absolute elbow JPE in the WAD group (P < 0.05), but did not affect elbow JPE in the control group (P = 0.4). There was a connection between pain during testing and the effect of changes in head position on elbow JPE (P < 0.05). Discussion: Elbow JPE is affected by movement of the head and neck, with smaller angles of neck rotation in people with WAD than in healthy individuals. This observation may explain deficits in upper limb coordination in people with WAD, which may be due to the presence of pain or reduced range of motion in this population.

Effect of knee joint angle on motor unit synchronization

Activity of the vasti has been argued to vary through knee range of movement due to changes in passive support of the patellofemoral joint and the relative contribution of these muscles to knee extension. Efficient function of the knee is dependent on optimal control of the patellofemoral joint, largely through coordinated activity of the medial and lateral quadriceps. Motor unit synchronization may provide a mechanism to coordinate the activity of vastus medialis (VMO) and vastus lateralis (VL), and may be more critical in positions of reduced passive support for the patellofemoral joint (i.e., full extension). Therefore, the aim of this study was to determine whether the degree of motor unit synchronization between the vasti muscles is dependent on joint angle. Electromyographic (EMG) recordings of single motor unit action potentials (MUAPs) were made from VMO and multiunit recordings from VL during isometric contractions of the quadriceps at 0 degrees, 30 degrees, and 60 degrees of knee flexion. The degree of synchronization between motor unit firing was evaluated by identification of peaks in the rectified EMG averages of VL, triggered from MUA-Ps in VMO. The proportion of cases in which there was a significant peak in the triggered averages was calculated. There was no significant difference in the degree of synchronization between the vasti at different knee angles (p = 0.57). These data suggest that this basic coordinative mechanism between the vasti muscles is controlled consistently throughout knee range of motion, and is not augmented at specific angles where the requirement for dynamic control of stability is increased. (D 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.