Q-angle and J-sign: indicative of maltracking subgroups in patellofemoral pain.

Mechanical factors related to patellofemoral pain syndrome and maltracking are poorly understood. Clinically, the Q-angle, J-sign, and lateral hypermobility commonly are used to evaluate patellar maltracking. However, these measures have yet to be correlated to specific three-dimensional patellofemoral displacements and rotations. Thus, we tested the hypotheses that increased Q-angle, lateral hypermobility, and J-sign correlate with three-dimensional patellofemoral displacements and rotations. We also determined whether multiple maltracking patterns can be discriminated, based on patellofemoral displacements and rotations. Three-dimensional patellofemoral motion data were acquired during active extension-flexion using dynamic MRI in 30 knees diagnosed with patellofemoral pain and at least one clinical sign of patellar maltracking (Q-angle, lateral hypermobility, or J-sign) and in 37 asymptomatic knees. Although the Q-angle is assumed to indicate lateral patellar subluxation, our data supported a correlation between the Q-angle and medial, not lateral, patellar displacement. We identified two distinct maltracking groups based on patellofemoral lateral-medial displacement, but the same groups could not be discriminated based on standard clinical measures (eg, Q-angle, lateral hypermobility, and J-sign). A more precise definition of abnormal three-dimensional patellofemoral motion, including identifying subgroups in the patellofemoral pain population, may allow more targeted and effective treatments.

Visual and proprioceptive feedback improves knee joint position sense.

Joint position sense (JPS), one method to assess proprioception, is the ability to replicate a target limb position. Feedback is commonly used to improve motor performance but it has not been demonstrated to improve JPS. The purpose of this study was to determine if feedback decreases error associated with knee JPS at three movement velocities. Healthy volunteers sat with their hip and knees flexed. The knee was passively extended at three velocities (0.5, 2, and 10 degrees/s). Subjects were instructed to stop knee motion, via a thumb switch, at a 20 degrees knee flexion target. Following movement, each subject received visual and proprioceptive feedback indicating final leg position relative to the target position. Movement velocities and times (4 s, 5 s, 6 s) were randomly presented so subjects could not predict the target position. Measures of JPS included constant error (CE), absolute error (AE), variable error (VE), and percent correct (%CORR). Significant decreases in CE, AE, and VE as well as an increase in %CORR were demonstrated. The majority of JPS improvement (85%) occurred by the tenth trial. Short-term improvements in JPS may be the result of temporary CNS adaptations via feedback that was provided to subjects. Long-term learning of JPS enhancement needs further investigation.

Kinematic and EMG characteristics of simple shoulder movements with proprioception and visual feedback.

The objective of this study was to determine if simple, shoulder movements use the dual control hypothesis strategy, previously demonstrated with elbow movements, and to see if this strategy also applies in the absence of visual feedback. Twenty subjects were seated with their right arm abducted to 90 degrees and externally rotated in the scapular plane. Subjects internally rotated to a target position using a custom shoulder wheel at three different speeds with and without visual feedback. Kinematics were collected with a motion analysis system and electromyographic (EMG) recordings of the pectoralis major (PECT), infraspinatus (INFRA), anterior and posterior (ADELT, PDELT) deltoid muscles were used to evaluate muscle activity patterns during movements. Kinematics changed as movement speed increased with less accuracy (p<0.01). Greater EMG activity was observed in the PECT, PDELT, and INFRA with shorter durations for the ADELT, PDELT and INFRA. Movements with only kinesthetic feedback were less accurate (p<0.01) and performed faster (p<0.01) than movements with visual feedback. EMG activity suggests no major difference in CNS control strategies in movements with and without visual feedback. Greater resolution with visual feedback enables the implementation of a dual control strategy, allowing greater movement velocity while maintaining accuracy.

The influence of external loads on movement precision during active shoulder internal rotation movements as measured by 3 indices of accuracy.

CONTEXT: Using constant, variable, and absolute error to measure movement accuracy might provide a more complete description of joint position sense than any of these values alone. OBJECTIVE: To determine the effect of loaded movements and type of feedback on shoulder joint position sense and movement velocity. DESIGN: Applied study with repeated measures comparing type of feedback and the presence of a load. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty healthy subjects (age = 27.2 +/- 3.3 years, height = 173.2 +/- 18.1 cm, mass = 70.8 +/- 14.5 kg) were seated with their arms in a custom shoulder wheel. INTERVENTION(S): Subjects internally rotated 27 degrees in the plane of the scapula, with either visual feedback provided by a video monitor or proprioceptive feedback provided by prior passive positioning, to a target at 48 degrees of external rotation. Subjects performed the internal rotation movements with video feedback and proprioceptive feedback and with and without load (5% of body weight). MAIN OUTCOME MEASURE(S): High-speed motion analysis recorded peak rotational velocity and accuracy. Constant, variable, and absolute error for joint position sense was calculated from the final position. RESULTS: Unloaded movements demonstrated significantly greater variable error than for loaded movements (2.0 +/- 0.7 degrees and 1.5 +/- 0.4 degrees, respectively) (P < .05), but there were no differences in constant or absolute error. Peak velocity was greater for movements with proprioceptive feedback (45.6 +/- 2.9 degrees/s) than visual feedback (39.1 +/- 2.1 degrees/s) and for unloaded (47.8 +/- 3.6 degrees/s) than loaded (36.9 +/- 1.0 degrees/s) movements (P < .05). CONCLUSIONS: Shoulder joint position sense demonstrated greater variable error unloaded versus loaded movements. Both visual feedback and additional loads decreased peak rotational velocity.

Measures of accuracy for active shoulder movements at 3 different speeds with kinesthetic and visual feedback.

STUDY DESIGN: Repeated-measures experiment. OBJECTIVE: To compare measures of end point accuracy (EPA) for 2 feedback conditions: (1) visual and kinesthetic feedback and (2) kinesthetic feedback alone, during shoulder movements, at 3 different speeds. BACKGROUND: Shoulder joint kinesthesia is typically reported with EPA measures, such as constant error. Reporting multiple measures of EPA, such as variable error and absolute error, could provide a more detailed description of performance. METHODS AND MEASURES: Subjects were seated with the shoulder abducted 90 degrees in the scapular plane and externally rotated 75 degrees, with the forearm placed in a custom shoulder wheel. Subjects internally rotated the shoulder 27 degrees to a target position at 48 degrees of shoulder external rotation for both conditions. Motion analysis was used to determine peak angular velocity and 3 EPA measures for shoulder movements. Each EPA measure was compared between the 2 feedback conditions and among the 3 speeds with a separate 2-way analysis of variance. RESULTS: Movements performed with kinesthetic feedback alone, measured by constant error (P<.01), variable error (P<.01), and absolute error (P<.01), were less accurate than movements performed with visual and kinesthetic feedback. Faster movements were less accurate when measured by constant error (P = .01) and absolute error (P<.01) than slower movements. Subjects tended to overshoot the target in the absence of visual feedback; however, movement speed played minimal role in the overshooting. CONCLUSIONS: Multiple measures of EPA, such as constant, variable, and absolute error during simple restricted shoulder movements may provide additional information regarding the evaluation of a motor performance or identify different central nervous system control mechanisms for joint kinesthesia.

Re-evaluating the functional implications of the Q-angle and its relationship to in-vivo patellofemoral kinematics.

BACKGROUND: The Q-angle is widely used clinically to evaluate individuals with anterior knee pain. Recent studies have questioned the utility of this measure and have suggested that a large Q-angle may not be associated with lateral patellofemoral translation, as often assumed. The objective of this study was to determine: 1) how accurately the Q-angle represents the line-of-action of the quadriceps and 2) if adding active quadriceps contraction or a bent knee position to the measurement of the Q-angle improves its reliability, accuracy, and association with patellofemoral kinematics. METHODS: The study included individuals diagnosed with chronic idiopathic patellofemoral pain and control subjects (n=43 and n=30 knees). Three measures of the clinical Q-angle (straight- and bent-knee with relaxed quadriceps and straight-knee with maximum isometric quadriceps contraction) were obtained with a goniometer and compared to a fourth MR-based measure of Q-angle. Patellofemoral kinematics were derived from dynamic cine-phase contrast images, acquired while subjects extended/flexed their knee from approximately 0° and 45°. FINDINGS: The Q-angle did not represent the line-of-action of the quadriceps. The average difference between each clinical and the MR-based Q-angle ranged from 5° to 8°. These differences varied greatly across subjects (range: -28.5° to 3.9(o)). Adding an active quadriceps contraction or a bent knee position, did not improve the reliability of the Q-angle. An increased Q-angle correlated to medial patellar displacement and tilt (r=0.38-0.54, P<0.001) in the cohort with anterior knee pain. INTERPRETATION: Clinicians are cautioned against using the Q-angle to infer patellofemoral kinematics.

McConnell taping shifts the patella inferiorly in patients with patellofemoral pain: a dynamic magnetic resonance imaging study.

BACKGROUND: Patellar taping is widely used clinically to treat patients with patellofemoral pain syndrome (PFPS). Although patellar taping has been demonstrated to reduce patellofemoral pain in patients with PFPS, the kinematic source for this pain reduction has not been identified. OBJECTIVE: The purpose of this study was to quantify the changes in the 6-degrees-of-freedom patellofemoral kinematics due to taping in patients with PFPS. DESIGN: A within-subject design and a sample of convenience were used. PARTICIPANTS: Fourteen volunteers (19 knees) who were diagnosed with patellofemoral pain that was present for a year or longer were included. Each knee had to meet at least 1 of the following inclusion criteria: Q-angle of > or =15 degrees, a positive apprehension test, patellar lateral hypermobility (> or =10 mm), or a positive "J sign." METHODS: Each knee underwent 2 randomly ordered testing conditions (untaped and taped). A full fast-phase contrast (PC) magnetic resonance image set was acquired for each condition while the participants volitionally extended and flexed their knee. Three-dimensional displacements and rotations were calculated through integration of the fast-PC velocity data. Statistical comparisons between baseline patellofemoral kinematics and the change in kinematics due to taping were performed using a 2-tailed paired Student t test. Correlations between baseline patellofemoral kinematics and the change in kinematics due to taping also were quantified. RESULTS: Patellar taping resulted in a significant patellofemoral inferior shift. The strongest correlation existed between the change in lateral-medial displacement with taping and baseline (r=-.60). CONCLUSIONS: The inferior shift in patellar displacement with taping partially explains the previously documented decrease in pain due to increases in contact area. The lack of alteration in 5 of the 6 kinematic variables with taping may have been due to the fact that post-taping kinematic alterations are sensitive to the baseline kinematic values.

Understanding patellofemoral pain with maltracking in the presence of joint laxity: complete 3D in vivo patellofemoral and tibiofemoral kinematics.

Patellofemoral pain is widely accepted as one of the most common pathologies involving the knee, yet the etiology of this pain is still an open debate. Generalized joint laxity has been associated with patellofemoral pain, but is not often discussed as a potential source of patellar maltracking. Thus, the objective of this study was to compare the complete 6 degree of freedom patellofemoral and tibiofemoral kinematics from a group of patients diagnosed with patellofemoral pain syndrome and maltracking to those from an asymptomatic population. The following null hypotheses were tested: kinematic alterations in patellofemoral maltracking are limited to the axial plane; knee joint kinematics are the same in maltrackers with and without generalized joint laxity (defined by a clinical diagnosis of Ehlers Danlos Syndrome); and no correlations exist between tibiofemoral and patellofemoral kinematics or within patellofemoral kinematics. This study demonstrated that alterations in patellofemoral kinematics, associated with patellofemoral pain, are not limited to the axial plane, minimal correlations exist between patellofemoral and tibiofemoral kinematics, and distinct subgroups likely exist within the general population of maltrackers. Being able to identify subgroups correctly within the omnibus diagnosis of patellar maltracking is a crucial step in correctly defining the pathophysiology and the eventual treatment of these patients.

Gastrocnemius fascicle length changes with two-joint passive movements.

Predicting muscle fascicle length changes during passive movements may lead to a better understanding of muscle function. The purpose of this study was to experimentally compare fascicle length changes in the gastrocnemius during two-joint passive movements with a previously derived kinematic model based on anatomical measures from a cadaver. The ratio of passive ankle to knee motion was manipulated to generate medial gastrocnemius fascicle elongation and lateral gastrocnemius fascicle shortening. Ultrasound images from both heads of the gastrocnemius fascicles were acquired at 10 degrees knee flexion increments and compared with this kinematic model. Our results suggest that the two-joint kinematic model from which we originally based our knee and ankle movements did not adequately reflect fascicle length changes during any of the movement conditions in this study. From our data, we propose that for every degree of ankle motion the medial and lateral gastrocnemius changes 0.42 mm and 0.96 mm, respectively, whereas changes of 0.14 mm and 0.22 mm are observed for the medial and lateral gastrocnemius, respectively, during knee movements.

Electromyographic changes in the gluteus medius during stair ascent and descent in subjects with anterior knee pain.

Ascending and descending stairs is a provocative activity for anterior knee pain (AKP) patients. The gluteus medius (GM) acts on the lower extremity in the frontal plane and can affect forces at the knee. Determining activation patterns of the GM in patients with AKP can help identify efficacy of training the GM in this population. This study examined electromyographic (EMG) firing patterns in lower extremity muscles in subjects with AKP while ascending and descending stairs. Subjects in the AKP group ( n=16) demonstrated general AKP for at least 2 months compared to the control group ( n=12); neither group had any history of knee trauma. Subjects were instrumented with EMG electrodes on the vastus medialis oblique (VMO), vastus lateralis (VL), and GM. Retroreflective markers were placed on lower extremities to determine knee flexion angle, and frontal plane pelvis orientation at toe contact. Subjects then performed a series of five stair (height=18 cm) ascent and descent trials. Repeated measures analyses of variance were performed on EMG and kinematic variables, between the two groups and between the symptomatic and asymptomatic sides. In the AKP group the GM demonstrated delayed onset and shorter durations for stair ascent and shorter duration during descent. There were no significant differences between sides in the AKP group. Consistent with previous studies, subjects in the AKP group demonstrated no difference in the VMO onsets relative to VL onsets compared to the control group. Changes in neuromuscular activity patterns may be a result of a compensations strategy due to AKP. Training of GM and other hip muscles is warranted during rehabilitation of AKP patients.

Electromyographic comparison of standard and modified closed-chain isometric knee extension exercises.

The purpose of this study was to compare electromyographic (EMG) activity during open kinetic chain (OKC) and a modified closed kinetic chain (MCKC) knee extension exercises. Both OKC and closed kinetic chain (CKC) exercises provide benefits when devising conditioning programs; however, there are no exercises that combine the benefits of both exercises. Subjects performed maximum isometric knee extensions for both traditional OKC and MCKC knee extension exercises. Surface electrodes were placed on 8 lower-extremity muscles. One second of integrated EMG activity followed 95% maximal knee extension force. The following muscles demonstrated greater EMG activity during the MCKC vs. the OKC knee extension exercises: vastus medialis, medial hamstring, lateral hamstrings, and gluteus maximus. There was no difference between force output between the 2 conditions. This study demonstrates that modifications to traditional OKC exercises demonstrate some characteristics of CKC exercises, and therefore provide another avenue of rehabilitation or strengthening.