Comparison of new medial linkage reciprocating gait orthosis and isocentric reciprocating gait orthosis on energy consumption in paraplegic patients: a case series

OBJECTIVES

As energy consumption during orthotics walking has main role in rehabilitation of walking in individuals with spinal cord injury (SCI), the aim of this study was comparison between new medial linkage orthosis (new MLO) and isocentric reciprocating gait orthosis (IRGO) on energy consumption in paraplegic patients.

METHODS

Four people with motor incomplete SCI (mean age 34.5 years, mass 73 kg and height 175 cm with injury levels ranging from T8-T12) participated in this study. Gait evaluation was performed using new MLO compared with using conventional IRGO. Walking speed and heart rate were measured to calculate the physiological cost index (PCI) to estimate metabolic energy consumption.

RESULTS

Reductions in energy consumption were observed using new MLO compared with using IRGO, but the difference was not statistically significant. However, walking distance and walking speed also improved, but not significantly.

CONCLUSION

All subjects had faster speeds of walking, walked longer distances and had lower PCI when using new MLO compared to walking with IRGO. Consequently, this orthosis should be examined and considered with larger sample size.

Stress-induced modulation of NF-κB activation, inflammation-associated gene expression, and cytokine levels in blood of healthy men

Acute psychosocial stress stimulates transient increases in circulating pro-inflammatory plasma cytokines, but little is known about stress effects on anti-inflammatory cytokines or underlying mechanisms. We investigated the stress kinetics and interrelations of pro- and anti-inflammatory measures on the transcriptional and protein level. Forty-five healthy men were randomly assigned to either a stress or control group. While the stress group underwent an acute psychosocial stress task, the second group participated in a non-stress control condition. We repeatedly measured before and up to 120min after stress DNA binding activity of the pro-inflammatory transcription factor NF-κB (NF-κB-BA) in peripheral blood mononuclear cells, whole-blood mRNA levels of NF-κB, its inhibitor IκBα, and of the pro-inflammatory cytokines interleukin (IL)-1ß and IL-6, and the anti-inflammatory cytokine IL-10. We also repeatedly measured plasma levels of IL-1ß, IL-6, and IL-10. Compared to non-stress, acute stress induced significant and rapid increases in NF-κB-BA and delayed increases in plasma IL-6 and mRNA of IL-1ß, IL-6, and IκBα (p's<.045). In the stress group, significant increases over time were also observed for NF-κB mRNA and plasma IL-1ß and IL-10 (p's<.055). NF-κB-BA correlated significantly with mRNA of IL-1β (r=.52, p=.002), NF-κB (r=.48, p=.004), and IκBα (r=.42, p=.013), and marginally with IL-6 mRNA (r=.31, p=.11). Plasma cytokines did not relate to NF-κB-BA or mRNA levels of the respective cytokines. Our data suggest that stress induces increases in NF-κB-BA that relate to subsequent mRNA expression of pro-inflammatory, but not anti-inflammatory cytokines, and of regulatory-cytoplasmic-proteins. The stress-induced increases in plasma cytokines do not seem to derive from de novo synthesis in circulating blood cells.

The impingement-dislocation risk of total hip replacement: effects of cup orientation and patient maneuvers

Hip dislocation is one of the most frequent complications after total hip arthroplasty. Impingement and dislocation might be caused due to misalignment of the acetabular cup during surgery, or performing dislocation-prone activities afterwards. A finite element model was developed to predict the impingement and dislocation behavior of the prosthetic joint, for different combinations of cup orientation and patient maneuver. Four dislocation-prone activities of daily life and 25 cup orientations were analyzed to determine how close they are to the impingement and subsequent dislocation events. The angular margin results obtained indicated that the sit-to-stand and standing while bending at the waist are prone to dislocation, in particular when the cup anteversion angle is small.

Response to induction therapy in a pediatric population of inflammatory bowel disease

Crohn's disease (CD) and ulcerative colitis (UC) are two inflammatory bowel diseases (IBD) characterized by chronic intestinal inflammation. In this study, the clinical characteristics of a cohort of pediatric patients with IBD are reviewed and their responses to induction therapy are evaluated. The severity of disease for 43 patients (20 with CD and 23 with UC) was determined using the PCDAI and PUCAI and based on the initial severity, before treatment was started. Following treatment, the severity of disease was re-evaluated at 6 months after the initial diagnosis. The patients in both groups had mild-to-severe disease. The mean PCDAI and PUCAI values were 60.62 +/- 16.48 and 50.95 +/- 9.35, for CD and UC patients, respectively. Most patients (83.7 %) responded to standard treatments with a significant reduction in the PCDAI and PUCAI scores from baseline (p value < 0.001). At the primary endpoint of 24 weeks, 54 % of all patients were in clinical remission; 16 of 23 in the UC group (70 %) and 6 of 20 in the CD group (30 %). The results of this study provide evidence that subgrouping pediatric patients with IBD into distinct clinical phenotypes based on severity of the initial presentation may provide better means of management of this group. This approach can result in a better response to treatment and reduce the side effects of unnecessary therapy.

Design and development of a hand robotic rehabilitation device for post stroke patients

Robot-mediated rehabilitation is a rapidly advancing discipline that seeks to develop improved treatment procedures using new technologies, e.g., robotics, coupled with modern theories in neuroscience and rehabilitation. A robotic device was designed and developed for rehabilitation of upper limbs of post stroke patients. A novel force feedback bimanual working mode provided real-time dynamic sensation of the paretic hand. Results of the preliminary clinical tests revealed a quantitative evaluation of the patient's level of paresis and disability.

The effect of pectin on swelling and permeability characteristics of free films containing Eudragit RL and/or RS as a coating formulation aimed for colonic drug delivery

BACKGROUND AND THE PURPOSE OF THE STUDY

The potential of pectin as a bacterially degradable polysaccharide for colon drug delivery has been demonstrated. Due to the high solubility and swelling properties of pectin in aqueous media, it is frequently used in combination with water insoluble polymers for targeting drugs to the colon. The aim of this study was to evaluate free films containing pectin as a bacterially-degradable polysaccharide in combination with Eudragit RL (ERL) and/or RS (ERS) as a coating formulation for colonic drug delivery.

METHODS

Isolated free films comprising 20% pectin and 80% ERL or ERS and their combination in 1:1 ratio were prepared by casting method. Then, free films were evaluated by water vapor transmission (WVT), swelling and permeability experiments for theophylline and indomethacin in different media.

RESULTS

Formulations containing ERL exhibited higher WVT, swelling and permeability compared with formulations containing ERS. The permeability of theophylline through free films composed of pectin and eudragit polymers in simulated colonic media was not significantly different from those obtained in other media. However indomethacin free films containing pectin and ERL showed higher permeation in simulated colonic fluid (SCF) compared to the other media.

MAJOR CONCLUSION

Formulation containing pectin and ERL may be suitable as a coating formulation for colon targeted delivery of drugs of low solubility such as indomethacin.

Design and evaluation of a novel triaxial isometric trunk muscle strength measurement system

Maximal strength measurements of the trunk have been used to evaluate the maximum functional capacity of muscles and the potential mechanical overload or overuse of the lumbar spine tissues in order to estimate the risk of developing musculoskeletal injuries. A new triaxial isometric trunk strength measurement system was designed and developed in the present study, and its reliability and performance was investigated. The system consisted of three main revolute joints, equipped with torque sensors, which intersect at L5—S1 and adjustment facilities to fit the body anthropometry and to accommodate both symmetric and asymmetric postures in both seated and standing positions. The dynamics of the system was formulated to resolve validly the moment generated by trunk muscles in the three anatomic planes. The optimal gain and offset of the system were obtained using deadweights based on the least-squares linear regression analysis. The R2 results of calibration for all loading courses of all joints were higher than 0.99, which indicated an excellent linear correlation. The results of the validation analysis of the regression model suggested that the mean absolute error and the r.m.s. error were less than 2 per cent of the applied load. The maximum value of the minimum detectable change was found to be 1.63 N m for the sagittal plane torque measurement, 0.8 per cent of the full-scale load. The trial-to-trial variability analysis of the device using deadweights provided intra-class correlation coefficients of higher than 0.99, suggesting excellent reliability. The cross-talk analysis of the device indicated maximum cross-talks of 1.7 per cent and 3.4 per cent when the system was subjected to flexion—extension and lateral bending torques respectively. The trial-to-trial variability of the system during in-vivo strength measurement tests resulted in good to excellent reliability, with intra-class correlation coefficients ranging from 0.69 to 0.91. The results of the maximum voluntary isometric torques exertion measurements for 30 subjects indicated good agreement with the previously published data in the literature. The extensive capabilities and high reliability of the system are promising for more comprehensive investigations on the trunk biomechanics in future, e.g. isometric strength measurement at symmetric and asymmetric postures, muscle endurance, and recruitment pattern analysis.

Design and implementation of series elastic actuators for a haptic laparoscopic device

The design of a laparoscopic haptic device based on a 4-DOFs mechanism and Series Elastic Actuators (SEA) is described and the results of the theoretical and experimental examinations are presented. With a sufficient bandwidth and low impedance, the system provided a stable interaction with soft tissues, e.g., human liver, in virtual environments.

Cyproheptadine for the treatment of functional abdominal pain in childhood: a double-blinded randomized placebo-controlled trial

AIM

The management of functional abdominal pain (FAP) in children and adolescents is challenging for health care professionals, and there are only limited or inconclusive studies of pharmacologic or behavioral therapy in childhood FAP. The objective of this randomized placebo-controlled clinical trial was to determine the potential efficacy and safety of cyproheptadine in the treatment of pediatric FAP.

METHODS

Between January 2006 and March 2007, 29 clinically referred children and adolescents with FAP (aged 4.5 to 12 years) completed a 2-week, double-blinded randomized placebo-controlled trial of cyprohetadine. Primary outcome measure was the self-reported change of frequency and duration of abdominal pain by using a 6-point scale, and the parents' impression or assessment of the children's improvement.

RESULTS

By week 1 and 2 of the intervention, the intensity and frequency of abdominal pain among the patients treated with cyproheptadine, were rated as complete resolved and very much improved or improved for 3 (20%), 10 (66.6%), respectively. However, in the placebo-receiver children, these scales had no change in 7 (50%), rated as improved or very much improved in 5 (35.7%), and become worse in 2 (14.3%). The patients' self-reported and the parents' impression in the cyproheptadine group were significantly better than it in the placebo group (P=0.003).

CONCLUSION

Among children with functional abdominal pain, cyproheptadine is enough effective to improve the intensity and frequency of abdominal pain in a short-term period.

The effects of trochlear groove geometry on patellofemoral joint stability-a computer model study

The effect of the variation in the femoral groove geometry on patellofemoral joint stability was studied using a two-dimensional transverse plane model with deformable articular surfaces. The femoral and patellar bony structures were modelled as rigid bodies with their profiles expressed by splines. The articular cartilage was discretized into compression springs, distributed along the femoral and patellar profiles, based on the rigid-body spring model. The medial and lateral retinacula were modelled as linear tensile springs, and the quadriceps muscles and patellar tendon as strings with known tension. The anatomical data were obtained from the transverse plane magnetic resonance images of a normal knee flexed at 20° and from the literature. A dynamic analysis approach was employed to solve the governing equations of the model, i.e. three static equilibrium equations of the patella and a constraint equation for each cartilage spring, explicitly. The results of the model suggest that alteration of the sulcus angle from 139° to 169° causes a lateral shift and tilt of less than 3 mm and 4°. This effect increased slightly with increasing total quadriceps force, however, to significantly more than 7 mm and 18° respectively when the medial retinaculum was released. It was suggested that this might be the combined effect of the medial retinaculum deficiency and trochlear dysplasia that is responsible for patellar subluxation and, particularly, dislocation disorders.

A new approach to C2 continuous piecewise bicubic representation of the articular surfaces of diarthrodial joints

Based on the force-deflection equation for a beam subjected to lateral point loads, a C2 continuous piecewise bicubic mathematical representation was proposed to model complicated geometrical surfaces, e.g. the articular surfaces of human joints. The method was then extended so that it could be used for mathematical modelling of incomplete nets of data points, as well as smoothing of noisy and/or filtering of erroneous data points. Mathematical techniques were also developed to calculate the required unknown parameters explicitly, with no need to solve the system of equations simultaneously. The performance of the proposed method was evaluated on a number of surface modelling problems, including two known analytical surfaces and the human femoral and patellar articular surfaces. The results indicate that the proposed method is precise, flexible, and easy to apply and has several advantages over the conventional smoothing methods, i.e. the B-spline approach.

Permeability and swelling studies on free films containing inulin in combination with different polymethacrylates aimed for colonic drug delivery

The aim of this study was to assess some permeability and swelling characteristics of free films prepared by combination of inulin as a bacterially degradable system and time- or pH-dependent polymers as a coating formulation for colonic drug delivery. Different free films were prepared by casting and solvent evaporation method. Formulations containing inulin with Eudragit RS, Eudragit RL, Eudragit RS-Eudragit RL, Eudragit FS and Eudragit RS-Eudragit S with different ratios of inulin were prepared. After preparation, free films were evaluated by water vapor transmission test, swelling experiment and permeability to indomethacin and theophylline in different media. Formulations containing Eudragit FS had high resistance to water vapor permeation; but were unable to protect premature swelling and drug release in simulated small intestine media. Also, combination of Eudragit RS and Eudragit S had no suitable characteristics for colon delivery. However, Eudragit RS and Eudragit RL in combination with inulin made free films which had more swelling and permeation of drug in the colonic medium rather than the other media. It was shown that formulations containing sustained release polymethacrylates in combination with inulin have more potential as a coating system for specific colon delivery compared with pH-dependent polymers.

Different amino acid substitutions at the same position in rhodopsin lead to distinct phenotypes

PURPOSE

Identification of a novel rhodopsin mutation in a family with retinitis pigmentosa and comparison of the clinical phenotype to a known mutation at the same amino acid position.

METHODS

Screening for mutations in rhodopsin was performed in 78 patients with retinitis pigmentosa. All exons and flanking intronic regions were amplified by PCR, sequenced, and compared to the reference sequence derived from the National Center for Biotechnology Information (NCBI, Bethesda, MD) database. Patients were characterized clinically according to the results of best corrected visual acuity testing (BCVA), slit lamp examination (SLE), funduscopy, Goldmann perimetry (GP), dark adaptometry (DA), and electroretinography (ERG). Structural analyses of the rhodopsin protein were performed with the Swiss-Pdb Viewer program available on-line (http://www.expasy.org.spdvbv/ provided in the public domain by Swiss Institute of Bioinformatics, Geneva, Switzerland).

RESULTS

A novel rhodopsin mutation (Gly90Val) was identified in a Swiss family of three generations. The pedigree indicated autosomal dominant inheritance. No additional mutation was found in this family in other autosomal dominant genes. The BCVA of affected family members ranged from 20/25 to 20/20. Fundus examination showed fine pigment mottling in patients of the third generation and well-defined bone spicules in patients of the second generation. GP showed concentric constriction. DA demonstrated monophasic cone adaptation only. ERG revealed severely reduced rod and cone signals. The clinical picture is compatible with retinitis pigmentosa. A previously reported amino acid substitution at the same position in rhodopsin leads to a phenotype resembling night blindness in mutation carriers, whereas patients reported in the current study showed the classic retinitis pigmentosa phenotype. The effect of different amino acid substitutions on the three-dimensional structure of rhodopsin was analyzed by homology modeling. Distinct distortions of position 90 (shifts in amino acids 112 and 113) and additional hydrogen bonds were found.

CONCLUSIONS

Different amino acid substitutions at position 90 of rhodopsin can lead to night blindness or retinitis pigmentosa. The data suggest that the property of the substituted amino acid distinguishes between the phenotypes.

Heart Sounds Separation From Lung Sounds Using Independent Component Analysis

Heart beat is an unavoidable source of interference during lung sound recording. This disturbance is more significant at low and medium breathing flow rates. Removing heart sounds (HS) from lung sound recordings or vice versa is a challenging task but of great interest for respiratory specialists and cardiologists. In this study, to separate the two signals, a novel HS separation method based on Independent Component Analysis (ICA) is developed. This method applies an ICA algorithm to the spectrograms of two simultaneous lung sound recordings obtained at two different locations on the chest and yields the independent spectrograms of the separated signals. Then, by implementing the Inverse Short Time Fourier Transform (ISTFT), the separated signals are reconstructed in the time domain. The method was applied to data of two healthy subjects. Analysis of the results as well as subjective inspections indicate the efficiency of the proposed method in terms of HS separation from lung sounds.

Antioxidant enzyme gene expression in congestive heart failure following myocardial infarction

Increased oxidative stress and reduction in antioxidant enzymes have been suggested to be involved in the pathophysiology of congestive heart failure subsequent to myocardial infarction (MI). The objective of the present study was to characterize changes in the mRNA abundance and protein levels for the enzymatic antioxidants, superoxide dismutase (SOD), glutathione peroxidase (GSHPx) and catalase during the sequelae of congestive heart failure in rats. MI was produced by the ligation of the left coronary artery and hearts from controls and 1, 4 and 16 week PMI groups were analyzed. Losartan treatment (2 mg/ml in drinking water, daily) was started at 4 weeks and continued for 12 weeks. The mRNA levels for SOD were reduced by about 40% at 1-week PMI, were near to the control levels at 4-week PMI and at 16 weeks PMI, the levels were reduced by about 73% below the controls. GSHPx mRNA levels remained unchanged at all time points. The mRNA levels for catalase remained unchanged at 1 and 4 weeks PMI and were significantly reduced by about 44% at 16 weeks PMI as compared to the controls. The protein levels for MnSOD, CuZnSOD, GSHPx at 1 and 16 weeks remained unchanged in treated and untreated PMI groups. However, the protein levels for catalase was significantly increased in the control and PMI groups treated with Losartan. It is concluded that changes in the SOD and catalase activities during severe heart failure correlated with changes in mRNA for these enzymes. The precise mechanism/s for the improvement in antioxidant reserve and protein levels after Losartan treatment is/are unclear at this time.

Quantitative measurement of patellofemoral joint stability: force-displacement behavior of the human patella in vitro

Patellofemoral joint instability is a common clinical problem. However, little quantitative data are available describing the stability characteristics of this joint. We measured the stability of the patella against both lateral and medial displacements across a range of knee flexion angles while the quadriceps were loaded physiologically. For eight fresh-frozen knee specimens a materials testing machine was used to displace the patella 10 mm laterally and 10 mm medially while measuring the required force, with 175 N quadriceps tension. The patella was connected via a ball-bearing patellar mounting 10 mm deep to the anterior surface to allow natural tilt and other rotations. Patellar force-displacement behavior was tested at flexion angles of 0 degrees, 10 degrees, 20 degrees, 30 degrees, 45 degrees, 60 degrees, and 90 degrees. Significant differences were found between the lateral and medial restraining forces at 10 mm displacement. For lateral displacement, the restraining force was least at 20 degrees of knee flexion (74 N at 10 mm displacement), rising to 125 N at 0 degrees and 90 degrees of knee flexion. The restraining force increased progressively with knee flexion for medial patellar displacement, from 147 N at 0 degrees to 238 N at 90 degrees. With quadriceps tension, the patella was more resistant to medial than lateral displacement. Our finding that lateral patellar displacement occurred at the lowest restraining force when the knee was flexed 20 degrees agrees with clinical experience of patellar instability.

Oxidative stress and functional deficit in diabetic cardiomyopathy

When the equilibrium between free-radical production and cellular antioxidant defences is disturbed in favour of more free radicals, it causes oxidative stress which can promote cellular injury. Oxidative stress has been suggested to play a role in the pathogenesis of diabetic cardiomyopathy. In streptozotocin-induced diabetes, there is a decrease in antioxidant enzyme activities and an increase in myocardial lipid peroxidation. Probucol, an antioxidant, was found to improve cardiac function which may have been due to an increase in myocardial antioxidant enzyme activities and a decrease in lipid peroxidation in the diabetic animals. Some of the beneficial effects of probucol may also be due to an improvement in plasma insulin levels and a decrease in the plasma glucose. The diabetic state is also associated with endothelial dysfunction, retinopathy, neuropathy and renopathy. Some of these secondary complications may also be mediated by oxidative stress. It is suggested that diabetic cardiomyopathy is associated with an antioxidant deficit and that antioxidant therapy may be useful in improving cardiac function in diabetes.

Oxidative stress in congestive heart failure

Heart failure is considered to be a complex clinical syndrome, with alterations in the multiple neurohumoral systems and subcellular cardiac sites that correlate with abnormal cardiac function. Strong evidence for the role of oxidative stress in the pathogenesis of heart failure has been provided by studies on experimental animals as well as humans. This concept is gaining more acceptance due to the fact that during heart failure, changes in different neurohormones, cytokines, nitric oxide, and activated inflammatory cells are closely linked to oxidative stress at the cellular and molecular levels. The present article provides a simple description of oxygen free radicals as well as the antioxidant defense system. Evidence for the role of oxidative stress in the pathogenesis of heart failure is reviewed in a concise manner.

Myocardial oxidative stress changes during compensated right heart failure in rats

The suggested role of oxidative stress in the pathogenesis of heart failure is largely based on utilizing left heart failure models. The present study on rats evaluated changes in antioxidants as well as oxidative stress in relation to hemodynamic function subsequent to the right heart failure induced by monocrotaline (50 mg/kg, i.p.). During the post-injection period, monocrotaline (MCT)-treated rats demonstrated a persistent growth depression. Two to three weeks after the injection, MCT-treated rats showed signs of fatigue, peripheral cyanosis and dyspnea. In these rats, right heart hypertrophy was confirmed by a significant increase in right ventricular weight as well as right ventricle to body weight ratio. In MCT-treated rats, there was also a significant increase in right ventricular systolic as well as end diastolic pressures. No change in lung and liver wet/dry weight ratios between MCT-treated and control animals was observed. Based on the hemodynamic data as well as other clinical observations, the functional stage achieved was compensated heart failure. Myocardial antioxidant enzymes, catalase, glutathione peroxidase and superoxide dismutase, in the MCT-treated rats were not different compared to control rats. Vitamin E levels were significantly depressed in the RV and there was no change in retinol levels. There was a significant increase in lipid hydroperoxide concentrations in MCT-treated rats as compared to the control group. These data provide evidence that right heart failure is associated with an increase in oxidative stress.

Mobilization of antioxidant vitamin pools and hemodynamic function after myocardial infarction

BACKGROUND

Although most previous studies have attempted to correlate plasma concentrations of vitamins with specific cardiovascular end points, metabolic considerations suggest that changes in myocardial tissue and storage organs may be better indicators of myocardial oxidative stress.

METHODS AND RESULTS

Rats fed commercial chow or a diet enriched with vitamin E for 2 weeks were subjected to either a surgical myocardial infarction (MI) or a sham procedure. Rats were hemodynamically assessed 16 weeks after surgery, and their heart, liver, kidney, and plasma were analyzed for antioxidant vitamins E (tocopherol) and A (retinol and total retinyl esters). At 16 weeks, MI rats on a control diet showed depressed peak systolic and elevated diastolic pressures in both right and left ventricles compared with their sham controls. Plasma concentrations of vitamins E and A in MI rats were not different from sham controls fed the same diet. However, concentrations of vitamin E in left ventricle and liver and of vitamin A in liver (retinol) and kidney (retinyl esters) were decreased in rats with MI compared with the sham controls. Vitamin E supplementation improved hemodynamic function in rats with MI and increased plasma, myocardial, liver, and kidney concentrations of vitamin E. The vitamin E diet also prevented the loss of total retinyl esters from the kidney but not of retinol from the liver in MI rats.

CONCLUSIONS

Dietary supplements of vitamin E can sustain better cardiac function subsequent to MI. Antioxidant vitamin levels in the myocardium or in storage organs and not in plasma may be better indicators of myocardial oxidative stress.

Lateral force-displacement behaviour of the human patella and its variation with knee flexion--a biomechanical study in vitro

This study measured the patellar lateral force-displacement behaviour at a range of knee flexion angles in normal human cadaver specimens. The knee extensor muscles were loaded in proportion to their physiological cross-sectional areas, the tensions being applied in physiological directions along the separate quadriceps muscles. Knee extension was blocked at a range of knee flexion angles from 0 to 90 degrees, and patellar lateral displacement versus force characteristics were measured. This experiment was repeated with three total muscle forces, 20, 175 and 350 N, which were held constant at all flexion angles. It was shown that similar stability variation was obtained with the different total muscle loads, and also the forces required to produce a range of patellar displacements (1.5, 9 mm) were examined. A 5 mm lateral patellar displacement required a constant displacing force (i.e. the patella had constant lateral stability) up to 60 degrees knee flexion, and then a significant increase at 90 degrees. The results were related to surgical and anatomical observations.

Quantitative study of the quadriceps muscles and trochlear groove geometry related to instability of the patellofemoral joint

This was a quantitative study of the major anatomical structures associated with instability of the patellofemoral joint: the quadriceps muscles and the femoral trochlear groove. The attachments of the muscles to the patella, their lines of action, and their relative sizes (physiological cross-sectional areas) were found. On the basis of the physiological cross-sectional areas, it was estimated that the central muscles-the rectus femoris and vastus intermedius-contributed 35% of the quadriceps strength, with 40% from the vastus lateralis and 25% from the vastus medialis. The vastus lateralis had the most variable results, with the ratio of the lateralis to the medialis ranging from 0.90 to 2.18; this may be associated with patellar instability. Both the long and oblique parts of the vastus medialis were more oblique than the corresponding parts of the vastus lateralis. Photographic "skyline" views of the trochlear groove produced data on the sulcus angle and ratio of depth to width. The data showed that the trochlear groove did not deepen in the area contacted by the patella with progressive knee flexion (p > 0.53), contrary to popular belief. These data are useful for objective analysis of patellofemoral stability and related surgical interventions.