Adipose tissue at entheses: the rheumatological implications of its distribution. A potential site of pain and stress dissipation?

In vivo interrelationships between the gluteus minimus and hip joint capsule in the hip internal rotation position with flexion

BACKGROUND

The flexion adduction internal rotation (FADIR) test is performed by the combined motions of hip flexion (with knee flexion), adduction, and internal rotation, and can often reproduce anterior hip pain consistent with an individual's presenting pain. Since it has high sensitivity for intraarticular pathology diagnosis but low specificity, understanding the extraarticular pathology that can induce anterior hip pain in the FADIR test may also be essential. This study hypothesized that the interrelationships between the joint capsule and gluteus minimus differ in individuals with and without FADIR-positive pain and aimed to elucidate the in vivo interrelationships at hip internal rotation in 90°-flexion, which is also often restricted in individuals with FADIR-positive pain.

METHODS

Ten hips were included in the FADIR-positive group, and ten hips without hip pain in the FADIR test were included in a control group. Based on the ultrasound images at the four hip rotation conditions (20° and 10° external rotations, 0° external/internal rotation, and 10° internal rotation), orientation measurements of the gluteus minimus (muscle belly portion) and joint capsule were performed and quantitatively compared between the FADIR-positive and control groups. Additionally, 3 hips of 3 participants were randomly selected from each of the control and FADIR-positive groups for magnetic resonance imaging analysis.

RESULTS

At 0°-external/internal and 10°-internal rotation, on ultrasound images, fibers of the gluteus minimus and joint capsule in the FADIR-positive group were significantly more oriented in the same direction than those in the control group. Magnetic resonance imaging showed that the loose connective tissue between the gluteus minimus and joint capsule was prominent at 10°-internal rotation in the control group, although this was not apparent in the FADIR-positive group.

CONCLUSIONS

At hip internal rotation in 90° flexion, the muscular belly portion of the gluteus minimus and joint capsule were oriented in the same direction to a greater extent in the FADIR-positive group than in the control group owing to a morphological change in the loose connective tissue between them. The pathological changes in the loose connective tissue may inhibit smooth movement of the gluteus minimus relative to the joint capsule in individuals with FADIR-positive pain.

Enhancing Bone Infection Diagnosis with Raman Handheld Spectroscopy: Pathogen Discrimination and Diagnostic Potential

Osteomyelitis is a bone disease caused by bacteria that can damage bone. Raman handheld spectroscopy has emerged as a promising diagnostic tool for detecting bone infection and can be used intraoperatively during surgical procedures. This study involved 120 bone samples from 40 patients, with 80 samples infected with either Staphylococcus aureus or Staphylococcus epidermidis. Raman handheld spectroscopy demonstrated successful differentiation between healthy and infected bone samples and between the two types of bacterial pathogens. Raman handheld spectroscopy appears to be a promising diagnostic tool in bone infection and holds the potential to overcome many of the shortcomings of traditional diagnostic procedures. Further research, however, is required to confirm its diagnostic capabilities and consider other factors, such as the limit of pathogen detection and optimal calibration standards.

Concentrations of Selected Adipocytokines in the Blood Plasma in Proximal Suspensory Desmopathy of Horses, with a Focus on Their Physical Activity-A Pilot Study

Chronic tendon and ligament diseases are commonly encountered in both athletic humans and animals, especially horses. Distal limb diseases, including suspensory ligament (SL) pathology due to anatomical, histological, and biomechanical properties, can be considered a model for tendon and ligament pathologies in humans. The appropriate selection of therapy is often crucial in optimising the healing process. One decisive factor influencing the possibility of returning to pre-disease training levels appears to be the utilisation of physical activity, including controlled movement, during the rehabilitation process. In the pathogenesis of musculoskeletal diseases and rehabilitation, adipocytokines play diverse roles. However, it is unclear what significance they hold in horses and in specific disease entities as well as the consequences of their mutual interactions. Recent studies indicate that in the pathogenesis of diseases with varied aetiologies in humans, their value varies at different stages, resulting in a diverse response to treatment. The results of this study demonstrate lower resistin concentrations in the venous blood plasma of horses with proximal suspensory desmopathy (PSD), while higher levels were observed in regularly trained and paddocked animals. The horses investigated in this study showed higher concentrations of resistin and IL-8, particularly in paddocked horses as well as in the working group of horses. The results suggest that these concentrations, including resistin in blood plasma, may be clinically significant. This attempt to explore the aetiopathogenesis of the processes occurring in the area of the proximal attachment of the suspensory ligament may optimise the procedures for the treatment and rehabilitation of horses.

The plantar proximal cortex of the third metatarsal bone shows raised longitudinal ridges at the suspensory ligament enthesis in normal equine isolated limbs - a radiographic, computed tomography, and MRI study

Introduction

Knowledge of normal radiographic appearance is essential to avoid misinterpretation of radiographs. This study aimed to assess the computed tomographic (CT) appearance of the plantar surface of the proximal metatarsus and evaluate the influence of the radiographic angle on the trabecular/cortical interface of the proximal plantar metatarsal cortex on lateromedial and slightly oblique radiographs.

Methods

Eight hindlimbs were collected from six horses with no known history of lameness and euthanized for reasons unrelated to the study. Limbs underwent computed tomographic (CT) and radiographic examination (dorsoplantar, lateromedial, and slightly oblique radiographic views obtained by angling the beam dorsally and plantarly from the plane used for the lateromedial projection). Standing magnetic resonance (MR) imaging and computed tomography (CT) were used to confirm normalcy. Images were compared side-by-side by two experienced readers.

Results

Limbs were normal at MR imaging. Longitudinal linear ridges were present on the proximal plantar metatarsal surface in all limbs (1-2 sagittal ridges and 1 ridge located at the medial or lateral margin of the suspensory ligament). Longitudinal ridges were positioned facing an adipose-muscular bundle of the suspensory ligament on CT images and were visible as linearly increased opacities on dorsoplantar radiographs. The delineation of the trabecular/cortical interface of the proximal metatarsus changed with radiographic projection and was the sharpest on the plantaro 85° lateral to the dorsomedial oblique view.

Conclusion

The proximal third metatarsal bone shows individual morphological variations, with longitudinal linear ridges that alter the bone homogeneity on dorsoplantar radiographs. An oblique plantaro 85° lateral to the dorsomedial view is suggested to better assess the presence of subcortical sclerosis when proximal suspensory enthesopathy is suspected.

In vivo magnetic resonance imaging study of the hip joint capsule in the flexion abduction external rotation position

Although the flexion abduction external rotation (FABER) test is a useful hip provocation test, hip soft tissue characteristics in the FABER position remain unclear. This study investigated the in-vivo joint capsule characteristics, including its articular cavity area and relation to the fat pad surrounded by the joint capsule and pericapsular muscles, in the FABER position using magnetic resonance imaging. Thirteen hips from 13 healthy volunteers were analyzed. The images were obtained, with the participant hips at 15°-extension, 45°-flexion, and in the FABER position, to analyze the articular cavity size and fat pad and calculate these ratios to size of the femoral neck. The articular cavity area and its ratio to the femoral neck were significantly greatest in the FABER position, followed by those in the hip flexion and extension. Additionally, the area of the fat pad in the inter-pericapsular muscle space and its ratio to the femoral neck in the FABER position were significantly larger than those in the hip flexion and, as a tendency, larger than those in hip extension. To the best of our knowledge, this is the first in-vivo study to show the interrelationship among the joint capsule, pericapsular muscles, and fat pad in the FABER position.

Function of peripheral nerves in the development and healing of tendon and bone

Although the functions of the peripheral nervous system in whole body homeostasis and sensation have been understood for many years, recent investigation has uncovered new roles for innervation in the musculoskeletal system. This review centers on advances regarding the function of nerves in the development and repair of two connected tissues: tendon and bone. Innervation in healthy tendons is generally confined to the tendon sheaths, and tendon-bone attachment units are typically aneural. In contrast to tendon, bone is an innervated and vascularized structure. Historically, the function of abundant peripheral nerves in bone has been limited to pain and some non-painful sensory perception in disease and injury. Indeed, much of our understanding of peripheral nerves in tendons, bones, and entheses is limited to the source and type of innervation in healthy and injured tissues. However, more recent studies have made important observations regarding the appearance, type, and innervation patterns of nerves during embryonic and postnatal development and in response to injury, which suggest a more expansive role for peripheral nerves in the formation of musculoskeletal tissues. Indeed, tendons and bones develop in a close spatiotemporal relationship in the embryonic mesoderm. Models of limb denervation have shed light on the importance of sensory innervation in bone and to a lesser extent, tendon development, and more recent work has unraveled key nerve signaling pathways. Furthermore, loss of sensory innervation also impairs healing of bone fractures and may contribute to chronic tendinopathy. However, more study is required to translate our knowledge of peripheral nerves to therapeutic strategies to combat bone and tendon diseases.

Is Real-Time Ultrasound Reliably Able to Determine Kager's Fat Pad Motion during Walking?

The distal calcaneal wedge of the Kager's fat pad (KFP) has the mechanical role of lubricating the region between the Achilles tendon and calcaneus during ankle movements. The purpose of this study was to determine the reliability of real-time ultrasound (RTUS) in visualizing the motion of the KFP during walking in adults. Recordings obtained using RTUS (13-MHz linear array transducer, IOE 323, MyLab 70, Esoate, Genoa, Italy) of the Achilles enthesis region (N = 52) of 47 participants (ranging from 21-79 years in age) while walking on a motorised treadmill at their preferred speed were analysed by three blinded assessors. Motion of the KFP was rated on a 4-point Likert scale (normal to absent). There was good agreement (κ [95% confidence interval] = 0.646 [0.643-0.649]) among the three examiners, with very good agreement (0.823 [0.818-0.828]) when classifying the motion as normal. There was a poor correlation between the motion of the calcaneal wedge and participants' age (0.23-0.32). RTUS provides an adjunct to routine clinical examination to determine if there is normal motion of the calcaneal wedge during walking. This may be of benefit in patients with posterior heel pain for whom abnormal KFP motion is implicated.

Inflammatory mechanisms linking obesity and tendinopathy

Chronic tendinopathy is a debilitating tendon disorder with disappointing treatment outcomes. This review focuses on the potential roles of chronic low-grade inflammation in promoting tendinopathy in obesity. A systematic literature search was performed to identify all clinical studies supporting the actions of obesity-associated inflammatory mediators in the development of tendinopathy. The mechanisms of obesity-induced chronic inflammation in adipose tissue are firstly reviewed. Common inflammatory mediators potentially linking obesity and the development of tendinopathy, and their association with mechanical overuse, are discussed, along with pre-clinical evidences and a systematic literature search on clinical studies. The potential contribution of local adipose tissues in the promotion of inflammation, pain and tendon degeneration is then discussed. The future research directions are proposed.

Translational potential statement

Better understanding of the roles of obesity-associated inflammatory mediators on tendons will clarify the pathophysiological drivers of tendinopathy in patients with obesity and identify possible treatment targets. Further studies on the mechanisms of obesity-induced chronic inflammation on tendon are a promising direction for the treatment of tendinopathy.

MRI signal and morphological alterations of the suprapatellar fat pad in asymptomatic subjects: are these normal variants?

OBJECTIVE

To study the prevalence of suprapatellar fat pad (SPFP) MR alterations in asymptomatic subjects, in relation to a wide range of clinical/imaging parameters, including muscle performance tests and physical activity data.

MATERIALS AND METHODS

We prospectively included 110 asymptomatic subjects as part of a cohort study. Inclusion criteria were no knee pain in the last year. Exclusion criteria were any medical/surgical history of a knee disorder. Subjects underwent knee and low-dose posture radiographs [EOS®], 3 T MRI, clinical examination including muscle performance tests, and physical activity monitoring. The presence/absence of SPFP alterations (hyperintensity and mass effect) were assessed through consensus reading on fluid-sensitive sequences. Differences between groups of knees with SPFP alterations and controls were tested for a total of 55 categorical/continuous clinical/imaging parameters, including SPFP relative-T2-signal, trochlear/patellar/lower-limb morphologic measurements. Wilcoxon-rank-sum and chi-square tests were used to compare groups of patients. The histological correlation was obtained in a cadaveric specimen.

RESULTS

SPFP alterations were common in asymptomatic subjects: hyperintensity 57% (63/110) and mass effect 37% (41/110), with 27% (30/110) showing both. Among the 55 imaging, clinical, or activity parameters tested, only increased patellar tilt angle (p = 0.02) and TT-TG distance (p = 0.03) were statistically different between groups of SPFP alterations and controls. The histological correlation showed more abundant connective tissue in SPFP compared to the prefemoral fat pad.

CONCLUSIONS

SPFP hyperintensity and mass effect are common MRI findings in asymptomatic knees, and they are not related to most imaging, clinical, and activity parameters. Care should be taken not to overcall them pathological findings as they most likely represent normal variants.

Anatomy and histomorphology of the flexor digitorum profundus enthesis: functional implications for tissue engineering and surgery

Background

The enthesis possesses morphological adaptations across the soft-hard tissue junction which are not fully restored during surgical avulsion repairs. This loss of anatomical structure, highly related to function, contributes to poor clinical outcomes. Investigating the native macro- and micro-structure of a specific enthesis can provide functional and biomechanical insights to develop specialised, novel tissue-engineered therapeutic options and potentially improve current surgical treatments for avulsion injuries.

Methods

This study examines the anatomy and histomorphology of the flexor digitorum profundus (FDP) enthesis in 96 fresh-frozen human cadaveric fingers, quantitatively and qualitatively analyzing the shape, size, angle of tendon fibres and histological architecture, and explores differences in sex, finger and distance along the enthesis using linear mixed effects models.

Results

Macroscopically, results showed a consistent trapezoidal insertion shape of 29.29 ± 2.35 mm² mean surface area, but with significant morphometric size differences influenced primarily by the smaller dimensions of the little finger. Microscopically, a fibrocartilaginous enthesis was apparent with a 30.05 ± 0.72^o mean angle of inserting tendon fibres, although regional variation in fibrocartilage and the angle change of tendon fibres before insertion existed.

Conclusions

The implication of these findings on native and specific FDP enthesis function is discussed whilst providing recommendations for optimal FDP enthesis recreation for interfacial tissue engineers and hand surgeons. The study emphasizes the importance of region-specific knowledge whilst also describing methods applicable to assessing any soft tissue insertion.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04922-1.

Spatial distribution of loose connective tissues on the anterior hip joint capsule: a combination of cadaveric and in-vivo study

Recently, pathological changes in the fat pad on the anterior inferior iliac spine (AIIS), between the proximal rectus femoris and joint capsule, have been highlighted as a cause of anterior hip pain. However, precise fat pad features, such as the spatial distribution distal to the AIIS, histological features, and in vivo tissue elasticity, remain unclear. This study aimed to investigate the morphological characteristics of the fat pad on the AIIS. Four hips from four cadaveric donors were both macroscopically and histologically investigated, and eight hips from four volunteers were assessed using ultrasonography. The fat pad on the AIIS was also surrounded by the iliopsoas and gluteus minimus, extending distally to the superficial portion of the vastus lateralis, and the anterior portion of the gluteus maximus tendon. Histological analysis revealed that the fat pad was composed of loose connective tissue. Based on the ultrasonography, the shear wave velocity in the fat pad was significantly lower than that in the joint capsule. Conclusively, the pathological adhesion between the joint capsule and pericapsular muscles, if caused by fat pad fibrosis, may occur following the abovementioned fat pad spatial distribution.

Presence of adipose tissue along the posteromedial tibial border

Purpose

The flexor digitorum longus and posterior tibial tendon as well as the perforating veins are located along the distal posteromedial tibial border. Adipose tissue may surround these structures and possibly play a role in reducing mechanical stress. This study aimed to examine the adipose tissue along the posteromedial tibial border via magnetic resonance imaging (MRI), ultrasound, and gross anatomical examination.

Methods

The lower legs of 11 healthy individuals were examined every 3 cm from the medial malleolus using MRI and ultrasound. The fat fraction was calculated using fat fraction images. In addition, the gross anatomy of the flexor digitorum longus origin and adipose tissue along the posteromedial tibial border was examined in seven fresh cadavers. The fat fraction was compared at different heights along the posteromedial tibial border and in Kager’s fat pads; we also compared the height of the flexor digitorum longus origin and adipose tissue.

Results

In vivo, the adipose tissue was identified along the entire posteromedial tibial border using MRI and ultrasound. There was no significant difference in fat fraction between Kager’s fat pads and the adipose tissue along the posteromedial tibial border, except at the 6 cm mark. All seven cadavers presented adipose tissue along the posteromedial tibial border, significantly more distal than the flexor digitorum longus origin.

Conclusion

The adipose tissue was identified along the posteromedial tibial border via MRI, ultrasound, and gross anatomical examination; thus, this tissue may play a role in reducing friction and compressive stress in tendons.

The equine navicular apparatus as a premier enthesis organ: Functional implications

Navicular syndrome has been traditionally characterized by progressive lameness with chronic degeneration of the navicular bone. Advances in imaging techniques have revealed that its associated soft tissue structures are also affected. This distribution of lesions is explained by conceptualizing the equine navicular apparatus as an enthesis organ that facilitates the dissemination of mechanical stress throughout the tissues of the foot. The navicular apparatus has the same structural adaptations to mechanical stress as the human Achilles tendon complex. These adaptations efficiently dissipate mechanical force away from the tendon's bony attachment site, thereby protecting it from failure. The comparison of these two anatomically distinct structural systems demonstrates their similar adaptations to mechanical forces, and illustrates that important functional insights can be gained from studying anatomic convergences and cross-species comparisons of function. Such a functional conceptualization of the equine navicular apparatus resolves confusion about the diagnosis of navicular syndrome and offers insights for the development of mechanically based therapies. Through comparison with the human Achilles complex, this review (1) re-conceptualizes the equine navicular apparatus as an enthesis organ in which mechanical forces are distributed throughout the structures of the organ; (2) describes the relationship between failure of the navicular enthesis organ and lesions of navicular syndrome; (3) considers the therapeutic implications of navicular enthesis organ degeneration as a form of chronic osteoarthritis; and based upon these implications (4) proposes a focus on whole body posture/motion for the development of prehabilitative and rehabilitative therapies similar to those that have already proven effective in humans.

The relationship between quadriceps fat pad syndrome and patellofemoral morphology: a case-control study

Background

The purpose of this prospective case–control study is to investigate the relationship between quadriceps fat pad syndrome (QFPS) and patellofemoral morphology.

Materials and methods

Twenty-two patients with QFPS and 22 age- and gender-matched healthy volunteers were included. The diagnosis of QFPS was supported both clinically and radiologically. On magnetic resonance imaging (MRI), patellofemoral morphology was evaluated with 13 radiological measurements including trochlear sulcus angle, trochlear sulcus depth, trochlear facet asymmetry, trochlear condyle asymmetry, lateral trochlear inclination angle, patellar translation, tibial tubercle–trochlear groove (TT–TG) distance, Insall–Salvati ratio, patellotrochlear index, patellar tilt, the ratio between lateral and medial facet lengths, interfacet angle, and quadriceps tendon thickness. The mean of measurements was compared between groups using the Mann–Whitney U test.

Results

There were 22 patients (12 male, 10 female) with mean age of 30.81 ± 1.41 (range 19–38) years in group I and 22 patients (12 male, 10 female) with mean age of 31.13 ± 1.31 (range 19–39) years in group II. The mean age and the gender distribution were statistically similar between groups (p = 0.845, p = 1, respectively). All measured values except for patellar tilt (p = 0.038) and TT–TG distance (p = 0.004) were similar (p > 0.05 for the other variables). However, all of the measured variables were within the normal range.

Conclusions

QFPS may not be associated with anatomical variations of the patellofemoral joint. Further studies are required to understand the etiology and risk factors.

Level of evidence

Level III, prospective case–control study

The relationship between patellar tilt and quadriceps patellar tendon angle with anatomical variations and pathologies of the knee joint

PURPOSE

To investigate the association between the knee joint anatomical variations and pathologies, and to describe the quadriceps patellar tendon angle (QPA).

METHODS

MRIs of 406 cases with a lateral patellar tilt angle (LPT)>5° and a control group of 40 cases with an LPT<5° were retrospectively evaluated. QPA, LPT, trochlear sulcus angle (TSA), tibial tubercle-trochlear groove distance (TT-TG), Insall-Salvati index (ISI), patellar tendon length (PTL), patellar height (PH), lateral trochlear inclination (LTI), trochlear facet asymmetry ratio (TFA) and trochlear depth (TD) were measured. Presence of fat-pad oedema, patellar and trochlear chondromalacia, patellar and quadriceps tendinosis and effusion were evaluated.

RESULTS

The medians of TSA, PTL, ISI and TT-TG were significantly higher; LTI, TFA and TD were significantly lower in the patient group. The prevalence of SL-Hoffa, non-SL-Hoffa, suprapatellar and prefemoral fat-pad oedema, effusion and chondromalacia were significantly higher in the patient group. LPT was found to be positively correlated with TSA and TT-TG, and negatively correlated with LTI and TD. Cases with trochlear dysplasia, patellar chondromalacia and quadriceps tendinosis had significantly higher LPT. There was a positive correlation between QPA and TSA and a negative correlation between QPA and LTI. Cases with trochlear dysplasia, non-SL-Hoffa oedema, prefemoral fat-pad oedema and quadriceps tendinosis had significantly higher QPA. We found 10°<LPT to be a cut-off value to cause SL-Hoffa fat pad oedema.

CONCLUSION

The anatomical variations of the knee joint are associated with fat-pad, cartilage and tendon pathologies.

On the morphological relations of the Achilles tendon and plantar fascia via the calcaneus: a cadaveric study

Current treatments of plantar fasciitis are based on the premise that the Achilles tendon (AT) and plantar fascia (PF) are mechanically directly linked, which is an area of debate. The aim of this study was to assess the morphological relationship between the AT and PF. Nineteen cadaveric feet were x-ray imaged, serially sectioned and plastinated for digital image analyses. Measurements of the AT and PF thicknesses and cross-sectional areas (CSA) were performed at their calcaneal insertion. The fiber continuity was histologically assessed in representative subsamples. Strong correlations exist between the CSA of the AT and PF at calcaneal insertion and the CSA of PF's insertional length (r = 0.80), and between the CSAs of AT's and PF's insertional lengths. Further correlations were observed between AT and PF thicknesses (r = 0.62). This close morphological relationship could, however, not be confirmed through x-ray nor complete fiber continuity in histology. This study provides evidence for a morphometric relationship between the AT and PF, which suggests the presence of a functional relationship between these two structures following the biological key idea that the structure determines the function. The observed morphological correlations substantiate the existing mechanical link between the AT and PF via the posterior calcaneus and might explain why calf stretches are a successful treatment option for plantar heel pain.

Pectoralis major tendon and enthesis: anatomic, magnetic resonance imaging, ultrasonographic, and histologic investigation

BACKGROUND

This study evaluates the pectoralis major (PM) tendon humeral insertion, using imaging and histologic assessment in cadaveric specimens. Current descriptions of the pectoralis major tendon depict a bilaminar enthesis, and clarification of the anatomy is important for diagnostic and surgical considerations.

MATERIALS AND METHODS

Fourteen fresh-frozen whole upper extremity specimens were used in this study. Magnetic resonance (MRI) and ultrasonographic (US) imaging of the PM muscles, tendons, and entheses were performed, followed by anatomic dissection and inspection. Morphology of the lateral tendon and entheses were evaluated, focused on the presence of layers. In 11 specimens, the lateral 3 cm of the PM tendon was carefully dissected from the footprint, whereas in 3 specimens, the tendon and humeral insertion were preserved and removed en bloc. Histology was performed in axial slabs along the medial-lateral length of the tendon and also evaluated for the presence of layers.

RESULTS

The superior-inferior and medial-lateral lengths of the PM footprint were 75 ± 9 mm and 7 ± 1 mm respectively. In all specimens, the clavicular and sternal head muscles and tendons were identified, with the clavicular head tendon generally being shorter. The medial-lateral length of the clavicular head tendon measured 19 ± 8 mm superiorly and 9 ± 3 mm inferiorly. The medial-lateral length of the sternal head tendon measured 38 ± 8 superiorly and 41 ± 18 mm inferiorly. All specimens demonstrated a unilaminar, not bilaminar, enthesis with abundant fibrocartilage on histology. Three specimens demonstrated interspersed entheseal fat and loose connective tissue at the enthesis on MRI and histology.

CONCLUSION

The PM tendon humeral insertion consists of a unilaminar fibrocartilaginous enthesis. US, MRI, and histology failed to identify true tendon layers at the enthesis. Delaminating injuries reported in the literature may originate from a location other than the enthesis.

Age-related decrease in collagen proton fraction in tibial tendons estimated by magnetization transfer modeling of ultrashort echo time magnetic resonance imaging (UTE-MRI)

Clinical magnetic resonance imaging (MRI) sequences are not often capable of directly visualizing tendons. Ultrashort echo time (UTE) MRI can acquire high signal from tendons thus enabling quantitative assessments. Magnetization transfer (MT) modeling combined with UTE-MRI—UTE-MT-modeling—can indirectly assess macromolecular protons in the tendon. This study aimed to determine if UTE-MT-modeling is a quantitative technique sensitive to the age-related changes of tendons. The legs of 26 young healthy (29 ± 6 years old) and 22 elderly (75 ± 8 years old) female subjects were imaged using UTE sequences on a 3T MRI scanner. Institutional review board approval was obtained, and all recruited subjects provided written informed consent. T1 and UTE-MT-modeling were performed on anterior tibialis tendons (ATT) and posterior tibialis tendons (PTT) as two representative human leg tendons. A series of MT pulse saturation powers (500–1500°) and frequency offsets (2–50 kHz) were used to measure the macromolecular fraction (MMF) and macromolecular T2 (T2_MM). All measurements were repeated by three independent readers for a reproducibility study. MMF demonstrated significantly lower values on average in the elderly cohort compared with the younger cohort for both ATT (decreased by 16.8%, p = 0.03) and PTT (decreased by 23.0%, p < 0.01). T2_MM and T1 did not show a significant nor a consistent difference between the young and elderly cohorts. For all MRI parameters, intraclass correlation coefficient (ICC) was higher than 0.98, indicating excellent consistency between measurements performed by independent readers. MMF serving as a surrogate measure for collagen content, showed a significant decrease in elderly leg tendons. This study highlighted UTE-MRI-MT techniques as a useful quantitative method to assess the impact of aging on human tendons.

Calcaneal Tendon Plasticity Following Gastrocnemius Muscle Injury in Rat

Cross-talk between skeletal muscle and tendon is important for tissue homeostasis. Whereas the skeletal muscle response to tendon injury has been well-studied, to the best of our knowledge the tendon response to skeletal muscle injury has been neglected. Thus, we investigated calcaneal tendon extracellular matrix (ECM) remodeling after gastrocnemius muscle injury using a rat model. Wistar rats were randomly divided into four groups: control group (C; animals that were not exposed to muscle injury) and harvested at different time points post gastrocnemius muscle injury (3, 14, and 28 days) for gene expression, morphological, and biomechanical analyses. At 3 days post injury, we observed mRNA-level dysregulation of signaling pathways associated with collagen I accompanied with disrupted biomechanical properties. At 14 days post injury, we found reduced collagen content histologically accompanied by invasion of blood vessels into the tendon proper and an abundance of peritendinous sheath cells. Finally, at 28 days post injury, there were signs of recovery at the gene expression level including upregulation of transcription factors related to ECM synthesis, remodeling, and repair. At this time point, tendons also presented with increased peritendinous sheath cells, decreased adipose cells, higher Young’s modulus, and lower strain to failure compared to the uninjured controls and all post injury time points. In summary, we demonstrate that the calcaneal tendon undergoes extensive ECM remodeling in response to gastrocnemius muscle injury leading to altered functional properties in a rat model. Tendon plasticity in response to skeletal muscle injury merits further investigation to understand its physiological relevance and potential clinical implications.

Anatomy and histology of the rabbit common calcanean tendon

Despite the great progress in the field of tendon injuries and chronic tendinopathies in recent years, treatment of these conditions is still challenging. Research utilising animal models is crucial for further advancement in tendon research, with the rabbit being a commonly used species in this field. The objective of the present study was to comprehensively describe the macro- and microanatomy of the common calcanean tendon (tendo Achillei), together with associated structures. Eight female New Zealand rabbits were subjected to anatomical dissection and histologic analysis, revealing significant species-specific features. The soleus muscle presented a thin, spindle shape with no tendon of insertion and attached directly to the lateral gastrocnemius muscle. Therefore, it does not contribute to the formation of the common calcanean tendon. The calcaneal tendon of the semitendinosus muscle was identified as a strong tendinous band at the medial side of the medial gastrocnemius muscle and the superficial digital flexor muscle and tendon distally. The saphenous artery was accompanied by the medial saphenous vein and characteristic accessory medial saphenous vein. The complex structure of the paratendinous connective tissue is described, with the paratenon being contiguous with the epitenon of the individual tendons and epimysium of associated muscles. At the level of the calcaneal tuber, the retromalleolar fat pad was identified, adhering to the cranial surface of the conjoint gastrocnemius tendon. Histologic studies confirmed the presence of the subtendinous calcaneal bursa of superficial digital flexor tendon and the bursa of calcaneal tendon.

MRI Findings Consistent with Peripatellar Fat Pad Impingement: How Much Related to Patellofemoral Maltracking?

Peripatellar fat pads are intracapsular extrasynovial adipose cushions that accommodate the changing shape and volume of articular spaces during movement. Variations in bone geometry, passive and active stabilization mechanisms and/or functional demands may lead to peripatellar fat pad abnormalities. While peripatellar fat pads may be affected a variety of conditions such as synovial inflammation, tumor and fibrosis, a mechanical origin should also be considered. Commonly, the clinical term "impingement" is used synonymously in the radiological literature to refer to three distinct entities of structural peripatellar fat pad abnormalities: superolateral the infrapatellar fat pad (Hoffa fat pad) edema, suprapatellar fat pad edema, and prepatellar fat pad edema, implying a mechanical origin of these conditions. The aim of this pictorial review is to describe the normal anatomy of the extensor mechanism of the knee, and discuss the relation of patellofemoral maltracking to the above-mentioned peripatellar fat pad conditions based on current evidence.

High pressure Raman study of type-I collagen

The high pressure response of type-I collagen from bovine Achilles tendon is investigated with micro-Raman spectroscopy. Fluorinert™ and methanol-ethanol mixtures were used as pressure transmitting media (PTM) in a diamond anvil cell. The Raman spectrum of collagen is dominated by three bands centred at approximately 1450, 1660 and 2930 cm^-1 , attributed to C-H deformation, C=O stretching of the peptide bond (amide-I band) and C-H stretching modes respectively. Upon pressure increase, using Fluorinert™ as PTM, a shift towards higher frequencies of the C-H stretching and deformation peaks is observed. Contrary, the amide-I band peaks are shifted to lower frequencies with moderate pressure slopes. On the other hand, when using the alcohol mixture as PTM, the amide-I band exhibits more pronounced C=O bond softening, deduced from the shift to lower frequencies, suggesting a strengthening of the hydrogen bonds between glycine and proline residues of different collagen chains due to the presence of the polar alcohol molecules. Furthermore, some of the peaks exhibit abrupt changes in their pressure slopes at approximately 2 GPa, implying a variation in the compressibility of the collagen fibres. This could be attributed to a pitch change from 10/3 to 7/2, sliding of the tropocollagen molecules, twisting variation at the molecular level and/or elimination of the D-gaps induced by kink compression. All spectral changes are reversible upon pressure release, which indicates that denaturation has not taken place. Finally, a minor lipid phase contamination was detected in some sample spots. Its pressure response is also monitored.

Prognostic value of MRI in arthroscopic treatment of chronic patellar tendinopathy: a prospective cohort study

Background

To date, prognostic outcome factors for patients undergoing arthroscopic treatment due to chronic patellar tendinopathy (PT) are lacking. The purpose of this study was to investigate whether preoperatively assessed MRI parameters might be of prognostic value for prediction of functional outcome and return to sports in arthroscopic treatment of chronic PT.

Methods

A prospective cohort study was conducted including 30 cases (4 female and 24 male competitive athletes) undergoing arthroscopic patellar release (APR) due to chronic PT. The mean age was 28.2 years (range, 18–49 years) at the time of surgery, and the mean follow-up period was 4.2 years (range, 2.2–10.4 years). Preoperatively assessed MRI parameters included bone marrow edema (BME) of the inferior patellar pole, patellar tendon thickening, infrapatellar fat pad (IFP) edema, and infrapatellar bursitis. Prevalences of preoperative MRI findings were correlated to functional outcome scores in order to determine statistically significant predictors.

Results

All athletes regained their preinjury sports levels. Athletes featuring preoperative IFP edema showed significantly inferior modified Blazina score (0.6 ± 0.7 vs. 0.2 ± 0.5), single assessment numeric evaluation (SANE; 86.0 ± 8.8 vs. 94.3 ± 7.5), and Visual Analogue Scale (VAS; 1.0 ± 1.2 vs. 0.3 ± 0.8) compared to subjects without IFP edema (p < 0.05). Return to sports required a mean of 4 ± 3.2 months. On average, patients with IFP edema needed significantly more time to return to sports than subjects without IFP edema (6.5 vs 2.8 months; p < 0.05). The simultaneous presence of BME and IFP edema was associated with significantly inferior outcomes by means of the Victorian Institute of Sport Assessment questionnaire for patients with patellar tendinopathy (VISA-P; 88.1 ± 11.9 vs. 98.6 ± 4.2), SANE (84.3 ± 10.2 vs. 93.1 ± 8.3), and VAS (1.3 ± 1.4 vs. 0.3 ± 0.9) compared to an isolated BME or isolated IFP edema.

Conclusions

This is the first study identifying prognostic outcome factors in arthroscopic treatment of chronic PT. Preoperative IFP edema alone or simultaneous BME and IFP edema on preoperative MRI were associated with inferior functional outcome and delayed return to sports. Knowledge of these predictive factors might improve risk stratification, individualize treatment and postoperative rehabilitation, and contribute to improve clinical outcome. Moreover, current findings offer the potential for novel therapeutic approaches.

Iliotibial Band Syndrome in Runners: Biomechanical Implications and Exercise Interventions

Iliotibial band syndrome (ITBS) has known biomechanical factors with an unclear explanation based on only strength and flexibility deficits. Neuromuscular coordination has emerged as a likely reason for kinematic faults guiding research toward motor control. This article discusses ITBS in relation to muscle performance factors, fascial considerations, epidemiology, functional anatomy, strength deficits, kinematics, iliotibial strain and strain rate, and biomechanical considerations. Evidence-based exercise approaches are reviewed for ITBS, including related methods used to train the posterior hip muscles.

Signal intensity alteration in the infrapatellar fat pad at baseline for the prediction of knee symptoms and structure in older adults: a cohort study

OBJECTIVE

To describe the associations between infrapatellar fat pad (IPFP) signal intensity alteration at baseline and knee symptoms and structural changes in older adults.

METHODS

A total of 874 subjects (mean 62.1 years, 50.1% female) selected randomly from local community were studied at baseline and 770 were followed up (only 357 had MRI at follow-up) over 2.6 years. T1-weighted or T2-weighted fat suppressed MRI was used to assess IPFP signal intensity alteration (0-3), cartilage volume, cartilage defects and bone marrow lesions (BMLs) at baseline and 2.6 years later. Knee pain was assessed by self-administered Western Ontario and McMaster Osteoarthritis Index questionnaire. Radiographic osteoarthritis (OA) was assessed.

RESULTS

In cross-sectional analyses, IPFP signal intensity alteration was significantly and positively associated with total knee pain as well as knee cartilage defects, BMLs and knee radiographic OA and negatively associated with patellar cartilage volume after adjustment for age, sex, body mass index and/or radiographic OA. Longitudinally, baseline signal intensity alteration within IPFP was significantly and positively associated with increases in knee pain when going upstairs/downstairs as well as increases in tibiofemoral cartilage defects and BMLs, and negatively associated with change in lateral tibial cartilage volume in multivariable analyses.

CONCLUSIONS

IPFP signal intensity alteration at baseline was associated with knee structural abnormalities and clinical symptoms cross-sectionally and longitudinally in older adults, suggesting that it may serve as an important imaging biomarker in knee OA.

Enthesopathies and enthesitis. Part 2: Imaging studies

The pathologies of tendon and ligament attachments are called enthesopathies. Enthesitis is one of enthesopathies and it is considered a characteristic sign of rheumatic diseases from the spondyloarthritis group, including peripheral spondyloarthritis. Therefore, enthesitis has been included in a number of clinical classifications for diagnosing these diseases. Clinical diagnosis of enthesitis is based on rather non-specific clinical signs and results of laboratory tests. It is believed that imaging examinations might improve diagnosis, particularly because numerous papers prove that differentiating enthesitis from other enthesopathic processes is possible. On the other hand, a number of authors report the lack of specific signs in imaging as well as typical histological and immunological features that would enable confirmation of clinical diagnosis of enthesitis. The first part of the publication presented theories on the etiopathogenesis of enthesitis (inflammatory, mechanical, autoimmune and associated with the synovio-entheseal complex) as well as on the formation of enthesophytes (inflammatory, molecular and mechanical). This paper - the second part of the article, is a review of the state-of-the-art on the ability of imaging examinations to diagnose enthesitis. It turns out that none of the enthesitis criteria used in imaging examinations is specific for inflammation. As enthesitis may be the only symptom of early spondyloarthritis (particularly in patients with absent HLA-B27 antigen), the lack of its unambiguous picture in ultrasound and magnetic resonance imaging prompts the search for other signs characteristic of spondyloarthritis and more specific features in imaging in order to make a diagnosis as early as possible.

The molecular composition of the extracellular matrix of the human iliolumbar ligament

BACKGROUND CONTEXT

The human iliolumbar ligament connects the transverse process of L5 to the iliac crest and contributes to lumbosacral stability and has been associated with low back pain. However, different opinions exist regarding the functional relevance of the ligament.

PURPOSE

In the present study, we analyze the regional molecular composition of the ligament extracellular matrix.

STUDY DESIGN

Special attention is given to the attachment sites, to determine whether the ligament is subjected to a certain mechanical environment.

METHODS

Iliolumbar ligament samples, extending from one enthesis to the other, were removed from 11 cadavers and fixed in methanol. Cryosections were immunolabeled with a panel of antibodies directed against collagens, glycosaminoglycans, proteoglycans, matrix proteins, and neurofilament.

RESULTS

The mid-substance of the ligament labeled for all the molecules normally found in dense fibrous connective tissue including types I, III, and VI collagen, versican, dermatan -, chondroitin 4 -, and keratan sulfate. However, both entheses were fibrocartilaginous and labeled for type II collagen, aggrecan, and chondroitin 6- sulfate. A common feature was fat between the fiber bundles near the entheses. Occasionally this fat contained nerve fibers.

CONCLUSIONS

The existence of fibrocartilaginous entheses suggests that the insertion sites of the ligament are subject to both tensile and compressive loading-probably because of insertional angle changes between ligament and bone during loading. Our findings support the suggestion that the iliolumbar ligament might play an important role in the stabilization of the lumbosacral junction.

Enthesopathies and enthesitis. Part 1. Etiopathogenesis

The pathologies of tendon and ligament attachments are called enthesopathies. One of its types is enthesitis which is a characteristic sign of peripheral spondyloarthropathy. Clinical diagnosis of enthesitis is based on rather non-specific clinical signs and results of laboratory tests. Imaging examinations are highly promising. Numerous publications prove that enthesitis can be differentiated from other enthesopathic processes in an ultrasound examination or magnetic resonance imaging. However, some reports indicate the lack of histological criteria, specific immunological changes and features in imaging examinations that would allow the clinical diagnosis of enthesitis to be confirmed. The first part of the publication presents theories on the etiopathogenesis of enthesopathies: inflammatory, mechanical, autoimmune, genetic and associated with the synovio-entheseal complex, as well as theories on the formation of enthesophytes: inflammatory, molecular and mechanical. The second part of the paper is a review of the state-of-the-art on the ability of imaging examinations to diagnose enthesitis. It indicates that none of the criteria of inflammation used in imaging medicine is specific for this pathology. As enthesitis may be the only symptom of early spondyloarthropathy (particularly in patients with absent HLA-B27 receptor), the lack of its unambiguous picture in ultrasound and magnetic resonance scans prompts the search for other signs characteristic of this disease and more specific markers in imaging in order to establish diagnosis as early as possible.

MR imaging of extrasynovial inflammation and impingement about the knee

The knee has unique anatomy regarding the relationship between the synovial and capsular layers, with interposed fat pads at certain locations. The extrasynovial impingement and inflammation syndromes about the knee are underdiagnosed and should be included in the differential diagnosis of anterior knee pain. MR imaging is the best imaging modality for evaluation of the anatomy and disorders of these extrasynovial compartments.

UTE imaging in the musculoskeletal system

Tissues, such as bone, tendon, and ligaments, contain a high fraction of components with "short" and "ultrashort" transverse relaxation times and therefore have short mean transverse relaxation times. With conventional magnetic resonance imaging (MRI) sequences that employ relatively long echo times (TEs), there is no opportunity to encode the decaying signal of short and ultrashort T2 /T2 * tissues before it has reached zero or near zero. The clinically compatible ultrashort TE (UTE) sequence has been increasingly used to study the musculoskeletal system. This article reviews the UTE sequence as well as various modifications that have been implemented since its introduction. These modifications have been used to improve efficiency or contrast as well as provide quantitative analysis. This article reviews several clinical musculoskeletal applications of UTE.

Tendon to bone healing and its implications for surgery

Entheses are complex structures which act to reduce stress concentrations between tendon and skeleton tissues. Understanding the development and function of the enthesis organ has implications for surgical repair, particularly in regards to healing and the regulation of tendon to bone engraftment. In this paper we review the development and function of entheses as well as the enthesis organ concept. Next we examine the process of tendon to bone healing and how this can be regulated, before addressing implications for surgical repair and post-operative care.

Distribution of sensory nerve endings around the human sinus tarsi: a cadaver study

The aim of this study was to analyse the pattern of sensory nerve endings and blood vessels around the sinus tarsi. The superficial and deep parts of the fat pads at the inferior extensor retinaculum (IER) as well as the subtalar joint capsule inside the sinus tarsi from 13 cadaver feet were dissected. The distribution of the sensory nerve endings and blood vessels were analysed in the resected specimens as the number per cm(2) after staining with haematoxylin-eosin, S100 protein, low-affinity neurotrophin receptor p75, and protein gene product 9.5 using the classification of Freeman and Wyke. Free nerve endings were the predominant sensory ending (P < 0.001). Ruffini and Golgi-like endings were rarely found and no Pacini corpuscles were seen. Significantly more free nerve endings (P < 0.001) and blood vessels (P = 0.01) were observed in the subtalar joint capsule than in the superficial part of the fat pad at the IER. The deep part of the fat pad at the IER had significantly more blood vessels than the superficial part of the fat pad at the IER (P = 0.012). Significantly more blood vessels than free nerve endings were seen in all three groups (P < 0.001). No significant differences in distribution were seen in terms of right or left side, except for free nerve endings in the superficial part of the fat pad at the IER (P = 0.003). A greater number of free nerve endings correlated with a greater number of blood vessels. The presence of sensory nerve endings between individual fat cells supports the hypothesis that the fat pad has a proprioceptive role monitoring changes and that it is a source of pain in sinus tarsi syndrome due to the abundance of free nerve endings.

Healing of subcutaneous tendons: Influence of the mechanical environment at the suture line on the healing process

Tendon ruptures remain a significant musculoskeletal injury. Despite advances in surgical techniques and procedures, traditional repair techniques maintain a high incidence of rerupture or tendon elongation. Mechanical loading and biochemical signaling both control tissue healing. This has led some researchers to consider using a technique based on tension regulation at the suture line for obtaining good healing. However, it is unknown how they interact and to what extent mechanics control biochemistry. This review will open the way for understanding the interplay between mechanical loading and the process of tendon healing.

Joint appendages: the structures which have historically been overlooked in arthritis research and therapy development

Rheumatologists have largely conceptualised joint disease in inflammatory and degenerative arthritis in terms of bone, cartilage and the synovial lining, but have tended to overlook other integral components of the joints which are attached close to joint margins. We discuss these structures under the umbrella term of 'appendages'. These structures include ligaments, tendons, entheses or joint insertions, regional fibrocartilages, bursae and other peri-articular joint structures including fat pads and nails. In this review, we highlight how these structures play key pathophysiological roles in inflammatory arthritis and we emphasise how an understanding of these structures is collectively important for both clinical practice and future rheumatological research.

Synovial folds - a pain in the neck?

The synovial folds of the cervical spine are regarded as a potential source of neck pain and headache, especially following whiplash injury. Damage to the synovial folds following motor vehicle trauma has been well documented in post-mortem studies. However, methods of identifying injury to the synovial folds in the survivors of motor vehicle trauma have proven elusive to date. Recently, it has been made possible to image the synovial folds in vivo using magnetic resonance imaging. This now makes it feasible to investigate the potential involvement of synovial folds in the generation of neck pain and headache and its relief using spinal manipulation. This paper reviews critically the morphology of the synovial folds of the cervical spine that underpins the hypotheses proposed to explain their functional and clinical significance and a new system of naming and classifying the synovial folds is presented. Although there is some evidence to support the contribution of the synovial folds to neck pain, several theories have little or no support and require investigation and further evaluation. These findings have implications for understanding the anatomical basis of neck pain and headache and the rationale for the use of spinal manipulation in their management.

The anatomical basis for a novel classification of osteoarthritis and allied disorders

Osteoarthritis (OA) has historically been classified as 'primary' where no discernible cause was evident and 'secondary' where a triggering factor was apparent. Irrespective of the triggering events, late-stage OA is usually characterized by articular cartilage attrition and consequently the anatomical basis for disease has been viewed in terms of cartilage. However, the widespread application of magnetic resonance imaging in early OA has confirmed several different anatomical abnormalities within diseased joints. A key observation has been that several types of primary or idiopathic OA show ligament-related pathology at the time of clinical presentation, so these categories of disease are no longer idiopathic - at least from the anatomical perspective. There is also ample evidence for OA initiation in other structures including menisci and bones in addition to articular cartilage. Therefore, a new classification for OA is proposed, which is based on the anatomical sites of earliest discernible joint structural involvement. The major proposed subgroups within this classification are ligament-, cartilage-, bone-, meniscal- and synovial-related, in addition to disease that is mixed pattern or multifocal in origin. We show how such a structural classification for OA provides a useful reference framework for staging the magnitude of disease. For late-stage or end-stage/whole organ disease, the final common pathway of these different scenarios, joint replacement strategies are likely to remain the only viable option. However, for younger subjects in particular, near the time of clinical disease onset, this scheme has implications for therapy targeted to specific anatomical locations. Thus, in the same way that tumours can be classified and staged according to their tissue of origin and extent of involvement, OA can likewise be anatomically classified and staged. This has implications for therapeutic strategies including regenerative medicine therapy development.

Quantifying the motion of Kager's fat pad

Kager's fat pad is located in Kager's triangle between the Achilles tendon, the superior cortex of the calcaneus, and flexor hallucis longus (FHL) muscle and tendon. Its biomechanical functions are not yet established, but recent studies suggest it performs important biomechanical roles as it is lined by a synovial membrane and its retrocalcaneal protruding wedge can be observed moving into the bursal space during ankle plantarflexion. Such features have prompted hypotheses that the protruding wedge assists in the lubrication of the Achilles tendon subtendinous area, distributes stress at the Achilles enthesis, and removes debris from within the retrocalcaneal bursa. This study examined the influence of FHL activity and Achilles tendon load on the protruding wedge sliding distance, using both dynamic ultrasound imaging and surface electromyogram. Intervolunteer results showed sliding distance was independent of FHL activity. This study has shown the protruding wedge to slide on average 60% further into the retrocalcaneal bursa when comparing the Achilles tendon loaded versus unloaded, consistently reaching the distal extremity. Sliding distance was dependent on a change in the Achilles tendon insertion angle. Our results support a number of hypothesized biomechanical functions of the protruding wedge including: lubrication of the subtendinous region; reduction of pressure change within the Achilles tendon enthesis organ; and removal of debris from within the retrocalcaneal bursa.

Structure-function relationships in tendons: a review

The purpose of the current review is to highlight the structure-function relationship of tendons and related structures to provide an overview for readers whose interest in tendons needs to be underpinned by anatomy. Because of the availability of several recent reviews on tendon development and entheses, the focus of the current work is primarily directed towards what can best be described as the 'tendon proper' or the 'mid-substance' of tendons. The review covers all levels of tendon structure from the molecular to the gross and deals both with the extracellular matrix and with tendon cells. The latter are often called 'tenocytes' and are increasingly recognized as a defined cell population that is functionally and phenotypically distinct from other fibroblast-like cells. This is illustrated by their response to different types of mechanical stress. However, it is not only tendon cells, but tendons as a whole that exhibit distinct structure-function relationships geared to the changing mechanical stresses to which they are subject. This aspect of tendon biology is considered in some detail. Attention is briefly directed to the blood and nerve supply of tendons, for this is an important issue that relates to the intrinsic healing capacity of tendons. Structures closely related to tendons (joint capsules, tendon sheaths, pulleys, retinacula, fat pads and bursae) are also covered and the concept of a 'supertendon' is introduced to describe a collection of tendons in which the function of the whole complex exceeds that of its individual members. Finally, attention is drawn to the important relationship between tendons and fascia, highlighted by Wood Jones in his concept of an 'ectoskeleton' over half a century ago - work that is often forgotten today.

Adipose tissue at entheses: the innervation and cell composition of the retromalleolar fat pad associated with the rat Achilles tendon

This study set out to determine whether the fat pad at the attachment of the Achilles tendon has features enabling it to function as an immune organ and a mechanosensory device, and to be a source of pain in insertional tendon injuries. Sections for histology and immunohistochemistry were cut from the Achilles tendon enthesis organ of 1 day old, 1 month, 4 month and 24 month old rats. For fluorescence and peroxidase immunohistochemistry, cryosections were labelled with primary antibodies directed against PGP9.5, substance P, neurofilament 200, calcitonin gene related peptide, CD68, CD36, myeloid related protein 14, actin and vinculin. The fat pad contained not only adipocytes, but also fibrous tissue, mast cells, macrophages, fibroblasts and occasional fibrocartilage cells. It was richly innervated with nerve fibres, some of which were likely to be nociceptive, and others mechanoreceptive (myelinated fibres, immunoreactive for neurofilament 200). The fibres lay between individual fat cells and in association with blood vessels. In marked contrast, the enthesis itself and all other components of the enthesis organ were aneural at all ages. The presence of putative mechanoreceptive and nociceptive nerve endings between individual fat cells supports the hypothesis that the fat pad has a proprioceptive role monitoring changes in the insertional angle of the Achilles tendon and that it may be a source of pain in tendon injuries. The abundance of macrophages suggests that the adipose tissue could have a role in combating infection and/or removing debris from the retrocalcaneal bursa.

Musculoskeletal Disorders of Pregnancy, Delivery and Postpartum

Gender-specific care of musculoskeletal impairments is increasingly important in women's health. This is most relevant and of paramount importance as it relates to identification and management of musculoskeletal and peripheral neurologic disorders of pregnancy, delivery, and postpartum. The specific anatomic and physiologic changes of pregnancy predispose to a specific set of diagnoses. Virtually all women experience some degree of musculoskeletal discomfort during pregnancy. This article provides an overview of the more common pregnancy-related musculoskeletal conditions and includes a discussion of epidemiology, risk factors, diagnosis, prognosis, and management.

The functional anatomy of the iliotibial band during flexion and extension of the knee: implications for understanding iliotibial band syndrome

Iliotibial band (ITB) syndrome is a common overuse injury in runners and cyclists. It is regarded as a friction syndrome where the ITB rubs against (and 'rolls over') the lateral femoral epicondyle. Here, we re-evaluate the clinical anatomy of the region to challenge the view that the ITB moves antero-posteriorly over the epicondyle. Gross anatomical and microscopical studies were conducted on the distal portion of the ITB in 15 cadavers. This was complemented by magnetic resonance (MR) imaging of six asymptomatic volunteers and studies of two athletes with acute ITB syndrome. In all cadavers, the ITB was anchored to the distal femur by fibrous strands, associated with a layer of richly innervated and vascularized fat. In no cadaver, volunteer or patient was a bursa seen. The MR scans showed that the ITB was compressed against the epicondyle at 30 degrees of knee flexion as a consequence of tibial internal rotation, but moved laterally in extension. MR signal changes in the patients with ITB syndrome were present in the region occupied by fat, deep to the ITB. The ITB is prevented from rolling over the epicondyle by its femoral anchorage and because it is a part of the fascia lata. We suggest that it creates the illusion of movement, because of changing tension in its anterior and posterior fibres during knee flexion. Thus, on anatomical grounds, ITB overuse injuries may be more likely to be associated with fat compression beneath the tract, rather than with repetitive friction as the knee flexes and extends.

Where tendons and ligaments meet bone: attachment sites ('entheses') in relation to exercise and/or mechanical load

Entheses (insertion sites, osteotendinous junctions, osteoligamentous junctions) are sites of stress concentration at the region where tendons and ligaments attach to bone. Consequently, they are commonly subject to overuse injuries (enthesopathies) that are well documented in a number of sports. In this review, we focus on the structure-function correlations of entheses on both the hard and the soft tissue sides of the junction. Particular attention is paid to mechanical factors that influence form and function and thus to exploring the relationship between entheses and exercise. The molecular parameters indicative of adaptation to mechanical stress are evaluated, and the basis on which entheses are classified is explained. The application of the 'enthesis organ' concept (a collection of tissues adjacent to the enthesis itself, which jointly serve the common function of stress dissipation) to understanding enthesopathies is considered and novel roles of adipose tissue at entheses are reviewed. A distinction is made between different locations of fat at entheses, and possible functions include space-filling and proprioception. The basic anchorage role of entheses is considered in detail and comparisons are explored between entheses and other biological 'anchorage' sites. The ability of entheses for self-repair is emphasized and a range of enthesopathies common in sport are reviewed (e.g. tennis elbow, golfer's elbow, jumper's knee, plantar fasciitis and Achilles insertional tendinopathies). Attention is drawn to the degenerative, rather than inflammatory, nature of most enthesopathies in sport. The biomechanical factors contributing to the development of enthesopathies are reviewed and the importance of considering the muscle-tendon-bone unit as a whole is recognized. Bony spur formation is assessed in relation to other changes at entheses which parallel those in osteoarthritic synovial joints.

Musculoskeletal aspects of pregnancy

Sex-specific care of musculoskeletal impairments is an increasingly important topic in women's health. This is clinically relevant and of paramount importance as it pertains to diagnosis and treatment of musculoskeletal and peripheral neurologic disorders of pregnancy and the puerperium. It is estimated that virtually all women experience some degree of musculoskeletal discomfort during pregnancy, and 25% have at least temporarily disabling symptoms. This review provides information on common pregnancy-related musculoskeletal conditions, including a discussion of anatomy and physiology, diagnosis, prognosis, and treatment of these disorders.