Dynamics of the suprapatellar bursa during knee joint extension.

PURPOSE: The suprapatellar bursa is located in the proximal deep layer of the patella and is thought to reduce tissue friction by changing from a single-membrane structure to a double-membrane structure during knee joint motion. However, the dynamics of the suprapatellar bursa have only been inferred from positional relationships, and the actual dynamics have not been confirmed. METHODS: Dynamics of the suprapatellar bursa during knee joint motion were observed in eight knees of four Thiel-fixed cadavers and the angle at which the bursa begins to show a double membrane was revealed. The flexion angles of knee joints were measured when the double-membrane structure of the suprapatellar bursa began to appear during knee joint extension. RESULTS: The suprapatellar bursa changes from a single membrane to a double-membrane structure at 91 ± 4° of flexion, when the knee joint is moved from a flexed position to an extended position. CONCLUSION: The suprapatellar bursa may be involved in limitations to knee joint range of motion and pain at an angle of approximately 90°. Further studies are needed to verify whether the same dynamics are observed in living subjects.

Anatomy of the congenital calcaneal bursae in the bovine.

OBJECTIVE: The objective of this study was to determine the anatomical relationship of the congenital calcaneal bursae in the bovine, and describe the computed tomography (CT), endoscopic and gross anatomy of these bursae. STUDY DESIGN: Ex vivo experimental. SAMPLE POPULATION: Eighteen clinically normal cadaver bovine hindlimbs. METHODS: Intrasynovial injection of iodinated contrast and methylene blue into the intertendinous calcaneal bursa (ICB) (n = 16) or gastrocnemius calcaneal bursa (GCB) (n = 2). Limbs were imaged post-contrast injection using multidetector CT. Endoscopic examination of the ICB was performed on two randomly selected limbs. All limbs underwent gross anatomical dissection. RESULTS: The anatomy of the congenital calcaneal bursae was consistent between CT imaging, endoscopic examination and gross dissection. The ICB and GCB were two separate synovial structures with no communication in all limbs. The distal and proximal extent of the ICB, defined as the distance from the point of tuber calcanei to the distal/proximal aspect of the ICB, was (median [IQR]) 7.4 (7.4 to 7.8) cm distally and 5.4 (4.7 to 6.0) cm proximally. CONCLUSION: Positive contrast CT and gross anatomical dissection revealed no communication between the congenital calcaneal bursae in any limb. Routine bursoscopy allowed complete endoscopic examination of the ICB. The proximal extent of the ICB is shorter than the distal extent. The use of a collective term for these bursae should be avoided in the bovine, as the ICB and the GCB are two separate synovial structures with no communication. CLINICAL SIGNIFICANCE: Knowledge of distinct anatomy and relationship between the congenital calcaneal bursae in the bovine may facilitate diagnosis and treatment of disorders affecting the region of tuber calcanei, including septic bursitis and osteomyelitis.

MR Imaging of the Knee Bursae and Bursal Pathology.

The main function of the knee bursae is to provide cushioning for the many periarticular ligaments, tendons, and osseous structures. Bursae can only be visualized when distended by fluid, therefore bursal anatomy is best evaluated by MR imaging using fluid-sensitive sequences. Knowledge of the normal bursal distribution is important to avoid incorrectly interpreting a distended bursa as a periarticular fluid collection or cyst. Bursal pathology usually results from trauma, chronic overuse, or inflammation, and may be associated with an underlying intra-articular process, given the presence of synovial lining and different degrees of communication with the joint.

The morphology of the subacromial and related shoulder bursae. An anatomical and histological study.

Shoulder bursae are essential for normal movement and are also implicated in the pathogenesis of shoulder pain and dysfunction. The subacromial bursa (SAB), within the subacromial space, is considered a primary source of shoulder pain. Several other bursae related to the subcoracoid space, including the coracobrachial (CBB), subcoracoid (SCB) and subtendinous bursa of subscapularis (SSB), are also clinically relevant. The detailed morphology and histological characteristics of these bursae are not well described. Sixteen embalmed cadaveric shoulders from eight individuals (five females, three males; mean age 78.6 ± 7.9 years) were investigated using macro-dissection and histological techniques to describe the locations, dimensions and attachments of the bursae, their relationship to surrounding structures and neurovascular supply. Bursal sections were stained with haematoxylin and eosin to examine the synovium and with antibodies against von Willebrand factor and neurofilament to identify blood vessels and neural structures respectively. Four separate bursae were related to the subacromial and subcoracoid spaces. The SAB was large, with a confluent subdeltoid portion in all except one specimen, which displayed a distinct subdeltoid bursa. The SAB roof attached to the lateral edge and deep surface of the acromion and coracoacromial ligament, and the subdeltoid fascia; its floor fused with the supraspinatus tendon and greater tubercle. The CBB (15/16 specimens) was deep to the conjoint tendon of coracobrachialis and short head of biceps brachii and the tip of the coracoid process, while the inconstant SCB (5/16 specimens) was deep to the coracoid process. Located deep to the subscapularis tendon, the SSB was a constant entity that commonly displayed a superior extension. Synovial tissue was predominantly areolar (SAB and SSB) or fibrous (CBB and SCB), with a higher proportion of areolar synovium in the bursal roofs compared to their floors. Blood vessels were consistently present in the subintima with a median density of 3% of the tissue surface area, being greatest in the SSB and SAB roofs (4.9% and 3.4% respectively) and least in the SAB floor (1.8%) and CBB roof and floor (both 1.6%). Nerve bundles and free nerve endings were identified in the subintima in approximately one-third of the samples, while encapsulated nerve endings were present in deeper tissue layers. The extensive expanse and attachments of the SAB support adoption of the term subacromial-subdeltoid bursa. Morphologically, the strong attachments of the bursal roofs and floors along with their free edges manifest as fixed and mobile portions, which enable movement in relation to surrounding structures. The presence of neurovascular structures demonstrates that these bursae potentially contribute blood supply to surrounding structures and are involved in mechanoreception. The anatomical details presented in this study clarify the morphology of the shoulder bursae, including histological findings that offer further insight into their potential function.

Ultrasound-Guided Versus Landmark-Based Approach to the Distal Suprascapular Nerve Block: A Comparative Cadaveric Study.

PURPOSE: To compare the accuracy of distal suprascapular nerve (dSSN) blockade performed with the use of ultrasound-guided regional anesthesia (USRA) versus with a landmark-based approach (LBA). A secondary aim was to describe the anatomic features of the sensory branches of the dSSN. METHODS: USRA and LBA were performed in 15 shoulders each from 15 cadavers (total of 30 shoulders). Then, 10 mL of methylene blue‒infused ropivacaine 0.75% was injected into the dSSN. Simultaneously, 2.5 mL of red latex solution was injected to identify the position of the needle tip. The division and distribution of the sensory branches originating from the SSN were described. RESULTS: The tip of the needle was identified at 1.3 cm (range, 0-5.2 cm) and 1.5 cm (range, 0-4.5 cm) with USRA and the LBA, respectively (P = .90). Staining diffused past the origin of the most proximal sensory branch in 27 cases. The most proximal sensory branch arose 2.5 cm from the suprascapular notch. Among the 3 failures that occurred in the USRA group, the sensory branches also failed to be marked. All 30 dSSNs gave off 3 sensory branches, which innervated the posterior glenohumeral capsule, the subacromial bursa, and the coracoclavicular and acromioclavicular ligaments. CONCLUSIONS: An LBA is as reliable and accurate as US guidance for anesthetic blockade of the dSSN. Marking of the suprascapular nerve must be proximal to the suprascapular notch to involve the 3 sensory branches in the anesthetic blockade. CLINICAL RELEVANCE: The present study demonstrates that a landmark-based approach to anesthetic blockade of the distal suprascapular nerve is accurate and can be performed by orthopaedic surgeons lacking experience in ultrasound-guided anesthetic techniques.

Communication between the distal interphalangeal joint and the navicular bursa in the horse at Computed Tomography Arthrography.

Diffusion of drugs injected into the distal interphalangeal joint or the navicular (podotrochlear) bursa can influence diagnosis and treatment of foot pain. Previous anatomical and radiographic studies of the communication between these synovial structures have produced conflicting results and did not identify the location of any communication if present. This anatomic study aimed to assess the presence and site of communication between the distal interphalangeal joint and the navicular bursa in the horse by computed tomography arthrography. Sixty-six pairs of cadaver forelimbs were injected with contrast medium into the distal interphalangeal joint and imaged by computed tomography arthrography. The presence of a communication, location of the communication and additional structural changes were assessed. Navicular bursa opacification occurred in 7 distal limbs (5.3%) following distal interphalangeal joint injection. One limb showed a communication through the T-ligament and 6 limbs showed a communication through the distal sesamoidean impar ligament. In 3 cases, the communication through the distal sesamoidean impar ligament was associated with a distal border fragment. Our study showed that communication between the distal interphalangeal joint and navicular bursa is uncommon and inconsistent. Clinically, the presence of a communication could (1) influence the interpretation of diagnostic analgesia of the distal interphalangeal joint or the navicular bursa by facilitating the diffusion of local anaesthetic between these structures; (2) allow the drug and its potential adverse effects to spread from the treated synovial cavity to the non-targeted synovial cavity; (3) be responsible for the failure of joint drainage in the case of sepsis.

Clinical Anatomy for the Innervated Pattern and Boundary of the Subdeltoid Bursa.

The aim of this study was to accurately identify the distribution of sensory nerve branches running to bursa with mesoscopic dissection and boundaries following the injection of gelatin into the bursa. Eighteen shoulders of 11 Korean soft cadavers (average age, 65 years; age range, 43 - 88 years) were dissected. The most prominent point of greater tubercle of the humerus (GT) was used as a reference point. The horizontal line passing through GT was used as the x-axis while the vertical line passing through the GT was used as the y-axis. Average distances of the anterior, posterior, superior, and inferior from the GT were 1.9±0.6, 2.4±1.3, 2.1±0.7, and 3.2±1.5 cm, respectively. In 15 cases of 18 shoulders, the anterior branch of the axillary nerve was distributed to the subdeltoid bursa that was running posteriorly. The muscular branch of the anterior and middle parts of the deltoid was distributed to the branch of nerve that was running into the subdeltoid bursa. A branch of the posterior cord of brachial plexus was distributed to the subdeltoid bursa that was running anteriorly in three cases. Most of the branches of the axillary nerve were distributed into the posterolateral area. The branches of the posterior cord of brachial plexus were distributed in the anterolateral area. These results might be useful for preventing residual pain on the anterior shoulder region following an injection for the relief of shoulder pain.

The anterior knee: normal variants, common pathologies, and diagnostic pitfalls on MRI.

The anterior aspect of the knee is host to an array of normal variants and potential pathology. These normal anatomic variants are often encountered and may mimic pathologies, leading to unnecessary work-up and treatments. On the other hand, there are several subtle abnormalities that may be easily overlooked or mistaken for variants or other injuries or diseases. Recognition of these diagnostic challenges is essential for radiologists to make an accurate diagnosis. This article reviews normal anatomical variants of ligaments, tendons, bones, and other important structures of the anterior knee, focusing on magnetic resonance imaging features. Commonly encountered injuries and abnormalities of the anterior knee and their diagnostic pitfalls are also discussed, highlighting findings on magnetic resonance imaging.

Normative size of the osseous part of calcaneal bursa and its comparison with other calcaneal articular areas.

The retro-calcaneal bursa presents a synovial and a non-synovial osseous part of variable dimensions. Studies objectively measuring the variability of the size of this osseous bursal surface cannot be found in literature. The objective of this study was to investigate (i) the dimension variability of the bony part of the bursa and (ii) the relationship of this surface to other articulating areas of the calcaneus. A digital planimeter was used to measure the bursae (n=86) and other articular surface areas of the calcaneus and statistically compared with ANOVA and correlation estimations. The osseous area measured 1.12 (±0.55) cm2, with only the superior articulating area demonstrating a weak correlation to this osseous surface. The osseous area presents a weak correlation with the axial articulating area of the calcaneus. Information on the size of the bony bursa may help safe excision of retrocalcaneal exostoses and in Achille's tendon repair around the posterior tuberosity.

Ultrasound evaluation of bursae: anatomy and pathological appearances.

A bursa is an extra-articular sac that may communicate with a joint and functions to decrease friction between tendons and either bone or skin. Bursae can be classified as native and non-native (adventitious) bursae. The native bursae are lined with a synovial membrane and occur at predictable anatomical sites; knowledge of these normal structures can help distinguish them from other pathological entities. An adventitious bursa can form at sites of friction rather than at predictable anatomical sites, but otherwise have imaging features similar to native bursae. Bursal distention can occur from many pathological processes, most commonly resulting from chronic overuse injury. When imaging bursal pathological conditions, there is often an overlap of imaging findings, regardless of the cause. In general, ultrasound of a distended bursa reveals a fluid collection with either simple anechoic or more complex hypoechoic fluid. Bursal distention is characteristically unilocular and compressible, unlike other structures such as ganglion cysts, which are usually multilocular and non-compressible. This article reviews the anatomical locations of common bursae and shows pathological examples using ultrasound. Knowledge of typical locations and imaging appearances of bursae can aid in narrowing the differential diagnosis and guiding further management and treatment decisions.

Distal border synovial invaginations of the equine distal sesamoid bone communicate with the distal interphalangeal joint.

OBJECTIVES: Macroscopic studies have suggested a link between distal border synovial invaginations of the navicular bone and the distal interphalangeal joint. However, many practitioners consider that these invaginations are directly and solely related to navicular disease. The objective was to investigate the communication pattern of these synovial invaginations with the synovial compartments of the distal interphalangeal joint and the navicular bursa, using minimally invasive imaging techniques. METHODS: In a prospective observational study, 10 cadaveric limbs with radiographically evident distal border synovial invaginations were randomly assigned to computed tomography arthrography or bursography groups, using iopamidol. RESULTS: In 5/5 limbs, contrast medium filled the invaginations following distal interphalangeal arthrography. In the other five limbs, no contrast medium filled the invaginations following bursography. CLINICAL SIGNIFICANCE: Contrary to existing beliefs, these invaginations are more likely associated with distal interphalangeal joint synovitis and may not be directly linked to primary navicular bone pathology, but might reflect distal interphalangeal arthropathy. Therefore, the rationale for assessment of these invaginations in stallion selection or pre-purchase examinations as a predictive sign for navicular disease is questionable. Nonetheless, comorbidities are frequent in the equine distal limb. Enlarged synovial invaginations may also be seen in limbs with concomitant primary navicular disease. Further studies are needed to elucidate possible inter-related pathological processes.

Development of a Novel Medial Synoviocentesis Approach to the Bicipital Bursa in an Equine Cadaver Model.

OBJECTIVE: To describe the volume and dimensions of the bicipital bursa and its position in relation to bony and soft tissue structures, in order to develop a novel medial synoviocentesis approach to the bicipital bursa. STUDY DESIGN: Cadaveric study. ANIMALS: Adult equine cadaver limbs (n=19). METHODS: Bicipital bursa dimensions, volume, and relationship to bony structures were obtained from positive contrast computed tomography images after distension of the bursa (n=7). Following an intra-bursal injection of polyurethane resin, the bicipital bursa (n=4) was dissected and its relationship to soft tissue structures described. After computed tomography and dissection, a novel medial bicipital bursocentesis approach was investigated on intact cadavers (n=8). RESULTS: Median (range) of measurements were: length 9.02 cm (8.48-9.45 cm); width 7.06 cm (6.71-8.01 cm); and volume 51 mL (45-58 mL). The medial aspect of the bicipital bursa was located at the junction of the subclavius and biceps muscles, which corresponds with the externally visible lateral pectoral sulcus. Needle insertion 5-10 mm craniolateral to the center of the lateral pectoral sulcus midway between the palpable distal aspect of the deltoid tuberosity and the cranial part of the greater tubercle was found to be a reliable landmark for the novel medial bursocentesis approach. This approach was successful in all cadavers. CONCLUSION: The novel approach to the bicipital bursa provided access to the medial aspect of the bursa and is an alternative to the lateral approaches. Further validation in live horses is warranted to establish the safety and efficacy of this technique.

Ex Vivo Assessment of an Ultrasound-Guided Injection Technique of the Navicular Bursa in the Horse.

Synovitis of the navicular bursa is common in performance horses. The objective of this study was to describe an ultrasound-guided technique to inject a distended navicular bursa and to evaluate its feasibility for use by a clinician not trained in the technique. Twenty distal limbs of horses of various breeds and sizes were used. To produce synovial distension, the navicular bursa of each limb was injected with contrast medium using a lateral approach and radiography was performed to confirm that the contrast medium was distending the bursa. The digit was positioned with the distal interphalangeal joint in hyperextension. A microconvex ultrasound probe was placed in the hollow of the pastern, palmar to the middle phalanx and the region was assessed in a transverse plane slightly oblique to the horizontal plane. The ultrasound probe was rotated to visualize both the lateral and medial recesses and to select which side was more distended to inject. A 21G 0.8 × 50 mm needle was inserted abaxially to the probe in the plane of the ultrasound beam into the proximal recess of this navicular bursa and a methylene blue solution was injected. Following injection, dissection was performed to assess whether the navicular bursa had been successfully injected. This ultrasound-guided technique was reliably performed with a success rate of 68%. The success of injection is influenced by hyperextension of the foot, quality of ultrasound images and degree of distension of the bursa.

Accessibility of extra-articular pathologies of iliopsoas tendon and bursitis of greater trochanter in hip arthroscopy.

PURPOSE: Different pathologies leading to psoas tendon pain and chronic bursitis of the greater trochanter are well known. The purpose of the study was to underline the accessibility of the psoas tendon at lesser trochanter, reproduce the results and measure the distances to anatomical landmarks. METHODS: Twelve hips of six human cadavers underwent hip arthroscopy. The accessibility of the iliopsoas tendon at the lesser trochanter and the bursa at the greater trochanter was documented with the camera. In addition to the usual access portals, alternative ventral ports were analysed concerning accessibility of the lesser trochanter. Afterwards, arthroscopy needles were placed along the extra-articular portals followed by dissection. The distances of the portals in relation to important anatomical landmarks were analysed. RESULTS: The accessibility to the iliopsoas tendon at the lesser trochanter and to the bursa at the greater trochanter throughout the conventional portals was reproducible. Sufficient distances to the important anatomical landmarks could be shown. The mean distance of the distal ventro-lateral and the wide distal ventro-lateral portal to the nervous cutaneous femoris lateralis was 26.8 ± 5.4 mm and 32.2 ± 3.9 mm. The mean distance from the more ventral located portals to the nervous arteria and vena femoralis was 28.3 ± 2.1 mm. CONCLUSION: This is the first study known to us that describes in detail the accessibility of the extra-articular structures underlined by anatomical preparation. In addition, it was demonstrated that a more ventrally located portal had sufficient distance to the important neurovascular structures of the ventral femur and can also be used in addendum if necessary.

An important Norwegian contribution to the study of the bursae of the upper and lower extremities.

We present a critical analysis of the monograph of A.S.D. Synnestvedt (1869) "En anatomisk beskrivelse af de paa over- og underestremiteterne forekommende Bursae mucosae". The analysis was completed using anatomical information from the historically oldest publications dealing with the bursae of the extremities: Albinus (1734) , Monro (1788) , Rosenmüller (1799) . We are of the opinion that Synnestvedt's publication is important, not only historically but also as a source of information for recent medical practitioners. Synnestvedt's monograph has a wealth of literary citations, unambiguous opinions of seasoned anatomists regarding the structure and function of the synovial membrane, and detailed descriptions of dissections he performed on fetal and adult cadavers. The information in this publication may enhance the diagnosis of bursopathies and enthesopathies of the extremities.

MR imaging of synovial disorders of the knee.

Synovial membranes line the diarthrodial (movable) joints, bursae, and tendon sheaths of the body. The primary function of this specialized, vascular tissue is to serve as a filter system that lubricates and nourishes the articular structures as well as serving as a shock-absorber. The synovium is affected by a variety of disorders that can be localized to a specific articulation or can be systemic in nature. These include inflammatory, infectious, degenerative, traumatic, or neoplastic categories of disease. Further, MR imaging provides an excellent non-invasive tool for the evaluation of the synovium and synovial-based processes. This article will discuss technical considerations pertinent to the MR imaging evaluation of synovial processes in the knee; will review the synovial and bursal anatomy of the knee as well as the imaging characteristics of general synovial abnormalities and their diagnostic implications. In addition, it will review specific synovial processes and their characteristic MR imaging findings.

MR imaging of the extensor mechanism.

Sports injuries of the knee involving the extensor mechanism are common. Specific conditions additionally affect the extensor mechanism in adolescents during growth and maturation, and in older patients as a result of degeneration. Prior to the advent of magnetic resonance (MR) imaging, the specific anatomical-pathological cause of anterior knee pain was often uncertain, with diagnosis limited to clinical examination and conventional radiographic assessment. MR imaging allows for the accurate and specific diagnosis of pathology of the extensor mechanism, impacting on decision making and clinical treatment of such conditions. In this article the anatomy, normal MR appearance, and common pathological conditions of the extensor mechanism of the knee are described.

Development of the human Achilles tendon enthesis organ.

The attachment of the Achilles tendon is part of an 'enthesis organ' that reduces stress concentration at the hard-soft tissue interface. The organ also includes opposing sesamoid and periosteal fibrocartilages, a bursa and Kager's fat pad. In addition, the deep crural and plantar fasciae contribute to Achilles stress dissipation and could also be regarded as components. Here we describe the sequence in which these various tissues differentiate. Serial sections of feet from spontaneously aborted foetuses (crown rump lengths 22-322 mm) were examined. All slides formed part of an existing collection of histologically sectioned embryological material, obtained under Spanish law and housed in the Universidad Complutense, Madrid. From the earliest stages, it was evident that the Achilles tendon and plantar fascia had a mutual attachment to the calcaneal perichondrium. The first components of the enthesis organ to appear (in the 45-mm foetus) were the retrocalcaneal bursa and the crural fascia. The former developed by cavitation within the mesenchyme that later gave rise to Kager's fat pad. The tip of the putative fat pad protruded into the developing bursa in the 110-mm foetus and fully differentiated adipocytes were apparent in the 17-mm foetus. All three fibrocartilages were first recognisable in the 332-mm foetus--at which time adipogenesis had commenced in the heel fat pad. The sequence in which the various elements became apparent suggests that bursal formation and the appearance of the crural fascia may be necessary to facilitate the foot movements that subsequently lead to fibrocartilage differentiation. The later commencement of adipogenesis in the heel than in Kager's pad probably reflects the non-weight environment in utero. The direct continuity between plantar fascia and Achilles tendon that is characteristic of the adult reflects the initial attachment of both structures to the calcaneal perichondrium rather than to the skeletal anlagen itself.

Distances to the subacromial bursa from 3 different injection sites as measured arthroscopically.

PURPOSE: The purpose of this study was to assess the distance for a standard needle to reach the subacromial bursa through 3 commonly used approaches. METHODS: Thirty patients without associated rotator cuff tears underwent arthroscopic evaluation of the shoulder. The bursa was entered without shaving or altering of the bursa. By use of standard arthroscopic portals, a spinal needle was inserted from an anterior, lateral, and posterior position and measured to define the distance to the subacromial bursa from the skin. RESULTS: The mean distance with anterior needle placement was 2.9 +/- 0.6 cm. The mean distance with lateral needle placement was 2.9 +/- 0.7 cm. The mean distance with posterior needle placement was 5.2 +/- 1.1 cm. The mean body mass index for the group of patients was 27.5. The minimum was 18.7, and the maximum was 42.8. CONCLUSIONS: The distance to the subacromial bursa from the anterior and lateral approaches appears to be consistent and within reach of a standard 22- or 25-gauge needle. The distance to the subacromial bursa from a posterior approach appears to be almost double that of the anterior and lateral approaches and may not be reachable by standard 22- and 25-gauge needles in all patients. There appears to be no correlation between distances to the subacromial bursa from the anterior, lateral, or posterior approaches and the patient's body mass index. CLINICAL RELEVANCE: Given the relative distances measured to the subacromial bursa from the anterior, lateral, and posterior positions, clinicians may choose a longer needle to improve the accuracy of placement when approaching the subacromial bursa from a posterior position. Use of a standard-length needle will provide reasonable accuracy from the anterior and lateral positions.

Clinical anatomy of the retrocalcaneal bursa.

The goal of the study was to perform a detailed anatomical description of the retrocalcaneal bursa (RB). Its morphological arrangement was studied on 10 fresh and 30 embalmed lower extremities by microdissection and light microscopy. The RB was present constantly and in all the cases contained 1-2 cm long synovial fold, beginning on the upper wall of RB and distally interposed between the anterior surface of the Achilles tendon and the posterior surface of the calcaneal tuberosity. The volume of RB was 1-1.5 ml. The histological analysis confirmed that the inner surface of the superior and posterior wall of RB have been covered by unilayered synovial membrane, projecting into synovial villi of different shapes and sizes. In the ceiling of RB, delicate fascicle of skeletal muscle fibers was discovered, radiating distally into the regularly present synovial fold. The whole bottom of RB has been covered by 200-500 microm layer of fibrous cartilage into which the calcaneal tendon attached. The cartilagineous layer continued anteroproximally to cover the whole bursal surface of the calcaneal tuberosity, where the thickness of the cortical bone was reduced on mere 50 microm. The obtained results can be used in the improvement of the differential diagnostics and therapy of diagnostics and therapy of the retrocalcaneal bursitis as well as of other kinds of achillar enthesopathies and heel pain.