Synovial Pouch Research Articles

Ultrasonography of the normal donkey tarsus (equus asinus)

Tarsal joint illness is a frequent source of hind limb lameness due to the complex anatomy of the region and the presence of numerous bony and soft tissue structures. Proper lameness diagnosis aims to discover the structure provoking lameness. Ultrasonography documents valuable information of soft tissues and characterizes soft tissue injuries that have heretofore been difficult to obtain either noninvasively or via radiography. The objectives of the current study were to develop and describe a standardized ultrasonographic protocol for investigation of the tarsal region in donkeys. The donkey tarsal anatomy was investigated in 5 cadavers and the tarsi of 11 healthy lameness free adult donkeys were echographically investigated. The dorsal, plantar, lateral and medial aspects of the tarsal region were substantially evaluated at four anatomical landmarks in both the longitudinal and horizontal planes using a multi-frequency 5–12 MHz linear transducer. Sonoanatomy of the extensor and flexor tarsal tendons, collateral and plantar ligaments, and synovial pouches was delineated and described. Systematic echography of the tarsal region allowed accurate localization and thorough exploration of various soft tissues of clinical interest in the donkey tarsus. Sonograms provided in this study should serve as a reference database for tarsal ultrasonography in clinical circumstances.

“Rice bodies” symptoms on magnetic resonance imaging of the shoulder in a patient with rheumatoid arthritis

The “rice bodies” symptom on magnetic resonance imaging of the shoulder joint in patients with rheumatoid arthritis is a rare but specific finding characterized by the presence of multiple small, round, rice-grain-like structures in the synovial fluid of the joint, synovial pouches, or sheaths. The etiology of the “rice bodies” is still not fully understood. They are suggested as the result of microinfarcts of the synovial membrane in patients with rheumatoid arthritis or other inflammatory joint diseases. Clinically, the “rice bodies” symptom may cause pain, but not in every case. Among radiological diagnostic methods, magnetic resonance imaging is the leading method for the detection of rice bodies. This article presents a clinical case of “rice bodies” symptoms diagnosed by magnetic resonance imaging in a patient with a long history of rheumatoid arthritis who presented with a painless enlargement in the left shoulder. Computed tomography and magnetic resonance imaging of the left shoulder could detect “rice bodies” as a manifestation of an underlying disease and determine further treatment techniques.

Arthroscopic approaches to and anatomy of the shoulder joint of cattle: a cadaver study

BackgroundArthroscopic surgery is described as a minimally invasive technique for diagnosis, exploration and treatment of joint disorders. It allows intraarticular structures to be assessed accurately, thereby improving the diagnostic capabilities, and it broadens the spectrum of surgical techniques feasible for treatment of articular pathologies in cattle.This study aimed to assess for cattle the described arthroscopic approaches to the shoulder joint of horses, and to describe the appearance of the corresponding intraarticular structures of the shoulder joint. Additionally, to perform histological examination where tissues were identified and assessed arthroscopically, but the tissue type was uncertain using cadaveric limbs from cattle of different age categories without any signs of orthopedic diseases of the front limbs.ResultsAn anatomic and arthroscopic investigation with 34-cadaveric forelimbs from 20-cattle was performed. The arthroscope was inserted either immediately cranial or 1-cm caudal to the tendon of the infraspinatus muscle for the cranial and caudal approaches, respectively. The shoulder joints were examined with the limbs in either horizontal non-pulled position, abducted non-pulled position using a three-pod limb holder adjustable in height, or horizontal manually pulled position. Arthroscopy was performed using a rigid 30°arthroscope (18-cm length, 4-mm outer diameter) to view the synovial pouches with their synovial villi and the following structures: cranial rim of the glenoid, cranial portion of the humeral head, incisura-glenoidalis, caudal rim of the glenoid, caudal portion of the humeral head, and cranial and caudal cul-de-sac. Abduction of the limb allowed improved visualization of the lateral portion of the joint. Pulling the limb facilitated investigation of the medial portion of the joint. Generally, the distention range was higher in younger as compared to adult cattle, and visualization of the medial portion of the joint was, therefore, facilitated in younger animals. The main complications observed were subcutaneous fluid extravasations and partial-thickness articular cartilages wear-lines.ConclusionThe described arthroscopic techniques allowed good overall visualization of the most relevant anatomical structures within the healthy cadaveric joint. Further investigations are warranted to evaluate the diagnostic and therapeutic applications of these techniques and the prognosis of arthroscopic surgery as a tool for the treatment of joint lesions.

Возможности сонографических исследований вспомогательных элементов интактного коленного сустава

The paper presents the results of sonographic studies of auxiliary elements (patella, patellar ligament, meniscus, cruciate ligaments) of 600 knee joints of adults from 21 to 80 years. It was established that it is possible to visualize these auxiliary elements by sonography, to determine their morphometric characteristics and age-related changes. It is shown that the age features of the cruciate ligaments structure of the knee joint are due to the change in their mineral composition and the strength of the connective tissue fibers. The obtained data indicate a wide range of variant anatomy of the investigated structures. Synovial pouches and pterygoid folds in the intact knee joint are not liable. The results of the study can be used as a control in the diagnosis of diseases and traumatic injuries of the knee joint.

Ultrasonographic imaging of the temporomandibular joint in healthy cattle and pathological findings in one clinical case

AIMS: To describe the normal ultrasonographic appearance of the temporomandibular joint (TMJ) in cattle, and to describe the ultrasonographic pathology of the TMJ as assessed in one cow with TMJ disease.METHODS: The TMJ of 12 healthy Holstein-Friesian cows were examined using a portable ultrasonographic unit with a 7.5 MHz linear probe and a 6.0 MHz convex probe. Each TMJ was scanned in a rostrolateral, lateral and caudolateral plane. In addition, the TMJ of one 2-year-old cow with clinical signs of food retention in the mouth, head tilt, swelling and pain in the right TMJ region and an infected horn fracture was examined ultrasonographically.RESULTS: The bone surfaces of the temporal process, the zygomatic process and the temporal bone, the larger muscles of the TMJ region, the superficial temporal vein, and the parotid salivary gland could be imaged in all normal healthy cattle. Using the linear probe, the joint capsule was visible in 17/24 (71%) cases in the caudolateral plane, but the articular disc could not be visualised. With the convex probe, the joint capsule could be imaged in all cases in the caudolateral plane, and the articular disc in 13/24 (54%) cases in the caudolateral plane. It was never possible to see the synovial pouch in healthy cattle using either probe. By contrast, in the cow diagnosed with septic arthritis of the right TMJ, a marked anechoic and heterogeneous hypoechoic effusion of the TMJ with distension of the joint capsule was visualised.CONCLUSIONS: The results of this descriptive study serve to provide a reference for ultrasonography of pathological conditions of the TMJ region in cattle.CLINICAL RELEVANCE: As many veterinarians are equipped with ultrasound machines with 5–8 MHz linear rectal probes, the authors recommend using these probes for further investigation of clinical cases with swelling of the TMJ region and/or masticatory problems of unclear origin to exclude or diagnose TMJ disorders.

Transthecal Arthroscopy of the Palmar Distal Interphalangeal Joint in the Horse: A Cadaver Study.

To describe a transthecal approach to the palmar pouch of the distal interphalangeal joint (DIPJ) in horses and compare it with the conventional blind arthroscopic technique. Ex vivo study. Cadaver forelimbs (n = 26 pairs) from mature horses. One limb from each pair was randomly assigned to each arthroscopic approach (conventional or transthecal). The conventional arthroscopic approach was performed as previously described and the transthecal approach was performed through sharp dissection of the distal reflection of the digital flexor tendon sheath (DFTS). The proportion (0-100%) of the navicular bone, palmar aspect of the condyles of the 2nd phalanx, collateral sesamoidean ligaments, and palmar synovial pouches of the DIPJ visualized by each approach was estimated. Limbs were dissected and iatrogenic damage of relevant structures was assessed. Nondirectional Mann-Whitney U-test was used to compare groups. Significance was set at P < .05. The transthecal approach provided greater visualization of the navicular bone (P < .001), palmar aspect of the 2nd phalanx (P < .001), and palmar synovial pouches of the DIPJ (P < .001) than the conventional approach. There were no significant differences in iatrogenic damage between approaches. The transthecal approach provides improved visualization of the palmar aspect of the DIPJ compared to the conventional blind approach and may be useful in nonseptic conditions of the DIPJ. However, because of the creation of communication with the DFTS, use of the transthecal approach for suspected synovial sepsis of the DIPJ may be contraindicated.

Reliability and sensitivity of the 20-meter walk test among patients with knee osteoarthritis

Purpose: The 20-meter walk test is a physical function measure commonly used in clinical research studies and rehabilitation clinics to measure gait speed and monitor changes in patients’ physical function over time. Unfortunately, the reliability and sensitivity of this walk test are not well defined and therefore limit our ability to evaluate changes in gait speed. The aim of this study was to assess the reliability and sensitivity of the 20-meter walk test, at a self-selected pace, among patients with knee osteoarthritis (OA). Methods: This was a measurement reliability study that included fifteen consecutive participants enrolled in a randomized-controlled trial of intra-articular corticosteroid injections for knee OA. The study sample included consecutive participants attending screening (Day 1) and baseline (Day 2) visits between July 2011 and December 2011. All participants met the American College of Rheumatology criteria for OA; had radiographic knee OA, as defined by Kellgren-Lawrence grade 2 or 3; and knee synovitis, defined by a synovial pouch depth greater than 2.0 mm measured by ultrasound. All participants were also required to have knee pain symptoms, defined as a WOMAC Osteoarthritis Index (version 3.1, 5-point Likert) pain subscore > 2 at the beginning of their first visit (Day 1). All participants completed 4 trials on 2 separate days, 7 to 21 days apart (8 trials total). Each day was divided into 2 sessions, which each involved 2 walking trials. Day 1 contained sessions 1 (trial 1 and 2) and session 2 (trial 3 and 4) and Day 2 contained session 3 (trial 5 and 6) and session 4 (trial 7 and 8). All trials were administered by the same investigator following a standardized script and protocol. We compared walk times between trials with Wilcoxon signed-rank tests. We also calculated Spearman correlation coefficients to assess the relationship between sessions. Finally, smallest detectable differences (SDD) were calculated to estimate the sensitivity of the 20-meter walk test. Results: Participants were 53% female, 67% (n 1⁄4 10) Caucasian, on average 61.0 7.8 years of age and had a mean body mass index of 28.9 5.4 kg/m2. Twelve participants (80%) had Kellegren-Lawrence Grade 1⁄4 3. WOMAC pain scores were 5.3 1.3 on Day 1 and 4.9 2.0 on Day 2. The figure depicts walk times across trials. We found that walking times in the first session were slower than the second session (median difference 1⁄4 0.53 seconds, -0.04 m/s; Table). We also found that the correlation between session 1 and sessions 3 and 4 were lower than the correlations between session 2 and sessions 3 and 4 (Table). Therefore, we considered the first session of each day a practice session and calculated the SDD between the second session of each day (session 2 and 4). SDD were -2.59 seconds (walking slower) and 1.65 seconds (walking faster). There was a potential systematic bias of participants walking slower during the second session on Day 2 compared to the second session of Day 1 (10 [67%] participants walked slower in session 4 compared to session 2; based on differences below zero). Conclusions:We found that the average of the first two 20-meter walk times did not agree with subsequent average walk times among participants with knee OA. Therefore, practice trials may be advised prior to a measuring a participants walk time. Despite concerns about thewalk times of session 1, the following sessions were reliable and had good agreement. Finally, changes in walk time between -2.59 seconds (walking slower) and 1.65 seconds (walking faster) should be considered within the range of normal variability of 20-meter walking speed.

Magnetic resonance imaging of the equine temporomandibular joint anatomy

In human medicine, magnetic resonance imaging (MRI) is considered the 'gold standard' imaging procedure to assess the temporomandibular joint (TMJ). However, there is no information regarding MRI evaluation of equine TMJ. To describe the normal sectional MRI anatomy of equine TMJ by using frozen and plastinated anatomical sections as reference; and determine the best imaging planes and sequences to visualise TMJ components. TMJs from 6 Spanish Purebred horse cadavers (4 immature and 2 mature) underwent MRI examination. Spin-echo T1-weighting (SE T1W), T2*W, fat-suppressed (FS) proton density-weighting (PDW) and fast spin-echo T2-weighting (FSE T2W) sequences were obtained in oblique sagittal, transverse and dorsal planes. Anatomical sections were procured on the same planes for a thorough interpretation. The oblique sagittal and transverse planes were the most informative anatomical planes. SE T1W images showed excellent spatial resolution and resulted in superior anatomic detail when comparing to other sequences. FSE T2W sequence provided an acceptable anatomical depiction but T2*W and fat-suppressed PDW demonstrated higher contrast in visualisation of the disc, synovial fluid, synovial pouches and articular cartilage. The SE T1W sequence in oblique sagittal and transverse plane should be the baseline to identify anatomy. The T2*W and fat-suppressed PDW sequences enhance the study of the articular cartilage and synovial pouches better than FSE T2W. The information provided in this paper should aid clinicians in the interpretation of MRI images of equine TMJ and assist in the early diagnosis of those problems that could not be diagnosed by other means.

Anatomy of the equine temporomandibular joint: study by gross dissection, vascular injection and section

The minute anatomy of the temporomandibular joint (TMJ) in horses is poorly documented in the literature. To examine in detail the anatomy of the normal equine TMJ and the relationship of the joint to adjacent structures. The anatomy of the TMJ was examined in 12 equidae using dissections, synovial and vascular injections and frozen and plastinated sections. Relevant structures were photographed. Rostral and caudal compartments were identified in the dorsal and ventral synovial pouches of the TMJ. Lateral and caudal ligaments were identified and attachments of the masticatory muscles over the TMJ were documented. Direct relationships between the TMJ and components of the ear were found, and the vascular supply described. This joint is related to some components of the ear as in man, and has its own peripheral vascular supply. A knowledge of the detailed anatomy of the equine TMJ is a prerequisite to interpreting the imaging techniques, and will enable improved diagnosis of TMJ pathologies.

Biocompatibility testing of simulated total joint arthoplasty articulation debris

Surface characterization was performed to evaluate the surface condition of an uncoated cobalt alloy disc (control), and discs with medium and thick boron coatings for total joint articulating surfaces. Discs were characterized by scanning electron microscopy before and after dissolution studies. Chemical analyses of elemental transfer to the solution were assessed to evaluate the surface stability of the new coating. An in vivo biocompatibility study for particulates [of boron (B), titanium alloy (Ti), cobalt alloy (Co), and combinations of B + Ti and B + Co] was performed using a rat air pouch model. The inflammatory reactions to particulates were evaluated histologically and histochemically. No physical alteration was seen in the discs after the dissolution studies, and the elemental transfer to the dissolution solution was minimal. The cytokines, tumor necrosis factor (TNFalpha), and histology results from these simulated debris showed similar and moderate level responses magnitudes for the boron and mixtures and the primary alloy particulates. The conclusion from this initial study was that assessments of the coated discs showed physical properties similar to control. Also results from the in vivo studies of simulated wear debris from boron coatings on titanium and cobalt alloys demonstrated biocompatibility profiles that were mild to moderate and similar to prior analyses of wear debris products in synovial pouch models.

ULTRASONOGRAPHIC ANATOMY OF THE TEMPOROMANDIBULAR JOINT IN HEALTHY PURE‐BRED SPANISH HORSES

The objective was to describe the normal ultrasonographic appearance of the soft tissue and bony structures of the temporomandibular joint in Pure-Bred Spanish horses using frozen and plastinated sections performed as anatomical references. The temporomandibular joint of five healthy Pure-Bred Spanish horses and the head specimens from 12 Pure-Bred Spanish cadavers that were subjected to euthanasia for reasons other than temporomandibular joint problems were studied sonographically and anatomically. An 11 MHz linear-array transducer was used to obtain longitudinal ultrasonographic images of the temporomandibular joint from rostral, lateral, and caudal approaches. For anatomic study, a gross dissection was performed on six temporomandibular joints. The other six head specimens were first frozen at -30 degrees C for 48h and then, at -70 degrees C for a week. Three millimeter thick anatomic sections were collected in the same plane as the sonographic planes. These sections were plastinated, photographed, and compared with the corresponding ultrasonographic images. The articular surfaces, the articular cartilage, the disc, the intra-articular fat tissue, the joint capsule, and other structures were clearly visualized sonographically. Structures identified on the ultrasonographic images were in accordance with those identified on the corresponding anatomic sections. We confirmed the appearance of structures of the equine temporomandibular joint that have been described previously but we also identified the caudal fibrous expansion of the disc, the caudal compartment of the dorsal synovial pouch, and the lateral ligament. Our results define a reference that will aid in sonographic evaluation of the equine temporomandibular joint region.

Arthroscopic Anatomy of the Equine Temporomandibular Joint

To develop an arthroscopic approach to, and describe the arthroscopic anatomy of, the equine temporomandibular joint (TMJ). Cadaveric study, after which the technique was tested in horses. Ten cadaveric equine heads and 5 normal horses (age, 5-13 years; weight, 425-545 kg). Specimens or horses were positioned in right lateral recumbency. After fluid distention of the TMJ, arthroscopic portals were made in the dorsal compartment over the most prominent portion of the joint outpouching (caudodorsal approach) and in rostral and intermediate locations. The joint was explored and photographed. Positional changes in the mandible were made to determine if observation of the joint could be improved. Instrument portals were created to assess the feasibility of surgical arthroscopy. Cadaveric heads were dissected to assess iatrogenic damage, whereas experimental horses were observed for postoperative complications for 30 days. A caudodorsal arthroscopic approach provided the best evaluation of the dorsal compartment of the TMJ. The approach allowed observation of the rostral and caudal synovial pouches and the lateral aspect of the joint including the articular disc. Examination of the medial aspect of the joint was limited to the most rostral and caudal aspects. Access to the lateral aspect of the ventral compartment of the TMJ was precluded by the position of the transverse facial artery and vein. In specimens, iatrogenic damage was minimal and limited to the articular fibrocartilage, articular disc, and penetration of the parotid salivary gland. If the latter also occurred in horses, no adverse effects were noted. In horses, mild fluid extravasation occurred and resolved within 1 day. All horses ate normally after surgery but had periarticular swelling and mild pain upon palpation of the TMJ for 2 days. A caudodorsal arthroscopic approach to the TMJ allowed adequate observation of the lateral aspect of the dorsal compartment of the joint. Access to the ventral compartment was precluded by the location of the transverse facial artery and vein. Conditions affecting the lateral and caudal aspects of the dorsal compartment of the TMJ should be visible by arthroscopy.

Aloe vera and the inflamed synovial pouch model.

Administration of air under the skin produced a pouch wall that closely resembled a synovium in that the inner lining was made up of macrophages and fibroblasts. Administration of 1% carrageenan directly into the 7-day-old air pouch produced an inflammation characterized by an increased number of mast cells in pouch fluid as well as an increase in wall vascularity. A punch biopsy weight of the pouch wall did not reveal an increase in 1% carrageenan-treated animals. However, a 10% Aloe vera treatment of carrageenan-inflamed synovial pouches reduced the vascularity 50% and the number of mast cells in synovial fluid 48%. The pouch wall punch biopsy weight was increased by A. vera, which was verified by histologic examination of the inner synovial lining. Aloe vera stimulated the synovial-like membrane, as evidenced by an increased number of fibroblasts, suggesting that A. vera stimulated fibroblasts for growth and repair of the synovial model. The synovial air pouch can be used to study simultaneously the acute anti-inflammatory and fibroblast stimulating activities of A. vera.

上外側穿刺法による顎関節鏡視診断について

In arthroscopic procedure, there are several methods to approach into the superior joint cavity of TMJ. However, it is difficult to obtain total vision of the superior joint cavity by a single approach. Here, we present a supero-mid-lateral approach by which almost all of the supeior joint cavity can be visualized. In this technique the point of insersion of trocar is perpendicular to the skin and at the highest point of lateral aspect of mandibular fossa. Arthroscope can be moved along the transverse axis of both the anterior and posterior synovial pouch, and longitudinally along the lateral discal groove in the superior joint cavity.This approach was applied in 24 joints of 15 closed-lock cases. Anterior displacement of the disk was observed in all 24 joints. Among these there were antero-medial disk rotation in 19 joints and antero-lateral in one joint. Disk adhesions were observed in 24 joints at lateral area, 23 joints at anterior synovial pouch, 11 joints at medial area and 4 joints at posterior synovial pouch. Nineteen perforations were observed in 18 joints of 11 cases. Sixteen of these perforations were in the lateral aspect of the disk and the remaining three were in posterior and medial aspects.The results of the presented cases suggest that the supero-mid-lateral approach is highly effective in tempromandibular joint arthroscopy.

けん修復に関する実験的研究 家兎膝関節内におけるけん修復像の組織学的検討

We engaged in experimental study modeled by Lundborg's studies in which he investigated the healing process of rabbit flexor tendon in synovial pouch of the knee joint. We studied the sutured tendons histologically which were placed in the rabbit knee joint and taken out after four five and six weeks. Adhesion of the sutured tendon to the synovial membrane was formed in strong granulation about the suturedsite but nonadhesive tendon was formed in weak granulation. We confirmed the intrinsic healing of tendon from this study.

Leakage of radioactive particle systems from a synovial joint studied with a gamma camera. Its application to radiation synovectomy.

We have determined rates of leakage of radioactivity from a rabbit synovial pouch in vivo for a number of particle systems of varying sizes and differing resistance to degradation. The estimates were made using a gamma scintillation camera and without killing the test animals. The lowest leakage at twenty-four hours was seen with inert carbonized microspheres and the highest rates were seen with surface-labeled particles of biodegradable denatured human serum albumin and with erythrocytes. The carbonized microspheres had no adverse long-term effects on the health of the animals' articular cartilage. Results obtained with inert particles indicate that reducing the biodegradability of the particle or increasing its diameter, or both, reduces radioactivity losses from the knee joint. Large (twenty-five-micrometer-diameter) microspheres of human serum albumin incorporating the radioactivity and carbonized microspheres are suggested as potential carriers of isotopes for human radiation synovectomy.

Extraarticular fluid dissection in tissues during arthroscopy. A report of clinical cases and a study of intraarticular and thigh pressures in cadavers.

Significant fluid extravasation occurred in four knees undergoing arthroscopic meniscectomy. In one knee, a partial compromise of peripheral blood flow was transiently detected. In cadaver studies, with the joint only moderately distended, a mean pressure of 158 mm of mercury was measured. With flexion of the knee to 90°, a mean pressure of 216 mm of mercury was recorded and rupture of the synovial pouch occurred in all knees. The fluid extravasated into the thigh due to rupture of the suprapatellar pouch. Fluoresceine labeled saline was utilized to follow the course of the extravasated fluid. The saline was found to loculate about the superficial femoral artery, easily dissecting up to the femoral triangle. Elevated femoral artery pressures and quadriceps muscle interstitial pres sures were documented at a relatively early point during the course of fluid extravasation. A second pathway of extravasation of intraarticular fluid was by rupture of the semimembranous bursa. The saline then dissected beneath the pes anserinus and into the calf muscles. The study arrived at the following conclusions. First, fluid extravasation may initially occur in a subtle man ner. The surgeon should be aware of any lack of joint distension, increased fluid to distend the joint, or increased thigh tension during arthroscopy indicating extravasation. Second, joint distension should be avoided prior to knee flexion past 30 to 45° since the added compression on the fluid may easily rupture the synovial pouch. Third, caution is required in using inflow irrigation systems that exert pressure to distend the joint; an adequate outflow system is mandatory to avoid excessive joint distension during arthroscopic procedures.

THE NATURAL HISTORY OF THE RHEUMATOID METACARPO-PHALANGEAL JOINT

1. One hundred and twenty-six metacarpo-phalangeal joints affected by rheumatoid arthritis were studied macroscopically at either synovectomy or arthroplasty. 2. The sites and extent of the initial erosion corresponded with the sites and size of the synovial pouches. 3. The areas of cartilage degeneration were related to the degree of flexion, ulnar deviation and subluxation of the proximal phalanx on the metacarpal head. 4. The routine radiographic findings were not a true reflection of all the pathological changes within the joint. 5. It is suggested that by encouraging joint movement and preventing deformity the degree of cartilage degeneration may be diminished.

THE ANTERIOR CAPSULAR MECHANISM IN RECURRENT ANTERIOR DISLOCATION OF THE SHOULDER

1 . The concept of the capsular mechanism of the shoulder joint with regard to recurrent anterior dislocation of the shoulder has been defined and a survey of the literature presented. 2. An anatomical, including an embryological, investigation of shoulder joints with special reference to the structure and function of the glenoid labrum and to the variations in the arrangement of the gleno-humeral ligaments and the synovial recesses of the anterior capsular mechanism is reported. The labrum, which is generally believed to be a consistent, fibrocartilaginous structure, is shown to be a redundant portion of capsular tissue and a continuation of the capsule as it attaches to the osseous glenoid rim. The fibrocartilaginous element is confined to a small transition zone at the capsular attachment in the great majority of cases. The great variability in the arrangement of the gleno-humeral ligaments and synovial recesses is stressed, and it is shown that an anterior pouch of variable size is present when the middle gleno-humeral ligament is attached to the scapular neck and not to the labrum. 3. The basic lesions of the anterior capsular mechanism found at operation for recurrent anterior dislocation of the shoulder in twenty-five consecutive cases using a modified Bankart procedure with a standard anterior approach to the joint are reported, and the findings are correlated with the results of the anatomical investigation. In most cases the lesions were found to be of the Bankart type with or without avulsion of the periosteum of the scapular neck. In four cases, however, the soft-tissue attachment to the anterior glenoid rim was intact; in those cases a large synovial pouch was present and the middle gleno-humeral ligament was either not discernible or it arose from the scapular neck. In all cases a postero-lateral notch on the humeral head was palpable and laxity of the subscapularis could be demonstrated. When measured, the joint capacity was always greatly augmented. 4. The present work shows, from a basic standpoint, that Bankart's original idea that the recurrent state was due to the failure of healing of the fractured fibrocartilaginous glenoid labrum is no longer tenable. 5. Finally, the anomalous attachment or the insufficient development of the middle gleno-humeral ligament in certain cases of recurrent anterior shoulder dislocation is shown to provide the anatomical basis for the recurrent state in these cases; this is the weak area in the antero-inferior part of the capsule which has been described in the literature for the past hundred years. Thus we have returned to the original view of Hippocrates.