M. articularis genus. Observations on arrangement and consideration of function

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.

Ultrasound Imaging of the Articularis Genus Muscle: Implications for Ultrasound-Guided Suprapatellar Recess Injection

Elucidating its dynamic interaction within the knee joint, this exploration delves into the awareness regarding the articularis genus muscle for ultrasound-guided suprapatellar recess injections. While injections into the infrapatellar recess may proceed without ultrasound guidance, we highlight concerns regarding the potential cartilage injury. In contrast, especially with ultrasound guidance, suprapatellar recess injections significantly mitigate this risk, especially in the case of collapsed recess. Originating from the distal femur and vastus intermedius, the articularis genus muscle influences the tension of the suprapatellar recess during knee motion. Sonographically identifying this muscle involves visualizing the slender linear structure of the suprapatellar recess, with guidance on differentiation from the vastus intermedius. We provide a succinct approach to ultrasound-guided suprapatellar recess injections, emphasizing needle insertion techniques and strategies to prevent fluid accumulation. In conclusion, this study serves as a concise clinician's guide, underscoring the significance of the articularis genus muscle's sonoanatomy in ultrasound-guided suprapatellar recess injections. Ultimately, procedural precision and patient safety can be advanced in this aspect.

The articularis genu muscle and its relevance in oncological surgical margins

Aims

The aticularis genu (AG) is the least substantial and deepest muscle of the anterior compartment of the thigh and of uncertain significance. The aim of the study was to describe the anatomy of AG in cadaveric specimens, to characterize the relevance of AG in pathological distal femur specimens, and to correlate the anatomy and pathology with preoperative magnetic resonance imaging (MRI) of AG.

Methods

In 24 cadaveric specimens, AG was identified, photographed, measured, and dissected including neurovascular supply. In all, 35 resected distal femur specimens were examined. AG was photographed and measured and its utility as a surgical margin examined. Preoperative MRIs of these cases were retrospectively analyzed and assessed and its utility assessed as an anterior soft tissue margin in surgery. In all cadaveric specimens, AG was identified as a substantial structure, deep and separate to vastus itermedius (VI) and separated by a clear fascial plane with a discrete neurovascular supply. Mean length of AG was 16.1 cm ( ± 1.6 cm) origin anterior aspect distal third femur and insertion into suprapatellar bursa. In 32 of 35 pathological specimens, AG was identified (mean length 12.8 cm ( ± 0.6 cm)). Where AG was used as anterior cover in pathological specimens all surgical margins were clear of disease. Of these cases, preoperative MRI identified AG in 34 of 35 cases (mean length 8.8 cm ( ± 0.4 cm)).

Results

AG was best visualized with T1-weighted axial images providing sufficient cover in 25 cases confirmed by pathological findings.These results demonstrate AG as a discrete and substantial muscle of the anterior compartment of the thigh, deep to VI and useful in providing anterior soft tissue margin in distal femoral resection in bone tumours.

Conclusion

Preoperative assessment of cover by AG may be useful in predicting cases where AG can be dissected, sparing the remaining quadriceps muscle, and therefore function.

Cite this article: Bone Joint Open 2020;1-9:585–593.

Isometric Contraction of the Quadriceps Improves the Accuracy of Intra-Articular Injections into the Knee Joint via the Superolateral Approach

Background:

Intra-articular injection is an important technique for treating rheumatoid arthritis and osteoarthritis of the knee. However, medication is often inaccurately injected outside of the joint. We devised an intra-articular injection method in which the needle is inserted into the suprapatellar bursa while the patient maintains isometric contraction of the quadriceps. This isometric contraction method is based on the concept that isometric contraction of the quadriceps induces contraction of the articularis genus muscle, thus expanding the lumen of the suprapatellar bursa.

Methods:

Intra-articular injections were performed on 150 osteoarthritic knees without effusion. The knees were alternately assigned to the isometric quadriceps method group (75 knees) and non-activated quadriceps method group (75 knees). Prior to joint injection, the anterior-posterior dimension of each suprapatellar bursa was measured to ascertain its expansion. The isometric quadriceps method was performed with the quadriceps and the articularis genus muscle maintained in a contracted state. The non-activated quadriceps method was performed in a relaxed state. Ultrasound guidance was not used for either method. Subsequently, an ultrasonic probe was used only to confirm whether the intra-articular injections were successful. We compared the accuracy of injections performed between the 2 groups.

Results:

Suprapatellar expansion was significantly larger (p < 0.001) using the isometric quadriceps method (2.1 ± 1.4 mm [range, 0 to 5 mm]) than using the non-activated quadriceps method (0.8 ± 0.7 mm [range, 0 to 2 mm]). The percentage of accurate intra-articular injections was significantly higher (p = 0.0287) using the isometric quadriceps method (93%) compared with the non-activated quadriceps method (80%).

Conclusions:

In comparison with the non-activated quadriceps method, the isometric quadriceps method led to a larger expansion of the suprapatellar bursa, which should lead to more accurate intra-articular injections. The isometric quadriceps method is effective in reducing inaccurate injections into the synovium or surrounding fatty tissues.

Clinical Relevance:

Putting force on the quadriceps muscle increases the success rate of intra-articular injection of the knee. The results of this study could provide a clinically relevant injection technique for future treatment.

The Anatomy of the Articularis Genus Muscle and Its Relation to the Extensor Apparatus of the Knee

Background:

The anatomy of the articularis genus muscle has prompted speculation that it elevates the suprapatellar bursa during extension of the knee joint. However, its architectural parameters indicate that this muscle is not capable of generating enough force to fulfill this function. The purpose of the present study was to investigate the anatomy of the articularis genus, with special emphasis on its relationship with the adjacent vastus intermedius and vastus medialis muscles.

Methods:

The articularis genus muscle was investigated in 18 human cadaveric lower limbs with use of macrodissection techniques. All components of the quadriceps muscle group were traced from origin to insertion, and their affiliations were determined. Six limbs were cut transversely in the middle third of the thigh. The modes of origin and insertion of the articularis genus, its nerve supply, and its connections with the vastus intermedius and vastus medialis were studied.

Results:

The muscle bundles of the articularis genus were organized into 3 main layers: superficial, intermediate, and deep. The bundles of the superficial layer and, in 60% of the specimens, the bundles of the intermediate layer originated from both the vastus intermedius and the anterior and anterolateral surfaces of the femur. The bundles of the deep layer and, in 40% of the specimens, the bundles of the intermediate layer arose solely from the anterior surface of the femur. The distal insertion sites included different levels of the suprapatellar bursa and the joint capsule. A number of connections between the articularis genus and the vastus intermedius were found. While the vastus medialis inserted into the whole length of the vastus intermedius aponeurosis, it included muscle fibers of the articularis genus, building an intricate muscle system supplied by nerve branches of the same medial deep division of the femoral nerve.

Conclusions:

The articularis genus, vastus medialis, and vastus intermedius have a complex, interacting architecture, suggesting that the articularis genus most likely does not act as an independent muscle. With support of the vastus intermedius and vastus medialis, the articularis genus might be able to function as a retractor of the suprapatellar bursa. The finding of likely interplay between the articularis genus, vastus intermedius, and vastus medialis is supported by their concurrent innervation.

Clinical Relevance:

The association between the articularis genus, vastus medialis, and vastus intermedius may be more complex than previously believed, and this close anatomical connection could have functional implications for knee surgery. Dysfunction, scarring, or postoperative arthrofibrosis of the sophisticated interactive mechanism needs further investigation.

UPDATING OF THE ANATOMY OF THE EXTENSOR MECHANISM OF THE KNEE USING A THREE-DIMENSIONAL VIEWING TECHNIQUE

The knee extensor mechanism is a complex structure formed by the quadriceps muscle and tendon, the patella, the patellar tendon and the ligaments that surround and help stabilize the knee. Through using a three-dimensional viewing technique on images of the knee extensor apparatus, we aimed to didactically show the structures that compose this bone-muscle-ligament complex. Anatomical dissection of the knee with emphasis on the structures of its extensor mechanism was performed, followed by taking photographs using a camera and lenses suitable for simulating human vision, through a technique for constructing three-dimensional images. Then, with the aid of appropriate software, pairs of images of the same structure from different angles simulating human vision were overlain with the addition of polarizing layer, thereby completing the construction of an anaglyphic image. The main structures of the knee extensor mechanism could be observed with a three-dimensional effect. Among the main benefits relating to this technique, we can highlight that in addition to teaching and studying musculoskeletal anatomy, it has potential use in training for surgical procedures and production of images for diagnostic tests.

Magnetic resonance imaging of the extensor mechanism

Anterior knee pain is associated with many different causes. The clinical diagnosis may be unclear when the patient initially presents for evaluation. Magnetic resonance (MR) imaging is a valuable modality with high diagnostic accuracy in the evaluation of extensor mechanism pathology, which commonly presents with anterior knee pain. The most common disorders include patellar fracture, patellofemoral tracking abnormalities, tendon trauma and degeneration. These injuries manifest with characteristic patterns on MR imaging. This article discusses normal anatomy, common injuries, and diagnostic pitfalls on MR imaging.

A study of the anatomy and injection techniques of the ovine stifle by positive contrast arthrography, computed tomography arthrography and gross anatomical dissection

Although ovine stifle models are commonly used to study osteoarthritis, meniscal pathology and cruciate ligament injuries and repair, there is little information about the anatomy of the joint or techniques for synovial injections. The objectives of this study were to improve anatomical knowledge of the synovial cavities of the ovine knee and to compare intra-articular injection techniques. Synovial cavities of 24 cadaver hind limbs from 12 adult sheep were investigated by intra-articular resin, positive-contrast arthrography, computed tomography (CT) arthrography and gross anatomical dissection. Communication between femoro-patellar, medial femoro-tibial and lateral femoro-tibial compartments occurred in all cases. The knee joint should be considered as one synovial structure with three communicating compartments. Several unreported features were observed, including a communication between the medial femoro-tibial and lateral femoro-tibial compartments and a latero-caudal recess of the lateral femoro-tibial compartment. No intermeniscal ligament was identified. CT was able to define many anatomical features of the stifle, including the anatomy of the tendinous synovial recess on the lateral aspect of the proximal tibia under the combined tendon of the peroneus tertius, extensor longus digitorum and extensor digiti III proprius. An approach for intra-articular injection into this recess (the subtendinous technique) was assessed and compared with the retropatellar and paraligamentous techniques. All three injection procedures were equally successful, but the subtendinous technique appeared to be most appropriate for synoviocentesis and for injections in therapeutic research protocols with less risk of damaging the articular cartilage.

Articularis genus: an anatomic and MRI study in cadavers

BACKGROUND

The articularis genus muscle is closely associated with the anterior aspect of the knee joint and may act to elevate or retract the suprapatellar bursa. Its form and function are poorly understood. The purpose of this study was to define the morphology of the articularis genus and its relationship to the suprapatellar bursa.

METHODS

The articularis genus muscle was investigated in twenty-two human lower limbs obtained from eleven donors (six men and five women; mean age at death, eighty-three years). Eighteen of these limbs underwent magnetic resonance imaging (MRI) followed by dissection. The number, length, physiological cross-sectional area, attachment sites, and orientation of individual fascicles, muscle bundles, and whole muscles were recorded. The remaining four limbs underwent immunohistochemical analysis to determine muscle fiber types.

RESULTS

The articularis genus comprised multiple layered muscle bundles originating from the anterior, anterolateral, and/or anteromedial surfaces of the distal third of the femur. Distal attachment sites included the proximal and/or posterior wall of the suprapatellar bursa, the deep surface of the distal tendon of the vastus intermedius, and the medial and lateral aspects of the knee joint capsule. On dissection, the muscle was observed to consist of a mean of seven muscle bundles (range, four to ten), but only a mean of four bundles were observed on MRI scans (p &lt; 0.0001). The mean cross-sectional area of the articularis genus (and standard deviation) was 1.5 ± 0.7 cm2, and its mean fascicular length and bundle physiological cross-sectional area were 5.9 ± 1.0 cm and 0.2 ± 0.1 cm2, respectively. The articularis genus displayed a mixed fiber type, with the proportion of type-I fibers varying among specimens (range, 39.9% to 76.4%).

CONCLUSIONS

These findings highlight the complex and variable anatomy of the articularis genus, particularly with respect to the number of bundles and the distal attachment sites. Distinguishing the superficial bundles of the articularis genus from the vastus intermedius on MRI can be difficult.

CLINICAL RELEVANCE

Given its relationship to the anterior aspect of the knee joint and its association with the suprapatellar bursa, the articularis genus may be a neglected cause of undifferentiated anterior knee pain.

Synovial recesses of the knee: MR imaging review of anatomical and pathological features

The knee joint is a complex anatomical structure playing host to a wide variety of pathological processes. Knowledge of the anatomy of the synovial recesses and plicae relating to the knee is important, as the appearance of pathology in these unusual locations may, even for commonly encountered conditions, lead to diagnostic uncertainty. This review article discusses the magnetic resonance imaging (MRI) anatomy of the knee joint with an emphasis on the synovial recesses and plicae. The MRI appearance of a variety of synovial and osteochondral diseases that may involve these sites is illustrated.

Insertion of the pectoralis major into the shoulder joint capsule

The pectoralis major muscle is subject to various morphologies. One presumably very rare variation is insertion of this muscle into the shoulder joint. During the routine dissection of the right upper extremity of an adult male cadaver a distinct separate tendinous insertion into the shoulder joint capsule was identified. This vertical tendon (7 mm x 6 cm) traveled just lateral to the long head of the biceps brachii muscle and terminated into the fibrous aspect of the joint capsule without penetrating it. Mechanical traction on the humeral attachment of the pectoralis major resulted in anteroinferior displacement of the shoulder joint capsule. The possible embryologic origin of this variation is discussed. Clinicians may wish to consider potential attachment of the pectoralis major into the capsule of the shoulder joint in diagnosing pathology of this region.