Sacroiliitis in a 55-year-old man with a history of COVID-192 months earlier and subsequent low back and perianal pain. After completing this journal-based SA-CME activity, participants will be able to: Discuss the pathophysiologic mechanisms associated with the most commonly seen MSK manifestations of COVID-19. There is an anterolateral, posteromedial and lateral compartment of the ankle typically superficial to the joint. This article is made available via the PMC Open Access Subset for unrestricted re-use and analyses in any form or by any means with acknowledgement of the original source. Once you've finished editing, click 'Submit for Review', and your changes will be reviewed by our team before publishing on the site. Axial CT image (bone window) of the chest shows subchondral serpentine lucency, adjacent sclerosis (arrows), and subchondral plate irregularity involving both humeral heads, especially on the left. Within the MSK system, COVID-19 may affect bones, muscles, the coagulation pathway, peripheral nerves, and joints. The teres minor originates at the lateral border of the scapula inferior to the infraspinatus. COVID-19 and thrombosis: searching for evidence, Rheumatological complications of Covid 19, SARS-CoV-2 and Guillain-Barr syndrome: molecular mimicry with human heat shock proteins as potential pathogenic mechanism, Are superantigens the cause of cytokine storm and viral sepsis in severe COVID-19? Alternatively, there may be effacement of the normal fascicles, producing a swollen featureless appearance (59). There is moderate subacromial-subdeltoid bursitis (solid white arrows), with tendinopathy at the junction of the supraspinatus and infraspinatus tendons and fraying (black arrow), and underlying superolateral humeral head marrow edema and irregularity (dashed arrow). Orthop J Sports Med. The articular capsule of the knee joint (commonly referred to as the capsular ligament) is the wide and lax joint capsule of the knee. The patient experienced progressive pain 3 days after her first dose of the vaccine and had no other trauma or prior shoulder injury. Although CT images may also show muscle thickening and effacement of intramuscular fat and fascial planes, MR images can better depict muscle edema, fascial stranding, and postcontrast enhancement. Many patients predictably present 13 weeks after the onset of infection with symptoms extending into the recovery phase. (A) Gray-scale US image of the right hemidiaphragm in the ninth intercostal space during the expiratory phase of respiration shows that the zone of apposition of the diaphragm measures 0.18 cm. Bony avulsion from anterior calcaneal process at the bifurcate ligament attachment site. The T2-weighted sequence is necessary to distinguish between pathologic fluid collections such as a bursa or cyst and the injected intra-articular contrast. Figure 12-17. (2000). Indeed, the pituitary can be accessed surgically by passing instruments through the sphenoid bone and sinus. Grade 6 separation differs from grade 5 injuries as the clavicle is inferiorly displaced. The sustentaculum tali is a horizontal shelf that arises from the anteromedial portion of the calcaneus.The superior surface is concave and articulates with the middle calcaneal surface of the talus.The inferior surface has a groove for the tendon of flexor hallucis longus.. Several ligamentous structures attach to the sustentaculum tali: Myonecrosis in a 44-year-old man with a history of COVID-19 acute respiratory distress syndrome and right shoulder and arm pain and swelling. Adobe Stock, Licensed to TeachMeSeries Ltd, [caption id="attachment_118647" align="aligncenter" width="787"], [caption id="attachment_15999" align="aligncenter" width="427"], [caption id="attachment_5603" align="aligncenter" width="850"]. Rotator cuff tendon tears reported in some patients may be preexisting, but the inflammatory response may contribute to symptom development. (C) Axial T2-weighted fat-suppressed MR image of the pelvis inferior to A shows edema of the left femoral nerve (arrow), consistent with compressive neuropathy. This articulation includes 3 facets: an anterior, middle and posterior facet. The end-stage of the process is arthritis and joint destruction. Make the changes yourself here! It is named after Jacques Lisfranc De Saint Martin(1790-1847), French surgeon 2. This classification was proposed by Geist 7 in 1914 and remains the most widely used classification system (c. 2021). Various roles have been suggested: The paranasal sinuses are formed during development by the nasal cavity eroding into the surrounding bones. Found an error? Gross anatomy. COVID-19 patients may present with articular or periarticular pain, which can be secondary to osteonecrosis (ON). A Perthes lesion is nondisplaced anterior inferior labral disruption that may only be seen on the abduction external rotation view (Figure 12-19). Microinstability (microtraumatic instability) is a general expression for lesions of the superior half of the glenohumeral joint. Web(OBQ06.131) A 14-year-old boy presents 6 months after spraining his right ankle. 4. The ACL tibial footprint substantially overlaps the anterior root lateral meniscus footprint 6.. SLAP tears (Figure 12-20) are common injuries in athletes. Occasionally, there can be leptomeningeal and spinal nerve root enhancement on brain MR images (56). The margins are then sutured together. - "Diagnosis of Anterolateral Ankle Impingement" An osseous Bankart may be repaired with a screw through the bone fragment. Structural causes for subacromial impingement are due to coracoacromial arch abnormalities: the shape and slope of the acromion, an os acromiale, coracoacromial ligament thickening, or acromioclavicular separation. It extends from the lower margin of the patella above, to the infrapatellar synovial fold below. Musculoskeletal (MSK) manifestations of COVID-19 are common but have been relatively underreported, possibly because of the severity of manifestations in other organ systems. Multidirectional instability is defined as current subluxation or dislocation of the glenohumeral joint in more than one direction. type 1 accessory navicular These include synovitis, bleeding, infection, or an allergic reaction. MR angiography, with a lack of normal enhancement in the area of thrombosis, may contribute to the diagnosis (40). Coronal oblique MRI shows findings of avascular necrosis with subchondral collapse of the medial aspect of the head (black arrow). Although US is helpful in detecting focal or patchy muscle atrophy compared with normal-appearing adjacent muscle, it may be more difficult to detect global balanced muscle abnormalities (64). There is debate in the literature about the term cytokine storm, since the circulating levels of many cytokines may be only modestly elevated despite an inflammatory dysregulation, similar to that in some patients with sepsis. Several possible mechanisms for the development of postCOVID-19 inflammatory arthritis have been proposed, the most common of which is molecular mimicry owing to viral epitopes on the spike protein causing production of autoantibodies. In general, the aetiology of impingement can The space between the supraspinatus and subscapularis is the rotator interval that contains the coracohumeral and superior glenohumeral ligaments and long head of the biceps tendon. As the disease progresses, there is formation of osteophytes, subchondral sclerosis/cyst formation, and synovitis (Figure 12-25). Gross anatomy. The depth of partial thickness tears is estimated based on a normal thickness of approximately 1.2 cm. Three main pathophysiologic pathways have been proposed to explain the effects of COVID-19 in the MSK system, including the cytokine storm, development of a prothrombotic state, and autoimmunity. Anticoagulation therapy is the biggest risk factor for developing spontaneous muscle hematoma. Multifocal ON of the foot in a 66-year-old nondiabetic woman who presented with COVID toes. SLAC tears are associated with anterior superior instability. Myonecrosis can result in substantial pain, and patients are treated supportively. Figure 12-1. (2013) American Journal of Roentgenology. (C) Three-dimensional reformatted coronal CT angiographic image shows absence of opacification of the left popliteal artery and its major branches (dashed arrow) owing to the arterial thrombosis. Each sinus is lined by a ciliated pseudostratified epithelium, interspersed with mucus-secreting goblet cells. Acute MSK symptoms, which occur within 4 weeks of infection, including fatigue and myalgia, are nonspecific (3). Figure 12-29. Capsular thickening is a normal postoperative finding on MRI. The Geist classification divides these into three types:. Additionally, patients with severe COVID-19 may have limited mobility, which promotes vascular stasis, platelet and erythrocyte aggregation, and thrombosis (9). Finally, multidirectional instability will be discussed. A full workup failed to show a gastrointestinal cause for the patients symptoms. AJR Am J Roentgenol. The maxillary nerve supplies both the maxillary sinus and maxillary teeth, and so inflammation of that sinus can present with toothache. As impingement evolves, tendinosis develops in the bursal aspect of the supraspinatus. Lesions of the labrum may be localized by quadrants or in terms of a clockface position. Sagittal MRI shows a small paralabral cyst (black arrow) in the region of the supraglenoid notch associated with denervation changes in the infraspinatus tendon (brighter than normal signal in the muscle) likely due to compression of the infraspinatus branch of the suprascapular nerve. Figure 19. The paranasal sinuses are air-filled extensions of the nasal cavity. {"url":"/signup-modal-props.json?lang=us\u0026email="}, Cruz A, Murphy A, Murphy A, et al. Patient lies supine with knee flexed 20-30 degrees over towel roll (as with anterior Knee Exam); Start with probe in long axis (LAX) anteriorly over the Patellar tendon in the infrapatellar region (as above). Note the additional enlarged supraclavicular lymph node (dashed arrow). It originates in the supraspinatus fossa (superior to the scapular spine) and attaches to the most superior aspect of the greater tuberosity. The arch stabilizes the humeral head preventing its superior subluxation. ORTHO-12A (04 )2393-1531#547279 Sequences may be tailored according to clinical indication. WebThe sinus tarsi is a tunnel between the talus and the calcaneus that contains structures that contribute to the stability of the ankle and to its proprioception but can get damaged in the sinus tarsi.. It is less common than in the hip. Sagittal MRI shows flat undersurface of the anterior lateral acromion consistent with type 1 acromion (black arrow). These findings are consistent with compete retear of the supraspinatus. Subacromial impingement is elicited in flexion or abduction. The sphenoid bone shares a close anatomical relationship with the pituitary gland. shoulder injury related to vaccine administration. Common Surgical Procedures/Associated Complications. The anterior labrum is normally larger than the posterior. (A) Axial T1-weighted nonfat-suppressed MR image of the retroperitoneum shows a heterogeneous left iliopsoas collection (arrow) with a thin peripheral dark rim related to a pseudocapsule and hemosiderin deposition, an inner ring of high signal intensity and a central core of lower signal intensity, related to blood products in various stages (concentric ring sign). Arterial thrombosis is described in 1%2% of COVID-19 patients who are critically ill. Anterior or lateral downsloping of the acromion may narrow the acromiohumeral interval and predispose patients to impingement. In contradistinction to degenerative osteoarthritis, cartilage loss is seen in a more uniform distribution and marginal erosions are characteristic. The deposits may be asymptomatic or cause mechanical or inflammatory symptoms. Figure 9. Check for errors and try again. The signal intensities of MSK hematomas are usually heterogeneous depending on the composition of blood products, without internal enhancement in the absence of an underlying mass (41). {"url":"/signup-modal-props.json?lang=us\u0026email="}, Knipe H, Parker R, Niknejad M, et al. The research exploring the configuration of the Lisfranc Ligament complex is variable 6, however typically the Lisfranc ligament extends obliquely from the lateral surface of the medial cuneiform to the medial aspect of the base of the second metatarsaland is comprised of three bands 1,4: The Lisfranc ligament can have a homogeneous low signal or striated appearance with low-to-intermediate signal intensity on MR images 1,3,4. Figure 12-10. Fig 3 The conchae have been removed, showing the various openings on the lateral wall of the nasal cavity. Each sinus is lined by a ciliated pseudostratified epithelium, interspersed with mucus-secreting goblet cells. The inferior and superior portions of the capsule are shifted to overlap each other. Os acromiale. Complete rotator cuff tear. Imaging findings for various COVID-19related MSK pathologic conditions across a variety of modalities are being recognized, which can be helpful for diagnosis, treatment guidance, and follow-up. The ligament complex acts as an important stabilizer of the midfoot, connecting the medial cuneiform to the base of the second metatarsal creating a keystone-like configuration between the medial and lateral cuneiforms. PMID: 28321426; PMCID: PMC5347434. The capsule consists of an inner synovial membrane, and an outer fibrous membrane separated by fatty deposits An incision is made in the anterior joint capsule. For example, Lucchese and Flel (11) showed cross-reactivity of SARS-CoV-2 epitopes with those on heat shock proteins 90 and 60, which could contribute to the development of Guillain-Barr syndrome (GBS). The online slide presentation from the RSNA Annual Meeting is available for this article. They are located laterally and slightly inferiorly to the nasal cavities. The muscle is an internal rotator, flexor, and adductor of the arm. Shear wave sonoelastography can be useful to quantitatively assess muscle stiffness and is an emerging technique that can help detect early abnormalities and follow progression of atrophy (65). CT and MRI are commonly performed to detect and follow findings of sarcopenia. (A) Coronal oblique T1-weighted nonfat-suppressed MR image of the sacroiliac joints shows bilateral sacroiliac erosions with irregularity of the subchondral bone plates (arrows) that are more pronounced on the iliac side of the joints. Foot pushed down and flexed up. Additionally, patients who have undergone sedation and who are critically ill are often unable to alert clinicians of their MSK symptoms. Diaphragm atrophy and poor contractility in a 46-year-old man with COVID-19 with persistent dyspnea, right hemidiaphragm dysfunction, and normal left hemidiaphragm function. Synovitis and clinical symptoms are often responsive to treatments used in other inflammatory arthropathies. Hematogenous Osteomyelitis in Infants and Children: Imaging of a Changing Disease, Put Your Shoulder Into It (and Elbow And Wrist For That Matter): Ultrasound-Guided Procedures of the Upper Extremity, Diagnostic Imaging of Inflammatory Myopathies: New Concepts and a Radiological Approach, Whole-Body MR Neurography: Clinical Applications and Imaging Findings. Full-thickness rotator cuff tear. Anterolateral impingement is thought to develop subsequent to a relatively minor injury usually consisting of forced ankle plantar flexion and supination [ 2, 6, 10 ]. The patient experienced subsequent sciatic mononeuropathy with long-standing hamstring and lower leg weakness. MR imaging of the normal hip. Intravenous contrast material is usually unnecessary since peripheral nerves in these conditions do not generally enhance. The contractility ratio, which is the thickness of the zone apposition with inspiration divided by the thickness during expiration, measures 1.1, and normal is at least 1.2. Thickening of the coracoacromial ligament as part of the coracoacromial arch may cause stenosis of the acromiohumeral interval. (J.S.W., M.S.T. Distal clavicular resection (Mumford procedure) is undertaken in advanced cases of acromioclavicular arthritis. With concurrent nerve injuries, patients may experience numbness, tingling and weakness of the ankle dorsiflexors and great toe extensors, or a footdrop.. CHARLES J. SUTRO, MAURICE M. POMERANZ, SYDNEY M. SIMON. Furthermore, the diaphragmatic excursion with deep breathing is much less than expected. The Buford complex is absence or hypoplasia of the anterior superior labrum associated with a thickened middle glenohumeral ligament. Anatomic region. An os acromiale (Figure 12-7) is an unfused acromial ossification center. Its cause is unknown. WebFigure 2. Uncommon mild flares of existing rheumatologic conditions such as RA or psoriatic arthritis have been described (79). Figure 2: Lisfranc ligamentous complex (illustration), doi:10.1148/radiographics.20.3.g00ma20819, posterior suprapatellar (prefemoral or supratrochlear) fat pad, anterior suprapatellar (quadriceps) fat pad, accessory anterior inferior tibiofibular ligament, superficial posterior tibiotalar ligament, superficial posterior compartment of the leg (calf), accessory extensor digiti secundus muscle, descending branch of the lateral circumflex, interosseous ligament ("Lisfranc ligament proper"), plantar ligament: sends bundles to the second and third metatarsal bases (variable), clearly display the transverse arch of the foot and clearly display the cross-section of the Lisfranc ligament, can clearly display the horizontal arch of the Lisfranc joint and more clearly display its surrounding ligaments and tendons, clearly display the corresponding situation of the Lisfranc joint bone and longitudinal arch of the foot, tolerably displays the Lisfranc joint dorsal ligament, poorly displays the Lisfranc ligament proper. No other findings to explain the patients symptoms were seen. Alternatively, vascular endothelial damage may allow virulent organisms to more easily penetrate vessels walls and seed surrounding tissues. 4. Clinical and imaging features established by the Assessment of SpondyloArthritis International Society (ASAS) can help confirm the diagnosis of seronegative spondyloarthropathy (31). The stability of the shoulder is maintained by static and dynamic stabilizers: principally the rotator cuff, the long head of the biceps tendon, the glenoid labrum, the joint capsule, and the coracoacromial arch. Is a Cytokine Storm Relevant to COVID-19? ABER view for MRI shows there is a tear of the anterior inferior labrum that could only be appreciated on the ABER view consistent with a nondisplaced Perthes type tear (black arrow). It is a fibrocartilaginous structure that deepens the shallow normally anteverted glenoid cavity. The joint between the talus and calcaneus is also known as the subtalar joint. Subcoracoid external impingement is associated with a narrowing of the coracohumeral interval to less than 7 mm. Although most reported cases of COVID-19related inflammatory arthropathy represent reactive postviral arthritis, other inflammatory arthropathies such as polyarticular RA, systemic lupus erythematosus, and seronegative spondyloarthropathies have been reported. However, COVID toes may be associated with ON of the small bones of the feet, diagnosed at MRI, in patients without other common causes for ON (Fig 3). These include the sublabral recess, sublabral foramen, and the Buford complex. It is important for radiologists to understand the common patterns of COVID-19 involvement in the MSK system, including relevant imaging findings seen with various modalities, as imaging can help identify several MSK manifestations of COVID-19, assess the distribution of disease, and provide quantifiable measurements to follow disease progression. The posterior supraspinatus fibers are intact. (A) Coronal T2-weighted fat-suppressed MR image of the shoulder shows typical findings often seen with adhesive capsulitis, including an edematous thickened inferior glenohumeral ligament (IGHL), particularly at its humeral attachment (arrows). (B) Gray-scale US image of the same region during the inspiratory phase of respiration shows that the zone of apposition of the diaphragm measures 0.20 cm. The coracoacromial arch is a static stabilizer of the anterior superior aspect of the glenohumeral joint. MRI and CT show similar findings, although MRI is more sensitive for helping detect areas of myonecrosis. Common benign tumors involving the shoulder include enchondromas and osteochondromas (Figure 12-27). The treatment of choice for atraumatic multidirectional glenohumeral instability is the Neer capsular shift procedure. Normal findings after the Bankart procedure include fraying/blunting of the labrum, metallic artifact at the anterior inferior glenoid, and thickening of the joint capsule. Capsule of right knee-joint (distended). the posterior recesses of the ankle and subtalar joint is consistent with a degree of active posterior impingement. Contrast extravasation from the arthrogram procedure is also demonstrated. Tim B. It is unclear if there is an association of human leukocyte antigen B27 (HLA-B27) with seronegative spondyloarthropathies that follow COVID-19 (32). WebAnterolateral impingement of the ankle. Three main processesthe cytokine storm, an autoimmune response, and hypercoagulabilitylead to a cascade of events contributing to many of the most common MSK clinical conditions (items in red). (B) Axial T2-weighted fat-suppressed MR image of the left shoulder in a 27-year-old woman who received the second dose of the Moderna mRNA COVID-19 vaccine 5 weeks earlier with continued shoulder pain and tenderness shows persistent mild ill-defined lateral deltoid muscle edema (arrow) at the site of maximal tenderness, thought to represent postinjection myopathy. The left second metacarpophalangeal (MCP) joint was among the affected joints. (B) Coronal T1-weighted fat-suppressed postcontrast MR image of the same area shows enhancement of the affected regions, indicating active inflammation and synovitis. Newer microvascular Doppler US techniques may detect slow-flow intraneural vascularity indicating focal nerve abnormality (60). The extraordinary range of the shoulder is due to the shallow osseous glenohumeral articulation. It occurs in ~20% (range 10-30%) of the population 1. Plantarflexion: 0-40 degrees. In this article, we review the current understanding of the pathophysiology of COVID-19 and the rare vaccine-related complications, particularly as they relate to MSK manifestations, as well as currently available descriptions of imaging findings in these conditions. (B) Axial T1-weighted nonfat-suppressed MR image at the same level shows posterior compartmentpredominant muscle atrophy and fatty infiltration, also more pronounced in the semimembranosus muscle (arrow). Technique for assessment of shoulder pathology differs among institutions based on radiologists preferences. Under fluoroscopic guidance, about 12 cc of a 1:200 gadolinium dilution solution is injected into the glenohumeral joint prior to imaging. (A) Axial T2-weighted fat-suppressed MR image of the left mid thigh shows left sciatic nerve edema (solid arrow). Labral tears may be associated with paralabral cysts. The shoulder in a conventional MRI exam is acquired in partial external rotation in the axial, coronal and sagittal planes. However, several authors have suggested vascular and immunologic causes, including vasospasm, perivascular lymphocytic aggregation involving small dermal vessels, endothelial damage, and fibrin microthrombi (18). Complete tear of the supraspinatus at the insertion site. Operative complications of shoulder surgery include fracture of the acromion, dehiscence of the deltoid, and axillary nerve injury. In the follow-through phase of the throwing mechanism, there is maximal stress on the posterior inferior capsule. Spontaneous bleeding most commonly occurs in skeletal muscle, especially the iliopsoas, as well as the pectoralis major and rectus abdominis muscles (41,42). Carpal, cubital or tarsal tunnel syndrome after SARS-CoV-2 infection: A causal link? Chronic repetitive trauma of the superiorly subluxed humeral head may lead to remodeling of the acromion and eventual collapse of the humeral head (rotator cuff arthropathy). Partial tears may be treated arthroscopically. The complex of the medial collateral ligaments of the ankle joint is collectively called deltoid ligament.It attaches the medial malleolus to multiple tarsal bones. Coronal oblique MRI shows calcium hydroxyapatite deposition in the supraspinatus at its insertion on the footprint is associated with mild adjacent edema (black arrow). Perthes on ABER. In October 2021, the World Health Organization released the following consensus definition: Post COVID-19 condition occurs in individuals with a history of probable or confirmed SARS CoV-2 infection, usually 3 months from the onset of COVID-19 with symptoms and that last for at least 2 months and cannot be explained by an alternative diagnosis Symptoms may be new onset following initial recovery from an acute COVID-19 episode or persist from the initial illness (61). Several of these symptoms, such as fatigue, shortness of breath, arthralgias, muscle pain and/or spasms, and postexertional malaise, can be related to the chronic impact of COVID-19 on skeletal muscle. If the needle is too lateral, it may result in axillary nerve injury; if it is too inferior, it can injure the radial neurovascular bundle; if it is too long it could result in chemical osteitis/osteomyelitis of the humerus; and if it is too short, it can result in local skin reaction and subcutaneous fat necrosis (73). Sarcopenia, which is generally seen with aging and deconditioning, can be more pronounced in COVID-19 patients who are critically ill and may affect the muscles of respiration, inhibiting the ability to wean patients from ventilators. Noninflammatory myalgias are generally self-limited and treated conservatively. This category only includes cookies that ensures basic functionalities and security features of the website. Lateral aspect. Spontaneous intramuscular hematoma resulting in acute muscle denervation from compressive neuropathy in a 60-year-old man with COVID-19 undergoing anticoagulation therapy who presented with left flank pain radiating to the left inguinal region. Posterior superior internal impingement is often seen in patients who engage in repetitive overhead athletic activities. Magnetic resonance imaging of the Lisfranc ligament. It is thin in front and at the side, and contains the patella, ligaments, menisci, and bursae of the knee. Subacromial decompression is the surgical treatment of choice for subacromial impingement. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. Coracoacromial ligament resection is part of the subacromial decompression operation. 1. The most common postvaccination condition is shoulder injury related to vaccine administration (SIRVA), which was first described in 2006 (70). The calcaneus transfers most Complications of direct arthrography are rare. [2], Anteriorly, the reflection of the synovial membrane lies on the femur; located at some distance from the cartilage because of the presence of the suprapatellar bursa. Rare COVID-19 vaccinerelated complications have also been reported. Summary. Impingement may be classified as external or internal and primary or secondary. More recent anatomical studies have shown a much more comprehensive set of six attachments 4to the acetabulum. (B) Axial CT image (bone window) of the chest at the level of the glenohumeral joints in a 54-year-old man with a history of COVID-19 (hospitalized for 6 weeks) and with left shoulder stiffness shows bilateral periarticular ossifications. Some patients may demonstrate synovial and capsular edema at fluid-sensitive imaging and synovial and capsular enhancement after intravenous contrast material administration (32). Long head of the biceps tenosynovitis may be associated with repetitive stress/microtrauma. The sphenoid sinuses are situated within the body of the sphenoid bone. Infraspinatus denervation. Classic findings of acute venous thrombosis are best diagnosed at gray-scale and color and spectral Doppler US (38). Secondly, several reported cases developed after only one dose of the vaccine. It is one of the most commonly disrupted ligaments in midfoot injuries. The short head of the biceps arises along with the coracobrachialis from the coracoid process. Tendinosis presents as thickening of and abnormal signal in the tendon. Figure 12-19. The middle glenohumeral ligament (Figure 12-3) is most easily appreciated deep to the subscapularis tendon. The fabella articulates with its respective (medial or lateral) femoral condyle. Figure 12-4. COVID-19, produced by infection with SARS-CoV-2, is a novel disease first described in patients in Wuhan, China, in December 2019.