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AJR 2001; 177:1377-1381
© American Roentgen Ray Society

Elbow Synovial Fold Syndrome

MR Imaging Findings

Hitomi Awaya1,2, Mark E. Schweitzer1, Sunah A. Feng3, Tamotsu Kamishima1, Phillip J. Marone4, Shella Farooki3, Debra J. Trudell3, Parviz Haghighi5 and Donald L. Resnick3

1 Department of Radiology, Thomas Jefferson University Hospital, 132 S. 10th St., 1096 Main Bldg., Philadelphia, PA 19107.
2 Present address: Department of Radiology, Shimonoseki City Hospital, 1-13-1 Kohyohcho, Shimonoseki, Yamaguchi 750-8520, Japan.
3 Department of Radiology, Veterans Affairs Medical Center and University of California, 3350 La Jolla Village Dr., San Diego, CA 92161.
4 Department of Orthopedic Surgery, Thomas Jefferson University Hospital, Philadelphia, PA 19107.
5 Department of Pathology, Veterans Affairs Medical Center and University of California, San Diego, CA 92161.

Received February 7, 2001; accepted after revision June 11, 2001.

 
Address reprint requests to M. E. Schweitzer.

Address correspondence to H. Awaya.


Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
OBJECTIVE. We describe the anatomy and MR imaging appearance of elbow plicae.

MATERIALS AND METHODS. First, five cadavers were evaluated by sectioning and using MR arthrography for evidence of normal or prominent synovial folds to determine the potential origin of elbow plicae. Next, 164 consecutive MR images were evaluated to determine the frequency of the plicae in a clinical population. Last, we retrospectively studied a selected group of eight patients who underwent preoperative MR imaging and in whom enlarged synovial folds were confirmed at surgery.

RESULTS. In the cadavers, the synovial fold appeared to originate from the synovium adjacent to a posterior fat pad. In the clinical population, half the patients showed a synovial fold at the same location; however, most folds were less than or equal to 2 mm in thickness. The eight patients presented clinically with symptoms mimicking an intraarticular body. The synovial fold in symptomatic patients was seen posteriorly just above the olecranon and averaged 3 mm in thickness.

CONCLUSION. A synovial fold extending from the posterior fat pad in the elbow is a frequent finding on MR imaging. In a subgroup of patients, plicae, when thickened, may present clinically as a locking elbow. However, overlap exists between the thicknesses of symptomatic and asymptomatic plicae.


Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
Plicae are prominent folds of synovial membrane. These plicae are remnants of the normal embryonic development of articular synovial membranes [1, 2]. Embryologically, the elbow joint is formed by mesenchymal cavitation first at the radiohumeral site, then in the ulnohumeral region, and finally in the radioulnar site. Subsequently, these three cavities merge [3]. Elbow synovial plicae or synovial folds are a septal remnant of this process [4]. Plicae are usually asymptomatic. On occasion, plicae may cause symptoms, sometimes termed the "plica syndrome" [1, 2, 5].

Imaging of the plica syndrome of the knee has been described [1, 2, 5,6,7], but imaging of elbow plicae is rarely described [4]. MR imaging of the elbow may be performed for possible intraarticular bodies [8, 9]. We became interested in the entity after clinically observing several cases of elbow plicae presenting as intraarticular loose bodies. Consequently, we sought to describe the MR appearance of a little-known syndrome in which a synovial fold or a plica catches in the elbow.


Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Cadaveric Study
Elbow joint specimens were obtained from freshly frozen nonembalmed cadavers (five men; age range, 57-89 years; mean, 74.4 years). The specimens had been amputated at the mid humeral level. Each specimen was radiographed with no abnormality detected.

After thawing, the specimen elbows were injected intraarticularly with 3-6 mL of gadopentetate dimeglumine solution (Magnevist [1 mL in 250-mL saline solution]; Schering, Berlin, Germany). For gadolinium administration, a 21-gauge needle was inserted into the anterior part of the radiohumeral joint space. This approach avoided violation of the radial collateral ligament. MR imaging was performed using a 1.5-T system (Signa; General Electric Medical Systems, Milwaukee, WI). Each elbow was placed in a flexible coil in full extension and supination. Coronal, axial, and sagittal T1-weighted spin-echo (TR/TE, 500/22) fat-suppressed images were obtained. A 10-cm field of view, 512 x 256 image matrix, 2.5-mm section thickness, and a 0.5-mm intersection gap were used, and two signals were acquired.

These cadaveric MR images were interpreted by two musculoskeletal radiologists, in consensus, for the presence, location, and appearance of synovial folds.

After imaging, two elbows were refrozen and sectioned with a band saw at 3-mm intervals in either the axial or the sagittal plane. Correlation of MR images and specimen sections was made, and a specimen with an obvious plica was submitted for histologic evaluation.

Clinical Study
Asymptomatic group.—From January 1997 to October 1999, 164 patients (105 males, 59 females; age range, 8-86 years; mean, 39.6 years) were evaluated. Any patient with a history of locking elbow, catching elbow, or possible intraarticular body was excluded. Eleven (6.7%) of the 164 patients with nonlocking elbows underwent direct MR arthrography. The remaining 153 (93.3%) of the 164 patients with nonlocking elbows underwent conventional MR imaging.

All patients underwent MR imaging with a 1.5-T system (Signa) using an extremity coil (General Electric Medical Systems). Patients were imaged in the supine position, with the elbow extended at the side and the forearm supinate.

Images were obtained in the coronal, axial, and sagittal planes with T1-weighted spin-echo sequences (TR range/TE range, 400-650/11-16) complemented by axial T2-weighted fast spin-echo (3000-4000/76-90) fat-suppressed images. In addition, sagittal or coronal three-dimensional spoiled gradient-recalled acquisition in a steady state sequence with fat suppression (TR/TE, 43.3/13.3; flip angle, 45°) and sagittal fast short tau inversion recovery sequences (5300-5516.7/66-80; inversion time, 150 msec) were obtained. The three-dimensional spoiled gradient-recalled acquisition in a steady state sequence was obtained with the following parameters: 14- to 16-cm field of view, 256 x 128-256 image matrix, and 1.3-mm section thickness. The fast short tau inversion recovery, T2-weighted fast spin-echo, and T1-weighted spin-echo sequences were obtained with the following parameters: 16- to 18-cm field of view, 256 x 224-256 image matrix, and 5-mm section thickness with a 1-mm intersection gap.

MR images were interpreted retrospectively in consensus by two musculoskeletal radiologists for the presence, location, and thickness of the plica.

Symptomatic group.—From January 1997 to October 1999, eight male patients underwent MR imaging with surgical confirmation of symptomatic elbow plicae. The age range of the patients was 17-37 years (mean, 28.3 years). Two patients were professional athletes.

Six of the eight patients presented clinically with symptoms mimicking an intraarticular body when performing snapping and catching motions. The two remaining patients also presented with a locking elbow and were suspected of having plicae. Arthroscopy or open exploration was performed within 1 month of the MR study.

MR imaging was performed using a 1.5-T system (Signa) with an extremity coil (General Electric Medical Systems) identical to that described for the asymptomatic group. Images were interpreted in consensus by two musculoskeletal radiologists for the presence, location, and appearance of the plica.

Elbow synovial folds were initially categorized as either posterior (olecranon recess) or anterior (anterior humeral recess) (Fig. 1). The olecranon recess was further divided into superior, medial, and lateral olecranon recesses. Folds were measured with electronic calipers at a workstation (PACS; Canon Medical Systems, Irvine, CA).



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  		Fig. 1. —Drawing shows anterior and posterior synovial folds.

 


Results
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 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Cadaveric Study
Four of the five cadavers had plicae. The plicae were seen anteriorly in two and posteriorly in three cadaver elbows. The plicae were uniformly thin (Table 1). The size of plicae on direct MR arthrography was in agreement with the size of plicae seen grossly. Histologically, the plicae of the cadaver elbows showed typical synovial membrane with polypoid projections (Fig. 2A,2B,2C,2D). No evidence of granulation or active inflammation was seen.


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  		TABLE 1 Size of Plicae of Five Cadavers as Seen on Direct MR Arthrography

 


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  		Fig. 2A. —Cadaver of 57-year-old man who had no history of locking syndrome. Axial T1-weighted spin-echo fat-suppressed MR arthrogram (500/22, TR/TE) shows curved synovial fold (black arrow) in posterolateral olecranon recess. Note small triangular enfolding (white arrow) of synovium in posterolateral olecranon. Such enfolding is considered a normal variant.

 


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  		Fig. 2B. —Cadaver of 57-year-old man who had no history of locking syndrome. Axial cadaveric section shows typical location of synovial fold (arrows).

 


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  		Fig. 2C. —Cadaver of 57-year-old man who had no history of locking syndrome. Photomicrograph of histologic specimen shows overall appearance of plica with synovial type configuration and polypoid projection of synovial-lined structure (arrows). (H and E,x16)

 


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  		Fig. 2D. —Cadaver of 57-year-old man who had no history of locking syndrome. Photomicrograph of histologic specimen of plica shows cuboidal synoviocytes (arrowheads) covering plica (arrow). (H and E,x100)

 

Clinical Study
Asymptomatic group.—On conventional MR imaging in the 153 patients with nonlocking elbows, 74 patients (48.4%) had plicae. Most of the plicae were in the superoposterior olecranon recess. On MR arthrography in the 11 patients with nonlocking elbows, nine patients (81.8%) had plicae, also all in the superoposterior olecranon recess.

Nine of the plicae greater than 2 mm showed linear patterns (Fig. 3). One 4-mm plica in the superior olecranon recess was wedge-shaped (Fig. 4). No plicae greater than 3 mm were seen in the medial and lateral olecranon recesses (Tables 2 and 3). In only 11 of the patients on nonarthrographic MR imaging were these plicae on other locations.



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  		Fig. 3. —15-year-old boy with pain. Sagittal three-dimensional spoiled gradient-recalled acquisition in steady state fat-suppressed MR image (TR/TE, 43.7/13.3; flip angle, 45°) shows 2-mm posterior synovial fold (arrow) at tip of olecranon in superoposterior olecranon recess.

 


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  		Fig. 4. —25-year-old woman with chronic pain. Sagittal T1-weighted spin-echo fat-suppressed direct MR arthrogram (TR/TE, 500/11) shows posterior synovial fold (arrow) as wedge shape above tip of olecranon in superoposterior olecranon recess.

 

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  		TABLE 2 Incidence of Thickness of Plicae on Conventional MR Imaging in 153 Patients Without Locking Elbow

 

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  		TABLE 3 Incidence of Thickness of Plicae on Direct MR Arthrography in 11 Patients Without Locking Elbow

 

Symptomatic group.—These plicae were located posteriorly above the olecranon (Figs. 5 and 6) and oriented in the sagittal and oblique planes. The shape was linear in the sagittal and oblique planes and triangular on cross-section. All these plicae were greater than or equal to 2 mm in thickness, averaging 3.1 mm (range, 2-5 mm) (Table 4). Three of these plicae also had a focal fat pad projecting into the superoposterior aspect of the olecranon recess (Fig. 7). These fat pads were distinguished from plicae arthroscopically. In these patients, the other plicae seen anteriorly or inferiorly were less than or equal to 2 mm (similar to those of the asymptomatic patients). All patients were operated on with isolated plicae resection, and symptoms completely resolved at 2 years. The resultant diagnosis on histologic examination was chronic synovitis.



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  		Fig. 5. —28-year-old man with locking elbow and pain. Sagittal T1-weighted spin-echo fat-suppressed MR arthrogram (TR/TE, 403.3/9) shows thick posterior synovial fold (arrows). This synovial fold was confirmed at surgery and extended from triceps to posterior humeral surface in superoposterior olecranon recess.

 


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  		Fig. 6. —38-year-old man with chronic pain. Sagittal three-dimensional spoiled gradient-recalled acquisition in steady state fat-suppressed MR arthrogram (TR/TE, 43.7/13.3; flip angle, 45°) shows prominent large posterior synovial fold (arrow) at tip of olecranon in superoposterior olecranon recess. Fold was confirmed at surgery.

 

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  		TABLE 4 Size of Plicae on Direct MR Arthrography in Eight Patients with Locking Elbow

 


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  		Fig. 7. —24-year-old man with chronic pain. Sagittal T1-weighted spin-echo fat-suppressed direct MR arthrogram (500/11, TR/TE) shows focal fat pad (arrow) projecting into superoposterior aspect of olecranon recess.

 


Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
In the elbow, the synovial membrane extends from the margin of the articular surface of the humerus and lines the coronoid, radial, and olecranon fossa on that bone; it is reflected over the deep surface of the capsule and forms a pouch between the radial notch, the deep surface of the annular ligament, and the circumference of the head of the radius [10]. Projecting between the radius and the ulna into the cavity is one crescentic fold of synovial membrane. In contrast, all asymptomatic plicae seen were anterior or inferior plicae and were thinner than superoposterior plicae. These superoposterior plicae are a synovial fold seen on the dorsal aspect of the articular capsule between the humerus and the radius [10]. We found this superoposterior fold in three of five cadavers and in 50% of patients with nonlocking elbows (Table 1).

A syndrome of limitation of full extension caused by impingement of a plica in olecranon fossa has been previously described [11, 12]. Some authors have also suggested a possible relationship with the pathogenesis of epicondylitis [13]. The normal synovial folds are thin, pink, and pliable. In contrast, chronic synovitis histologically shows thickening of the synovial layer and enlargement of the villi. Also in chronic synovitis, loose areolar elements of the subsynovial tissue are replaced with fibrous tissue, the vessel walls are thickened, and, occasionally, a mononuclear infiltrate is present [14]. Macroscopically, chronically inflamed synovial folds are thick, white, and fibrotic. In the cadaveric study, plicae were usually 1-2 mm without histologic evidence of granulation or inflammation. In the locking group, the plicae were thickened and appeared synovitic. After resection, locking symptoms resolved.

We studied eight patients with locking symptoms from elbow plicae. These plicae were posterior to and just above the tip of the olecranon. This location and the shape of plicae are similar to those noted in previous clinical and cadaveric studies [11,12,13]. Those posterior plicae were almost always thicker than those seen in cadavers or in patients without locking symptoms.

Quinn et al. [15] reported that MR imaging can reliably depict intraarticular bodies in the elbow. Intraarticular bodies may lie anywhere within the elbow joint but are more commonly seen anteriorly, in contradistinction to locking plicae [16]. It is important to recognize plicae because they may simulate the appearance of intraarticular bodies on cross section. The normal anterior and posterior fat pads can also project into the joint and may mimic synovial folds, a condition that was found in two of our symptomatic patients. Another two of our patients were throwing athletes.

Synovial folds in the superior olecranon recess were seen on conventional MR images in half our patients even without symptoms from the plicae. Even quite thickened (>3 mm) folds appeared in 8% of patients without mechanical symptoms. A 2-mm plica in the superior olecranon recess on MR arthrograms in a cadaver showed no histologic abnormalities, although some patients with plica syndrome had a 2-mm plica at the same location on MR arthrograms. Therefore, both symptomatic and asymptomatic patients may have thickened synovial folds. These synovial folds may be considered physiologic elements in the elbow and are only occasionally responsible for clinical symptoms. Symptoms from the synovial fold may occur after repetitive microtrauma and overloading. This repetitive injury creates an inflammatory reaction with a thickening of the synovial fold. Athletic injury was postulated in six of our eight patients.

When the elbow is in flexion, the posterior plicae extend and become taut, and the anterior plicae fold. On cross-sectional imaging, the appearance of the plicae may become more linear. Clinically, the locking symptom for plicae may occur when the elbow is flexed or extended because the plicae infold into the joint.

Our study is limited by the small number of clinical cases with surgical confirmation. Another limitation is the lack of surgical confirmation of our frequency data. Moreover, the synovial folds could be missed or thickness of the plica could be less than evaluated on nonarthrographic MR images if there was no fluid in the joint. In addition, we did not precisely evaluate all the patients but relied on the lack clinical suspicion for locking or catching. Also, we may have missed some plicae in patients without joint fluid. Therefore, our frequency data may be underdescribed. Because of logistics, we could evaluate only a small number of cadaveric cases.

In conclusion, on elbow MR arthrography, a locking synovial fold of the elbow has a characteristic appearance extending from the posterior fat pads. Such an elbow may present clinically as a locking elbow. Rarely do patients without locking symptoms have a similar fold. Nearly half of all patients have small plicae in a similar posterior location.


References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

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