Abstract
Introduction:
Synovial plicae are often observed when performing arthroscopic surgery, but their pathological nature and the necessity for treatment are still controversial. There are few reports regarding lateral synovial plicae because it is considered extremely rare. The purpose of this study was to report the clinical outcomes of athletes with symptomatic lateral synovial plicae who underwent arthroscopic surgery.
Methods:
Ten patients with lateral synovial plica underwent arthroscopic surgery. Of the 10 patients, 5 were male and 5 were female, and their average age was 19.1 years. The chief symptoms were anterolateral knee pain, limited range of motion due to pain, and catching. All patients failed nonoperative management.
Results:
The average period between the onset of lateral synovial plica syndrome and the knee surgery was 5.6 months. The average follow-up period after surgery was 8.4 months. The arthroscopic findings revealed that a plica-like structure existed in the lateral patellofemoral joint. After surgery, pain and limited range of joint motion were improved in all cases and catching and locking disappeared. No complications were observed; however, the pain relapsed after surgery in one patient who had slow onset. In this patient, another resection of the synovial plica provided symptomatic improvement.
Conclusions:
Arthroscopic resection of symptomatic lateral synovial plicae was performed with good results. Lateral synovial plica syndrome is a rare condition. However, when treating athletes with anterolateral knee pain, lateral synovial plicae should be considered.
Introduction
Synovial plicae are often observed when performing arthroscopic surgery and generally represent incidental findings of no real clinical consequence. However, their pathological nature and necessity for treatment are still controversial. Knee overuse and trauma may cause a plica to become inflamed and thickened, thereby leading to anterior knee pain and resulting in “plica syndrome”. Among the plica syndromes, it is well-known that the medial synovial plica, the so-called medial synovial shelf, has clinical significance as a potential cause of anteromedial knee pain. 1,2 There are few reports regarding lateral synovial plicae because it is considered extremely rare. 3,4 Furthermore, there have been no case series regarding patients with symptomatic lateral synovial plicae. We present the clinical outcomes of 10 athletes with symptomatic lateral synovial plicae who underwent arthroscopic surgery. Characteristic features of lateral plica syndrome are also discussed.
Materials and methods
A retrospective review of data collected from patients with a diagnosis of a symptomatic lateral synovial plica who underwent surgical resection using arthroscopy was completed. Between April 2009 and March 2011, 10 patients (10 knees) with lateral synovial plica syndrome underwent arthroscopic surgery. Those patients and/or their families who provided informed consent that data from the case would be submitted for publication were included for the study. Of the 10 patients, 5 were male and 5 were female; their average age was 19.1 years (standard deviation (SD) 8.77; range 13–40). All patients were skeletally mature and were involved in some type of sports activity. A 0.4-T APERTO MRI system (HITACHI Medical) was used. T1- and T2-weighted fast spin echo magnetic resonance imaging (FSE MRI) was performed in the sagittal, coronal, and axial planes, and the slice thickness was 2.5 mm. Surgical intervention for lateral synovial plicae was indicated for patients who had failed nonoperative management, had been getting better at least temporarily after a local corticosteroid injection to the lateral patellofemoral joints, and had not experienced a meniscal injury or cartilage damage.
The chief symptoms were anterolateral knee pain and limited range of motion due to pain. We found that all patients had tenderness in the lateral patellofemoral joint. There was a palpable mass in the lateral patellofemoral joint in four cases. Three patients had a loss of 15–30° of extension of the knee. Catching was confirmed in seven patients, and two of them had severe symptoms such as locking (Table 1). One or more local corticosteroid injections were administered to the lateral patellofemoral joints in all cases of tenderness. Pain decreased but relapsed after a few days for these 10 patients. These cases could have been lateral synovial plica syndrome, which is resistant to conservative medical treatment. Knee surgery was performed using arthroscopy.
Cases.
F: female; M: male; R: right; L: left; op.: operation; y.o.: years old; M: month.
The average period between the onset of lateral synovial plica syndrome and the knee surgery was 5.6 months (SD 5.23; range 1–15). The average follow-up period after surgery was 8.4 months (SD 3.50; range 6–16). The formation of a plica-like structure was observed in the lateral patellofemoral joint on MRI axial imaging for three cases; however, no clear invaginations were observed (Figure 1). In seven cases, there were no abnormal findings on MRI imaging. No other diseases such as lateral meniscus damage or cartilage damage were seen. The result was graded as excellent if the patient had no pain and return to full functional and sports activity. A patient with a good result demonstrated occasional mild discomfort and the ability to participate at the previous level of activity. A patient with a fair result demonstrated occasional pain and the ability to participate at sports activity, despite less than the previous level. A patient with a poor result reported the almost unchanged pain and was unable to perform at the acceptable level of functional or sports activity.
The formation of a plica-like structure was observed in the lateral patellofemoral joint on MRI axial imaging; however, no clear invaginations were observed.
Results
We performed arthroscopic surgery and lateral synovial plicae were found in all cases. The arthroscopic findings revealed that a plica-like structure existed in the lateral patellofemoral joint. After withdrawing the perfusion fluid, the plica invaginating into the lateral patellofemoral joint was observed (Figure 2). When reinfusing the perfusion fluid, the plica again appeared from the lateral patellofemoral joint. This lateral synovial plica was resected using a shaver and punch until the plica no longer invaginated into the lateral patellofemoral joint when the perfusion fluid was withdrawn and the knee was extended or flexed. According to the arthroscopic findings of the lateral synovial plica, no damage was observed in the lateral meniscus or other parts of the knee. According to the histological findings, infiltration of inflammatory cells was observed in fibrous tissues covered with synovial membrane cells. In addition, it was confirmed that edema-like stroma existed in some parts (Figure 3). Postoperative rehabilitation included early weight-bearing as tolerated and a short period of immobilization (1–2 days), followed by unrestricted range of motion of the knee. Returning to sports activities was not recommended until a minimum of 2 weeks postoperatively.
The arthroscopic findings revealed that a plica-like structure existed in the lateral patellofemoral joint (a). After withdrawing the perfusion fluid, this plica invaginate into the lateral patellofemoral joint (b).
Histological findings. Infiltration of inflammatory cells was observed in fibrous tissues covered with synovial membrane cells (a), and it was confirmed that edema-like stroma existed in some parts (b) stained with hematoxylin and eosin (original magnification ×40).
After surgery, pain and limited range of joint motion were improved in all cases and catching and locking disappeared. No complications were observed. Nine cases were rated as excellent, but one case was graded as poor (Table 1). In one case graded as poor that had slow onset, the pain relapsed when she resumed sports activity 3 weeks after surgery. In this case, another resection of the synovial plica provided symptomatic improvement.
Discussion
Synovial plicae are embryonic residues that remain in the joint cavity of the knee; they are also observed in normal knees as a septal wall or impaired septal wall. 5 There are four types of synovial plica, namely suprapatellar plica, infrapatellar plica, medial parapatellar plica, and lateral parapatellar plica. 2,3,6 –9 Medial plica is most commonly associated with symptoms, and the incidence of medial plica ranges from 18.5% to 80%. 10 –12 Several researchers reported that lateral synovial plicae occur in approximately 1% of normal knees. 3,4,13,14 In addition, there are many patients with lateral synovial plicae in Asia, thus suggesting its race specificity. 3,12 We have few opportunities to see lateral synovial plicae because they are extremely rare.
Lateral synovial plicae are relatively wider, shorter, and thicker than medial synovial plicae. 15 It has been reported that lateral synovial plicae are formed and exteriorized by thickening of the lateral parapatellar adipose–synovial fringe, which is a normal structure. 3 Histopathological findings of the present cases showed that lateral synovial plicae often involve nonspecific inflammation of fibrotic scar tissues covered with synovial membrane cells. Therefore, the histological structure of lateral synovial plicae is slightly different from that of medial synovial plicae, which are characterized by fibrocartilaginous metaplasia, progressive collagenization, and widespread calcification. 1,8,16 Thus, we considered that lateral synovial plica syndrome does not simply arise due to the incarceration of residues. In other words, lateral synovial plicae may not be a residual septum; instead, it may be derived from a normal structure. This study suggests that the development of lateral synovial plica syndrome involves relatively large residues that are congenitally seen in some cases (true lateral synovial plicae) or normal structures (lateral parapatellar adipose–synovial fringe, etc.) and are stimulated by repeated stress, including overuse, which causes inflammation. The inflamed site becomes scarred and impinges the patellofemoral joint, resulting in the development of symptoms. Histological findings of the cases in the present study are consistent with this mechanism of development.
It was previously reported that incarceration of lateral synovial plicae and knee snapping were observed at 20–60° of flexion, 3 which occurs with symptomatic medial synovial plicae, which usually intrude upon the patellofemoral joint at 30–50° of flexion. 1,8,17 According to arthroscopic findings, the lateral synovial plicae of the present two cases with locking seemed to be relatively larger and somewhat thicker and harder than those of other cases; however, they were not large enough to entirely cover the anterior surface of the lateral femoral condyle. If patients have pain during snapping, then an antalgic limitation of the range of motion increases, resulting in locking-like symptoms (pseudo-locking). Moreover, factors other than synovial plicae including alignment of the lower limb and patellar tracking may also be involved in the occurrence of incarceration symptoms such as locking. Regarding the pathology of lateral synovial plica syndrome, further investigation is required.
The most important factor to note regarding lateral synovial plica syndrome symptoms is that tenderness does not occur in the femorotibial joint space but rather in the lateral patellofemoral joint. In addition, there is often a palpable mass in the lateral patellofemoral joint. For patients with mild symptoms, conservative treatments such as rest, quadriceps strengthening, hamstring stretching, administration of nonsteroidal anti-inflammatory drugs, and corticosteroid injections may be effective as well as for cases of symptomatic medial synovial plicae. 1,9,18,19 Even in our cases, during the study period, 26 patients with anterolateral knee pain suspected to be symptomatic lateral synovial plicae had been successfully treated by nonsurgical treatment. These patients were suspected to have lateral synovial plicae from their symptoms, although they did not have any arthroscopic surgery and we did not get definitive diagnosis. However, if patients wish to continue participating in sports activities, then it should be expected that the mechanical stress that caused lateral synovial plica syndrome will be repeated, even after treatment. In addition, if the synovial plicae become scarred or hardened, then they may cause cartilage damage in the patellofemoral joint. 3 Therefore, resection of lateral synovial plicae using arthroscopy during an early stage should be considered for patients who do not respond to conservative treatments or for patients who have incarceration symptoms such as locking or catching. Several reports of treatment for symptomatic medial synovial plicae also suggested that arthroscopic resection is a very good option for symptomatic synovial plicae that do not respond to conservative treatment; factors associated with favorable outcomes are young patient age, localized symptoms of short duration, and the absence of any other intra-articular pathology. 1,8,13,20 –23 In our cases, one case that had slow onset was graded as poor and another resection was needed. In this case, resection of the synovial plica in the first surgery might have been inadequate.
This study suggests that the lateral synovial plica syndrome should be considered when treating athletes with anterolateral knee pain. In addition, when the lateral synovial plica syndrome is suspected, focus should be on the following two points, although they are basic techniques. First, it is important to perform careful observation through the anteromedial portal because it is difficult to observe lateral synovial plicae through the usual anterolateral portal. Second, it is easy to see lateral synovial plicae invaginating into the lateral patellofemoral joint when withdrawing a small amount of perfusion fluid. In the previous study, Gurbuz et al. 24 evaluated plicae in 318 knees using arthroscopy and also investigated plicae in 14 cadaveric knees. Lateral synovial plicae were found in 66 (20.7%) of the 318 knees using arthroscopy. Arthroscopic evaluation was conducted using both anterolateral and anteromedial portals. On the other hand, lateral synovial plicae were found in 7 (50%) of the 14 cadaveric knees. This indicates that it was not easy to find lateral synovial plicae using arthroscopy. This may be why the incidence and prevalence of lateral synovial plica syndrome were underestimated.
There are some limitations to our study. First, there were some patients who had been successfully treated by nonsurgical treatment. Arthroscopic surgery was not performed for these cases and none of them exhibited the plica-like structure on MRI. Therefore, we cannot define the sensitivity and specificity of any clinical findings. Second, we only assessed the cases based on the clinical symptoms and did not use any common scoring system for the evaluation. Third, short follow-up period is another limitation. The follow-up period might not be enough. Longer observations might be needed to confirm that lateral synovial plica does not recur after many months, although most of the patients who achieve satisfactory pain relief and returned to their previous sports activity have stopped continuing to have regular follow-up visit.
Conclusion
Arthroscopic resection of symptomatic lateral synovial plicae was performed with good results. Lateral synovial plica syndrome is a rare condition. However, when treating athletes with anterolateral knee pain, lateral synovial plicae should be considered.
Footnotes
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.