Abstract
Purpose
The goal is to introduce a reproducible exam technique that allows clinical diagnosis of symptomatic plical bands and associated synovium about the knee. We then aimed to assess the accuracy of the exam technique through arthroscopic confirmation of these tissues. Lastly, we hope to determine whether arthroscopic plicectomy and partial synovectomy is an effective treatment for alleviating the pain associated with symptomatic plica.
Methods
This retrospective study evaluated 80 consecutive symptomatic knees under the care of a single physician diagnosed with symptomatic plica and associated painful synovium from 2001-2011. These patients underwent diagnostic and therapeutic arthroscopy to verify the presence of a plica and painful synovium with plicectomy and partial synovectomy if necessary. Statistical analysis was performed to determine the sensitivity and positive predictive value of the exam.
Results
The medial parapatellar region was the most common location for symptomatic plica and associated synovial tissue. The exam technique described in this study had a sensitivity of 83.8% with a positive predictive value of 98.6% in the specific patient population described.
Conclusions
This study suggests that while the medial plical band is the most common, there is frequently sensitive synovial tissue found in multiple locations about the knee. This study also suggests that a thorough exam technique can accurately diagnose both the plical bands as well as the sensitive synovial tissue.
Level of Evidence
Level II, Diagnostic Study. See the Guidelines for Authors for a complete description of levels of evidence.
Introduction
Symptomatic synovial plicae about the knee have been a topic of discussion in the medical literature for quite some time, with much debate about the incidence of the synovial plicae in the population today. A common scenario fifteen years ago was to discover a plica at the time of arthroscopic evaluation for knee pain and remove it, without determining causality between the plica and a patient’s clinical presentation of pain. This often resulted in less than optimal post-operative success rates and failure to relieve the knee pain. The actual incidence of plical tissue in normal knees has also been called into question. Ogata and Uhthoff studied the incidence and location of plicae during embryologic development of the knee. At 8-20 weeks gestation, the infrapatellar plica was found in 50%, the suprapatellar was found in 33%, the mediopatellar was found in 37%, and the lateral plica was found in only one embryo1. However, a review of the more recent literature shows high variability from arthroscopic and cadaveric studies: suprapatellar 55.5% to 87.0%, medial 24.5% to 72%, infrapatellar 65.5% to 86.0%, and the lateral 0% – 1.3%2,3.
There is no consensus on the incidence of symptomatic synovial plica of the knee. Normally, plicae of the knee are pliable in nature. However, when they become thick and fibrotic, plicae can cause significant pain as they impinge on the femoral condyles or patellar facets during movement4 (Figure 1). It is hypothesized that one cause of significant chronic and acute-on-chronic knee pain is a mechanically based synovitis that can occur in a patient with congenitally present synovial plicae. During Scott Dye’s arthroscopic inspection of his own knee joint without intraarticular anesthesia, he noted that even light touch to the unanesthetized synovium resulted in exquisite and substantial pain, whereas direct probing to his Grade III chondromalacia was asymptomatic5. It is still not fully understood what causes the synovial- plical complex to become symptomatic. Trauma to the knee or repetitive movements may cause inflammation of the synovial tissue surrounding the plica, leading to increased fibrocity, loss of elasticity, and varying degrees of synovitis6. It has been shown that trauma and overuse can increase the number of nerve endings within plicae, causing a decreased pain threshold7.
Figure 1. Suprapatellar view with 70 degree arthroscope looking down on a medial synovial-plical complex demonstrating excessive synovial tissue of the left knee. With passive motion, one can appreciate the impingement between the femoral condyle and patella.
Unfortunately, the literature has focused primarily on the diagnosis and treatment of medial synovial plica8-11. Many patients have more widespread synovial involvement due to plicae in other areas about the patella rather than the medial parapatellar plicae most frequently reported in the literature. The presence of this sensitive tissue can be detected on clinical exam, and for patients who fail conservative measures, surgical excision can be highly effective.
The aims of this study are to: (1) demonstrate a unique physical exam that is reproducible for diagnosis of the symptomatic synovial-plical complex, (2) provide statistical evidence that the physical exam is accurate, as verified by arthroscopy, which is considered to be the gold standard for symptomatic plica diagnosis, (3) show that synovial plicectomy and partial synovectomy is an effective treatment for alleviating the chronic pain syndrome, and (4) provide an updated clinical picture of the patient with the symptomatic synovial-plical complex.
It is our observation that many people may have congenitally present plical band(s) and associated excessive, sensitive synovial tissue found incidentally at the time of routine clinical exam. Occasionally these individuals will develop severe anterior knee pain requiring treatment but few will require surgical intervention to alleviate symptoms. Contrary to the history of plical discovery and excision at the time of arthroscopy, it is our hypothesis the diagnosis can be made in the clinical setting. Most often these will respond to non-operative measures such as nonsteroidal anti-inflammatory medications, physical therapy, and rest. However, in this study we report a group of patients who have failed conservative measures and required surgery. It is also our observation that the plica and excessive, sensitive synovial tissue are often found together in varying relationships. In our work we have referred to the pain syndrome associated with a symptomatic plica and its sensitive synovial tissue as the Synovial-Plical Complex.
Hypothesis: The diagnosis of a symptomatic synovial- plical complex can be made in the clinical setting.
Methods
This retrospective study reviewed consecutive surgically managed patients with the diagnosis of synovial- plical complex from 2001-2011 under the care of a single physician at a single institution who did not respond to conservative treatment modalities. The electronic medical record was queried in order to identify all patients under the care of a single physician whose primary pre- or postoperative diagnosis was symptomatic synovial plica. Preoperative diagnosis of symptomatic plica was made using a unique physical exam described in this study. These patients subsequently underwent diagnostic and therapeutic arthroscopy to verify the diagnosis. Patients with coexisting, advanced chondromalacia, osteoarthritis, and patellofemoral instability were excluded. Also, workman’s compensation and those with pending legal action were also excluded. The query produced 73 patients with 80 symptomatic knees with suspected synovial-plical complex. Of the 80 knees surgically managed, 78 were seen in follow-up (97.5%). Of the two knees that did not return to follow up, one knee was correctly diagnosed by clinical exam and underwent plicectomy, while the other was pre-operatively diagnosed with a lateral meniscus tear but instead a medial plica was found and excised at surgery. The average age at surgery was 24 years. The causal relationship of the plica to the pain-syndrome was confirmed by the post-operative relief of pain.
Plica diagnosis was made arthroscopically by looking for impingement of tissue between the patella and the femur, as well as associated excessive or thickened synovial tissue. This was viewed from the standard infrapatellar portals as well as the superior patellar portals with a 70-degree arthroscope. The tissue inferior to the patella was resected through the arthroscope. The tissue in the supra-patellar pouch was resected either arthroscopically or through a mini-lateral incision.
Exam findings
The initial step in the workup of anterior knee pain was to determine the existence of patellofemoral surface pathology by performing a patellar compression test with the patient’s leg relaxed in 30, 60, and 90 degrees of flexion. If pain was present, the patient was asked to distinguish whether the pain was directly beneath the patella or around the periphery. Mild patellar chondromalacia may have subpatellar pain with provocative testing as the only finding, whereas more severe grades of chondromalacia will typically have palpable crepitus during active range of motion of the knee in addition to subpatellar pain. Parapatellar pain during flexion of the knee is distinct from subpatellar pain and may indicate a plica trapped between the patella and femur. However, the finding of pain alone is neither sensitive nor specific for synovial-plical complex. Further examination requires methodical palpation of the parapatellar region in order to palpate a soft, popping plica during active flexion and extension of the knee as described below.
Medial Synovial-Plical complex
With the patient’s leg relaxed in extension, force the patella laterally while palpating for a thickened band along the medial edge of the widest portion of the patella. Once palpated, press the band toward the patella. Passively moving the leg into flexion often produces a palpable pop along the medial edge of the patella. Active flexion will also produce a palpable pop and is often accompanied by appreciable pain recreating the patient’s symptoms (Figure 2) (Figure 3).
Figure 2. Suprapatellar view with 70 degree arthroscope looking down on a medial synovial-plical complex with a larger fibrous band showing significant inflammation and synovitis.
Figure 3. Confirmation of the soft tissue popping that occurs can be achieved with the patient actively extending and flexing their knee.
Lateral Synovial-Plical complex
With the patient’s leg relaxed in extension, force the patella medially while palpating for a thickened band along the lateral edge of the widest portion of the patella. Once palpated, press the band toward the patella. Passive and active range of motion produce findings similar to the medial synovial-plical complex as described previously.
Suprapatellar Synovial-Plical complex
Deeply palpate the tender suprapatellar region while having the patient actively flex his or her quadriceps (Figure 4). If pain decreases or resolves completely with activation of the muscle, suspect a suprapatellar synovial-plical complex.
Figure 4. Examination of the suprapatellar synovial-plical complex involves palpation of this sensitive area with the quadriceps relaxed, followed by contracted. The relaxed state is the only one which will provide pain and tenderness.
superolateral synovial-Plical complex
The synovial-plical complex in this location often occurs concomitantly with medial or lateral synovial-plical complexes and are often so large that they are frequently missed. Palpate along the superolateral edge of the patella with an index finger to locate the band while the patient’s leg is relaxed in extension (Figure 5). While palpating the band ask the patient to slowly contract the quadriceps. Doing so helps distinguish a large synovial-plical complex from the overlying vastus lateralis. Once again, palpation often results in pain that reproduces the patient’s symptoms.
Figure 5. The superolateral synovial-plical complex detected as a large soft tissue mass which is exquisitely tender just superior and lateral to the patella.
Central Infrapatellar Synovial-Plical complex
The central infrapatellar synovial-plical complex may be palpated directly beneath the patellar tendon. Much like the palpation for the suprapatellar plica, if the pain decreases or resolves completely with activation of the quadriceps muscle, suspect the infrapatellar synovial- plical complex as the origin of the patient’s pain.
Medial Infrapatellar synovial-Plical complex
Begin with the patient in 90 degrees of flexion. Palpate the edge of the patellar tendon located medial to the inferior pole of the patella while having the patient actively move their leg into full extension. As they move into extension, you will be able to feel the medial synovial- plical complex emerging from the infrapatellar fat pad and this palpation will recreate the pain that the patient with the symptomatic medial synovial-plical complex would experience.
Lateral Infrapatellar synovial-Plical complex
Repeat the exam for a medial infrapatellar synovial- plical, focusing on the lateral edge of the patellar tendon.
Existence and location of the synovial-plical complex was always verified by at least two physicians.
Results
In the 70 knees that were verified at time of surgery for a symptomatic synovial-plical complex, 20 had medial bands, 15 had lateral bands, 3 had superior bands, and 14 had superolateral bands. Multiple bands were found in 15 knees. Three knees did not have palpable bands using the described physical exam technique but were still scheduled for diagnostic arthroscopy based on a combination of nonspecific symptoms including popping, catching, locking, and crepitus suggestive of symptomatic synovial-plical complex (Table 1).
Table 1.
Suspected synovial-plical complex location based on physical exam and verified with arthroscopy
| Location of plica(e) | Number |
|---|---|
| Medial | 20 |
| Lateral | 15 |
| Superolateral | 14 |
| Superior | 3 |
| Multiple Locations: | |
| Medial + Lateral | 7 |
| Medial + Superolateral | 2 |
| Medial + Superior | 2 |
| Lateral + Superior | 2 |
| Medial + Superior + Lateral | 1 |
| Medial + Superior + Lateral + Inferomedial | 1 |
| None | 3 |
| Total | 70 |
Females accounted for 57 of the 80 (71.2%) symptomatic knees evaluated in this study. Males accounted for the remaining 23 (28.8%) of symptomatic knees. Trauma was the inciting event for anterior knee pain in 27 of the knees. Sports or repetitive activities were responsible for symptoms in 25 knees, and an insidious onset was described in 28 knees. Other associated subjective findings on physical exam were as follows: popping noted in 47 knees, catching in 20 knees, locking in 19 knees, and crepitus in 19 knees.
Sixty-seven of the 80 knees were diagnosed with symptomatic synovial-plical complex preoperatively by the physical and were subsequently confirmed by arthroscopy. Nine knees carried a false negative diagnosis in that the synovial-plical complex was not identified until arthroscopy but plicectomy and partial synovectomy led to symptomatic relief. One of the false negative patients was lost to follow-up. One patient carried a false positive diagnosis in that the clinical exam indicated the existence of a synovial-plical complex but none was found. The clinical exam carries a sensitivity of 83.8% and a positive predictive value of 98.6%. Specificity was not calculated because the exam technique was not performed on asymptomatic individuals and no asymptomatic individuals underwent arthroscopy.
Of the 78 patients that returned for follow-up, all reported symptomatic relief in the short-term with average follow-up of seven weeks (range 2-36 weeks). Four patients required manipulation under anesthesia after the plicectomy and partial synovectomy in order to regain their motion, with an average time of nine weeks after the original procedure.
Discussion
There is a paucity of literature describing symptomatic plicae that are not located in the medial parapatellar region. Our results suggest that while the symptomatic medial parapatellar plica plays a role in the majority of patients with symptomatic synovial-plical complex, the associated sensitive synovial tissue that often accompanies these plical bands are often found in multiple parapatellar locations which lead to the development of the symptomatic synovial-plical complex.
One of the most important steps in correctly diagnosing a symptomatic synovial plica is receiving a thorough and accurate history of the patient’s anterior knee pain. Patients may note a traumatic episode at which point they began to notice pain, others may describe a history of athletic activity or repetitive flexion/extension of the knee, and some may not be able to note any particular event. Our cohort of patients showed an even distribution of inciting events among these three categories that were used. Past surgical treatments, including arthroscopic procedures, in the knee joint have been shown to increase the risk of a symptomatic plica12,13. Twenty-five of our 79 knees with verified synovial-plical complex (32%) had at least one previous knee operation prior to their plicectomy and partial synovectomy.
Patients often describe chronic pain that progressively worsens over time and is worse with activity or after long periods of sitting or standing. The majority of our patients experienced subtle, painful popping in the parapatellar region suspected to be caused by the symptomatic synovial-plical complex snapping over the respective femoral epicondyle. Painful catching and locking of the knee joint are also commonly noted by the symptomatic synovial-plical complex patient and confirmed by our study2,12,14. Upon physical examination of the knee, there may be mild swelling, along with quadriceps wasting14. The patient will have tenderness where the synovial-plical complex is located in the parapatellar region. The frequency and location of complex described in this study and previous studies can be seen in Table 2.
Table 2.
Study comparison of frequency and location of plica(e)
| Study | Year | Mediopatellar | Suprapatellar | Lateral | Multiple |
|---|---|---|---|---|---|
| McCunniff et al. | 2013 | 20 (29%) | 17 (24%) | 15 (21%) | 15 (21%) |
| Dorchak et al. [2] | 1991 | 43 (84%) | 3 (6%) | 4 (8%) | 1 (2%) |
| Johnson et al. [7] | 1993 | 12 (27%) | 42 (48%) | 7 (16%) | 32 (69%) |
Patients will often gain relief from symptoms by eliminating the activity that aggravates the plica, whether this is their sport, running, walking, or any other repetitive flexion/extension of the knee joint. Medications such as NSAIDS and other pain relievers are of limited help to the synovial-plical complex patient. However, intra- articular cortisone and lidocaine injections often produce immediate relief and can be used as a diagnostic tool. Injections and physical therapy serve as the primary conservative treatment modality for symptomatic plicae. However, conservative treatment has yielded poor results, with success rates between 0%-16% reported in the literature12,15. It was noted that those patients who did well with conservative measures were younger (21.5 years) than the other patients (28.5 years)12.
Previous literature suggests that while the physical exam may place symptomatic plica in the differential, arthroscopy is required for definitive diagnosis2,12,14,16. On the contrary, the clinical exam used in this study demonstrated a sensitivity of 88.6% and a positive-predictive value of 98.6%. The nine incorrect preoperative diagnoses were subsequently identified arthroscopically as follows: six medial meniscus tears, two lateral meniscus tears, and one focal chondral defect on the femur. The single false positive was diagnosed as symptomatic synovial- plical complex prior to surgery but intraoperatively chondromalacia of the patellofemoral joint was the only identifiable pathology. Following arthroscopic plicectomy and partial synovectomy, relief of preoperative symptoms are typically noted 2 to 4 weeks postoperatively2. Because of this, our analysis did not use follow-up data from patients within two weeks of surgery. For the two patients lost to follow-up, relief of preoperative symptoms cannot be assumed. Although they were correctly diagnosed with symptomatic synovial-plical complex prior to arthroscopic confirmation, we cannot assume that the excision of the complex led to the relief of their symptoms. In this case, the sensitivity of the clinical exam would be 89.6% with a positive predictive value of 98.5%.
We excluded patients with secondary synovitis from chondromalacia, osteoarthritis, and others where one can envision the debris causing a reaction from the normal synovium, creating false positive findings on clinical exam for our synovial-plical complex.
Limitations
True negative patients in this report were not investigated because we did not prospectively record arthroscopic findings in patients with a history and physical suggestive of an etiology other than the synovial-plical complex. Such etiologies including rheumatoid arthritis, severe chondromalacia, or patellofemoral osteoarthritis. While our focus was providing immediate relief of clinical symptoms post-operatively, a limitation of this study is the short-term follow-up, with a mean postoperative follow-up at 7 weeks. Dorchak et al. addressed long-term results following plicectomy of plica limited to the medial shelf, describing 51 patients, 38 (75%) with excellent or good results at an average follow-up of 47 months. All patients in this cohort had improved clinical outcome scores postoperatively compared to preoperatively15. Hardaker et al. reviewed the results of plicectomy of plica in all locations and reported excellent or good results in 97% of 61 patients at an average follow-up of 19 months12.
While videos are available for the complete findings on physical exam, this journal does not have the online capability at this time.
Conclusion
Our findings suggest that a careful physical exam can correctly identify the presence of the symptomatic synovial-plical complex. Several authors have suggested that the clinical diagnosis of a pathological plica is one of exclusion and arthroscopy is the only way to verify or disprove a symptomatic synovial-plical complex. However, we have demonstrated a unique physical exam that is reproducible and can accurately diagnose the congenitally present, symptomatic synovial-plical complex. We have also demonstrated causality because the surgical removal of the synovial-plical complex in recalcitrant cases brings immediate relief of the pain syndrome. The existence of the symptomatic synovial-plical complex should always be made preoperatively in order to avoid the errors of the past.
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