Plica of the knee - the great mimic

"A young soccer player finds himself frustrated, unable to find out what is wrong with his knee. After submitting to extensive physiotherapy and two lots of surgery he finds out that his symptoms are due to a thickened plica." - case presentation by Dr Angus Strover.

footballer

J.L. is a 16 year old schoolboy. He is a talented sportsman, playing soccer, tennis, squash and running to keep fit.

About 18 months ago he tried to get fit enough to compete in middle distance athletics but had to give it up because he developed pain in his right knee which developed after running. The pain was quite severe and was situated above the knee cap and on the inner side of the knee. The pain was aggravated by going downstairs but not by going up. He was unaware of any swelling, but said that the knee felt hot on occasion. The pain was associated with a regular click under the kneecap. He noticed the clicking more in the morning on first getting up and going downstairs to the bathroom. Besides the pain and clicking, J.L. noticed that his knee became stiff and ached when he sat in one position for any length of time.

Struggling for a diagnosis

J.L. sought treatment from the club physiotherapist (PT) who taped the kneecap and gave him V.M.O exercises (vastus medialis obliquus - ie the inner quads muscle). Although this seemed to help in the first instance, as time went on the exercises made the pain worse and his physio suggested that he sought advice from a podiatrist as J.L. had pronated (flat) feet which is known to often aggravate knee pain. The physio felt that the problem might be corrected by appropriate inserts into his footware.

J.L. spent £300 (about $500) on inserts for his shoes and trainers but his knee pain got worse until he noticed that he could only run about a mile or play soccer for about 20 minutes before the pain stopped him from continuing the exercise. Pain on stairs was becoming an everyday occurrence and J.L. stopped playing soccer and stopped jogging.

He sought advice from his G.P. (primary care practitioner) who did some blood tests and prescribed anti-inflammatory tablets, rest and ice. The pain and clicking settled down during this period, but immediately returned when he went back to sporting activities. He asked for a referral to an orthopaedic surgeon with an interest in sports medicine.

Surgery fails to reveal diagnosis

This orthopaedic surgeon examined J.L.'s knee and suspected chondromalacia and maltracking of the patella, or else some damage to his joint surface or his meniscal cartilages. He ordered an X-ray, which was normal, and an M.R.I. scan which was also reported as normal. He decided to do an arthroscopy as a day case.

The arthroscopy showed normal appearances to the meniscal cartilages, ligaments and joint surfaces, but the surgeon took photographs and kept a video of the procedure. He also did a biopsy of the synovial membrane.

The biopsy showed 'non-specific synovitis' (inflammation without obvious cause) and the surgeon advised that a steroid injection into the joint might help.

The injection into the knee did help for about 6 weeks, but then the symptoms came back.

More rehab but still no diagnosis

The surgeon sent J.L. to another physiotherapist, who decided to do an isokinetic test. This tests the muscles working the joint at maximum strength at a pre-determined speed through a full range of movements. The test was painful and the physio asked J.L. to score the pain on a scale of 1 to 10. J.L. said that at its worst the pain was about 5 out of 10.

Again he was given quadriceps exercises, but J.L.'s pain returned when he went back to playing squash and running.

Ah-haa!

Finally J.L. was referred to another surgeon who felt that the story was typical of 'the plica syndrome'. He explained that a synovial plica is a fold of the synovial membrane - the inner lining of the knee joint. These folds are normal structures which develop in the first eight weeks of a pregnancy when the embryo's joints are developing in its limbs. In most people synovial plicae (plural of plica) do not give problems. But in some people, often following a minor injury such as a direct blow on the knee, a synovial plica becomes inflamed and loses its normal elastic compliant nature. It then forms scar tissue which clicks as it slides across the surfaces of the joint and with exercise the plica becomes painful and inflamed. The process is on-going and progressively becomes worse with time especially after sporting activities.

The surgeon explained that a plica can be missed during arthroscopy if the knee was not examined from above. He also explained that it is frequently unreported on MRI scan as a plica is generally considered a normal finding. But in his own clinical experience it is a frequent cause of problems.

J.L. was persuaded to have another arthroscopy during which this surgeon inspected the joint from an entry portal (small surgical cut) above the kneecap. A thickened plica was found and a video showed the entrapment of the plica between the patella and the femur whilst the knee was being bent to 90 degrees.

The plica was completely removed during the surgery.

After the operation J.L.'s knee was swollen for four weeks and he was given gentle mobilisation, anti-inflammatory tablets and ice on the knee. During the next three months the knee became stronger, the swelling went completely, the clicking diminished and was not painful and, finally, at six months after the operation J.L. returned to soccer, running and squash. Stairs are now no problem and J.L is delighted with the complete absence of any pain in his knee.

Plica Syndrome

What is a Plica?

A plica is a fold of synovial membrane most commonly in the anteromedial aspect of the knee. Plica are present in about 50% of the population and are thought to be the remnants of embryonic connective tissue that failed to fully resorb during your foetal development. Luckily, most plicae are asymptomatic.

While your knee potentially has four plica it is the medial plica that is most likely to be symptomatic (Dupont 1997). It runs parallel to your medial patella just below your medial retinaculum and inserts into your fat pad.

What is Plica Syndrome?

Plica syndrome is essentially an inflammed plica. Your plica can catch during:

repetitive knee straightening and bending,

blunt trauma or knee twisting,

fat pad irritation,

altered knee motion,

internal knee derangements eg meniscal tears. (Schindler 2004)

This is particularly the case if you have experienced persistent pain and weakness in the quadriceps muscles. Plica syndrome often does not always occur in isolation, but concurrently with other knee conditions such as meniscal injuries, patellar tendonitis and Osgood-Schlatter’s Disease.

What are the Symptoms of Plica Syndrome?

Plica syndrome can be suspected when you have:

Anteromedial knee pain - esp medial femoral condyle.

Visible and palpably tender plica.

Audible clicking or snap during knee motion - painful arc 30 to 60 degrees. (Dupont 1997).

Positive Duvet test: pain eased by using a duvet between your knees to ease pain in bed.

Pain with activities: ascending and descending stairs, squatting, rising from a chair and/or sitting for extended periods. (Shetty et al 2007).

Quadriceps atrophy is common on chronic cases.

How is Plica Syndrome Diagnosed?

Your physiotherapist will be able to clinically diagnose plica syndrome. It is more important that you have your knee thoroughly assessed by a physiotherapist or sports doctor to exclude other knee pathologies, in particular meniscal injuries.

X-ray may be useful to rule out other associated pathologies but will not identify a plica. MRIs can identify plica inflammation. However, MRI is more useful for diagnosing other pathologies that may be related to the plica irritation. A comprehensive examination by your physiotherapist or sports physician is preferable.

Plica Syndrome Treatment

Studies show that about 60% of patients with plica syndrome will settle successfully with conservative physiotherapy treatment within 6 to 8 weeks. (Lu et al 2010).

Your physiotherapy treatment will aim to:

Reduce pain and inflammation.

Improve patellofemoral (knee cap) alignment via taping, bracing and exercises.

Normalise your muscle lengths.

Strengthen your knee: esp quadriceps (esp VMO) starting with closed-chain exercises and eventually progressing to open-chain exercises

Strengthen your hip and lower limb muscles.

Address foot biomechanics issues.

Improve your proprioception, agility and balance.

Improve your lower limb function and quality of movement eg walking, running, squatting, hopping and landing.

Minimise your chance of re-aggravating your plica syndrome.

We strongly suggest that you discuss your knee injury after a thorough examination from a knee specialist such as a sports physiotherapist, sports physician or knee surgeon.

Plica Surgery

Should your symptoms persist beyond 3 to 6 months, arthroscopic knee surgery for a plica syndrome may be considered. The most successful surgery involves lateral retinacular release to allow the patella to track more medially and thereby alleviate plica irritation as it rolls over the medial femoral condyle. Success rates exceed 85%. (Gerbino et al 2007).

How to Prevent Plica Syndrome?

Since plica syndrome usually occurs concomitantly with other knee conditions, it is important to be proactive in managing your other knee injuries. This involves maintaining normal knee joint alignment, adequate strength and flexibility in the muscles around the knee joint plus the rest of the lower limb.

Ensuring that you wear adequate footwear that supports your foot biomechanics. Also, weight-management can play a role in the pressure exerted on lower limb joints, and thus should be something considered as a long-term preventative measure.

For more advice, please consult your physiotherapist.

Braces for Plica Irritation

Many patients will try a knee brace. Brace that improve patellofemoral joint alignment seem to be the most effective to ease plica-related pain.

Patellofemoral Brace

An effective patellofemoral brace can be useful as an alternative to kneecap taping.

What is the Plica Syndrome?

The 'plica syndrome' is a group of symptoms that are commonly associated with the presence of an abnormally thickened plica.

Illustration of medial plica

A plica is a fold of the soft inner lining of the knee joint (this lining is called the 'synovium', so a plica is also often called a 'synovial plica'). Plicae (plural) are remnants of structures which existed in the foetus (in the womb) and which subsequently fell away to a lesser or greater extent as the knee developed. In some people they are still significant stuctures and in other people they may be completely absent.

Symptoms of the plica syndrome will depend upon which plica is causing the problem. A problematic medial plica may have the following associated with it:

pain along the inner aspect of the patella

a string-like cord under the skin in this area

intermittent 'catching' of the joint at a particular point in extension

occasional 'pseudo'-locking, ie the joint seems to lock but can be easily unlocked

stiffness and pain after sitting still for a long time, eg at a movie

occasional giving-way

Typically plicae are found in three positions -

suprapatellar (SPP) (above the patella or kneecap)

infrapatellar (IPP) (below the patella), sometimes called the 'ligamentum mucosum' or 'filmy ligament' as it mimics the cruciate ligament inside the knee, but is not a ligament at all.

medial (MPP) (on the inner aspect of the knee). It may form a shelf-like band and is then referred to as a 'medial shelf'.

Image showing plicae in the straightened knee

In the illustration on the left, looking at the knee bones of the right knee from its inner aspect, you can see the relationship of the media and suprapatellar plica. Here the leg is straight.

Image of a bent knee to show how the plicae taughten

When the knee is bent (see image on the right), the plicae taughten, and a medial plica can snap abruptly over the medial femoral condyle, while the suprapatellar plica may be nipped between condyle and the quadriceps tendon.

Image of a bent knee to show the medial plica being nipped between patella and femur

The medial plica can also become nipped (see left) between patella and condyle, causing momentary pain and 'giving way'.

A damaged plica may settle on its own, or respond to non-surgical measures such as physiotherapy or injections. However, sometimes the nipping continues and the joint cartilage becomes damaged and arthritis may set off. In this case surgery to remove the plica is the best option.

Plica Syndrome

A plica is a thin wall of fibrous tissue that are extensions of the synovial capsule of the knee. During fetal development, the knee is divided into three (3) separate compartments. As the fetus develops these compartments develop into one large protective cavity (synovial membrane). The majority of people have remnants of these three cavities referred to as a plica. Most often the plica is on the medial (inside) of the knee at the level of the medial femoral condyle. Most individuals are not adversely affected by the presence of plicas.

The plica only becomes a problem when the knee is irritated, causing an inflammation in the synovial sack. When the synovium is inflamed, the area of the plica becomes thicker. This thickened area then begins to catch on the femur as the knee moves. This in turn keeps the plica inflamed resulting in a viscous cycle.

The plica can be located anywhere in the knee. The exact symptoms will be determined by the plica’s location. The most common location is along the medial (inside) side of the knee. The plica can tether the patella to the femur, be located between the femur and patella, or located along the femoral condyle. Regardless of location the pain is due to the plica catching or being pinched between the patella and femur. If the plica connects the patella to the femoral condyle, symptoms will mimic patello-femoral syndrome.

With out a complete clinical examination, the plica may be missed, resulting in an inappropriate rehabilitation plan. For example, if the patella is tethered by the plica, the clinician may design a rehab plan to address a patello-femoral disorder. This may only exacerbate the condition. If the plica is truly tethering the patella, the rehab should focus on decreasing the inflammation, and increasing the overall strength of the quad muscles.

Treatment of Plica Syndrome

The first concern is to decrease the inflammation of the synovial capsule. This can be attacked with numerous methods. First, the orthopaedic surgeon may prescribe a non-steroidal anti-inflammatory medication. Examples of these medications are Motrin®, DayPro®, Naprosyn®, Celebrex®, and Indocin®. These medications act systemmically to slow the inflammation process. Theraputic exericses and modalities may also be used to treat the plica. To attack the inflammation, modalities such as iontophoresis (utilizing low intensity electric current to transport medications through skin), phonophoresis (using ultrasound to transport medications through skin), and ice are most commonly utilized.

Rehabilitative exercises should be instituted when the inflammation has been controlled and pain levels are falling. These exercises should focus on increasing overall quadriceps, hamstring, and calf strength., as well as increasing overall muscular flexibility. Examples of appropriate exercises are: pain-free squats that progress to one-leg squats, side step-ups, closed chain terminal knee extension, and applicable sport-specific exercises. Care should be taken to avoid deep squats as this can increase pain and inflammation.

The exercises should be performed utilizing PRE (progressive resistance exercises) principles, gradually increasing load and intensity as pain and inflammation allows.

Case Study

An 18 year old male football player presents with a history suspicious of a medial meniscal tear. This was confirmed by MRI. Surgery was performed to repair the medial meniscal tear. Upon arthroscopic evaluation the plica was found. The MRI did not visualize the plica. This plica was located on the medial synovial lining, running superiorly into the suprapatellar pouch. As can be seen in the picture, the plica is distending the synovial lining into the knee joint. The picture on the left shows the same view of the knee with the plica removed. Notice that the synovial lining is no longer pulled into the joint. The torn meniscus was also addressed.

The athlete was seen in the training room for 5 total visits in a two week span. Treatment emphasized basic quadriceps strength and range of motion. Following his 10 day post-op physician’s visit, the athlete was released to normal strength training (10 day gradual return to previous routine) in the weight room.

Plica Syndrome Treatment & Management

Medical Therapy

Medical treatment of plica syndrome has been driven largely by empirical evidence. A structured program of stretching and strengthening exercises often leads to some improvement. This may include short-arc quadriceps extension exercises (terminal approximately 20° of extension). These exercises are aimed at optimizing patellofemoral biodynamic relationships in an effort to control symptoms. A patellar knee sleeve worn during sporting activities (usually a neoprene-type brace) may also be a useful adjunct for many athletes. In addition, nonsteroidal anti-inflammatory medications are a time-tested and confirmed aid for many athletes with plica syndrome.

Surgical Therapy

Surgical therapy for plica syndrome is virtually always arthroscopic. The arthroscopic surgeon needs to exclude other potential intra-articular causes of knee pain and then address any pathologic plicae. Plica resection may be performed with arthroscopic hand instruments, a motorized soft-tissue resector, or certain commercially available electrothermal devices.

Preoperative Details

The preoperative phase of treatment involves optimizing the patient's knee strength and flexibility in an effort to streamline postoperative rehabilitation. Preoperative preparation of the patient also involves education and appropriate goal setting. For instance, the patient should understand that therapeutic exercises typically begin shortly after surgery (hours to days) and that a full return to sports can be realized soon thereafter (days to weeks). Patients who know this in advance tend to achieve these goals quite readily.

Intraoperative Details

After arthroscopic evaluation establishes that no other intra-articular abnormalities need to be addressed, the plica can be resected. Using whatever tools work best in the surgeon's hands, the plica should be resected back to a point where it no longer impinges on articular structures. With beefy synovitic plicae that extend into the patellofemoral joint space (typically 50% or more), as in the first image below, this may require extensive debridement, as in the second image below. With tough, fibrotic plicae that drape over the medial femoral condyle, this may involve little more than disruption of the tight band.

Plica syndrome. Preoperative appearance of medial

Plica syndrome. Preoperative appearance of medial parapatellar plica (a 4+ plica by the Jee classification, extending across more than two thirds of the medial facet of the patella).

Plica syndrome. Postoperative appearance of the sa

Plica syndrome. Postoperative appearance of the same patient as in Image 5 after plical resection.

At times, even a suprapatellar plica may lead to symptoms. Strover et al reported on an arthroscopic technique demonstrating the pathomechanics of such suprapatellar plicae.[31] They recommended that the arthroscope should be inserted through a lateral suprapatellar portal. Proximal visualization is then optimized. In those patients in whom the suprapatellar plica is symptomatic, progressive flexion of the knee results in the plical tissue becoming taut. It also makes contact with the medial femoral condyle and even becomes entrapped between the quadriceps tendon and medial femoral condyle.

Postoperative Details

Postoperatively, the patient is started on a structured course of therapeutic exercise that initially emphasizes reestablishment of active quadriceps control and firing. This progresses to regaining full range of motion and then full strength. The patient concludes therapeutic recovery by gradually performing more and more sport-specific exercises until a controlled reentry to the sport is achieved.

Follow-up

Follow-up care focuses on confirmation that symptoms have abated. True recurrence of the original plical pathology is quite rare and is more likely to represent either an incomplete resection or entirely new knee pathology. Continued use of a patellar stabilizing-type brace is preferred by many patients.

Complications

Complications of surgical treatment of plica syndrome are really complications associated with arthroscopic surgery of the knee. These include septic arthritis, neurapraxias or neuromas, and synovial fistulae. Reflex sympathetic dystrophy may also occur following such surgery. The rate of each of these complications is extremely small (< 1% in most cases). Only patients with particular risk factors (eg, diabetes, steroid dependence, history of RSD) may be at a significantly higher risk.

Outcome and Prognosis

The outcome of surgical treatment for well-selected patients with plica syndrome is very good.[32, 33, 34] A clinical trial conducted by Johnson et al in England demonstrated a success rate of more than 80%. In this same study, nearly 50% of patients in the control group experienced continued symptoms severe enough that they later returned for definitive arthroscopic resection of their plicae.

In a predominantly adult population (average age 25 y, age range 11-56 y), Kasim and Fulkerson reported 88% moderate-to-substantial improvement at an average of more than 4 years following resection of localized segments of painful retinacula (ie, plicae) about the knee.

Future and Controversies

Synovial plicae within the knee are clearly normal anatomic structures that can become potent pain generators.[36] Therefore, little debate exists as to whether they may become pathologically involved. Future treatment of plica syndrome may be supplemented further by improved brace designs and pharmacological treatments. Earlier recognition of patients with the syndrome might facilitate syndrome resolution by such means, in contrast to patients who experience years of symptoms.

Plica syndrome

Plica Syndrome (also known as Synovial Plica Syndrome) is a condition which occurs when a plica (an extension of the protective synovial capsule of the knee) becomes irritated, enlarged, or inflamed.This inflammation is typically caused by the plica being caught on the femur, or pinched between the femur and the patella. The most common location of plica tissue is along the medial (inside) side of the knee. The plica can tether the patella to the femur, be located between the femur and patella, or be located along the femoral condyle. If the plica tethers the patella to the femoral condyle, the symptoms may cause it to be mistaken for Patello-femoral Syndrome or ligamental plague. Plica are very well visable on MRI.

The plica themselves are remnants of the fetal stage of development where the knee is divided into three compartments. The plica normally diminish in size during the second trimester of fetal development, as the three compartments develop into the synovial capsule. In adults, they normally exist as sleeves of tissue called synovial folds. The plica are usually harmless and unobtrusive; Plica Syndrome only occurs when the synovial capsule becomes irritated, which thickens the plica themselves (making them prone to irritation/inflammation, or being caught on the femur).

Detecting a plica is nearly impossible externally. They may be confirmed via MRI or during surgery.

Plica Syndrome treatment focuses on decreasing inflammation of the synovial capsule. A non-steroidal anti-inflammatory medication NSAID is often used in conjunction with therapeutic exercise and modalities. Iontophoresis and phonophoresis have been utilized successfully against inflammation of the plica and synovial capsule. Failing these, surgical removal of the plica of the affected knee may be necessary.