Popliteal cyst 2

Popliteal cyst is the most common cystic disease around the knee joint. Alyssa M. Herman from the University of Buffalo in the United States reviewed the current literature on popliteal edema, and its findings were published in the orthopedics of August 2014. This review mainly discusses the anatomy and etiology of Popliteal cyst, describes clinical manifestations, reviews differential diagnosis, provides appropriate diagnostic methods, contrasts conservative treatment, minimally invasive treatment and traumatic treatment, and discusses the results of treatment.

Popliteal edema is usually caused by the expansion of the gastrocnemius-half-membrane muscle sac on the medial part of the popliteal fossa, which was first reported by Baker, also known as Baker's cyst. The gastrocnemius-half-membrane muscular synovial sac is a normal anatomical tissue, which is located between the gastrocnemius muscle and the half-membrane muscular tendon. The synovial SAC is communicated with the knee sac through a transverse hole, which is located at the posterior part of the articular capsule at the lateral femoral condyle level, and the gastrocnemius tendon is connected with the knee joint sac at the medial condyle of the femur.

The transverse hole is usually a horizontal crack of 4 to 24 mm in size. The synovial sac usually does not communicate with the articular cavity in the child stage, and the chance of a gap increases as the age increases. The integrity of the knee joint is reduced with age, and there is a theory that the gap is caused by a degenerative knee sac tear. Rauschning observed that the joint SAC can still be observed in the same area of the cyst for people without joint gaps, suggesting that the popliteal edema may be caused by synovial hernia. A true sheath cyst is usually a fluid formed from a diagonal line or a horizontal medial meniscus fissure, characterized by the formation of a thick fibrous connection to the tissue wall (Fig. 1).

Fig. 1 MRI images of tendon sheath cyst around meniscus

The joint surgery showed that the joint fluid was moving between the gastrocnemius-half-membrane muscle synovial sac and the two cavities of the knee joint sac. The valve mechanism was found in some communication gaps, allowing only the single direction of the joint fluid flow to the synovial sac. To measure the internal pressure and intra-articular pressure of popliteal cyst in rheumatoid patients, the internal pressure of all patients was higher than that of intra-articular pressure. The fluid accumulates inside the cyst, although the internal pressure is high, but does not flow away, indicating the existence of a one-way valve mechanism.

There are some different viewpoints about valve-like mechanism, and some bunsen-type mechanism is proposed. Other people think that it is a functional valve mechanism, that is, from the gastrocnemius muscle, half-membrane muscle, the tendon of the half tendon tension and extrusion of the formation of the interaction. In either mode, the single-direction flow of joint fluid plays an important role in the formation of popliteal cyst. According to the above view, tendon sheath cysts are usually formed when exudation occurs, such as intra-articular lesions and arthritis or degeneration. The extra fluid was squeezed into the gastrocnemius-half-membrane muscle synovial sac to maintain normal knee pressure, causing the inner pressure of the synovial sac to be higher than normal.

The prevalence of popliteal cyst is determined by population research methods and diagnostic techniques. In asymptomatic adults, the rate of detection is 4.7% to 37%. Different definitions can also lead to different prevalence rates, Johnson et al believes that only the gastrocnemius-half-membrane muscle synovial sac and the joint cavity, do not need to appear synovial lesions, can be called popliteal edema. It has been reported that the prevalence of popliteal edema is 6.3% in children. In adults, although the prevalence of popliteal cyst is different, often secondary to intra-articular lesions.

Sansone et al found 94% of popliteal cyst associated with knee disease. The most common is meniscus injury, followed by anterior cruciate ligament rupture and cartilage lesions. Meniscus injury, 70.2% is the medial meniscus tear, usually the posterior angle. Of the 180 145 patients with popliteal edema, 50.6% had osteoarthritis, 20.6% had rheumatoid arthritis, 13.9% had gout, 7.8% had a serum-negative spinal disease, and 7.2% had a focal phosphate joint lesion.

Clinical manifestations

In children, popliteal edema is often found in physical examinations. Sometimes the parents find the cyst by a lump. Usually formed before the age of 15, and asymptomatic, and the knee is not related to exudation. Occasionally, cysts are associated with intra-articular lesions (exfoliative osteoarthritis, meniscus tearing). When the cystic mass around the knee is visible, the imaging examination should be done.

In adults, there is often a palpable pain in the posterior part of the knee, local swelling and lumps, and a tension in the popliteal fossa area. The history and physical examination found that cysts are usually associated with joint lesions, such as meniscus injury and arthritis. Soft lumps can be reached in the medial popliteal fossa. Most cysts are inside the posterior part of the knee, rarely on the outside, round, smooth, fluctuating, and may be tense when dilated. When the knee is stretched, the cyst hardens and softens when buckling, called Foucher.

Large popliteal masses can limit the knee flexion and stretch activities. It is reported that less than half of the patients diagnosed with the popliteal cyst have positive signs. The differential diagnosis of popliteal fossa tumors mainly includes benign and malignant tumors (synovial, bone, fat, hamartoma), popliteal fossa aneurysm, deep venous thrombosis (DVT), meniscus cyst, and tendon sheath cyst. As the popliteal cyst is lined with synovial membranes, it is often associated with other diseases such as inflammation, osteoarthritis, pigmented chorionic villus nodules synovitis and synovial sarcoma.

The cyst squeezes the posterior part of the knee and the other anatomical structures are related to their size and location. Compression of the popliteal artery and popliteal vein respectively caused ischemia and thrombosis, and the compression of the tibial and peroneal nerves caused peripheral neuropathy. Usually popliteal edema is chronic condition, if the cyst breaks into soft tissue, also can acute attack, typical performance calf ache, sometimes accompany calf swelling. After the patient complained of the calf swelling, the lump in the popliteal fossa disappeared.

DVT and superficial thrombophlebitis may also present these symptoms, so it is necessary to have an imaging examination to exclude DVT. The clinical manifestations of pseudo-thrombotic phlebitis are the same as DVT and superficial thrombophlebitis, but they are caused by ruptured popliteal cyst. It is also possible that pseudo-thrombotic phlebitis and DVT occur simultaneously, but this is rarely the case. Discoloration or bruising on the calf, ankle or back of the foot is a specific characteristic of the rupture of the cyst.

It is reported that ruptured popliteal edema may occur after anticoagulation therapy without prior treatment, but may also be a result of mechanical and pharmacological specific effects. When combined with arthritis, inflammatory fluid flows into the surrounding tissues, causing the patient's calf skin to continue to itch. Patients with a history of arthritis and rheumatoid arthritis, the onset of sudden pain swelling in the calf often suggests a rupture of the cyst. The treatment of the cyst after rupture is usually treated with the corresponding complication, but the non-complication rupture cyst can be relieved by the conservative supportive treatment.

Imaging diagnosis

Multiple imaging methods can be used to diagnose and evaluate popliteal cyst. The flat sheet is simple enough to provide only limited information. But it helps to identify related joint diseases, such as free body, osteoarthritis, arthritis. Other imaging methods are more suitable for diagnosing popliteal cyst. In the past, the use of joint contrast surgery, but like the operation of traumatic and contrast agent may be extravasation and other shortcomings. The injection of contrast agent causes the internal pressure of the knee to increase, the liquid is squeezed into the flounder muscle-half membrane muscle slide sac, expands the normal synovial sac, affects the popliteal lump swelling. Compared with the joint radiography and ultrasonography, some of the popliteal masses detected in the joint radiography were not detected in the ultrasound examination. The same cyst was larger than the ultrasound examination in the joint radiography.

Because the ultrasound is simple, relatively inexpensive, non-invasive, non-radiation, so quickly replace the joint radiography examination. The popliteal edema showed clear boundary on the ultrasound, and there was no echo or low echo liquid zone between the gastrocnemius muscle and the medial head tendon of the half membrane muscles. Ultrasound could evaluate the size of cysts, adjacent muscles, tendons, blood vessels, free body in the capsule and segmentation. In addition, ultrasound can be identified with the popliteal fossa aneurysm and the cyst of the tendon sheath and other diseases. Three-dimensional ultrasound systems combine two-dimensional images to automatically calculate cyst volume using measurement software. However, ultrasound is not sensitive to intra-articular lesions, so it is necessary to further identify related intra-articular diseases.

MRI is a gold standard for identifying masses around the knee joint. MRI can not only evaluate the relationship between the cyst and the surrounding tissue and intra-articular anatomy, but also show the related intra-articular lesions. In addition, MRI is non-invasive and has no radiation advantages. The popliteal cyst was shown as T1 weighted low-signal mass on MRI. The unique advantage of MRI is the axial presentation of the cyst with the fluid-filled neck of the joint transport (Fig. 1), which facilitates the selection of surgical treatment options. After rupture of Popliteal cyst, the surrounding soft tissue and fascia showed high signal.

There are a number of factors to consider when choosing a diagnostic method. MRI is more expensive than joint radiography and ultrasound. Ultrasound may be the right choice for diagnosing popliteal edema. MRI is necessary to determine the presence of cysts and the diagnosis of knee joint lesions.

Treatment and effectiveness

The method of treating popliteal edema depends on the underlying etiology and related diseases. Sometimes no treatment or simple support treatment can also alleviate the symptoms of popliteal edema. If conservative treatment is ineffective, minimally invasive surgical treatment should be chosen.

Ultrasound-guided aspiration and corticosteroid injection in the treatment of knee arthritis with popliteal edema is a low-risk and more successful method. In the Acebes et al study, the use of aspiration and intra-articular corticosteroid injection to treat knee arthritis patients with popliteal edema, 4 weeks after follow-up found that the knee pain and swelling significantly reduced, the size of the cyst decreased significantly, 43% patients with the wall thinning, 66% of patients with improved joint activity. The decrease of cyst volume is related to the improvement of joint activity. The long-term effects of this method were not reported, although there were no cases of cyst thickening and thickening of the cystic wall after 4 weeks.

Another similar approach is to inject corticosteroids directly into the popliteal cyst. In another study, this method was used to divide the knee patients into two groups based on the complexity of popliteal edema. About 25% of patients with cysts have a separation or other abnormalities that are attributed to complex groups. After ultrasound-guided aspiration, these patients were treated directly to the cyst after 1 weeks, 1 months, and 6 months follow-up. After 6 months, the size of the cyst decreased before treatment, and the knee pain was relieved. The recurrence of the cyst occurred in 6 patients, and it is worth mentioning that all recurrent patients were from complex groups. Complex cysts are very difficult to aspirate due to the presence of capsular septum and residue in the sac. Given the long-term efficacy of corticosteroid injections in complex cysts, the classification of popliteal edema is helpful in choosing the appropriate treatment modality.

Recently, the effects of intra-articular injection and intra-capsular corticosteroid therapy were compared. In the 2 weeks after treatment, the volume of the two groups was decreased and the size of the cysts was not changed. However, at 4 weeks and 8 weeks, the cyst diameter and the thickness of the sac wall were significantly smaller than intra-articular injection. Direct injection in the SAC will reduce the size of the cyst more greatly.

Hardening therapy, which injects irritating substances into the SAC, has a long history. Injecting agents such as alcohol, phenol, tetracycline, and A Group of purulent Streptococcus were used to harden the sac cavity. Hardening therapy is suitable for patients with meniscus injury and frequent onset of symptoms. After 7 months of hardening therapy (12.5% dextran cod liver oil), the size of the cyst was significantly reduced in MRI. Although the results of this approach are acceptable, more evidence is needed to support the safe and effective treatment. The use of fibrin glue as sealant has attracted attention, but there is no reported support in the literature.

Although Conservative and minimally invasive therapies are suitable for some patients with popliteal edema, some patients still need surgical intervention. At present, due to open surgery in the popliteal fossa line S or Z-shaped incision, often left complications. Therefore, arthroscopy is most commonly used for the treatment of popliteal edema, the direct treatment of cysts.

The main objective of surgical treatment is to resolve potential intra-articular lesions and to reduce chronic joint exudation. There is a theory that only removing exudation lesions can cause popliteal edema spontaneous remission. This has been confirmed in a group of 20 patients who underwent meniscus tear, cartilage injury, synovitis treatment. Meniscus Tear was partial meniscus excision, mild cartilage injury was not treated, moderate cartilage injury was removed, and severe cartilage injury using micro fracture technique. Synovitis was removed by synovial membrane. No treatment is done for the cyst and the Transport Department. The 1-3-year follow-up showed that the cyst of 16 patients with 11-digit patient was still present. 11 patients with remaining cysts had 10 anterior articular cartilage injury at 3 to 4 levels, which meant that arthroscopic treatment of severe cartilage injury was limited, at least not by reducing exudation, and the cyst was self-relieving. This result raises a new question as to whether exudation is the only cause of the disease, and whether the restricted Gastrocnemius-semi-membranous muscle and intra-articular traffic can impede the normal flow of fluid after the exudation occurs.

It is reported that the other surgical method is the use of standard arthroscopic treatment of intra-articular lesions, and then use a mechanical knife to expand the valve mouth to 3 to 4 mm. The principle of operation is to increase the width and emptying of the joint with the cyst between the transport, restore the two sides to the fluid flow, repair gastrocnemius-half membrane muscle synovial sac. After the 3-month ultrasound follow-up, all patients showed a smaller cyst, and most of the cysts subsided 12 months after surgery.

Some scholars believe that the best treatment for popliteal edema is to close the traffic between the cyst and the joints. 22 patients underwent arthroscopic treatment of meniscus tear, cartilage injury, or both, through posterior medial entrance arthroscopic suture of the cyst and joint traffic (Fig. 2). The 2-year MRI follow-up revealed that 64% patients had disappeared, 27% cysts were smaller, and 9% cysts still existed. 96% patients with clinical symptoms improved.
Fig. 2 Arthroscopic repair of the opening of the valve of the popliteal cyst. Through the absorbable suture (A), use the probe to hook back the suture (B) and knot the closure of the cyst opening (C).

There are also surgical methods, in addition to the treatment of joint diseases, and excision of cysts. Excision ranges include fibrous membranes, diaphragms, and cysts in the nodules. A 36-month follow-up study, which included 31 patients with this procedure, found that 94% patients underwent significant improvement in clinical symptoms. The 8.6-month MRI follow-up showed that 55% patients had disappeared and the remaining 45% cysts were smaller. A similar study, which included 105 patients, also supported the procedure.

Arthroscopic treatment of popliteal edema is better than open surgery due to the small and low risk of arthroscopic treatment, the direct solution of intra-articular lesions and cysts, and the creation of opportunities for early rehabilitation.

Baker ' s Cyst-topic Overviewbaker's cyst guide

• Topic Overview
• References
• Credits

What is a Baker ' s cyst?

A Baker's cyst is a pocket of fluid that forms a lump behind the knee. It is also called a popliteal cyst. See a picture of a Baker ' s cyst.

What causes a Baker ' s cyst?

A Baker's cyst was caused when excess joint fluid was pushed into one of the small sacs of tissue behind the knee. When this sac fills with fluid and bulges out, it's called a cyst. The excess fluid is usually caused to conditions such as rheumatoid arthritis or osteoarthritis that irritate the knee. It may also is caused by an injury.

What is the symptoms?

Often a Baker ' s cyst causes no pain. When symptoms occur, they may include:

• tightness or stiffness behind the knee.
• Swelling behind the knee that could get worse when you stand.
• Slight pain behind the knee and into the upper calf. You is most likely to feel if you bend your knee or straighten it all the.

Sometimes the pocket of fluid behind the knee can tear open and drain into the tissues of the lower leg. This can cause swelling and redness in the the leg.

How is a Baker s cyst diagnosed?

Your doctor would examine Your knee and ask you questions on Your past health and when the pain and swelling started. Your doctor may order tests, such as an MRI, to see a picture of the inside of Your knee.

How is it treated?

A Baker's cyst may go away in its own.

If arthritis or another problem is causing the Baker's cyst, your doctor may treat that problem. This usually makes the pain and swelling of a Baker's cyst go away.

If a cyst does not go away, or if it's causing a lot of pain, your doctor could drain the fluid with a needle. You also is given a shot ofsteroid medicine to reduce swelling. Need to use a cane or crutch and wrap your knee in an elastic bandage. In rare cases, a Baker's cyst is removed by surgery.

There is things you can does at home to help you feel better.

• Rest your knee as much as you can.
• Take over-the-counter medicines to reduce pain and swelling. These include ibuprofen (Advil, Motrin) and naproxen (Aleve).
• Use a cane, crutch, Walker, or another device if your need help to get around. These can help rest your knee.
• If you wear a elastic bandage around your knee, make sure it's snug but isn't so tight that your leg is numb, tingles, or Swells below the bandage. Loosen the bandage if it is too tight.
• Follow your doctor ' s instructions about what much weight you can put on your knee.
• Stay at a healthy weight. Being overweight puts extra strain on your knee.

Popliteal cyst 2