Popliteal cyst

Introduction Also known as "Baker's cyst", is the synovial cyst in the medial head of the gastrocnemius. The axillary cyst is the general term for synovial cyst in the armpit. It can be divided into congenital and acquired, the former is more common in children, the latter can be caused by the disease of the bursa itself, such as chronic injury, but some patients are complicated by chronic knee joint disease.

Cause

The incidence of the elderly is mostly related to knee joint disease and proliferative arthritis.

The most common axillary cyst is the expansive gastrocnemius and semimembranosus fascia sac. The bursa is often connected to the posterior joint capsule. It is more common in middle-aged cases and has the highest incidence. Males are more than females, resulting in mechanical knee extension and The knee flexion is limited, the pain is lighter, and the tension is obvious. The patient's complaint is often characterized by a gradual swelling of the axillary area with pain in the back of the knee. Occasionally cysts can be oppressed to block venous return, causing calf edema.

an examination

Related inspection

General photo inspection

Axillary cysts occur mostly in children and the elderly, and the incidence of children is congenital and bilaterally symmetrical. The elderly are often characterized by weakness, weakness, and pain in the back of the joint. When the cyst is large, it can hinder the flexion and extension of the knee joint, and even affect the venous return of the axilla, and there may be local or sub-abdominal edema. But most patients feel that there are not many symptoms. When the cyst grows to a certain extent, the knee flexion and extension activity is limited.

Physical examination: The elastic part of the armpit can be touched. The surface is smooth, the texture is soft, the tenderness is not obvious, and it does not adhere to the skin or other tissues.

X-ray examination: Injecting air into the capsule to take X-ray films, you can find that the bursa is connected to the joint, so that the diagnosis can be confirmed.

Differential diagnosis

1. Meniscus cysts: A small number of meniscus cysts can occur in a portion far from the meniscus. Cysts originating from the medial meniscus are usually larger than those from the lateral side. When the medial meniscus cyst is involved, knee flexion is performed. Due to the pressure of the medial patellar ligament of the knee, it can disappear from the inner side of the knee and show it from the axillary fossa.

2, sacral sheath cyst: some soft tissue mass of the same hardness, this mass is easy to be confused with lipoma. The cause is unknown.

3, axillary aneurysm: axillary mass, should think of the possibility of this disease. Axillary aneurysm is not uncommon, but often missed diagnosis. Because the knee joint degeneration can be complicated by popliteal cysts, atherosclerosis can be complicated by aneurysms, both of which occur in the same age group; in addition, axillary aneurysms and axillary cysts are similar, often symmetrical and have no obvious symptoms. Therefore, the two are very confusing. When there is a popliteal cyst, the axillary artery is covered by a cyst. It is not easy to get. If the axillary part can reach the pulse in the wide range, it may have an aneurysm. In addition, if found Tremors and murmurs can strengthen the diagnosis of aneurysms. However, if the cyst of the aneurysm is embolized, these two signs are difficult to find.

4, axillary arterial cystic changes: the cause of this disease is still unclear, is considered to be associated with atherosclerosis of the adrenal mucosal degeneration. Repeated mild injury to the radial artery may be the cause Because the lesion is close to the knee joint, the regular movement of the joint may be the cause of the injury. The onset may be slow or sudden. The foot becomes cold and pale during exercise. One of the characteristics of this disease is that the mass does not always exist. The mass is only Occasionally found, this helps to avoid misdiagnosis.

5, isolated exostosis: from the femoral triangle can grow exogenous osteophytes, accompanied by a sac. This epiphysis is often associated with the above axillary aneurysms. Whether the epiphysis exists, X-ray film Inspection can be confirmed or excluded.

6, axillary varicose veins: knee joints do rapid flexion and extension exercises, a mass in the armpits, in addition to cysts, may also be a group of varicose veins, which is often another finding when the axillary exploration surgery is negative.

7, semi-membrane muscle rupture or hypertrophy: axillary mass can be unilateral semi-membrane muscle fracture or bilateral semi-membrane muscle localized hypertrophy. This mass is characterized by: the knee flexion muscle contraction resistance, the volume of the mass increases. If the disease is performed under general anesthesia, no positive findings can be found.

8, biceps tendon cysts and cysts from the lateral iliac crest: the former is low, the latter may be associated with nerve palsy. The two may also be misdiagnosed as lateral meniscus cyst.

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