There is a lump behind the knee joint

Popliteal cysts, also known as Baker's cysts, are the most common lumps behind the knee, most of which are located at the back of the knee joint. The incidence of synovial fluid in 70% of patients is related to an increase in joint fluid in the posterior horn of the medial meniscus. Hypertrophic joint fluid forms cysts through weak spots or leads to the armpit muscles behind the knee joint. The cyst opening is a one-way valve. Therefore, the joint fluid can only enter the cyst and cannot return to the knee joint cavity, so the cyst will become larger and larger.

What is the best way to perform the surgery?

Traditional open surgery can only remove popliteal cysts outside the joint from the posterior approach, and the primary lesions inside the joint cannot be resolved. It is not only traumatic but also has a high recurrence rate.

Arthroscopic knee joint cleaning + medial meniscus posterior horn repair + popliteal fossa drainage

Arthroscopic knee joint cleaning + repair and shaping of the posterior horn of the medial meniscus + internal drainage of the popliteal fossa has incomparable advantages over traditional surgical methods. The operation can be completed with only three small incisions of 5-10 mm.

First, the meniscus is treated through a conventional approach, and then a posterior medial knee access is established to find the one-way valve opening of the cyst and enlarge the opening, ultimately achieving a two-way flow of fluid between the joint cavity and the cyst.

Surgical steps 1. Incision: Make a transverse midline incision on the surface of the popliteal cyst, with the two ends slanting upward and downward to form an "S"-shaped incision. 2. Exposure: Cut the skin and subcutaneous tissue along the incision direction, expose between the deep and superficial fascia, pull the skin flap to both sides, and the cyst can be seen protruding outward. Separate along the cyst wall, trying not to break the cyst, until it reaches the pedicle of the cyst or connects to the joint capsule. 3. Cyst resection: Flex the knee joint to relax the hamstring and gastrocnemius muscles, making the cyst located between the semimembranosus and the medial head of the gastrocnemius muscle easier to expose. Then use scissors or a scalpel to further peel off the root of the cyst and completely remove it at the pedicle. 4. After closing the incision and flushing with saline, if the cyst is connected to the knee joint cavity, the joint capsule should be sutured continuously. A rubber drainage strip is placed in the incision and the incision is closed layer by layer.

Points to note during surgery

1. Nerves and blood vessels should be protected during cyst separation.

2. If the cyst wall is found to be obviously adhered to the surrounding muscles, the surface fascia should be removed together to prevent postoperative recurrence.

3. When the cyst is connected to the knee joint cavity, if the joint capsule defect is too large after cyst removal and cannot be sutured, the medial head of the gastrocnemius muscle or the tendinous part of the semitendinosus muscle can be used to suture the defect between the cyst and the joint capsule.

Postoperative care

Postoperative treatment of popliteal cyst:

1. The rubber drainage strip of the incision is retained for 2 days.

2. Apply pressure bandage to the incision after surgery.

3. Remove the stitches 2 weeks after surgery, and then start knee flexion and extension activities.

4. After the operation, the lower limbs are fixed with plaster for 2 weeks.