Lymphoma Behind the Knee: Causes, Symptoms, and Treatments

What is Lymphoma?

Lymphoma is a type of cancer that begins in the lymphatic system, an essential part of the body’s immune system. The lymphatic system includes a network of lymph nodes, vessels, and organs, such as the spleen and thymus gland, which work together to fight infections and remove waste from the body. 

Lymphoma occurs when lymphocytes, a type of white blood cell, grow uncontrollably and form tumors in the lymph nodes or other parts of the lymphatic system.

Lymphoma can occur almost anywhere in the body since the lymphatic system is widespread. It can affect people of all ages, but certain factors might increase the risk, such as age, genetics, and exposure to certain infections or chemicals.

Types of Lymphoma

There are two main types of lymphoma:

• Hodgkin Lymphoma (HL): This type of lymphoma is characterized by the presence of Reed-Sternberg cells, which are large, abnormal lymphocytes. Yale Medicine reports that approximately 8,500 to 9,000 individuals in the U.S. are diagnosed with Hodgkin's lymphoma annually. HL is less common than non-Hodgkin lymphoma and tends to affect younger adults. It usually starts in the upper body, such as the chest, neck, or underarms.
• Non-Hodgkin Lymphoma (NHL): NHL includes a diverse group of lymphomas that differ in how they develop and spread. As reported by the American Cancer Society, non-Hodgkin lymphoma is among the most prevalent cancers in the United States, comprising about 4% of all cancer cases. It is more common than Hodgkin lymphoma and can occur at any age. NHL can develop in various parts of the body, including the lymph nodes, spleen, and other organs.

Causes of Lymphoma

Lymphoma, including behind the knee, can develop due to a variety of factors:

• Genetic Factors: Genetic mutations, whether inherited or occurring spontaneously, can cause lymphocytes to grow uncontrollably, leading to lymphoma. Although genetic testing can identify some risks, most lymphoma cases are not directly linked to known genetic mutations.
• Immune System Deficiencies: A weakened immune system, such as in individuals with HIV/AIDS or those on immunosuppressive drugs, significantly increases the risk of lymphoma. A healthy immune system, supported by proper nutrition, exercise, and infection prevention, is crucial in lowering this risk.
• Infections: Certain infections like Epstein-Barr Virus (EBV) and Hepatitis C Virus (HCV) are associated with a higher risk of lymphoma. These infections can cause chronic inflammation or directly alter lymphocytes, leading to cancerous growth.
• Environmental and Lifestyle Factors: Long-term exposure to chemicals like pesticides and radiation, along with lifestyle choices such as smoking, can increase the risk of lymphoma. Reducing exposure to these factors and maintaining a healthy lifestyle can help lower the risk.
• Age and Gender Considerations: The risk of lymphoma generally increases with age, particularly for non-Hodgkin lymphoma. Hodgkin lymphoma often affects younger individuals, especially those in their 20s and 30s. Cleveland Clinic notes that non-Hodgkin lymphoma is slightly more prevalent in men and individuals assigned male at birth compared to women and those assigned female at birth.

General Symptoms of Lymphoma

Lymphoma, whether it occurs behind the knee or elsewhere in the body, often presents with a range of general symptoms that can sometimes be mistaken for other illnesses. 

These symptoms are typically related to the body's response to the abnormal growth of lymphocytes and the immune system's efforts to fight the disease.

Common general symptoms of lymphoma include:

• Swollen Lymph Nodes: Painless swelling in lymph nodes, commonly in the neck, armpits, or groin.
• Fever: Persistent, unexplained fever that doesn’t seem to be linked to an infection.
• Night Sweats: Excessive sweating at night, often drenching bedclothes and sheets.
• Fatigue: A constant feeling of tiredness that doesn’t improve with rest.
• Weight Loss: Unintentional and significant loss of weight without trying.
• Itching: Persistent itching, either localized or generalized, without a clear cause.

Lymphoma Behind the Knee

Lymphoma behind the knee is a rare manifestation of lymphoma that occurs when cancerous lymphocytes develop in the lymph nodes located in the popliteal fossa, the area behind the knee joint. 

The popliteal lymph nodes are part of the larger lymphatic system, which plays a critical role in the body’s immune defense. When lymphoma affects these nodes, it may not only cause discomfort but also signal the spread of cancerous cells from other parts of the body.

Specific Symptoms Related to the Knee

When lymphoma affects the lymph nodes or tissues behind the knee, it can cause specific symptoms that are often localized to that area:

• Swelling in the Knee Area: The lymph nodes behind the knee may become enlarged, leading to visible swelling or a noticeable lump under the skin.
• Knee Pain or Discomfort: Swelling of the lymph nodes can press on surrounding nerves or tissues, causing pain ranging from a dull ache to a sharp, stabbing sensation.
• Restricted Movement: The swelling or mass behind the knee can limit the range of motion in the knee joint, making it difficult to fully bend or extend the leg.
• Redness and Warmth: The area around the swollen lymph nodes may appear red and feel warm to the touch, indicating inflammation.

If you're experiencing any of these specific symptoms behind the knee, it's wise to use a Symptom Checker tool to evaluate your condition. However, remember that this tool is not a replacement for professional medical advice, so always follow up with a healthcare provider for accurate diagnosis and treatment.

Diagnosis of Lymphoma Behind the Knee

Accurately diagnosing lymphoma behind the knee requires a combination of assessments and tests to ensure a comprehensive understanding of the condition.

• Medical History and Physical Examination: The doctor will inquire about symptoms like knee swelling, pain, restricted movement, and general signs of lymphoma such as fatigue, fever, and night sweats. They will also consider any family history of cancer, autoimmune diseases, and exposure to risk factors like infections or chemicals. During the physical exam, the doctor will check for lumps, palpate lymph nodes to assess size and tenderness, and examine the knee for redness, warmth, and range of motion.
• Blood Tests: Blood tests play a crucial role in diagnosing lymphoma. A Complete Blood Count (CBC) measures levels of various blood cells, while blood chemistry tests evaluate organ function. Elevated Lactate Dehydrogenase (LDH) levels can indicate tissue damage, often seen in aggressive lymphomas. These tests are typically combined with imaging and biopsy for a definitive diagnosis.
• Imaging Tests: Imaging is essential for visualizing lymph nodes and assessing the extent of lymphoma. X-rays help detect bone involvement, while CT scans provide detailed cross-sectional views, revealing swollen lymph nodes and masses. MRI scans, particularly useful for soft tissue evaluation, highlight areas of edema and cellularity, helping to clearly visualize the tumor's extent.
• Lymph Node Biopsy: A lymph node biopsy is the definitive test for diagnosing lymphoma. It involves removing a tissue sample from the swollen lymph node behind the knee for microscopic examination. This can be done via needle biopsy or excisional biopsy, depending on the node's size and location, to determine the specific type of lymphoma and guide treatment.
• Bone Marrow Biopsy: If there's a suspicion that lymphoma has spread to the bone marrow, a bone marrow biopsy may be performed. This involves extracting a small sample of bone marrow, typically from the hip bone, to check for lymphoma cells and assess the stage and spread of the disease, which is vital for treatment planning.

Treatment Options for Lymphoma Behind the Knee

Once the diagnosis is confirmed, the next step is to explore the various treatment options available for managing lymphoma behind the knee:

• Chemotherapy: Chemotherapy uses powerful drugs to kill or stop the growth of cancer cells. It can be systemic (affecting the whole body) or localized, depending on the lymphoma's type and stage. Typically, chemotherapy involves multiple cycles administered orally, intravenously, or through injections over several weeks or months.
• Radiation Therapy: Radiation therapy targets and destroys cancer cells in specific areas, such as the knee. It’s often used when lymphoma is confined to one area or to shrink a tumor before surgery. This treatment is delivered in several sessions, precisely targeting the tumor to minimize damage to healthy tissue.
• Targeted Therapy: Targeted therapy uses drugs that specifically attack cancer cells based on their genetic mutations or proteins, sparing normal cells. These therapies generally have fewer side effects than traditional chemotherapy and are effective in treating certain types of lymphoma.
• Immunotherapy: Immunotherapy boosts the body’s immune system to better recognize and attack cancer cells. It includes treatments that either stimulate the immune system or use lab-made substances to enhance the immune response. Immunotherapy is often combined with other treatments and has shown promising results for certain lymphomas.
• Stem Cell Transplant: For aggressive or recurrent lymphoma, stem cell transplants may be recommended. This procedure involves replacing damaged bone marrow with healthy stem cells, either from the patient (autologous) or a donor (allogeneic). It's typically used after high-dose chemotherapy or radiation.
• Localized Treatment for Knee Lymphoma: When lymphoma affects the knee, localized treatments may be necessary. This can include targeted radiation, surgery to remove the tumor or affected lymph nodes, and physical therapy to restore knee mobility and strength after treatment.