Knee bone cancer is a condition of abnormal, uncontrolled proliferation of bone cells in the knee area. Although rare, bone cancer often progresses silently, causing the disease to be detected at a late stage. Recognizing the signs of knee bone cancer is important for patients to be diagnosed and treated promptly.
1. Types of bone cancer
Bone cancer occurs when bone cells proliferate abnormally, without control, destroying normal bone tissue.
Not all bone tumors are bone cancer, but benign bone tumors account for the majority. Benign bone tumors, although non-invasive and non-metastatic to other organs of the body, can still weaken bones and lead to fractures. Some common types of benign bone tumors are osteochondroma, giant cell tumor, osteoid osteoma, osteoblastoma, and enchondroma.
Bone cancer includes two main types: primary bone cancer and secondary bone cancer.
1.1. Primary bone cancer
Primary bone cancer (osteosarcoma) is a malignant tumor that originates from the body's skeletal system. The cause of primary bone cancer is still being studied, but genes may be related to this disease.
The most common types of primary bone cancer are:
• Osteosarcoma: Osteosarcoma often appears around the knees and arms. The most common age of Osteosarcoma is adolescents and young adults. Adults with Paget's disease of bone are also at risk of Osteosarcoma.
• Ewing's sarcoma: The disease usually occurs between the ages of 5-20. Common lesions of Ewing's sarcoma are in the ribs, pelvis, legs and arms. Sometimes the disease originates from the soft tissue around the bone.
• Chondrosarcoma: Chondrosarcoma originates from cartilage cells, patients with Chondrosarcoma are usually between the ages of 40-70. The hips, pelvis, legs, arms and shoulders are common lesions of the disease.
It should be noted that multiple myeloma is not a primary bone cancer, but a disease of the bone marrow.
1.2. Secondary bone cancer
In addition to primary bone cancer, which is cancer originating from the bone, secondary bone cancer is bone damage caused by cancer in other organs that metastasizes to it, such as: Breast cancer metastasizes to the bone, lung cancer metastasizes to the bone, prostate cancer metastasizes to the bone, etc.
2. Causes and risk factors of knee bone cancer
The cause of bone cancer in general and knee bone cancer in particular is due to the abnormal division of bone-forming cells, leading to the formation of malignant bone lesions. As mentioned above, genetic factors may play a role in leading to primary knee bone cancer. Secondary knee bone lesions may be caused by primary cancer in other organs that metastasizes to it.
In addition, it is found that knee bone cancer may be associated with a number of risk factors such as:
• History of cancer treatment: The use of chemotherapy, radiotherapy, stem cell transplantation, etc. to treat cancer in the past increases the risk of bone cancer, including knee bone cancer.
• Li-Fraumeni syndrome, retinoblastoma: These diseases increase the risk of bone cancer.
• Paget's disease of bone: Although Paget's disease of bone is a benign disease, it can be a risk factor for the disease to progress and become bone cancer.
• Young age: Young people are at higher risk of bone cancer. The average age of bone cancer patients is 20 years old.
3. Symptoms of knee bone cancer
If knee bone cancer is detected and treated early, up to 80% of patients live more than 5 years. However, knee bone cancer can develop silently, and by the time symptoms appear, the disease may have metastasized to other organs. The disease may be accidentally discovered when the patient has a knee injury, or some other problems that the patient is prescribed an X-ray of the knee area. Some symptoms of knee bone cancer may include:
3.1. Knee bone pain
Knee bone pain is the most common sign of knee bone cancer, the bone tumor in the knee area causes the patient to feel pain and discomfort. Initially, the pain is usually mild, intermittent, and increases when the patient moves the knee joint, then the frequency of pain increases, the level of pain also increases and increases at night, and is less responsive to normal pain relievers. This causes the patient to limit movement, affecting daily life.
It should be emphasized that trauma is not the cause of bone cancer, however, the disease can be detected after a minor injury to the knee area that causes the patient to be hospitalized and have an X-ray or CT scan.
3.2. Swelling of the knee area
Patients with knee bone cancer may show symptoms of swelling in the knee area around the bone. This symptom can be confused with benign bone and joint diseases such as: Arthritis, osteoarthritis, ...
3.3. Limited mobility
Knee bone cancer with bone loss, swelling and pain in the knee area can cause patients to limit knee joint mobility. Patients may limp to avoid pain, or due to abnormal bone structure in the knee area. Some patients with knee bone cancer also have muscle atrophy due to limited mobility.
3.4. Pathological fracture
Patients with a fracture after a slight impact on the knee area may have a manifestation of pathological fracture, including knee bone cancer. Bone cancer makes the bone tissue weaker, reduces its load-bearing capacity, and even a slight trauma can cause a fracture.
3.5. Systemic symptoms
Knee bone cancer, or cancer in general, often causes patients to feel tired and lose weight. Some patients with knee bone cancer have fever or night sweats.
In addition, patients may experience some other systemic symptoms due to metastasis of knee bone cancer to other organs (most commonly lung metastasis).
4. Paraclinical diagnosis of knee bone cancer
After clinical examination and medical history, the patient will be assigned the necessary tests to diagnose knee bone cancer.
4.1. Imaging diagnosis
Imaging diagnostic techniques that allow examination and assessment of bone lesions include:
• X-ray: This technique shows the image of the bone tumor in the knee area and its size.
• Computed tomography (CT Scan): Also uses X-rays like X-ray, however, the image of the bone tumor on CT scan will be more detailed and clearer, helping to assess the size and characteristics of the tumor more accurately. In addition, patients with knee bone cancer may be prescribed a whole-body computed tomography scan to evaluate the stage of primary bone cancer, or find the primary cancer organ that has metastasized to the knee bone.
• Magnetic resonance imaging (MRI): Magnetic resonance uses the properties of magnetic fields to examine the knee bones as well as the soft tissues and organs surrounding the bones.
• PET Scan: This technique helps detect cancer cells more quickly and accurately.
• Bone scan: Bone scan is a technique of injecting radioactive material into the vein, then using a scanner to detect malignant bone tissue.
• The doctor can also do a blood test to look for two types of enzymes that can be a sign of leukemia.
4.2. Pathology
The standard for diagnosing cancer is generally histopathology. The doctor will perform a biopsy of the bone tumor in the knee area and send it to a pathologist to examine the specimen from a macroscopic and microscopic perspective, thereby making a definitive diagnosis of whether the bone tumor is benign or malignant, primary or secondary bone cancer, etc.
5. Treatment of knee bone cancer
Good cancer treatment should be agreed upon after a multidisciplinary consultation between plastic surgeons, chemotherapy, radiotherapy, palliative care, psychologists, etc. The treatment method will be discussed and selected depending on the pathological characteristics of knee bone cancer, the stage of the disease, the age and physical condition of the patient as well as concomitant diseases (if any), etc. The treatment of bone cancer in the localized stage and the distant metastatic stage is completely different.
Common bone cancer treatment methods include:
5.1. Surgery
• Conservative surgery: The doctor will perform surgery to remove the malignant bone tumor but limit the impact on surrounding tissues such as tendons or soft tissues. The patient may be prescribed a knee replacement to support movement, the defect of the pathological bone in the knee area can be replaced with a metal implant,
• Amputation: If the knee bone tumor is large or touches the nerves or blood vessels, amputation may be indicated and the patient is fitted with a prosthetic leg to move.
5.2. Radiation therapy
Radiotherapy may be prescribed along with surgery to destroy cancer cells and shrink the bone tumor.
5.3. Internal medicine
• Chemotherapy: Chemotherapy is a method of using chemical drugs to destroy cancer cells. Depending on the stage of knee bone cancer, chemotherapy may be prescribed before surgery / after surgery, or prescribed for cases of distant metastasis.
• Targeted therapy: Targeted therapy also uses drugs to treat cancer, but this therapy targets certain characteristics (genes, proteins), or other changes in cancer cells.
In summary, knee bone cancer in particular and bone cancer in general is a rare malignancy with many different types of disease. The disease often has late onset symptoms, making treatment more difficult and complicated. Therefore, recognizing the early signs of knee bone cancer is important for timely diagnosis and effective treatment.
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