From the Guidelines
The patient's symptoms and radiographic findings are highly suggestive of a bone tumor, specifically a primary malignant bone tumor.
Key Findings
- The patient has a one-month history of generalized left knee pain, primarily localized inside the knee, with initial swelling on the left upper side, and no preceding trauma or injury.
- Radiographic findings include left knee joint effusion, mild degenerative changes, and an oval-shaped lucency in the proximal tibial metadiaphysis.
Diagnostic Considerations
- The presence of persistent non-mechanical pain in any bone lasting more than a few weeks should cause concern and lead to further immediate investigation 1.
- The patient's age and symptoms, such as duration, intensity, and timing of complaints, are crucial in determining the likely diagnosis of a suspected bone tumor 1.
- Conventional radiographs in two planes should always be the first investigation, and when the diagnosis of malignancy cannot be excluded with certainty on radiographs, the next imaging step is magnetic resonance imaging (MRI) of the whole compartment with adjacent joints 1.
Next Steps
- The patient should be referred to a bone sarcoma reference center or an institution belonging to a specialized bone sarcoma network before biopsy 1.
- A biopsy of the suspected primary malignant bone tumor should be carried out at the reference center by the surgeon who is to carry out the definitive tumor resection or a radiologist member of the team 1.
- The patient's symptoms and radiographic findings are consistent with a primary malignant bone tumor, such as osteosarcoma, which typically arises around the knee and presents with pain, swelling, and limitation of joint movement 1.
From the Research
Diagnosis Considerations
The patient's symptoms, including a one-month history of generalized left knee pain, primarily localized inside the knee, with initial swelling on the left upper side, and radiographic findings, suggest several potential diagnoses.
- The presence of left knee joint effusion, mild degenerative changes, and an oval-shaped lucency in the proximal tibial metadiaphysis may indicate a localized tenosynovial giant cell tumor (TGCT) of the knee, as described in 2.
- The patient's age and lack of preceding trauma or injury are consistent with the presentation of TGCT, which can remain asymptomatic for a long time but may cause mechanical symptoms as the mass grows.
- The radiographic findings, including the oval-shaped lucency, are also consistent with the MRI characteristics of an intraarticular localized TGCT, as described in 2.
Differential Diagnosis
Other potential diagnoses to consider include:
- Patellofemoral joint osteoarthritis (PFJOA), which can cause pain and disability, as described in 3.
- However, the patient's symptoms and radiographic findings do not strongly suggest PFJOA, as the disease typically presents with distinctive clinical features such as dramatic swelling, valgus deformity, and markedly reduced quadriceps strength.
- Candidal periprosthetic joint infection is unlikely, as the patient has not undergone total knee arthroplasty, and the presentation is not consistent with the symptoms described in 4.
- The relation of patellofemoral joint alignment, morphology, and radiographic osteoarthritis to frequent anterior knee pain, as described in 5, may not be directly relevant to this patient's presentation, as the pain is not localized to the anterior knee.
Further Evaluation
A thorough evaluation, including a detailed patient history, physical examination, and imaging studies, is necessary to confirm the diagnosis.
- The patient's symptoms and radiographic findings should be correlated with the results of additional imaging studies, such as MRI, to confirm the presence of a localized TGCT.
- A biopsy or histopathological examination may be necessary to confirm the diagnosis and rule out other potential causes of the patient's symptoms.