Imaging Findings

The patient is a 13-year-old boy who has experienced pain at the posteromedial side of the right knee for 3 months. MRI, CT, and X-ray examinations were performed. The imaging findings are as follows:

• X-ray: A round or nearly round radiolucent lesion is seen in the distal femoral epiphysis (near the articular surface) of the right knee. There is a mild sclerotic margin and the lesion is well-demarcated.
• CT Scan: The lesion is also confined to the distal femoral epiphysis, showing a well-defined lytic change. The local cortical bone is intact without obvious interruption, but slight expansion or thinning may be observed. A small amount of calcification or calcified spots can be seen, suggesting chondroid components.
• MRI Findings: The lesion has a relatively clear border and appears hyperintense on T2-weighted images with a multilocular or multi-lobulated internal structure. There is surrounding bone marrow edema signal. Soft tissue around the lesion does not show obvious swelling or signs of an abnormal soft tissue mass.

In summary, the lesion is primarily located in the epiphysis, shows a well-demarcated area of bone destruction with scattered calcifications, and appears hyperintense on T2-weighted imaging with surrounding edema.

Potential Diagnoses

1. Chondroblastoma
   It commonly occurs in adolescents when the growth plate is still open, and often involves the epiphysis or apophysis of long bones. It frequently presents as a lytic lesion affecting the adjacent joint and may show minimal calcification. This patient’s age and location are characteristic of chondroblastoma, making it a top consideration.
2. Giant Cell Tumor (GCT)
   Most commonly found in individuals aged 20–40, often extending across the growth plate to the metaphyseal-epiphyseal region, and usually occurs after the epiphyseal plate has closed. Given this patient’s younger age and open growth plate, GCT is less likely.
3. Intraosseous Ganglion Cyst
   Typically found in the shaft or subchondral region of the proximal joint, presenting as a cystic lesion. It often lacks marked calcification, and most affected patients are adults. The lesion in this case is more specifically located in the epiphysis and thus does not fully match a typical bone cyst.
4. Clear Cell Chondrosarcoma
   A rare malignancy, usually seen in adults. It contains cartilaginous tissue and can appear as a lucent bone lesion on imaging, but tends to be more aggressive with rapid progression. Given the patient's age and the imaging features, a malignant tumor is less likely.
5. Brodie’s Abscess
   A localized abscess of chronic osteomyelitis, usually located in the metaphysis or metaphyseal-epiphyseal region. This case strongly suggests a chondroid lesion in the epiphysis rather than an infectious process, making an infectious cause less likely.

Final Diagnosis

Based on the patient’s age, the typical location of the lesion in the epiphysis, the well-defined lytic appearance with scattered chondroid-type calcifications on imaging, and histopathological findings, chondroblastoma is the most likely diagnosis.

Treatment Plan and Rehabilitation

Treatment Strategy:

• Surgical Treatment: In cases with significant symptoms or larger chondroblastomas, curettage of the lesion and bone grafting or bone filling are typically performed to maintain bone stability and reduce the risk of recurrence.
• Other Considerations: For smaller lesions with mild symptoms, observation can be considered, but surgical intervention is generally preferred to prevent local progression and preserve joint function.

Rehabilitation and Exercise Prescription (FITT-VP Principle):

1. Early Stage (0–6 weeks postoperatively)
   • Frequency: 1–2 times per day of mild rehabilitation exercises.
   • Intensity: Focus on passive range of motion and isometric muscle contractions, staying within the pain threshold.
   • Time: 10–15 minutes each session, progressing gradually.
   • Type: Gentle exercises for knee joint mobility, such as straight leg raises and isometric quadriceps contractions; a brace may be used if necessary.
   • Progression: Increase the angle and frequency of passive movements based on tissue healing status.
2. Intermediate Stage (6–12 weeks)
   • Frequency: 3–4 times per week.
   • Intensity: With minimal pain, gradually increase muscle strength and joint stability, potentially initiating limited weight-bearing.
   • Time: 20–30 minutes each session.
   • Type: Introduce light resistance training (e.g., resistance bands or low-weight equipment) and gait training (partial weight-bearing or using crutches), focusing on maintaining knee stability.
   • Progression: Gradually transition to partial weight-bearing while monitoring knee response and pain levels.
3. Late Stage (12 weeks and beyond)
   • Frequency: 3–5 times per week.
   • Intensity: As joint function significantly improves, progress to full weight-bearing and incorporate more functional exercises.
   • Time: 30–45 minutes each session.
   • Type: Emphasize improving joint flexibility, muscular strength, and coordination with activities such as walking on level ground, cycling, or swimming, avoiding high impact and rotational stress.
   • Progression: If tolerated without discomfort, gradually increase difficulty, such as step training or short-distance light jogging, under the guidance of a specialist or physical therapist.

Regular follow-up imaging is required throughout rehabilitation to rule out recurrence or complications. In the event of significantly increased pain or marked restriction in joint mobility, immediate medical evaluation should be sought.

Safety Note: Since the growth plate in adolescents is not fully closed, it is essential to avoid high-impact and excessive weight-bearing exercises. Continuous monitoring of joint and bone development is necessary to prevent secondary injuries.

Disclaimer: This report is based on current imaging and clinical information and is for reference only. It is not a substitute for in-person consultation or advice from a medical professional. Specific diagnosis and treatment should be determined by an orthopedic or relevant specialist according to the patient’s actual condition.