Medical Imaging Analysis Report

1. Radiological Findings

Based on the provided X-ray, CT, and MRI images:

• Knee Joint Area: A cystic lucent lesion with relatively clear margins but irregular edges is seen near the articular surface of the lateral femoral condyle of the left distal femur (appearing as a low-density lucent lesion on X-ray). The lesion has a relatively large diameter, close to 50 mm.
• CT Scan: A cystic lesion is occupying a large portion of the lateral condyle of the femur, with thinning of the cortical bone. There is a risk of pathological fracture (potential or already present). Inside the lesion, imaging reveals a cystic structure without obvious signs of solid tumor tissue.
• MRI: The lesion appears as high signal intensity on T2-weighted images, suggesting that the contents may be fluid or semiliquid. Chronic changes can be observed in the surrounding bone, with evident involvement of the subchondral bone, while the soft tissue component mainly shows mild edema. Currently, there is no evident infiltration of malignant tumors.

The overall radiological findings are consistent with a large subchondral cystic lesion (“giant geode”) located in a weight-bearing region near the joint, with significant cavitation of the local bone and involvement of the subchondral bone.

2. Potential Diagnoses

Taking into account the patient's age, symptoms, and imaging findings, the following diagnoses or differential diagnoses should be considered:

1. Large Subchondral Bone Cyst (Geode): Also known as a giant cystic lesion related to degenerative joint disease. Commonly seen in osteoarthritis or when subchondral bone is under excessive load or there is inflammatory stimulation within the joint. Radiological manifestations often appear in the epiphyseal region of weight-bearing joints and may be accompanied by cartilage pathology and degenerative changes.
2. CPPD (Calcium Pyrophosphate Deposition Disease) with Subchondral Cyst: Chondrocalcinosis can cause changes similar to osteoarthritis, leading to articular cartilage degeneration and the formation of large cystic lesions. However, such cases often show calcification or evidence of calcium deposits.
3. Giant Cell Tumor: Common in relatively younger adults, frequently occurring in the epiphyses of long bones. Caution is required when the lesion is large, involves the cortex, and forms a soft tissue mass. However, in this case, there is no apparent solid tumor, and both initial examinations and surgical findings do not support malignancy.
4. Other Benign Bone Tumors or Tumor-like Lesions: Such as giant cell reparative granuloma, chondromatous lesions, etc. Imaging findings in those conditions often display some degree of calcification or trabecular changes; in this case, the lesion mainly presents as a cystic fluid accumulation with relatively uniform local bone destruction.

Based on the imaging findings and clinical presentation, after ruling out infection or malignancy, a large subchondral bone cyst (Geode) is the most likely diagnosis.

3. Final Diagnosis

Combining the patient’s age, degenerative factors, imaging findings, and surgical exploration results (the cystic lesion contained a yellowish-white fluid without any solid tumor component) as well as pathology that confirms no malignancy or infection, a diagnosis of “giant subchondral bone cyst (large Geode)” can be established.

4. Treatment Plan and Rehabilitation

4.1 Treatment Strategy

• Surgical Treatment: For a subchondral cyst of such size, with an existing or highly suspected pathological fracture risk, curettage of the lesion, debridement, bone graft filling, and internal fixation (such as using cancellous screws/plates) may be performed. In this case, curettage plus implantation of allograft and bone substitute, followed by screw fixation, was carried out.
• Assessment and Repair of Articular Cartilage: If there is evident degenerative change in the articular cartilage, procedures such as cartilage repair (microfracture technique or cartilage transplantation) or arthroscopic exploration may be considered.
• Medication: If comorbid conditions such as rheumatoid arthritis, gout, or chondrocalcinosis (CPPD) exist, additional treatment with uric acid-lowering drugs, anti-inflammatory pain relievers, or agents targeting CPPD may be prescribed under specialist guidance. Postoperatively, appropriate use of analgesics and anti-inflammatory drugs can speed up recovery.

4.2 Rehabilitation Plan (Based on the FITT-VP Principle)

The postoperative rehabilitation and exercise prescription must be individualized, preventing re-injury or premature weight-bearing. A recommended plan is as follows:

1. Early Stage (0–2 weeks post-op):
   • Frequency: 2–3 sessions of mild activity per day.
   • Intensity: Primarily passive movements and very light weight-bearing exercises, focusing on maintaining joint range of motion.
   • Time: 5–10 minutes per session, avoiding excessive fatigue.
   • Type: Straight leg raises (in sitting or supine position), ankle pumps, and other foundational exercises to prevent deep vein thrombosis and promote circulation.
   • Progression: As pain and swelling subside, begin gentle, pain-free knee flexion and extension.
2. Mid Stage (2–6 weeks post-op):
   • Frequency: 3–5 sessions per week, depending on postoperative healing and physician instructions.
   • Intensity: Gradually increase the intensity of active movement. Under the guidance of a physician or physical therapist, low-resistance exercises (e.g., using resistance bands) can be performed to strengthen the quadriceps.
   • Time: 15–20 minutes per session, extending the duration as tolerated but avoiding overexertion.
   • Type: Seated flexion-extension exercises, stationary biking (with the seat set higher to reduce knee stress), progressively increasing range of motion.
   • Progression: Once X-ray follow-up confirms good bone healing progression, gradually add weight-bearing exercises.
3. Late Stage (after 6 weeks post-op):
   • Frequency: 3–5 sessions per week, possibly incorporating activities of daily living.
   • Intensity: Gradually increase weight-bearing activities, focusing on lower-limb muscle strength and functional training such as partial squats and balance exercises.
   • Time: 20–30 minutes per session or adjusted according to individual tolerance.
   • Type: Under professional supervision, perform gait training, advanced muscle strengthening, and stability exercises to restore knee function.
   • Progression: Maintain local stability over a long period. Once bone healing is complete and muscle strength meets the target level, gradually resume low-impact sports (e.g., swimming, elliptical).

At all stages, closely monitor joint pain and swelling, increase exercise load gradually, and work under the guidance of a professional medical team.

Safety Note: If the patient has comorbid conditions such as osteoporosis, compromised cardiopulmonary function, or other chronic systemic diseases, it is crucial to communicate with orthopedic, rehabilitation, and internal medicine specialists. Adjust exercise techniques and intensity accordingly.

Disclaimer:

This report is a reference analysis based on the provided medical history and imaging data. It does not replace an in-person consultation or professional medical advice. Specific treatment and rehabilitation plans require evaluation by professional orthopedic specialists and a rehabilitation team.