Medical Analysis Report

I. Imaging Findings

1. X-ray (lateral view of the knee joint): The bony structure and articular surfaces of the knee joint appear largely normal, with no obvious bony destruction or fracture lines. The patella is in a normal position. Soft tissue swelling is observed in the posterior aspect of the knee joint, but no obvious erosion or abnormal changes of the bony structures are seen.
2. Ultrasound: In the posterior aspect of the knee joint (possibly in the popliteal fossa or within the deep soft tissue), there is an oval-shaped soft tissue mass with fairly well-defined borders. The internal echo is predominantly hypoechoic, and the capsule is not clearly delineated. The course of deep nerves is not clearly visualized.
3. MRI: In the deep soft tissue of the posterior knee, there is a round or oval soft tissue lesion with relatively clear margins. On T1-weighted images, it appears isointense or slightly hypointense, while on T2 or PD-weighted images it appears hyperintense. Post-contrast imaging shows varying degrees of enhancement. No obvious abnormal signal erosion into or around bone is observed, nor any significant bony destruction. The lesion shows relatively homogeneous or slightly heterogeneous enhancement; no clear imaging of any nerve bundles entering or exiting the lesion is seen.

II. Possible Diagnoses

1. Neurilemmoma (e.g., Neurofibroma or Schwannoma): A soft tissue mass that grows slowly and may be associated with the course of a nerve. Neurofibromas often show a fusiform shape along the nerve trunk without a well-defined capsule, while Schwannomas are usually eccentric and well encapsulated. On imaging studies, they typically appear hyperintense on T2-weighted images and can enhance with contrast.
2. Lipoma or other fat-containing lesions: These usually show high signal intensity on T1-weighted images, but in this case, the T1 signal does not suggest obvious fat components, thus ruling out a purely adipose lesion.
3. Popliteal cyst (Baker’s cyst): Typically presents as a synovial cystic protrusion from the knee joint, showing high signal intensity on T2 (fluid characteristics), often communicating with the joint space. In this case, the lesion appears more like a solid mass rather than a cystic lesion.
4. Other soft tissue tumors (e.g., leiomyoma, myxoma, chondrosarcoma, etc.): Additional characterization with enhancement patterns and clinical presentation is needed for further differentiation. The absence of significant bone erosion or soft tissue destruction makes a highly malignant lesion less likely.

III. Most Likely Final Diagnosis

Taking into account the patient’s history of having this mass since childhood, its gradual enlargement over the past two years, and resulting limitation in knee flexion, along with MRI findings of a relatively well-defined boundary and some degree of enhancement—but without definitive evidence of nerve “extension” into or out of the lesion—there is a strong suspicion of a “solitary neurofibroma.” Typically, this is a benign peripheral nerve sheath tumor with a slow growth pattern. There is no clinical evidence supporting neurofibromatosis (NF), which further supports the likelihood of a solitary lesion.

IV. Treatment Plan and Rehabilitation

1. Treatment Strategy
   1) Conservative Observation: If the tumor grows slowly, causes mild symptoms, and does not significantly impair nerve function or joint activity, regular follow-up and imaging are possible to monitor its size and relationship with surrounding structures.
   2) Surgical Removal: If the tumor significantly impairs function (e.g., restricted knee movement in this case) or causes persistent pain or nerve compression symptoms, surgical resection is usually recommended. During surgery, maximal care should be taken to preserve the involved nerve structure. Pathological analysis after surgery is needed to confirm the diagnosis.
2. Rehabilitation and Exercise Prescription
   Whether the patient opts for watchful waiting or undergoes surgical resection, maintaining or restoring joint function is crucial. The FITT-VP principle can be applied systematically:
   • Frequency: Perform joint function training 3–5 times per week, adjusting based on muscle fatigue and recovery status.
   • Intensity: Start with low to moderate intensity, avoiding excessive stress on the joint. Gradually increase according to tolerance.
   • Time: Each session can last about 20–30 minutes and may be divided into segments; if tolerated, it can be gradually extended to around 45 minutes.
   • Type: Include both active and passive joint exercises, light resistance training (e.g., resistance bands), and low-impact aerobic exercises (such as cycling or using an elliptical machine) to maintain knee flexibility.
   • Progression: As joint mobility and strength improve, resistance or training intensity can slowly be increased. Reassess every 2–4 weeks for appropriate adjustments.

   During rehabilitation, avoid excessive stretching or manipulation of the affected area to prevent nerve irritation or microtrauma. In the postoperative phase, once the surgical incision is healed and upon medical clearance, gentle joint movement exercises and a tailored physical therapy program should commence.

Disclaimer

The above report is based on the available imaging and clinical history for reference, and does not replace an in-person diagnosis or professional physician’s clinical opinion. In case of any questions or changes in condition, seek medical attention promptly and follow up with specialized examinations and recommendations from clinical experts.