Imaging Report

I. Radiological Findings

Based on the provided knee MRI images and the patient’s history (47-year-old female with several months of left knee pain and a palpable mass in the popliteal fossa), the lesion is primarily located within the deep soft tissue near the left popliteal fossa and shows a relatively large area of fat density/signal. The specific findings are as follows:

• On T1-weighted images, the lesion presents a uniformly high signal, similar to normal subcutaneous fat signal.
• On T2-weighted sequences, the lesion signal does not appear markedly increased, with some fibrous septa showing slightly lower signal.
• On STIR or fat-suppression sequences, the fatty signal of the lesion becomes significantly darker (suppressed), suggesting the lesion is mainly composed of fatty tissue.
• The lesion boundary remains clear, with no obvious erosion or destruction of adjacent bone, and no apparent soft tissue infiltration or significant enhancement changes.

Overall, the imaging demonstrates typical features of a fatty soft tissue mass, with no noticeable inflammatory reaction in surrounding tissues.

II. Potential Diagnoses

Based on the patient’s age, clinical symptoms (popliteal pain and a palpable mass), and the MRI findings showing a fat-containing lesion, the potential diagnoses include:

1. Lipoma
   A common benign adipose tumor that appears on imaging with a high T1 signal similar to fat. Fibrous septa may be visible but without obvious enhancement, and the lesion has a well-defined boundary with minimal infiltration into surrounding tissue. Deep and/or intramuscular lipomas are more common in males but also occur in females.
2. Well-differentiated Liposarcoma
   Although less common, it must be considered in the differential diagnosis of deep fatty tumors. It often presents with heterogeneous signal in some areas or mild enhancement of fibrous septa, as well as nodular enhancement on contrast imaging. However, the current imaging does not show any obvious evidence of malignancy.

III. Final Diagnosis

Based on the patient’s age, symptoms, imaging findings, and growth pattern of the mass, the most likely diagnosis is: a deep lipoma (suspected intramuscular lipoma).

If there is still concern about malignancy, a further pathological biopsy can be considered to clarify the nature of the tumor. However, based on the existing imaging data and the patient’s clinical presentation, a lipoma is more likely.

IV. Treatment Plan and Rehabilitation

1. Treatment Strategy

• Observation and Follow-up: If the tumor size is stable, pain is mild, and there is no significant functional impairment, consider temporary observation with periodic MRI or ultrasound monitoring of the mass.
• Surgical Treatment: Since the tumor is located deep and is relatively large, surgery (marginal excision) may be considered in the following cases:
  • Significant pain or impairment of knee function.
  • Evidence of neurovascular compression or concern about potential malignancy.
  Surgery typically involves a complete marginal excision, with a good prognosis and a low recurrence rate after complete removal.

2. Rehabilitation and Exercise Prescription

For patients undergoing postoperative rehabilitation or conservative treatment, it is recommended to develop an individualized exercise program under the guidance of a professional physician or rehabilitation therapist, progressively restoring joint range of motion and muscle strength.

• Joint Range of Motion Training (Early Stage)
  Passive or assisted active flexion and extension exercises of the knee can be performed 2–3 times a day, each session lasting 5–10 minutes. Avoid excessive stretching that may cause pain or tissue damage.
• Muscle Strength Training (Mid Stage)
  After pain relief, gradually increase resistance exercises for the quadriceps, hamstrings, and other knee-surrounding muscle groups. Use resistance bands or light weights 2–3 times per week, with 8–12 repetitions for each exercise. Maintain proper form and allow adequate rest.
• Aerobic and Functional Training (Later Stage)
  If the surgical incision or condition allows, low-impact aerobic exercise (e.g., cycling, swimming) can be performed 3–4 times a week for 20–30 minutes per session. Gradually transition to light jogging or other higher-level functional activities to improve cardiopulmonary fitness and lower-limb muscle coordination.
• Principles of Exercise (FITT-VP)
  Frequency: 2–4 times per week, depending on tolerance and pain relief.
  Intensity: Begin at low intensity and gradually progress to moderate intensity.
  Time: Start each session with a 5–10 minute warm-up, continue the main training for 20–30 minutes, and finish with a 3–5 minute cool-down.
  Type: Emphasize joint flexibility exercises, muscle strength training, and low-impact aerobic activities.
  Volume and Progression: Increase the training load or duration every 2–3 weeks according to the patient’s recovery, while monitoring pain and knee stability.
• Safety Precautions
  If knee swelling, marked increase in pain, or incision-related discomfort occurs, exercise should be paused or reduced, and medical evaluation should be sought promptly.

Throughout the rehabilitation process, close communication with specialists, rehabilitation therapists, or sports medicine professionals is essential. Continually evaluate any changes in the condition and adjust the program accordingly.

Disclaimer

This report is based on the provided medical history and imaging information solely for reference purposes. It cannot replace in-person consultation or professional medical advice. If you have any doubts or if symptoms worsen, please seek medical attention promptly.