Medical Analysis Report

1. Imaging Findings

Based on the MRI images of the patient’s left knee joint, the following main features are observed:

• Within the anterior cruciate ligament (ACL), an unevenly high signal suggests mucoid-like changes.
• On T1-weighted images, the ACL fiber bundles appear less clearly delineated, but still maintain overall continuity. On T2/PD-weighted images, more pronounced high signal suggests possible mucoid degeneration or small cystic lesions within the ligament.
• The ligament appears slightly thickened or “bulky.” Small cystic changes are seen in the surrounding area, and at the femoral or tibial attachment, there may be small intraosseous cystic lesions (suspected bone cysts).
• No obvious loose bodies are detected within the joint space, and no definite acute tear is observed in the meniscus or cartilage.
• No high-signal extension to the ligament surface is noted, and there are no other imaging signs of ligament instability.

2. Potential Diagnoses

Based on the above MRI findings, together with the patient’s age and symptoms, the following diagnoses are considered:

1. Mucoid Degeneration of the Anterior Cruciate Ligament (ACL):
   Common in middle-aged and older adults. Characterized by uneven high signal within the ACL but with intact fibers and no clear signs of instability, which aligns with the imaging features in this case.
2. Ganglion Cyst of the ACL Sheath:
   Appears on MRI as a cystic structure, often coexisting with mucoid degeneration. Larger cysts may cause mechanical symptoms.
3. Chronic Partial Tear or Scar Changes of the Ligament:
   A chronic partial tear may show irregular thickening or increased signal of the ligament, but usually presents with underlying or explicit instability. Since no significant clinical instability is evident here, this possibility is lower on the list.
4. Intraosseous Ganglion:
   Commonly located at the ligament attachment site, appearing as a high-signal cystic change within the bone on MRI. It has a relatively high rate of coexistence with mucoid degeneration of the ACL.

3. Final Diagnosis

Considering the patient’s prolonged left knee pain (18 months), the MRI findings of an intact yet clearly mucoid-degenerated ACL, and no functional instability, the most likely diagnosis is:

Mucoid degeneration of the ACL.

If necessary to definitively rule out associated ganglion cyst or other lesions, further clinical evaluations or arthroscopic assessment may be considered.

4. Treatment Plan and Rehabilitation

1. Treatment Strategies:

• Conservative Treatment (First Choice): If pain is mild and there are no major activity limitations, physical therapy and reduction of excessive weight-bearing activities can be employed, along with oral pain relievers or non-steroidal anti-inflammatory drugs to alleviate symptoms.
• Arthroscopic Treatment: If there is significant mechanical locking, limited range of motion, or persistent pain, arthroscopic exploration and necessary debridement or decompression could be considered.
• Regular Follow-up: Check every 3–6 months to evaluate symptom relief and ligament stability. Imaging follow-up may be done as needed.

2. Rehabilitation/Exercise Prescription (Following the FITT-VP Principle):

• Frequency: Engage in knee-focused functional exercises 3–5 times per week.
• Intensity: Start with low-intensity exercises to avoid excessive load on the knee joint, gradually introducing resistance bands or elastic cords.
• Time: 20–30 minutes each session, which can be split into sets (e.g., 5–10 minutes per set with a 1–2 minute rest in between), based on tolerance.
• Type: Emphasize non-weight-bearing or low-impact exercises such as seated knee extension, straight leg raises, seated or recumbent cycling, and resistance band training for the lower limbs.
• Progression: Once symptoms improve, gradually introduce prolonged standing, slow walking, or aquatic exercises, followed by light squats or wall-sits.
• Individualization (Volume & Progression): Adjust session duration and intensity according to patient tolerance and knee pain levels. Discontinue exercise and seek medical advice if significant discomfort or pain worsens.

During rehabilitation, pay particular attention to the following:

• Avoid sudden rotational movements or abrupt impact loading.
• For middle-aged or older patients with existing risks (e.g., osteoporosis or other joint disorders), ensure exercise movements are stable and progress gradually.
• Regularly consult with a rehabilitation therapist or orthopedic specialist to adjust the rehabilitation plan.

Disclaimer:
This report is a reference analysis based on existing imaging data and clinical information. It does not replace in-person consultations or professional medical advice. If you have any questions or experience worsening symptoms, please seek medical attention or consult the appropriate specialist.