Imaging Analysis Report

I. Imaging Findings

Based on the patient’s complaint of flexion-extension difficulties and inability to fully extend the knee at 9 months post-surgery, combined with a history of anterior cruciate ligament (ACL) reconstruction, the MRI examination of the knee shows the following main features:

• A focal, spore-like (nodular) soft tissue lesion is observed in front of the ACL graft, exhibiting a slightly higher signal compared to typical fibrous tissue, with relatively well-defined margins.
• This nodular lesion is located between the femur and the tibia, potentially becoming compressed when the knee is fully extended.
• The reconstructed ACL graft has relatively uniform signal intensity without clear evidence of fiber rupture. Graft positioning appears acceptable, with no indications of significant bony impingement.
• Other intra-articular structures remain largely intact, with no evident new meniscal tears or bone contusions.

II. Potential Diagnoses

Based on the imaging findings and clinical history, the following diagnoses or differential diagnoses are considered:

1. Focal anterior joint fibroproliferation (Cyclops lesion): Commonly seen after ACL reconstruction, characterized by a small nodular fibrous or fibrocartilaginous mass in the anterior portion of the joint, which can cause limited knee extension (extension deficit).
2. Graft impingement: If the ACL graft is placed too anteriorly or if the notch space is insufficient, the graft may impinge against the femoral notch or surrounding soft tissues, causing pain or limited mobility. However, no obvious evidence of a graft positioned too far anteriorly or a narrowed notch was found in this case.
3. Extensive joint fibrosis (Arthrofibrosis): Typically presents more diffusely with widespread intra-articular fibrous adhesions or scarring on imaging, rather than a single focal lesion as seen here.

III. Most Likely Final Diagnosis

Considering the limitation in knee extension 9 months post-surgery, the nodular fibrous proliferative lesion noted on the anterior aspect of the joint on MRI, and the common presentation of a “Cyclops lesion” after ACL reconstruction leading to mechanical extension block, the most likely diagnosis is:

“Cyclops lesion” (focal anterior joint fibroproliferation)

If there is still diagnostic uncertainty, arthroscopic evaluation for direct visualization and possible lesion resection can be considered.

IV. Treatment Options and Rehabilitation Plan

1. Treatment Strategy
   • For a confirmed Cyclops lesion causing significant extension deficit, arthroscopic resection of the lesion is the primary treatment, effectively alleviating mechanical impingement.
   • If the lesion is small and symptoms are not severe, initial conservative management may be attempted, including NSAIDs (non-steroidal anti-inflammatory drugs) for pain control and physical therapy to improve knee extension. However, for cases severely affecting knee function, arthroscopic surgery is generally recommended.
2. Rehabilitation and Exercise Prescription
   During postoperative rehabilitation or conservative treatment, a training program can be developed following the FITT-VP principle (Frequency, Intensity, Time, Type, Progression, Personalization):
   • Frequency: Initially, rehabilitative exercises can be done 1–2 times daily, adjusted based on the knee’s response.
   • Intensity: Exercise intensity should not provoke significant pain or discomfort, with particular emphasis on restoring knee extension. Gradual intensity increases under the guidance of a professional physical therapist.
   • Time: Each session is typically 20–30 minutes and includes warm-up, stretching, range-of-motion exercises, and cooldown.
   • Type:
     • Range-of-motion training: Emphasize passive or assisted-active exercises for knee extension to prevent recurrent adhesions.
     • Muscle strengthening: Focus on isometric and isotonic exercises targeting the quadriceps and other muscles around the knee, while also considering balanced training of the hamstring muscles.
     • Balance and proprioception training: Aimed at improving knee stability and enhancing proprioceptive feedback.
   • Progression: Gradually increase the difficulty level as knee range-of-motion and pain tolerance improve, for example by introducing weight-bearing exercises for the lower limbs or adding resistance bands.
   • Personalization: If other knee pathologies or health conditions (e.g., osteoporosis, limited cardiopulmonary function) exist, frequency, intensity, and exercise modes should be appropriately adjusted. Collaboration with rehabilitation and sports medicine specialists may be necessary.

Disclaimer

This report is a reference analysis based on current imaging and clinical information, and cannot replace an in-person consultation or professional physician assessment. Specific diagnosis and treatment should be conducted by a qualified clinician, taking into account the patient’s actual condition.