1. Radiological Findings

Based on the patient’s knee X-ray and MRI findings:

• A small structure within the left knee medial meniscus (posterior horn or root) exhibiting signal intensity similar to normal bone, suggesting the presence of a “meniscal ossicle.”
• An irregular signal and discontinuity in a portion of the meniscus, indicating a possible posterior root tear.
• MRI demonstrates a small increase in joint fluid, with some slices showing signs of effusion.
• No obvious large-scale fracture is observed, but the stability of the left knee joint may be affected, consistent with the patient’s history of instability.

2. Potential Diagnoses

1. Meniscal Ossicle with Meniscal Tear: Considering the history of trauma from a bicycle accident, along with MRI findings of a bone marrow-like signal within the meniscus and evidence of a meniscal tear, this is the primary consideration. A meniscal ossicle in the posterior horn or root area is typical.
2. Loose Body (intra-articular bone or cartilage fragment): A focal dense lesion seen on a plain X-ray can suggest a loose body, but MRI shows that this lesion is connected to the meniscal tissue and exhibits a bone-like signal. This finding is more indicative of a meniscal ossicle rather than a separate loose body.
3. Local Calcification or Other Ectopic Calcification: In certain trauma or degenerative processes, calcification can occur in joint cartilage or ligaments. However, in this case, confirming the presence of bone marrow components supports the diagnosis of an ossicle.

3. Final Diagnosis

Taking into account the patient’s age (29 years), history of trauma (bicycle fall), occasional knee “giving way” or “locking,” and imaging findings showing a clear bone signal within the medial meniscus along with signs of tearing, the final diagnosis is:

“Left Knee Medial Meniscal Ossicle (meniscal ossicle) with Posterior Root Tear”

4. Treatment Plan and Rehabilitation

Based on the patient’s symptoms, age, and imaging findings, the following treatment and rehabilitation strategies are recommended:

• Arthroscopic Surgery:
  • For patients with significant symptoms, functional limitations, or instability, a meniscal ossicle combined with a meniscal tear often requires treatment via arthroscopy. This may include removal or debridement of the ossicle, as well as meniscal repair/suture (if the edges of the meniscal tear are suitable for repair).
  • If there is concomitant anterior cruciate ligament (ACL) instability or tearing, ACL reconstruction can be performed concurrently to restore joint stability and reduce the risk of future cartilage damage.
• Conservative Treatment: If the patient’s symptoms are mild, with no significant joint locking or instability, and no major tear is present, conservative management (reduced weight-bearing, anti-inflammatory medications, physical therapy, etc.) can be considered, accompanied by regular follow-up.
• Postoperative Rehabilitation and Exercise Prescription (FITT-VP Principle):
  • Early Phase (0-2 weeks post-surgery): Focus on range of motion (ROM) exercises and isometric quadriceps training. Avoid excessive weight-bearing and deep squatting.
  • Intermediate Phase (2-6 weeks post-surgery): Under medical or physical therapy guidance, gradually increase the range of motion, strengthen the thigh muscles (using light resistance bands, straight-leg raises, seated hip extensions, etc.), and introduce low-impact aerobic exercises such as stationary bicycling, following the “low load, high frequency” principle.
  • Late Phase (6-12 weeks post-surgery): Gradually restore functional activities, including postural stability and balance training. Depending on muscle strength and functional improvement, add light running or small-scale plyometric movements.
  • Strengthening Phase (3 months post-surgery and beyond): Once stability is secure and pain-free, return to running, interval running, or lateral movement drills. Further enhance ligament stability and coordination (e.g., single-leg stability training, lateral agility exercises).
  • Individualization: For patients with fragile bone structures or other chronic conditions (e.g., poor cardiopulmonary function, obesity), reduce exercise intensity and extend the progression period to ensure safe participation.

Note: The specific treatment and rehabilitation plan must be tailored to the patient’s clinical presentation, surgical details, and individual differences and implemented under the supervision of an orthopedic specialist or qualified rehabilitation therapist.

Disclaimer

This report is a reference analysis based on existing imaging and the provided medical history. It should not replace in-person medical consultation or professional medical advice. The actual treatment plan must be determined by a clinician, who will consider the patient’s complete medical history, perform a physical examination, and conduct any necessary additional investigations.