After a first patellar dislocation, X-rays may be normal or show only modest findings. Magnetic resonance imaging (MRI) allows for the evaluation of ligamentous and osteochondral lesions that can alter treatment.
A systematic review from 2026 collected 12 pediatric studies with MRI performed after the first episode. [1]
Most Frequent Findings
The aggregated frequencies reported in the review were high:
- complete MPFL rupture: 47%;
- partial MPFL lesion: 41%;
- osteochondral damage: 50%;
- intra-articular loose bodies: 34%. [1]
When the osteochondral lesion was isolated, the most frequent location was the medial facet of the patella compared to the lateral femoral condyle.
These findings do not automatically constitute a surgical indication. However, a significant osteochondral fragment or a loose body can quickly change the treatment pathway compared to simple conservative management.
When MRI is Particularly Useful
Hemarthrosis or significant swelling, marked pain, locking, mechanical symptoms, and radiographic or clinical suspicion of an osteochondral lesion are situations where I more readily use MRI.
MRI also helps to define the MPFL lesion and the anatomy predisposing to instability, information useful in counseling about the risk of recurrence.
MRI for Everyone After the First Episode?
The review shows a high frequency of associated findings, but the included studies are heterogeneous in terms of indication and timing of the examination. [1]
In centers where MRI is quickly available, a relatively low threshold can be adopted, especially in cases with hemarthrosis. In other contexts, rigorous clinical selection remains reasonable.
The important point is that a negative X-ray does not exclude significant osteochondral damage. If the clinical picture is not that of a simple episode, MRI offers information that X-rays cannot provide.
Disclaimer: informational content, not a substitute for an individual specialist evaluation.
Reference
[1] Reed JM, et al. Frequency of Adjunctive MRI Findings on First-Time Patellar Dislocations in Pediatric Patients: A Systematic Review. Am J Sports Med. 2026. DOI: 10.1177/03635465251383851. PMID: 41508815.
