A 29-year-old female presents with chronic right knee pain. She has a history of right knee injury after a fall 4 years ago.
Diagnosis: Chronic injury of the medial collateral ligament
Knee radiographs demonstrate mineralization adjacent to the medial femoral condyle. MRI demonstrates thickening and intermediate signal of the proximal medial collateral ligament without associated surrounding edema. There is ossification within the proximal portion of the medial collateral ligament.
There is also cortical irregularity and mild depression of the lateral tibial plateau without associated edema.
There is no knee joint effusion.
The radiographic and magnetic resonance imaging findings are consistent with a chronic injury of the medial collateral ligament.
Acute medial collateral injury typically occurs when a valgus force is applied to the knee (eg, a direct lateral blow). This can occur in isolation or as part of a more complex injury mechanism. Associated injuries include anterior or posterior cruciate ligament injury and medial or lateral meniscal tears. Acute injuries are graded on a scale of I to III with increasing severity. Grade I represents a mild sprain with edema surrounding the ligament, grade II represents a partial tear with abnormal signal within the ligament, and grade III represents a complete disruption.
Prior injury may result in dystrophic calcification or ossification of the ligament, typically of the proximal portion. This is known as Pellegrini-Stieda disease. The ligament appears thickened, but without abnormal signal or surrounding edema. The ossific fragment is typically low in signal intensity on both T1- and T2-weighted images, but may be high signal in T1-weighted images if it contains fatty marrow.
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