Spontaneous Rupture of the Rectus Femoris Masquerading as a Pseudotumor in a 60-Year-Old Male Patient: A Case Report.

Quadriceps tendon ruptures (QTR), often involving the rectus femoris due to its superficial position, primarily affect men aged 50-60 with comorbidities weakening tendon collagen. Tears typically occur 1-2 cm above the patella or at the osteotendinous junction in older adults. Rupture of the rectus femoris muscle can sometimes mimic a pseudotumor, presenting as a soft tissue mass in the anterior thigh, with or without a clear history of trauma. In chronic cases, unrecognized or repetitive microtrauma often leads to fibrosis and incomplete healing. Isolated distal ruptures of the rectus femoris are rare, especially in young athletes. Differential diagnosis should rule out soft tissue tumors or sarcoma. Systemic diseases, obesity, or long-term steroid/quinolone use may contribute to ruptures, though in our cases, no such factors were found, suggesting old age is a potential risk. Nonsurgical healing is slow, leading to scar tissue and hindering recovery. Surgical repair is critical to prevent poor outcomes in untreated or chronic ruptures and to restore knee extensor function.