Patients with spinal cord injury are predisposed to knee effusions owing to osteoporosis, heterotopic ossification, trauma, and benign hydrarthrosis. This retrospective review discusses 11 patients with spinal cord injury and knee effusions seen during two years. One objective is to correlate the initial diagnosis based on clinical findings with the final diagnosis based on synovial fluid analysis and radiographic studies. Another is to describe the variety and complexity of clinical situations that involve knee effusions in spinal cord injury. The initial diagnosis was different from the final diagnosis in all of our cases. The final diagnoses were trauma (6 cases), pseudogout (2 cases), spasticity, fracture of the tibial plateau, septic joint, and tears of the anterior cruciate and lateral collateral ligaments. Knee effusions in this unique population must be carefully investigated to avoid erroneous diagnoses based on the initial clinical presentation, which can be complicated by multiple medical problems.