Noninflammatory knee joint effusions in spinal cord-injured and other paralyzed patients. Four case studies

Four patients with knee effusions are described. Three had spinal cord injuries and the fourth had Guillain-Barrè syndrome. Of the spinal cord-injured patients, the effusions were unilateral in one case and bilateral in another. The third patient developed effusions on two separate occasions with bilateral involvement once and unilateral involvement once. The patient with Guillain-Barrè syndrome had bilateral knee joint effusions. All effusions were tapped and revealed type I synovial fluid except for one joint that contained some blood cells. Two of the three spinal cord-injured patients had heterotopic ossification at the knees documented by 99mTe bone scans and two were lying prone for the treatment of decubitus ulcers. Similar knee joint effusions have been described by several authors in the past. The etiology is unknown; however, we offer the hypothesis that paralysis of the muscles adjusting intra-articular knee joint structures may be the cause. It is important for clinicians to recognize that benign knee joint effusions are likely to be encountered in paralyzed patients. They can be evaluated with a simple synovial fluid analysis.