Eight women and two men had multiple episodes of idiopathic painful osteoporosis of the bones of a joint of one or both lower extremities. There was tenderness and pain with use of the involved joint in all cases, and slight swelling, erythema, and warmth were noted frequently. Within six to eighteen months, the symptoms and findings in each episode spontaneously resolved completely or nearly completely. The features of the episodes among these patients and patients recently reported by others are similar enough to suggest a clinical syndrome. Recognition of this syndrome in a patient with a painful joint of a lower extremity should help in the choice of proper treatment.