Technical Abstract: Femoral head disarticulation (FHD) and necrosis is a sporadic leg problem of unknown etiology in broiler breeders. To determine the underlying physiology of FHD, the blood chemistry and the histopathology of the femoral heads of the affected chickens were compared with their age matched controls. Chickens were categorized on the basis of their leg problems determined at necropsy as, (1) femoral heads separated from articular cartilage without growth plate laceration (FHD), (2) FHD with lacerations and lesions in the growth plate (FHDL), and (3) tibial dyschondroplasia (TD), identified by a widened growth plate and unresorbed cartilage at the proximal tibia. Control birds were without any femoral or tibial problems. The histopathology of FHDL growth plates revealed occasional chondrocyte death, hypocellularity, dysplasia in the prehypertrophic zones, and the absence of inflammatory infiltrate in the lesion areas. Hematoxylin/ eosin staining showed brown chromogenic deposits in the metaphyseal bone marrow areas. Blood chemistry of chickens with FHDL showed modest but a significant elevation of cholesterol, triglycerides, and low density lipoproteins (LDL). Only cholesterol and LDL were moderately elevated in FHD groups. Other blood parameters such as protein, blood urea nitrogen (BUN), magnesium, and iron levels showed differential changes in birds with leg problems but without any specific trends. Neither blood ovotransferrin (OVT), a marker of chronic inflammation, nor corticosterone, a marker of stress, showed significant differences from the controls. These results suggest that FHD is a metabolic problem in poultry which may be related to fat metabolism disorders.