Expression ranges from small black spots on the distal end of the femur or proximal end of the tibia to severe cases in which the tibia, femur and bases of the coxae are encapsulated in a dark brownish-black, glossy covering. The phenotype is not fully penetrant. The legs are often stuck together or to the body due to the black substance. The legs are weak. Viability is reduced and is poor under crowded conditions.

Expression ranges from small black spots on distal end of femora or proximal end of tibiae to cases in which the tibiae, femora and bases of coxae are encapsulated in a dark, brownish-black, glossy covering. Legs weak. Some overlap wild type. Viability reduced. RK2.