A nurse assesses an audible grating sound (crepitus) when a client with osteoarthritis moves his knees. What is the cause of this sound?

Choice A reason: A susceptible host is not an infectious disease, but a factor that influences the transmission of an infectious disease. A susceptible host is a person who is vulnerable to infection due to factors such as age, health status, immunization, or genetic predisposition. A susceptible host may become infected by a communicable disease, but it is not the disease itself.

Choice B reason: A communicable disease is an infectious disease that can be transmitted directly from one person to another. A communicable disease is caused by a pathogen, such as a virus, bacterium, fungus, or parasite, that can spread through contact, droplet, airborne, vector, or vehicle transmission. Examples of communicable diseases are influenza, tuberculosis, measles, malaria, and HIV/AIDS.

Choice C reason: A portal of entry to a host is not an infectious disease, but a factor that influences the transmission of an infectious disease. A portal of entry to a host is a route through which a pathogen can enter the body of a susceptible host and cause infection. A portal of entry to a host may be a break in the skin, a mucous membrane, or a body opening, such as the mouth, nose, eyes, or genitals. A portal of entry to a host may facilitate the transmission of a communicable disease, but it is not the disease itself.

Choice D reason: A portal of exit from the reservoir is not an infectious disease, but a factor that influences the transmission of an infectious disease. A portal of exit from the reservoir is a route through which a pathogen can leave the body of an infected person or animal and reach another susceptible host. A portal of exit from the reservoir may be a body fluid, such as blood, saliva, urine, or feces, or a body part, such as the skin, hair, or nails. A portal of exit from the reservoir may enable the transmission of a communicable disease, but it is not the disease itself.

Choice A reason: Psoriasis is a skin abnormality that causes patches of thick, red skin with silvery scales, usually on the elbows, knees, scalp, lower back, or genitals. Psoriasis is a chronic, inflammatory, autoimmune condition that affects the life cycle of skin cells, causing them to build up rapidly on the surface of the skin. Psoriasis can cause itching, burning, pain, or bleeding.

Choice B reason: Rosacea is a skin abnormality that causes redness, flushing, swelling, or pimples, usually on the face, especially the cheeks, nose, chin, or forehead. Rosacea is a chronic, inflammatory, vascular condition that affects the blood vessels and sebaceous glands of the skin. Rosacea can cause sensitivity, stinging, or dryness.

Choice C reason: Scabies is a skin abnormality that causes small, red bumps, blisters, or burrows, usually on the hands, wrists, feet, ankles, or genitals. Scabies is a contagious, parasitic infection that is caused by tiny mites that burrow into the skin and lay eggs. Scabies can cause intense itching, especially at night.

Choice D reason: Stasis dermatitis is a skin abnormality that causes swelling, redness, scaling, or ulcers, usually on the lower legs or ankles. Stasis dermatitis is a chronic, inflammatory condition that results from poor blood circulation in the veins of the legs, causing fluid to leak into the surrounding tissues. Stasis dermatitis can cause pain, itching, or infection.