Popliteal artery entrapment syndrome (PAES) is a rare vascular disease that affects the legs of some young athletes. When you have this syndrome, the muscle behind your knee compresses your popliteal artery — the main artery that runs from your thigh to your calf. The attachment of your gastrocnemius muscle to your thigh bone causes compression. When your gastrocnemius muscle contracts during …

Peripheral artery disease (PAD) is plaque buildup in your leg arteries. Your leg arteries carry oxygen and nutrient-rich blood from your heart to your arms and legs. Other names for this are peripheral vascular disease or peripheral arterial disease. Shaped like hollow tubes, arteries have a smooth lining that prevents blood from clotting and promotes steady blood flow. When you have peripheral artery disease, plaque (made of …

Osteoporosis is a progressive bone disease characterized by decreased bone density and weakened bone structure, which increases the risk of fractures. It often develops silently over many years and is most common in older adults, especially postmenopausal women. Bones most frequently affected include the spine, hips, and wrists. Symptoms Osteoporosis is often called a “silent disease” because bone loss occurs …

Osteosarcoma is a rare but aggressive type of bone cancer that typically develops in the long bones, such as the arms, legs, or near the knees. It primarily affects children, adolescents, and young adults. Osteosarcoma arises from immature bone-forming cells and can spread (metastasize) to other parts of the body, most commonly the lungs. Early diagnosis and treatment are critical …

Osteochondritis dissecans is a joint condition in which a small segment of bone and the overlying cartilage loses its blood supply and begins to separate from the surrounding bone. This can lead to pain, swelling, and impaired joint movement. The condition most commonly affects the knee but can also involve the elbow, ankle, or other joints. It is seen more …

Orthostatic hypotension, also known as postural hypotension, is a condition in which blood pressure drops significantly when a person stands up from a sitting or lying position. This sudden drop reduces blood flow to the brain and can cause dizziness or fainting. It is more common in older adults but can occur at any age, especially in individuals with underlying …

Orchitis is an inflammatory condition of one or both testicles, most commonly caused by infection. It can occur suddenly and may be painful, leading to swelling and discomfort in the scrotum. Orchitis often develops as a complication of viral or bacterial infections and may occur alone or together with inflammation of the epididymis. Symptoms Symptoms of orchitis can range from …

Optic neuritis is an inflammatory condition affecting the optic nerve, which transmits visual information from the eye to the brain. Inflammation of this nerve can disrupt vision, often developing rapidly over hours to days. Optic neuritis commonly affects young adults and may be associated with neurological disorders, particularly demyelinating diseases. Symptoms Symptoms of optic neuritis typically affect one eye, though …

Oligodendroglioma is a rare type of primary brain tumor that originates from oligodendrocytes, the cells responsible for producing myelin, the protective covering of nerve fibers in the central nervous system. These tumors are generally slow-growing and are most commonly diagnosed in adults, particularly in middle age. Oligodendrogliomas often develop in the cerebral hemispheres and can affect brain function depending on …

Ovarian Hyperstimulation Syndrome (OHSS) is a medical condition that can occur as a complication of fertility treatments, particularly those involving injectable hormone medications to stimulate ovulation. OHSS causes the ovaries to become swollen and painful, and in severe cases, it can lead to fluid accumulation in the abdomen and chest, blood clots, and other serious complications. Early recognition and monitoring …