What are Degenerative Diseases?

Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

In this lesson we'll explain what degenerative diseases are. We'll then look at four examples: osteoarthritis, Alzheimer's disease, amyotrophic lateral sclerosis, and muscular dystrophy.

What are Degenerative Diseases?

Picture your favorite pair of running shoes. You probably remember when you first got them and took them out of the box. The colors shone, the material was firm, and even the soles were clean. However, as you lovingly used your running shoes daily--since you are a dedicated runner--they started to wear out. First maybe the soles started to wear away. Then the cushioning started to flatten a bit. The shoelaces might have frayed and stepping in puddles wore away at the mesh.

Like your shoes, your body takes a beating every day. Over time we age and our joints, muscles, and bones wear out. However, unlike this normal process of aging, degenerative diseases speed up the wear and tear, causing tissue to degrade faster than normal. This would be as if you took some sandpaper and mud to your shoes, wearing them out much faster than normal. To fully understand what happens to the body during degenerative diseases, let's look at some examples.


Osteoarthritis is a disease where the cushioning in our joints wears out. Fibers called cartilage fill the spaces between our bones in the joints. This material protects the bones from scraping against each other and acts as a shock absorber for some joints, like the knees. Similar to running shoes, the cartilage in your joints absorbs some of the impact in your knees and ankles when you run.

Example of the hip and knee joints with osteoarthritis

Symptoms of osteoarthritis include increased pain and tenderness in the joints as well as stiffness and decreased mobility. Although there is no cure, anti-inflammatory drugs like ibuprofen can decrease inflammation at the joint and relieve pain. Physical therapy exercises strengthen the muscles around the joint, which can help prevent further injury.

Alzheimer's Disease

Memory loss is the key symptom of Alzheimer's disease, a neurodegenerative disorder in which brain tissue, made of cells called neurons, breaks down over time. Neurons in the hippocampus, an area of the brain involved in making memories, die off. Patients' initial forgetfulness turns into full-blown dementia as the disease progresses, preventing them from understanding where they are in space and time.

A healthy brain versus a brain with Alzheimers disease (AD)
AD brain

Patients often forget loved ones and have trouble with even the simplest activities, such as brushing their teeth. There is no cure for Alzheimer's disease, although some medications may help with symptoms. Donepezil, rivastigmine, and galantamine are drugs used to moderate chemicals in the brains of patients with mild Alzheimer's disease to relieve symptoms. However, the drugs will not stop the progression of the disease and eventually most patients need full time support in a nursing facility.

Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is another neurodegenerative disorder, also known as Lou Gehrig's disease for the famous baseball player with the disease. During ALS, motor neurons, or brain cells that control movement, die off. There are motor neurons in the brain that tell our bodies what to do, called upper motor neurons. Lower motor neurons in the body relay the messages. In people with ALS, both of these motor neurons die, and messages about movement can no longer be communicated to their muscles.

Patients with ALS might experience muscle cramps or stiffness initially. They may feel some difficulty chewing, swallowing, and speaking. These symptoms may be attributed to something else at first, but patients with ALS soon lose much more motor control and may not be able to get out of bed, walk, or talk on their own.

President Obama speaks with world famous physicist Stephen Hawking, who suffers from ALS
Stephen Hawking

Eventually, patients die from respiratory failure when the muscles in the diaphragm can no longer expand and contract the lungs, unless they are put on a ventilator. Like many other degenerative diseases, there is no cure for ALS. Riluzole, a medication that slows damage to motor neurons, can slow the disease's progression but won't stop the end result. Other drugs that ease muscle cramps and treat emotional symptoms like depression can be prescribed. Patients also benefit from physical therapy to strengthen muscles and keep the rest of the body healthy through exercise.

Muscular Dystrophy

Muscular dystrophy is group of diseases characterized by the wasting away of muscle. Mostly, skeletal muscle, or the muscle we use to move, breaks down over time but some forms of muscular dystrophy also affect the heart, or cardiac, muscle.

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