Final answer:
The medical term for chronic flexion of a joint due to muscle atrophy is contracture, which is associated with conditions like sarcopenia, an irreversible muscle mass decline with age. Sarcopenia and muscle atrophy can lead to reduced joint mobility, also causing connective tissue and fat to replace muscle fibers. While exercise may delay sarcopenia, some age-related changes are inevitable.
Step-by-step explanation:
The medical term for chronic flexion of a joint due to muscle atrophy is contracture. This condition occurs when diminished muscle mass leads to reduced functionality and joint flexibility. Muscle atrophy can be a consequence of various diseases and conditions, and it becomes more likely with age due to sarcopenia, a decline in the ability to maintain skeletal muscle mass in later adulthood.
Sarcopenia represents the normal, age-related loss of muscle mass and function, which is largely irreversible unlike atrophy caused by disuse that might be improved through exercise. Diseases like cancer, AIDS, and Duchenne muscular dystrophy, which cause muscle fibers to degrade or impede their maintenance, can also lead to atrophy. As the human body ages, muscle fibers decrease in number and are replaced by connective tissue and adipose tissue, which do not contract like muscle fibers do, thus leading to decreased muscle strength and joint stability, and increasing the risk of falls and other injuries. Subsequently, this process might result in a joint being stuck in a flexed position, also known as a contracture.
It is important to note that while exercise might delay the onset of sarcopenia by increasing muscle mass and capillary density, the age-related changes in muscle and connective tissues are an inevitable component of aging that can contribute to joint contractures.