Medicine
Range of Motion
Quick fact
The average human knee can flex up to 135 degrees, but some individuals can achieve hyperextension beyond 0 degrees, often without injury.
Why this is interesting
You bend your knee to take a step, but have you ever wondered how far your knee can actually bend? The answer is your range of motion.
Read the full explanation
Understanding Range of Motion
Range of motion (ROM) is the distance and direction a joint can move between its flexed and extended positions. It is measured in degrees using a tool called a goniometer. ROM can be active—when you move a joint using your own muscles—or passive—when someone else moves your joint for you. Factors such as age, genetics, activity level, injury, and disease can all influence ROM. For example, aging often reduces ROM due to changes in connective tissues.
A deeper explanation
The mechanism behind range of motion involves the interplay of bones, joint capsules, ligaments, tendons, and muscles. Each joint has a specific structure that determines its natural limits. For instance, the hinge joint of the knee allows flexion and extension but limited rotation. During movement, muscles contract to pull on tendons, while ligaments and the joint capsule provide stability and prevent excessive motion. When ROM is limited (hypomobility), it may be due to tight muscles, scar tissue, or joint swelling. Excessive ROM (hypermobility) can result from lax ligaments, increasing injury risk. Understanding ROM is crucial for diagnosing joint disorders, designing rehabilitation protocols, and improving athletic performance.