Knee flexion is a fundamental movement of the knee joint, involving the bending of the lower leg towards the thigh. This motion decreases the angle between the two segments. It is a necessary component for many daily activities, enabling movements such as sitting, squatting, walking, and climbing stairs.
Understanding Typical Ranges
Knee flexion is measured in degrees, often using a goniometer. The normal range of knee flexion varies among individuals, typically falling between 120 and 140 degrees. Some healthy knees can flex up to 150 degrees. This measurement helps healthcare professionals evaluate joint health and mobility.
Everyday tasks require varying degrees of knee flexion. Walking on level surfaces generally requires less than 90 degrees, while climbing stairs and sitting in a standard chair typically need 90 to 120 degrees. More demanding activities, like sitting in a bathtub, may require approximately 135 degrees. Actively achieving at least 110 degrees of knee flexion is considered necessary for performing activities like walking and climbing stairs.
The full range of motion includes both active and passive flexion. Active flexion is the movement an individual can achieve using their own muscles, while passive flexion involves external assistance. After surgical procedures, such as total knee arthroplasty, regaining knee flexion is important for daily functioning, with a common rehabilitation goal of at least 110 degrees of active flexion. Most adults maintain a functional range of motion from 0 degrees of extension (straight leg) to about 135 degrees of flexion.
Influences on Knee Movement
Several factors affect an individual’s knee flexion range. Younger children often exhibit greater knee flexion than older adults. As individuals age, a gradual decline in knee range of motion can occur due to factors like decreased muscle flexibility and joint changes.
Activity level and body mechanics also play a role in knee movement. A lack of muscle flexibility or strength can increase the risk of knee issues and limit range of motion. Conditions causing general stiffness, such as muscle and ligament tightness or fluid buildup in the joint, can restrict knee movement. Chronic pain can also lead to reduced activity, causing muscles and ligaments around the knee to weaken and tighten, which contributes to stiffness and reduced range of motion.
When to Seek Guidance
It is important to consult a healthcare professional if knee flexion is outside a typical range or if symptoms arise. Difficulty bending or straightening the knee fully, especially if accompanied by pain, can indicate an underlying issue. Pain during movement or activity is a common symptom that warrants evaluation.
Swelling or inflammation around the knee joint can also limit mobility and signal a problem. Stiffness or tightness, particularly after periods of rest, is another symptom that suggests a need for professional assessment. If the knee feels unstable or gives out, or if there is excessive hyperextension (the knee bending too far backward), medical guidance should be sought. These symptoms can significantly impact daily activities, making routine tasks difficult and uncomfortable.