Knee flexion describes the bending motion of the knee joint, which decreases the angle between the shin and the thigh. A healthy knee can flex to about 135 to 145 degrees, though the required range for daily tasks is often less but still substantial. Limited flexion severely impacts functional mobility, making everyday actions like walking (requiring 65 to 70 degrees), climbing stairs (90 to 100 degrees), and sitting comfortably (over 110 degrees) challenging. The following steps provide a framework to safely and progressively increase this range of motion.
Foundational Steps for Joint Preparation
Preparing the joint and surrounding soft tissues before stretching can significantly improve the effectiveness of the exercise. Applying warmth to the knee for 10 to 15 minutes, perhaps with a heating pad or warm bath, helps to increase local blood flow and relax the muscles and connective tissues surrounding the joint. Heat application makes the tissues more pliable and receptive to movement, allowing for a safer stretch into the restricted range.
Swelling, or effusion, is a major physical barrier that mechanically limits the ability of the knee to bend fully. If swelling is present, light compression and elevation can help manage this fluid accumulation, which may be more important than stretching initially. Gentle patella mobilization involves carefully shifting the kneecap side-to-side and up-and-down with relaxed muscles to ensure the patella is gliding smoothly before movement begins.
Targeted Active and Passive Range of Motion Exercises
Once the joint is prepared, the focus shifts to specific movements designed to push the current end range of motion. The simplest active exercise is the heel slide, performed while lying on the back. The individual actively slides the heel toward the buttocks as far as possible, holding the maximum bend for about five to ten seconds before slowly straightening the leg.
To progress beyond the active range, a passive or assisted stretch is introduced, often using a towel or strap looped around the foot. After actively performing the heel slide, the individual uses the strap to gently pull the heel closer to the hip, applying a sustained, mild overpressure to increase the bend. This passive pull should be held for 20 to 30 seconds and repeated several times, working within a tolerable stretch discomfort but never into sharp pain.
Gravity-assisted techniques provide another method for sustained, gentle force to encourage flexion. One example involves sitting on a surface high enough so the lower leg can hang freely, letting gravity pull the foot toward the floor to deepen the bend. Another is the seated scoot, where the individual sits in a chair with their foot flat on the floor and uses their arms to scoot their hips forward, which forces the knee to bend further over the foot.
Strengthening Muscles to Support New Flexion
The surrounding musculature must be strong enough to stabilize and control the joint within that newly acquired range to maintain it. The hamstring muscles, which are the primary flexors of the knee, need to be strengthened to actively pull the knee into deeper flexion. Standing hamstring curls, where the heel is lifted toward the buttocks against gravity or resistance, are effective for building this power.
Equally important is strengthening the quadriceps, which provides eccentric control and stability as the knee bends. Exercises like the wall sit or partial squats build the endurance and strength necessary for the quadriceps to stabilize the knee during the controlled lowering phase of movements like climbing down stairs. Integrating exercises that target the hips, such as calf raises and bridging, also supports overall leg mechanics and reduces strain on the knee joint.
Consistency, Safety, and Professional Guidance
Progress in restoring knee flexion requires consistent, daily effort, often requiring multiple short sessions throughout the day. The body responds best to frequent, gentle exposure to the restricted range rather than infrequent stretching sessions. It is important to distinguish between the tolerable, pulling sensation of a true stretch and a sharp, sudden pain, which signals the need to immediately stop the movement.
Progression should be gradual, increasing the duration of the hold or the number of repetitions only when the current level is comfortably tolerated. Avoid attempting to force the joint into a deep bend, as this can cause inflammation and set back progress. If the range of motion plateaus, if pain increases, or if the limitation is severe following a surgery or injury, consult a physical therapist or physician.