Flexion is one of the basic functions of the knee joint, and although a slight deficit in flexion has less impact than extension, a large deficit in flexion can still have a significant impact on daily life and sports. Generally speaking, flexion flexibility of at least 60° has no effect on normal walking on a flat road; flexion flexibility of at least 90° has no effect on putting on and taking off shoes and socks and jogging; flexion flexibility of at least 110° has no effect on going up and down steps of normal height; flexion flexibility of at least 120° has no effect on squatting. As can be seen, the various levels of flexion angle stage, still have different degrees of impact on daily life, in order to minimize its adverse effects, or try to flexion function practice to close to or even reach the normal level. This is a method I personally commonly use, taking the affected limb as the left leg, for example, sitting in front of the patient, the left arm is placed between the patient’s N fossa below and the treatment bed, playing the role of a fulcrum, and the right arm holds the heel and pushes it medially with force. Because of the passive deficiency of the rectus femoris, the patient can be made to adopt a lying or sitting position as needed (simply put: sitting position mainly pulls the periarticular tissues, lying position mainly pulls the rectus femoris), and one’s arms can also be stretched by the left arm along the femur axially to the distal end and by the right arm along the tibia axially to the distal end as needed to reduce the intra-articular pressure during the exercise to relieve some of the pain. At the same time, the pivot of the left arm increases the strength of the advancement. Note! Axial distraction in this direction is generally not performed for 3 months after ACL reconstruction. This approach is mandatory after posterior cruciate ligament reconstruction of the knee. This is another technique that I personally use, using the right leg as the affected limb as an example, with the patient lying flat on his back, flexing the hip, placing the right and left arms in the position shown, clamping the affected limb in the right armpit and applying downward pressure with the assistance of his own weight, while the left arm can be lifted upward with the right arm as the fulcrum as needed, while the right arm is pushed forward to achieve distal distraction along the femoral axis and distal distraction along the tibial axis, respectively. Cautions are the same as above. This method is generally applied after the flexion angle exceeds 90°, taking the left side as the affected limb for example, standing on the patient’s affected side, the right arm holds the distal calf (try to avoid exerting force on the distal ankle joint to avoid the formation of excessive plantar flexion of the ankle joint causing its injury), the left hand can be padded to the patient’s N fossa as needed, the right arm presses down or the right arm fixes the affected limb in front of the body, the body leans to the left and exerts downward pressure with its weight. At this time, the left arm plays the following roles: fixing the patient’s body position, as a fulcrum to strengthen the downward pressure, as a “wedge” to try to open the joint gap, if the patient feels that the N fossa is too much pressure, a soft pillow can be used instead of the palm of the hand stuffed in the N fossa to play a similar role, with the same precautions. This is a self-practice flexion function, patients lying on their back, hip flexion, holding the distal thigh with both hands, or use a cloth belt like a “ribbon” over the shoulder, the length of the belt is adjusted to make the calf basically parallel to the horizontal plane is appropriate, according to the need to place the sandbag at the ankle, fully relaxed, to the calf’s self-weight and sandbag suspension, generally can do 10-15 minutes each time. 15 minutes each time, of course, the exercise should be fully relaxed to ensure the effect. This is also a self-practice angle method, the specific posture and direction of force need not be introduced too much, this way is suitable for patients with less resistance to joint movement and better flexibility (such as early postoperative patients), the advantage of this action is that the actual angle can be quantified simply by the distance from the heel to the hip, which is more conducive to the flexion exercises according to the normal rehabilitation program. This method is suitable for patients with a knee flexion angle of at least 90°. The patient lies prone, binds an inelastic cloth band around the ankle, and pulls with both hands to achieve hip extension and knee flexion, or if available, a pulley in front and weights suspended instead of hands, usually for 10 to 20 minutes each time. When the passive knee flexion angle exceeds 100 degrees, try to consolidate the active angle by means of a stationary bicycle, riding with the body upright and the foot of the affected limb firmly fixed on the pedal, in a very standard posture, the seat height should ensure that the knee flexion angle is both slightly difficult and that the effort can be made to pass the highest point in a more standard posture, usually following the passive exercise for 10 to 15 minutes and 1 to 2 times per day. As the passive angle increases, the seat height can be lowered to achieve a higher active angle while maintaining the riding stance. When the passive angle exceeds 130 degrees, you can try squatting down with the protection of your hands and use your body weight to assist in consolidating the established angle. The exercise requires the weight to be placed on the feet, no more than the toes forward and no more than the heels backward, avoiding excessive back sitting, usually following after the passive exercise, 2 to 5 minutes each time. Therefore the method incorporates the influence of body weight and increased joint pressure, which may aggravate discomfort for patients with N-fossa pain during knee flexion exercises, so be sure to pay attention to gradual progress and not overly forceful exercises. If you have the conditions, you can try to design and manufacture your own pulley pull at home, the mechanical structure of the pulley is shown in the figure, usually this method is suitable for the anterior thigh group of muscles and other soft tissue contracture caused by knee flexion disorder, that is, for patients who feel the pulling pain in front of the knee when flexion exercises, usually with moderate weight, under the premise of full relaxation pulling not less than 15 minutes times. The above are some of the knee flexion functional training methods that I personally use, all of which have the following commonalities: 1. Patients need to fully cooperate and understand, and overcome psychological tension and muscle (antagonist muscle) tension caused by various reasons, which is a prerequisite to ensure the safety of all exercises. 2. Avoid violence during exercises to avoid causing unnecessary additional injuries. 3. If the antagonist muscle is not fully relaxed or has a high tension, do the antagonist muscle maximum force isometric resistance at a certain angle 2 to 3 times, until the antagonist muscle is fatigued, which can inhibit the antagonist muscle tension and appropriate pulling effect, but this method is not suitable for patients involved in early knee extension device injury. 4, other precautions and exercise settings can be found in my “post joint injury mobility (ROM) exercises” article. “The article.