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 his own 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 axilla 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 affected side of the patient, the right arm holds the distal calf (try to avoid applying force to the distal end of the ankle joint to avoid the formation of excessive plantar flexion of the ankle joint causing 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 applies pressure downward with the 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, with 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 can be placed 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, and usually follows 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 my personal common knee flexion functional training methods, all of which have the following commonalities: 1, the need for full cooperation and understanding of the patient, to overcome the psychological tension and muscle (antagonist muscle) tension caused by various reasons, which is the premise to ensure the safety of all exercises. 2. Avoid violence during the exercises to avoid unnecessary additional injuries. 3, before the exercise if the antagonist muscle can not be fully relaxed or tension, can first do the antagonist muscle maximum force isometric resistance at a certain angle 2 to 3 times, do until the antagonist muscle fatigue, can play a role in inhibiting antagonist muscle tension and appropriate pulling, but this method is not applicable to patients involved in the early stage of knee extension device injury. 4. Other precautions and exercise settings can be found in my article “Mobility (ROM) exercises after joint injury”.