Under normal circumstances, the stability of the knee is maintained by the surrounding bony structures, ligaments, joint capsule and muscle tissue. Knee hyperextension exists in hemiplegic patients after stroke and is caused by insufficient muscle strength of the affected lower limb, decreased balance and coordination, the emergence of primitive movement patterns and incorrect exercise patterns, and is difficult to correct once it occurs. According to statistics, about 75% of stroke patients have lower limb dysfunction, and knee hyperextension is a common phenomenon in rehabilitation training, especially in patients in the posterior phase of rehabilitation in the community. Because this poor gait affects the patient’s ability to walk, knee hyperextension will have to be taken seriously to improve the quality of life of stroke patients. Knee hyperextension is also known as knee dystocia or knee dorsiflexion deformity, also known as “trivial knee” phenomenon, which means that during walking or standing, the lower limb on the affected side is hyperextended (knee extension angle greater than 5°) during the support period, the body weight is shifted back, the affected hip is hyperextended and the body tends to lean back. Rehabilitation Center of the First Affiliated Hospital of Henan College of Traditional Chinese Medicine, Huadong 1 Causes of post-stroke knee hyperextension It is generally believed that post-stroke knee extension is a result of weak quadriceps muscle strength, which cannot fully support the body weight; weak flexor muscle strength, which cannot maintain the normal flexion angle of the knee joint during the support period; and spasm of quadriceps muscle, which cannot mildly flex the knee joint. Methods: 1.1 Weak quadriceps muscle strength, not enough to support the weight When standing or walking because the affected leg is unstable in knee extension during the support period, patients often compensate by leaning forward to the upper body, so that the body weight reaches the front of the knee joint, and passively straighten the knee joint to increase its stability, which leads to the occurrence of knee hyperextension. 1.2 Weakness of knee flexor muscle (N cord muscle) The knee joint cannot be maintained in mild flexion of 0° to 15° during the support period. 1.3 Appearance of primitive movement patterns High spasm of the quadriceps muscle causes hyperextension of the knee joint and inability to actively flex, combined with weakness of the ankle dorsiflexion or foot drop due to spasm of the gastrocnemius muscle, forcing the affected limb to develop a hemiplegic gait. 1.4 Loss of proprioception above the ankle joint and uncoordinated contraction of anterior and posterior muscles leading to knee hyperextension The proprioceptive nerve impulses from the musculoskeletal and tendon organs around the knee joint are transmitted to the spinal cord by the Ⅰa fibers, which directly excite the motor neurons of the muscle and inhibit the activity of the antagonist muscle through the activity of inhibitory interneurons, so that the active and antagonist muscles cooperate and restrain each other to complete coordinated movements. When there is cross-inhibition of the affected limb due to proprioceptive impairment, the patient cannot easily obtain accurate position awareness of the affected knee and cannot inhibit excessive quadriceps muscle tone, resulting in dysfunction in the coordination of knee flexion and extension and knee hyperextension. The essential cause of knee hyperextension is still not clearly reported in the literature. 2 Training program for knee hyperextension after stroke 2.1 Resistance muscle training 2.1.1 Early separation and resistance exercise training Since knee hyperextension will be difficult to correct once it occurs, prevention is particularly important. For patients within 3 weeks of stroke, lower extremity rehabilitation was performed gradually and early with separation and resistance training, including normal position placement, hip extension, knee flexion, weight bearing of the affected limb and knee flexion control from 0° to 15°, etc. The training intensity was 1 time/d, 40-60 min/time, 5 times/week, for a total duration of 6 months. The results showed that the incidence of knee hyperextension in the rehabilitation group was significantly lower than that in the control group without rehabilitation training (P<0.01), and the treatment efficacy was significantly higher than that in the control group (P<0.05). In stroke patients with a disease duration of less than 2 weeks, with muscle strength of lower limbs <2, and unable to stand, the rehabilitation group underwent early knee stability training (including training to promote the recovery of deep sensation in the knee joint, such as distraction and compression of the affected lower limb, as well as training to strengthen the quadriceps, N cord and tibialis anterior muscles, together with medium-frequency electrical therapy), and then performed standing training after the muscle strength of the affected lower limb reached 3. After 3 months of treatment, the incidence of knee hyperextension in the rehabilitation group was significantly lower than that in the control group, which only underwent conventional training. 2.1.2 Resistance training of N cord muscle For patients who could walk independently after stroke and had knee instability without sensory cognitive impairment, maximum centripetal isotonic knee flexion and terminal isometric resistance training of N cord muscle was performed with suppression of upper limb and trunk muscle spasm, each resistance lasted 10s, and each 2 exercises were repeated for 20min at an interval of 30s, once a day, together with EMG biofeedback therapy. The treatment course was 60 days. The isometric muscle strength test showed that the knee flexion/extension muscle strength ratio of the affected side was significantly higher than that before the treatment at all angular velocities, i.e., the N cord muscle strength was increased and the stability of the knee joint was improved. 2.1.3 Strengthening the anterior tibial muscle Using biofeedback, the patient was allowed to do ankle dorsiflexion training actively, and through visual feedback, the patient kept working toward a high threshold to achieve the effect of active exercise. If biofeedback is not available, medium-frequency electrical stimulation can be used to stimulate the anterior tibial muscle and increase weight-bearing training. 2.2 Acupuncture method 2.2.1 Milli-needle flying method Take a 50mm milli-needle, and diagonally stab the milli-needle into Yanglingquan, Fuhu, Guizhong and Chengshan, and perform acupuncture for two minutes at each point once a day for 15 days, with a 3-day rest, for a total of 2 courses of treatment. As shown in the electromyographic H-reflex, the wave amplitude of knee hyperextension spasm burst was reduced, the time duration was shortened, the frequency of burst was significantly reduced, and the latency rate was reduced after treatment using the milli-needle flying method, and the difference was highly significant when compared with that before treatment. 2.2.2 Acupuncture with rehabilitation technology treatment Take No. 30 1. 5-inch stainless steel needle, select Liangqiu, Blood Sea, Foot Sanli, Yanglingquan, all straight stab; middle calf nose upward oblique stab, flat tonic and flat diarrhea technique. After obtaining the Qi, the G6805 electro-acupuncture instrument was connected, the sparse and dense wave was selected, the power was as much as the patient could tolerate, and the needle was kept for 1 h, 1 time/day, 10 times a course of treatment, together with the rehabilitation training based on the control of knee flexion within the range of 0° to 15°. The results showed that the total effective rate of knee hyperextension treatment was 98% in 52 stroke patients. 2.3 Lower extremity orthoses If there is no severe knee deep sensory disorder after stroke, the formation of knee hyperextension can mostly be prevented with early formal rehabilitation. Once formed and after unsatisfactory rehabilitation, cases have been reported in which orthoses had to be used. It has been proposed to use a long lower limb orthosis to control the angle of the knee and ankle joints, and a knee hinge to keep the knee joint in a mildly flexed position of 10° to 20° to inhibit knee hyperextension; it has also been proposed to use a long lower limb orthosis early in hemiplegia to promote postural response from the onset, prevent muscle atrophy, and strengthen the muscle strength of the healthy lower limb. It is generally accepted that the use of an AFO that prevents plantarflexion of the ankle joint is effective in preventing knee hyperextension when the stroke patient is standing. 2.4 For deficits in proprioception in stroke patients, early joint distraction and compression are preferred to promote recovery; if proprioception is lost, therapists can enhance their functional gait training or compensate using visual and auditory compensation, such as a biofeedback device with a limb load indicator that cues the patient when the foot touches the ground and provides information on the strength of muscle contraction during intensive training. Knee hyperextension severely affects the walking ability of stroke patients and is an urgent issue to be addressed in order to improve their quality of life. At present, studies on knee hyperextension after stroke have not clearly reported its essential causes. As far as the existing summary is concerned, the causes of knee hyperextension after stroke can be divided into weak lower limb muscles, primitive motor patterns, and lower limb proprioceptive deficits, and the causes of above ankle proprioceptive deficits and weak quadriceps muscles are particularly prominent. Most of the targeted rehabilitation treatment methods also advocate gradual progress, early promotion of detachment movement, restoration of proprioception, when the lower extremity muscle strength is sufficient to support weight and lower extremity detachment movement, followed by standing and walking training, avoid premature standing and walking before the lower extremity muscle strength reaches level 3 (Lovett's muscle strength 6 level scale); if the patient has already appeared knee hyperextension phenomenon and no improvement after rehabilitation training, then can If the patient has already developed knee hyperextension and it does not improve with rehabilitation, then appropriate lower limb orthoses can be selected to correct the gait.