Lower extremity pain in children is very common in pediatric surgery clinics, and there are many illnesses associated with this symptom, which can be a minor symptom or a serious disease, but they should not be ignored and should be diagnosed and treated appropriately as soon as possible. Before consultation, the child should be asked about the location of the pain, unilateral or bilateral, and the gait of the child should be observed for lameness and fast pounding gait. Lower extremity pain fixed unilaterally with claudication should be given more attention. The main types of pediatric lower limb pain that need to be differentiated are as follows. 1 Acute transient synovitis of the hip Acute transient synovitis of the hip is a self-limiting aseptic non-specific inflammatory disease of unknown origin. It is the most common cause of hip pain in children under 10 years of age. The main symptom is femoral or knee pain with claudication, which is more frequent in preschool children, often with a history of upper respiratory tract infection or minor trauma before onset. The clinical features are rapid onset and severe symptoms with relatively mild signs. The onset of the disease is often sudden and normal before going to bed, but after waking up in the morning, the child refuses to walk on the ground due to pain in the lower limbs, thus causing anxiety among parents; while the physical examination of the hip joint is less restricted in movement. Sometimes the pain in the hip radiates to the ipsilateral knee, so the doctor can be misled to take an X-ray of the knee and ignore the examination of the hip joint, resulting in an untimely diagnosis. There is usually no obvious abnormality in hip X-ray examination. The treatment principle is bed rest, avoid weight bearing on the affected limb, and traction treatment should be given to the affected hip with flexion deformity. The prognosis for children is good, with the pain relieved within 2-3 days and the hip joint moving as usual afterwards. To prevent recurrence, weight-bearing should be avoided for 7 to 10 days after resumption of hip activity. It is worth noting that the early manifestation of ischemic necrosis of the femoral head is similar to this disease, so the hip X-ray should be taken routinely 2 to 3 months after clinical cure to exclude the femoral head lesion. 2 Ischemic necrosis of the femoral head Ischemic necrosis of the femoral head (Legg-Perthers disease) occurs in boys. The main clinical manifestations are hip pain, claudication and restriction of hip movement in multiple directions, with limitation of internal rotation prominent. x-ray can make a clear diagnosis. Early onset of the disease is not easily distinguished from transient synovitis of the hip joint. The treatment options are not uniform and mainly include symptomatic pain management, brace inclusion therapy and surgical inclusion therapy. 3 Knee valgus Knee valgus (genuvalgum, X-shaped leg) is often found in children before the age of 3 years, and gradually develops after the age of 3 years. This is one of the common reasons why children complain of lower limb pain. Some complain of inward pointing of the foot and easy falling. The severity of symptoms is related to the severity of the deformity. Ankle spacing within 5 cm is mostly a developmental deformity, i.e., the femoral muscles are not enough to maintain the stability and normal anatomical relationship of the knee, which can be corrected by itself with growth. If the ankle spacing is about 10 cm, the cause of the ankle spacing should be investigated, such as rickets, and sometimes it needs to be corrected with braces along with the treatment of the original disease. If the ankle spacing is 10-15 cm or more, systemic diseases such as anti-D rickets or renal rickets should be ruled out and osteotomy orthopedic surgery should be performed after the primary disease is cured. 4 tibial tubercle osteochondritis The age of onset of tibial tubercle osteochondritis (Osgood’s disease) is between 10 and 12 years old, often with a history of soccer, and the current pathology is considered to be ectopic bone caused by cumulative injury to the patellar tendon in the tibial tubercle joint. The lower extremity pain caused by this disease is limited to the tibial tuberosity and can occur unilaterally or bilaterally. Treatment includes suspension of exercise, wearing a knee brace and local braking. 5 Fatigue fracture of the tibia A fatigue fracture of the tibia is a stress fracture. The disease can be caused by sudden and prolonged overexertion due to lack of exercise. The pathology is a fracture caused by repeated muscle pulling and stepping on the ground with normal bone elasticity. The fracture may appear on x-ray as a subtle traumatic fracture line interspersed with reparative new bone. The fracture can be cured by lower limb braking. 6 Posterior heel pain Posterior heel pain was previously referred to as Sever’s disease or metaphyseal epiphysitis of the heel bone. It is a cumulative injury of the Achilles tendon at the heel attachment or a maladjustment to the usual frequent exchange of thick heeled shoes and flat shoes. The heel can heal spontaneously in 2 to 4 weeks with high heel padding. The pain below the heel bone is caused by a heavy gait or an uneven force point of the heel landing. Adding soft cushions in shoes can relieve the symptoms. Growing pain, also known as growing lower limb pain, is common in girls aged 4 to 8 years old, with lower limb pain occurring mostly at night and disappearing during the day, often complaining of bilateral lower limb pain, with symptoms not increasing with the progress of the disease and no limp. It should be noted that the diagnosis of growing lower extremity pain relies on methods to exclude other diseases in addition to the above-mentioned history, physical examination, and follow-up. Treatment includes oral vitamin C and local muscle traction physiotherapy. In conclusion, the etiology of pediatric lower extremity pain encountered in pediatric surgery clinics is diverse. Questions and answers of a consultative nature take up most of the time, and mostly simple conservative therapies are used to relieve the child of the pain. The key issue is not to miss individual serious diseases from the larger number of self-curable conditions.