Sports are the number one factor in adolescent injuries, for which the most attention is paid to acute injuries and overuse injuries are often overlooked. Overexertion injuries in adolescents are most common in soccer, basketball, and gymnastics and account for about half of all sports-related injuries in adolescents. Chronic injuries can result if not treated appropriately and in a timely manner. Repetitive microtrauma with inadequate rest after each injury is the pathogenesis of overuse injuries. Children are more susceptible to overuse injuries due to muscle-tendon imbalances, poor posture, and poor perception. Injuries can involve bone, cartilage and tendons and are difficult to diagnose. Hip pain The femoroacetabular impingement syndrome is due to an anatomical and structural abnormality of the acetabulum and proximal femur, which occurs when the acetabulum and femoral head and neck collide during hip flexion and internal rotation. Depending on the location of the impingement and the morphologic abnormalities of the acetabulum and proximal femur, it can be categorized into cam-type impingement, pincer-type impingement, and mixed impingement. Cam-type impingement is an abnormal bony growth at the anterolateral aspect of the femoral head-neck junction, which may be congenital, secondary to slipped capital femoral epiphysis or aseptic femoral head necrosis. It is most common in male adolescents. Repetitive kicking such as in soccer may accelerate the progression of the modified type of injury. The pincer-type impingement type has a bony abnormality from the acetabular side, mostly caused by over-inclusion of the acetabulum, which results in hip flexion and movement in all directions, where the abnormally protruding acetabular rim collides with the femoral head and neck, leading to damage to the tissues around the hip joint, especially the cartilage and acetabular labrum. The mixed type is the most common and results from abnormal femoral and acetabular anatomy. Patients with osteo-acetabular impingement syndrome often complain of pain in the front of the acetabulum that worsens with movement. The patient often identifies the site of pain with the thumb and index finger over the C-shaped greater trochanter. Pain can be triggered by passive hip flexion, adduction, and internal rotation. X-rays should be performed to visualize the local bony anatomy and may reveal a concave chakra injury or sign of eight (acetabular retroversion). However, these imaging findings should not be over-interpreted, as a recent study found that 93% of plain hip radiographs in adolescents without hip symptoms were suggestive of osteo-hip impingement syndrome. In patients with hip pain and imaging, MRI should be performed to evaluate for damage to the acetabular labrum and articular cartilage. Although all types of impingement can cause damage to the acetabular labrum and cartilage, cogwheel impingement is associated with delamination of the articular cartilage in the anterior superior aspect of the acetabulum, whereas the pincer type is more likely to cause acetabular labral damage. Conservative treatment is preferred, and surgery is required if conservative treatment fails. Surgery should eliminate intra-articular deformities, relieve symptoms and reduce the incidence of osteoarthritis. Most acetabular labral and cartilage injuries and some femoral acetabular deformities can be corrected by arthroscopic surgery. Sports can be resumed after surgical treatment. Fatigue fracture of the femoral neck Fatigue fractures have been increasing in incidence over the past decade and are most commonly seen in athletes during periods of increased physical activity. In children they are most common in the tibia, fibula and femur. The female athlete triad is an important risk factor: amenorrhea, dietary abnormalities, and osteoporosis. Dietary abnormalities are not only seen in women, but also in male athletes who often go on diets to control their weight. Therefore, young patients with fatigue fractures should also be screened for dietary abnormalities. Approximately 7% of fatigue fractures are fatigue fractures of the femoral neck, which can be categorized as either tension or compression depending on the mechanism of injury. The pulling type accumulates anteriorly and superiorly to the neck of the femur and is most common in adult patients, whereas the compression type of injury accumulates inferiorly to the neck of the femur and is most common in pediatric patients. The patient has groin pain that worsens with exercise, may be unable to stand on one leg or perform resisted straight leg raises, and has a positive Trendelenburg test. A positive Trendelenburg test is seen. Plain radiographs may not be able to detect this in time and an MRI should be performed. Failure to make a timely diagnosis can have serious consequences, as a fatigue fracture of the neck of the femur may progress to an acute displaced fracture, and the patient is at increased risk of ischemic necrosis of the femoral head. Distraction type injuries have an increased risk of displacement and should be fixed with hollow screws. The compression type is generally more stable and does not require surgery; protective weight bearing, activity restriction, and close follow-up are indicated. Although they may cause mild internal derangement, they generally do not cause significant body shape changes. Snapping Hip It is characterized by pain at the hip joint and snapping when the hip is flexed or extended. It is categorized into lateral, medial and intra-articular types. The medial type is due to the relative movement of the hyperplastic iliopsoas tendon on the femoral head, pubic symphysis or iliopsoas muscle, or the relative movement of the iliopsoas tendon after it splits into two bundles. It is most often triggered by hyperflexion of the hip and is common in dancers, gymnasts and soccer players. The lateral type is the most common type and is due to popping of the thickened portion of the iliotibial bundle or the anterior portion of the quadriceps muscle as it crosses the greater trochanter during internal rotation of the lower extremity. The intra-articular type is due to intra-articular deformities such as intra-articular free bodies or acetabular labral injuries. Its diagnosis is mainly based on clinical manifestations. Damage to the intra-articular joint, ligaments, tendons, and muscles may be observed on MRI, and other imaging studies are negative. Initially, the mainstay of treatment is rest, anti-inflammation, iliopsoas tendon relaxation and stretching, and steroid injections if necessary. Surgical incision or arthroscopic release can be performed when conservative treatment fails. Arthroscopic release is mainly indicated for both medial and lateral types and facilitates the treatment of intra-articular abnormalities. Pelvic osteochondritis dissecans is seen in skeletally immature adolescents and young adults who are over-exercising. Iliopsoas osteochondritis dissecans is often seen when the torso is twisted frequently, as in figure skaters. Excessive swing of the upper arm during running is also a risk factor. Running, especially sprinting, can lead to iliopsoas, anterior superior iliac spine, and sciatic osteochondritis. The onset of the disease can be differentiated from an osteochondral tear. Patients with osteochondritis dissecans complain of pain in the area of the relevant bony prominence during exercise, and there is no local deformity on examination; whereas pain, redness and swelling are found in the area of the bony prominence tear. The pain is aggravated by passive pulling of the attached muscles, and the imaging examination is mostly normal. Generally, conservative treatment is used to avoid excessive weight bearing. Avoid excessive muscle pulling in the early stage of recovery. This type of injury should be detected and treated early, or it may progress to an acute synostosis tear. Knee pain Patellofemoral pain syndrome Patellofemoral pain syndrome is the most common overuse injury of the knee, but its pathogenesis remains poorly understood. Risk factors include patellar malalignment, malalignment, muscle imbalance and ligamentous laxity. Studies of patients with patellofemoral pain syndrome by dynamic imaging have revealed significant motion abnormalities. It has been suggested that this motion abnormality leads to stress on the inter-articular contact, with increased pressure in some areas leading to pain. Knee pain can be triggered by activity, sedentary behavior, and climbing stairs. Most are symptomatic bilaterally. Pain can be induced by patellar grinding test. Treatment is mainly rest therapy with strengthening of the medial oblique femoral muscle to increase the grip on the patella. In patients with abnormal patellar motion, a patellar stabilizing brace or patellar taping may be used. Tibial tuberosity epiphysitis Tibial tuberosity epiphysitis mainly affects the tibial tuberosity and is the most common form of pulling epiphysitis. It is often seen in sports that involve jumping and squatting, such as soccer and basketball. It is most common in patients aged 10-15 years, who often complain of swelling and pain at the tibial tuberosity, which is exacerbated by running, jumping, and kneeling. Symptoms may be bilateral. Tenderness on the surface of the tibial tubercle and pain induced by resistance to knee extension. Plain radiographs are not helpful in the diagnosis but should be taken routinely to exclude other lesions. Rupture and irregular ossification are seen at the tibial tuberosity. The disease is self-limiting and conservative treatment is the mainstay. An infrapatellar brace may be used. Patients with tibial tuberosity epiphysitis have been reported to have a displaced tuberosity when jumping, and an association between tibial tuberosity epiphysitis and tibial tuberosity tears has been suggested. Open reduction and internal fixation can be performed in these patients. However, most patients can be treated conservatively and return to normal activity after a few weeks. It is not uncommon for symptoms to persist into adulthood. Approximately 60% of patients experience knee pain when kneeling. Surgery to remove the small painful bone is an option for those with residual symptoms despite conservative treatment. However, even after surgery, some patients continue to experience discomfort. Sundin-Larsen-Johnson’s disease Sundin-Larsen-Johnson’s disease is an osteochondritis dissecans of the lower pole of the patella. The cause is similar to that of tibial tuberosity epiphysitis, and it is most common in patients aged 9 to 12 years. The patient presents with anterior knee pain with activity, which is exacerbated by running and jumping. The lower pole of the patella is painful and fragments of the lower pole of the patella can be seen on imaging. The disease is self-limited and does not require surgical intervention. Some patients continue to have symptoms into adulthood and surgical treatment may be an option. Patellar Ligament Disease Partial thickening and tearing of the patellar tendon due to weight-bearing contraction of the quadriceps muscle as a result of running and jumping exercises. Muscle imbalance is one of the risk factors, and patients are associated with increased tension in the quadriceps, posterior leg muscle groups and Achilles tendon. The pain is exacerbated by sedentary behavior and after exercise. The patellar tendon sheath is tender to palpation and pain is induced by resistance to straightening the knee. Imaging is negative or shows ligament calcification. Conservative treatment is the mainstay, with rest and ice physiotherapy. Injections of platelet-rich plasma may be effective. Opinions differ on the use of NSAIDs, as the disease is degenerative rather than an inflammatory response. Incisional or arthroscopic surgery can be used when conservative treatment fails with comparable results. Exfoliative osteochondritis Dissecutive osteochondritis refers to necrosis of a small area of subchondral bone. It is most common in adolescents aged 10-15 years and its etiology is unknown. Chronic repetitive microtrauma is thought to be the main pathogenetic factor. It most commonly involves the medial condyle of the femur, followed by the lateral condyle, trochanter, and patella. Patients often complain of knee pain and swelling after activity. There is tenderness in the affected area when the knee is flexed. Tunnel X-ray is more sensitive. In the early stages, MRI should be performed, which is also the gold standard for distinguishing whether the damage is stable or not. There are several classification criteria: the interface between the fragment and the surrounding bone on the T2 enhancement image, the presence or absence of a cyst, the presence or absence of a fracture line in the articular cartilage, and the presence or absence of a fluid-filled cartilage defect. Determining whether a lesion is stable is important for both diagnosis and treatment planning. Stabilizing injuries to the growth plate in children have a good prognosis, with a recent study showing that 2/3 of children recovered within 6 months after nonoperative treatment. Conservative treatment measures include weight restriction and immobilization with braces. However, other studies have found failure rates of up to 50% for non-operative treatment, and it is believed that some patients may benefit from early surgical intervention. Factors associated with a better prognosis include younger age, less extensive damage, and the absence of cyst-like damage. Unstable damage, on the other hand, has a low likelihood of self-healing and generally requires surgical intervention. Surgery should be performed either when the growth plate is about to close or after conservative treatment has failed. Mild, stable damage can be treated with drilling, and unstable damage can be treated with internal fixation. Autologous or allogeneic cartilage grafting should be performed when the damage is severe, but the results are not definitive. Growth Plate Fatigue Fractures The growth plate is less tolerant of shear and tension than normal bone, making fractures in this area more common. Prolonged stress on the growth plate can lead to fatigue injuries and epiphyseal detachment, especially during periods of rapid growth. It is common in the distal femoral epiphysis and proximal tibial epiphysis of the lower extremities, and is most often triggered by running. Widening of the epiphysis can be seen on plain radiographs, but the mechanism is unknown. MRI is usually indicated. Most cases improve spontaneously with rest, but some can lead to premature healing of the growth plate and lead to inversion of the knee. Anterior tibial pain, or medial tibial pressure syndrome, is the leading cause of calf pain in adolescents after running. A recent 3-year follow-up of 230 high school runners found that about half had anterior shin pain. The pain was bilateral and located in the distal third of the calf, and risk factors included pronation and calf muscle weakness. Other possible factors include poor running shoes, hard surfaces, hills, and individual factors such as poor hypoxic tolerance and high body mass index.MRI is associated with bone marrow and periosteal edema, but is less specific. Conservative treatment, rest, NSAIDs, change in training pattern. Foot orthoses are not effective. Tibial Fatigue Fractures Fatigue fractures in athletes are most commonly associated with tibial fractures. They often complain of recent increased training and localized pain and swelling. Pain can be induced on downward pressure or jumping in the mid-tibia, which can be distinguished from anterior tibial pain. Plain films are unremarkable in the early stages and the diagnosis relies on MRI.Tibial fatigue fractures can be proximal or distal, posteromedial or anterolateral. Anterior cortical fractures of the mid tibia show a “black line” sign on lateral views and have a poor prognosis. Non-operative treatment may result in non-union or complete fracture. Patients with closed epiphyses are fixed with intramedullary nails, and those with unclosed epiphyses are braced with casts. Intramedullary nail fixation may cause anterior knee pain, which is more bothersome to the athlete. The use of pressurized tension banded splints has been suggested. Stress fractures in other areas can be rested and protected weight bearing with a good prognosis. Because of the long clinical course of these fractures, early diagnosis and treatment are very important. Chronic Osteofascial Spacer Syndrome Exercise increases the pressure in the osteofascial spacer while inducing pain. The exact mechanism is unknown. Decreased tissue perfusion and subsequent local ischemia are thought to play an important role in its pathogenesis, but there is no perfusion abnormality on imaging. It is most common in runners and the anterior fascial septum is most frequently involved. They often complain of pain and calf tightness after exercise, which disappears after rest. The pain is often anterolateral or posterior, while anterior tibial pain is most often medial. It is not often accompanied by transient neurologic symptoms such as foot drop or sensory abnormalities. Measurement of intra-interval pressure at rest and immediately after exercise is the gold standard for diagnosis. Gait analysis is an important part of initial conservative treatment. The condition is associated with a heel-first touchdown gait, and changing to a forefoot-first touchdown gait can help improve symptoms. If conservative treatment fails, fasciotomy can be performed. There is a 45% chance of recurrence after surgery, but satisfaction is higher than with non-surgical treatment. Satisfaction with anterolateral dissection alone is higher than with medial and lateral dissection, and satisfaction with surgery is also higher in younger patients. Recently, arthroscopic surgery has been attempted. Botulinum toxin helps to relieve pain and reduce intramuscular pressure. Side effects are lower extremity weakness. Long-term efficacy is unknown. Ankle pain Anterior ankle impingement syndrome Also known as basketball foot, it develops as a result of repetitive dorsiflexion, repetitive ankle sprains and subclinical ankle instability. Impingement is caused by bone spurs in the distal tibia or talar neck, scar tissue, synovitis, or hypertrophied anterior tibiofibular ligament due to joint instability. Ballet dancers and gymnasts are at high risk for this condition due to excessive dorsiflexion. They often complain of ankle pain induced by dorsiflexion. Plain radiographs may reveal bone spurs on the distal tibia or the neck of the talus. If plain radiographs are negative, MRI is performed. Conservative treatment is ineffective. Arthroscopic joint debridement may be performed. A case study of 13 adolescents found that none of them were able to play sports after conservative treatment. The results of arthroscopic debridement were variable, but 10 adolescents were able to return to sports. Another study showed that 97% of patients returned to normal sports. Osteochondral injuries Osteochondral injuries of the ankle most commonly involve the talus. Injuries to the lateral aspect of the talus apex are most often due to ankle sprains, and the mechanism of injury to the medial aspect of the talus apex is unknown. Most medial injuries are non-traumatic and related to overuse. Patients complain of pain, persistent or intermittent swelling. Plain radiographs may reveal talus injuries, and the diagnosis relies on MRI.Ankle immobilization in a brace and avoidance of weight-bearing are indicated in the absence of displaced injuries. Surgical treatment is indicated in cases where conservative treatment fails or displaced injuries are present. Treatment may include drilling for repositioning, internal fixation, or osteochondral grafting. A survey of athletes and amateurs with postoperative talar injuries found that almost all patients were able to perform normal physical activities. Changing training patterns Overuse injuries have an insidious onset, but are long and severe. If it is not diagnosed in time, it can hinder sports activities and even cause joint degeneration and deformity. Once an overuse injury is detected, not only rest but also a change in training rules are needed at a later stage. These changes will not only help to return to the pre-injury level of sport, but will also prevent other overuse injuries. All training programs should include the following: warm-up, proper fit, proper footwear, and the use of foot orthotics if necessary. Avoid excessive repetition of a physical activity. Motor function screenings and kinesiology evaluations can help detect muscle movement incongruities. The American Academy of Pediatrics recommends that athletes rest at least one day per week. Increases in exercise should be no more than 10% per week. There should be a 2-3 month break from the sport each year. Children and adolescents are most susceptible to overuse injuries due to anatomical and social factors, and adult training programs should not be directly applied to adolescents. Although adolescents may achieve similar results to adults, their bones are immature and cannot withstand excessive force, and they are less able to recognize and communicate discomfort. Parental and coaching pressure may cause them to continue to train despite symptoms. Conclusion The range of lower extremity overuse injuries is large. Physicians should consider the possibility of overuse injuries in young patients complaining of hip, knee, kneecap, or ankle pain. A detailed physical examination is important. Lower limb strain injuries are mainly treated conservatively, but surgery should be performed if necessary. If left untreated, an overuse injury may affect normal mobility or cause long-term dysfunction.