There are no set standards for the diagnosis of suspected<unk> , so the amount of investigations will depend on the need to exclude other, more serious diseases. It is of great importance to exclude the diagnosis of septic arthritis. This is because if septic arthritis is missed in children, grave complications can occur. The exclusion of septic arthritis is mainly built upon the physician's clinical expertise and is supplemented by basic laboratory test and relevant imaging modalities. Additionally, beware to exclude the diagnosis of acute osteomyelitis, because it not uncommonly cooccurs with septic arthritis of the hip in children. Inflammatory parameters in the blood may be slightly raised (these include erythrocyte sedimentation rate, C-reactive protein and white blood cell count), but raised inflammatory markers are strong predictors of other more serious conditions such as septic arthritis. X-ray imaging of the hip is most often unremarkable. Subtle radiographic signs include an accentuated pericapsular shadow, widening of the medial joint space, lateral displacement of the femoral epiphyses with surface flattening (Waldenström sign), prominent obturator shadow, diminution of soft tissue planes around the hip joint or slight demineralisation of the proximal femur. The main reason for radiographic examination is to exclude bony lesions such as occult fractures, slipped upper femoral epiphysis or bone tumours (such as osteoid osteoma). An anteroposterior and frog lateral (Lauenstein) view of the pelvis and both hips is advisable. An ultrasound scan of the hip can easily demonstrate fluid inside the joint capsule (Fabella sign), although this is not always present in<unk> . However, it cannot reliably distinguish between septic arthritis and<unk> . If septic arthritis needs to be ruled out, needle aspiration of the fluid can be performed under ultrasound guidance. In<unk> , the joint fluid will be clear. In septic arthritis, there will be pus in the joint, which can be sent for bacterial culture and antibiotic sensitivity testing. More advanced imaging techniques can be used if the clinical picture is unclear; the exact role of different imaging modalities remains uncertain. Some studies have demonstrated findings on magnetic resonance imaging (MRI scan) that can differentiate between septic arthritis and<unk>  (for example, signal intensity of adjacent bone marrow). Skeletal scintigraphy can be entirely normal in<unk> , and scintigraphic findings do not distinguish<unk>  from other joint conditions in children. CT scanning does not appear helpful. Differential diagnosis Pain in or around the hip and/or limp in children can be due to a large number of conditions. Septic arthritis (a bacterial infection of the joint) is the most important differential diagnosis, because it can quickly cause irreversible damage to the hip joint. Fever, raised inflammatory markers on blood tests and severe symptoms (inability to bear weight, pronounced muscle guarding) all point to septic arthritis, but a high index of suspicion remains necessary even if these are not present. Osteomyelitis (infection of the bone tissue) can also cause pain and limp. Bone fractures, such as a toddler's fracture (spiral fracture of the shin bone), can also cause pain and limp, but are uncommon around the hip joint. Soft tissue injuries can be evident when bruises are present. Muscle or ligament injuries can be contracted during heavy physical activity —however, it is important not to miss a slipped upper femoral epiphysis. Avascular necrosis of the femoral head (Legg-Calvé-Perthes disease) typically occurs in children aged 4–8, and is also more common in boys. There may be an effusion on ultrasound, similar to<unk> . Neurological conditions can also present with a limp. If developmental dysplasia of the hip is missed early in life, it can come to attention later in this way. Pain in the groin can also be caused by diseases of the organs in the abdomen (such as a psoas abscess) or by testicular disease. Rarely, there is an underlying rheumatic condition (juvenile idiopathic arthritis, Lyme arthritis, gonococcal arthritis, ...) or bone tumour.
Transient synovitis
Facet joint arthrosis
Post-traumatic arthritis
Calcific bursitis
Osteochondritis
Bursitis
Ischial bursitis
Femoroacetabular impingement