A child with a limp is an important field of medicine, purely because of the potential consequences of missing a serious condition. Of course, most cases, such as a minor injury or a splinter in the foot, are not dangerous, but one cannot afford to be complacent.
Many children will have been born with an obvious cause for their limp - for example, spinal deformity or discrepancy between the length of their legs. Others will have been found to have muscular diseases that can cause leg weakness and limp.
Very young children may be born with hips that are dislocated or easily dislocatable. Developmental dysplasia of the hip (DDH) may affect around one in 200 babies when they are born, although four out of five cases resolve by three weeks of age. The condition often runs in families and affects females more than males.
Breech-birth children are more at risk, and the left hip is more commonly affected than the right. At-risk children such as breech babies often have a scan to check for DDH. Skin creases in the thigh of the affected leg may be different from the other side. If both sides are affected, skin-crease asymmetry will not be apparent. Once walking, the child may limp or even waddle.
Failure to detect DDH, often referred to as congenital dislocation of the hip, may result in significant deformity, back problems including scoliosis, and arthritis of the hip.
Fractures may cause a child to limp or refuse to walk. In most cases, there will be a plausible explanation to a fracture. Further investigation should be made when a child has multiple fractures, there is a delay in presentation or parents give a story that doesn't explain the injury. In a few cases, the child will be found to have a brittle bone disease.
COMMON CONDITION
Irritable hip, otherwise known as transient synovitis, is a relatively common condition that affects boys more than girls. Around one in three cases are triggered by an upper respiratory infection. Hip pain and limp start over a short period of time and resolve over a week or so. The child is usually well in themselves.
Septic arthritis describes an infection of the joint itself, whereas osteomyelitis is an infection of the bone. Septic arthritis is a serious condition normally caused by bacteria floating around the bloodstream and settling in the joint. In addition, a wound, skin infection or osteomyelitis may all be complicated by a septic joint.
Children who have a poor immune system, such as diabetics or those receiving chemotherapy, are particularly at risk. Septic arthritis most commonly affects the hip or the knee and causes the child to be unwell with a fever. They will have a painful joint which looks red and swollen. Without treatment, septic arthritis may cause complete destruction of a joint and arthritis in later life.
INFECTION
Osteomyelitis may come on quickly (acute), or have more of an indolent onset (chronic). It may be caused a number of microbes, including bacteria such as staphylococcus aureus and tuberculosis. Children with sickle cell anaemia may be more susceptible to oesteomyelitis caused by salmonella.
Bone pain, limp and fever are common presentations. Very young children may fail to thrive and become irritable. Without treatment, the infection may spread to other structures and alter the normal growth of the bone.
In addition to infection, children with sickle cell anaemia may experience dactylitis, in which fingers and toes become inflamed due to poor blood supply. The growth of the fingers or toes may be affected.
Other conditions affecting blood supply to bones in children include Perthe's disease, where the top of the femur (thighbone), known as the femoral head, loses its blood supply and starts to become deformed - so called avascular necrosis. It may occur in children as young as three and usually presents with pain and limping. Males are affected more than females. Without action, Perthe's disease may cause joint destruction, arthritis and growth problems.
Childhood cancers are, fortunately, rare. A number of different tumours can cause a limp, including those in the brain, spinal cord or any affecting muscle or bone. In addition, leukaemia can cause bone pain and a limp. In some cases cancers may weaken a bone, causing a 'pathological fracture'.
Arthritis can affect children as well as adults. Still's disease is an auto-immune condition where the body attacks parts of itself. It may present with a fever, rash, large lymph glands and painful swollen joints. Quality of life, growth and many other organs, including the eyes, may be affected.
Rheumatic fever and Henoch-Schonlein purpura are also conditions that affect many parts of the body, including the joints that may result in a limping child. In addition to neurological, muscular and joint problems, children may also limp with appendicitis or a hernia.
Dr Raj Thakkar BSc(Hons) MBBS MRCGP MRCP(UK) is a full-time GP in Buckinghamshire
