Bone and joint problems – a guide for families

Children's bones and joints are quite different to those in adults. The main difference is that they are still growing, which can lead to some unique problems, as well as some unique solutions.

The skeleton is what gives us our shape. It lets us stand, sit, walk and run. It also acts as a cage to protect our vital organs. There are 206 bones in an adult skeleton. The longest bone is our thighbone (femur). The smallest bones are the tiny ones inside the ear.

Bones are very light but they are very strong too. Bones are made up of living cells that can repair themselves. They are covered in a layer of periosteum, which contains blood vessels and nerves. This is what hurts when you break a bone. Most tissues heal with a scar (like skin or muscle) but bone is unusual because it can heal by joining back together again without a scar.

Bones are complex structures made of minerals containing calcium and phosphorus bonded to fibres made of collagen (protein). Some bones are hollow, with a spongy centre. These contain the bone marrow, where blood cells are made.

Unlike adult’s bones, children’s bones grow. They get longer by adding extra bone to the ends, near the joints, from special seams of cartilage called growth plates. Bones also get wider as extra layers are added to the outside, like extra plaster being added to a wall. Children grow most rapidly in the first six months of life, then they grow more slowly until the teenage years, when they undergo the so-called ‘growth spurt’. Usually girls stop growing at about 14 years old, boys at about 16.

Bones are quite complicated structures, and sometimes the body does not manufacture them correctly. For example, the ‘instructions’ (genes) to make them might contain a mistake (mutation). Usually this results in a bone that is small, incomplete, or curved at an early age, often noticeable at birth (so-called ‘congenital’ conditions).

Sometimes bones form fine, but become damaged by an injury or an infection (‘acquired’ conditions). In children, the growth of bones can be affected, making them grow at an angle, or making them short. There are a few conditions that make bones grow longer than they should be. In quite a few conditions, the exact cause of the problem is actually unknown.

Our limbs – our arms and legs – are each made of several bones, joints, muscles, nerves and blood vessels The bones in the arm are the humerus (upper arm) and radius and ulna (lower arm). The bones in the leg are the femur (thighbone), tibia (shinbone) and the fibula.

Bones are connected by joints, and the arms and legs contain different types. For instance, our upper arms and upper legs join the body using a ‘ball and socket’ joint – this gives a wide range of movement in all directions. However, our elbows and knees have a ‘hinge’ joint, which allows movement in only one direction. Muscles are the ’motors‘ which move the joints, and they receive their instructions to do this from nerves, which carry electrical signals from the brain, which plan the movements in the first place. Muscles are connected to the bones by tendons.

Joints are covered in cartilage which is very slippery and allows the joint surfaces to glide over each other when we move. If cartilage become damaged, it has very limited ability to repair itself (unlike bone), which is why arthritis is quite common in adults. Joints have tough fibrous ‘capsules’ around them, which are usually flexible, but can become stiff in some medical conditions, or sometimes after operations.

In order to treat conditions which affect the limbs, our team combines our skills to design a programme specifically designed for your child’s problems. Sometimes operations are required, but sometimes other techniques like physiotherapy, plaster casts or plastic splints (‘orthoses’) do the job. Often we recommend a combination of these techniques. Some conditions improve by themselves without needing treatment at all.

When operations are needed, we tailor the techniques to the particular child depending on the cause of the problem, their age, and the goals we are trying to achieve. Sometimes we operate to lengthen tendons which are short, or to release joints which have become too tight. Sometimes we straighten bones which have become bent and hold them straight while they heal in their new position. We also have techniques to ‘grow’ bone straight again, to grow new bone which is missing, and to lengthen bones which are short. Which technique we use depends on the individual case.

As children are growing and constantly changing, we frequently use these techniques in combination, and often we will make a plan for a series of operations at different ages. Planning is very important and in complicated cases we usually discuss the best way forward as a group at our regular case conferences. We often operate in teams, for example alongside plastic surgeons who can help with particular techniques that might be needed (skin grafting and microsurgery, for example).