Sickle cell disease can predispose to large joint problems particularly the hip and knee. As the viscosity of blood is high due to the abnormal shape of the red blood cells, blood is likely to stagnate and occlude small end arterioles in the bone. The head of the femur( thigh bone) is likely to suffer from a condition called avascular necrosis which means a death of the bone due to lack of blood supply. This may not be obvious on X-rays in the initials stages but only on MRI scans and a bone scan.
As the problem is an inborn error, nothing can alter it. Sickle cell crises are likely to develop when there is dehydration, cold temperature( keep him warm at all times), and after less oxygen (hypoxia). If he has advanced joint destruction then hip replacements may be necessary.