1. Sprain:- injury to joint capsule, due to stretching or tearing etc. it causes pain in joints.
2. Arthritis:- (aching joints ) it is inflammation (swelling) of joints, commonly occurs at old age.
3. Osteoarthritis:-  here synovial fluid stops secreting due to which joints causes pain at movement. 
4. Rheumatoid arthritis: - here synovial membrane swells. It usually occur in small parts like in hand etc. starts at 20-40 years. And affects women more.
5. Osteoporosis: - it is reduction in skeletal strength. When calcium & phosphorus scarcity occurs.
6. Fractures :- it is a break of bone. As children have very flexible bones, so fractures occur rarely in children.

Types of fractures :-

1. Green-sick fracture :- it is a small crack. So bone remains in its place (original).
2. Simple fracture :- bone breaks completely into each other 2 pieces. Which remains close.
3. Comminuted fracture :- bone breaks completely into more than 2 pieces.
4. Compound fractures :- bone breaks into a fragment which shows out of skin.
5. Avulsion fractures:- a small piece breaks off fully from bone but remains attached to ligament.