It is a derangement of the normal process of bone growth which occurs at various ossification centers during the period of greatest activity.

Causes-

1.   Trauma- A history of preceding injury can be obtained in majority of cases.

2.   More frequent in boys.

3.   More frequent in weight bearing joints.

4.   Infection- Osteochondritis is sometimes seen following some previous infective state or after general septicemia.

5.   Aseptic necrosis- After partial excision of the synovial membrane in which the nutrient vessels are carried, extensive areas of necrosis developed in the epiphysis.

Types-

1.   Crushing osteochondritis.

2.   Splitting osteochondritis.

3.   Pulling osteochondritis.

1.   Crushing osteochondritis- is caused by-

• Trauma- either a single definite injury or a series of minor injuries.
• Metabolic disorders.
• Endocrinal disorders.

Examples of this disease are- Perthes disease, metatarsal osteochondritis, navicular osteochondritis, lunate osteochondritis, thoracic spine.

2.   Splitting osteochondritis- is caused by-

• Trauma.
• Genetic, constitutional and hormonal factors.

Mainly three joints are affected- knee joint, followed by elbow and rarely the ankle joint.

3.   Pulling osteochondritis- It is usually an excessive strain on the tendon inserted to the apophysis which becomes affected. The affected apophysis becomes dense, fragmented and slightly separated. The commonest site is the knee followed by the heel.