Osteoarthritis is one of the types of arthritis that is caused due to degeneration and eventually loss of the cartilage of joints. Cartilage is a tissue that covers the inside of the joints and acts as a cushion between the two bones forming a joint. When the cartilage starts undergoing degeneration, the bone becomes inflamed as its protective covering is lost. This causes pain during weight-bearing activities such as standing, walking, etc.

The exact cause of osteoarthritis is often multifactorial, involving a combination of genetic, environmental, and biomechanical factors. Here are some common causes and risk factors associated with osteoarthritis:

1) Age: Osteoarthritis is more common with aging. The wear and tear on joints over the years can contribute to the breakdown of cartilage.

2) Genetics: There is a genetic component to osteoarthritis. If there's a family history of OA, individuals may be at a higher risk.

3) Joint Overuse or Injury: Repetitive use or overuse of joints can lead to the breakdown of cartilage. Joint injuries, such as fractures or ligament tears, can also increase the risk of developing osteoarthritis in the affected joint.

4) Obesity: Excess body weight puts increased stress on weight-bearing joints, such as the knees and hips. This additional stress can accelerate the breakdown of cartilage and contribute to the development of osteoarthritis.