What is osteoarthritis? Definition

Osteoarthritis referred to as OA in short is a chronic joint disorder. There are certain causes and risk factors leading to this condition but primarily, it is caused by damage to the cartilage in the joint and its surrounding tissues.

It is characterized by symptoms of joint pain, joint stiffness, and loss of its function. There is inflammation present in the joint between two bones. It is usually progressive with no stops or reverses.

Osteoarthritis is more likely to develop in older people with the risk increasing as you age and the changes in the joint usually progress slowly over many years,

A patient of osteoarthritis is handicapped, physically and mentally, taking painkillers and harboring the knowledge that he has to live with this condition all his life. Daily activities become painful and cumbersome affecting his job performance. It does add to his mental agony.

It is also referred to as degenerative arthritis or degenerative joint disease because it causes degeneration of the protective cartilage in the joint and the underlying bone. The cartilage is present between the two bones in the joint.

The cartilage is a protein substance present in the joint and acts as a cushion between the two bones of the joint. It allows one bone to slide over another and helps to facilitate various movements of the joint. You may develop osteoarthritis of the hip, the knee, spine, hands, or even of the fingers.

Of the about a hundred arthritis conditions, osteoarthritis is the most common form of arthritis and is seen affecting millions of middle age and above people worldwide.

Who is likely to develop osteoarthritis?

OA affects people of all races and both genders. It usually is a disease of people of age 40 years and above. However, it can occur earlier if you have other risk factors.  People likely to have OA are:

  • Older people
  • Those having family members with OA
  • Obese people
  • Those with a previous traumatic joint injury or repetitive overuse of joints
  • People with joint deformities such as unequal leg length, bow-legs, or knock knees

Pathological features of osteoarthritis

It is important to note that OA is not a disease of just the articular cartilage but of the entire synovial joint in which there is damage to all the tissues of the joint such as the subchondral bone, the ligaments, the tendons, the periarticular muscle, the synovial sac, the sensory nerves, the menisci, and of course the cartilage.

Main pathological changes in the joint affected by osteoarthritis:

  • Softening and later loss of articular cartilage
  • Degeneration of the exposed bone at the site of cartilage loss
  • Remodeling of bone
  • Formation of osteophytes
  • Formation of subchondral cysts
  • Inflammation of the synovial sac called synovitis
  • Thickening of the capsule of the affected joint
  • Degeneration of the menisci
  • Atrophy of the periarticular muscles

These pathological changes in the joint are clearly visible on the imaging tests done to diagnose this condition. Once diagnosed, treatment is started but there is no cure for it. Conservative treatment gives relief from symptoms and may slow disease progression. In advanced cases, surgery is the last resort.

Joints affected by osteoarthritis

Osteoarthritis is the most common type of joint disease and is the leading cause of chronic disability in older adults.

The joints most often affected in generalized OA include the following:

  • Knee
  • Hip
  • Intervertebral disks and the joints in the cervical and lumbar vertebrae
  • Distal interphalangeal (DIP) and proximal interphalangeal (PIP) joints
  • Thumb carpometacarpal joint
  • First metatarsophalangeal joint

The lifetime risk of developing OA of the knee is about 46%, and of the hip it is 25%, according to the Johnston County Osteoarthritis Project,


You develop osteoarthritis usually after the age of 45 years and is found more common amongst men. Between 55 years to 70 years, it is present equally in men and women. After the age of 70 years, it is more common in women.

This rise in osteoarthritis in women of advanced age is probably due to weight gain caused by menopause. According to the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), osteoarthritis affects about 27 million people in the United States.

Half of these cases of osteoarthritis are in the knee, according to the Centers for Disease Control and Prevention (CDC). About 8 million suffer from osteoarthritis in the United Kingdom.

A higher incidence is seen in the Japanese population while it is seen less among the South-African blacks, East Indians, and Southern Chinese.