Knee Arthritis (Inflamed Joint Pain) – Types, Causes, Symptoms, Treatment

Arthritis is a common joint problem that can occur at any time in life, even in childhood. Most of us are familiar with arthritis among older people although the underlying problem may have started years or even decades earlier. There are different types of arthritis which can affect any joint although some of these types of arthritis have a predilection for specific joints in the body. One commonly affected joint is the knee.

What is knee arthritis?

Knee arthritis is inflammation of the knee joint. It usually presents with pain and stiffness. In addition swelling, heat and redness over the joint is also present in may cases of knee arthritis. The term arthritis refers to inflammation of the joint which can occur with many different causes. However, the three most common types of arthritis to affect the knee are osteoarthritis (OA), rheumatoid arthritis (RA) and posttraumatic arthritis.

The knee is a commonly affected joint for osteoarthritis and posttraumatic arthritis because it is prone to strain and injury, respectively. As a large joint that has to bear most of the body weight (head, upper limbs, torso and thighs) in addition to lying superficially, the knee joint is constantly contending with force and is exposed to a host of possible environmental insults. However, arthritis may sometimes arise irrespective of joint strain and injury, as may be seen with rheumatoid arthritis.

Types and Causes of Knee Arthritis

Inflammation is the body’s respose to tissue injury or damage. The cause of this tissue injury or damage can be diverse which gives rise to the different types of knee arthritis. Prolonged and severe inflammation can cause permanent tissue damage, especially without proper treatment and management. Of the different types of arthritis,  osteoarthritis, rheumatoid arthritis and posttraumatic arthritis are the most common types affecting the knee.

Knee Osteoarthritis

Osteoarthritis (OA) is a common joint condition that affects at least 50% of adults over the age of 65 years. It is a degenerative rather than an inflammatory condition which is due to wear-and-tear of the joint cartilage. Due to age and ongoing strain, the cartilage may not repair itself rapidly enough to replacement loss due to wear-and-tear. Eventually the joint cartilage can fully degenerate and expose underlying bone in the joint.

Read more on osteoarthritis.

Who is at risk?

  • Advancing age (people older than 60).
  • Women.
  • Genetics.
  • Being overweight or obese.
  • Previous knee trauma.
  • Repetitive stress injuries to the knee.

Knee Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune joint condition that tends to affect the small joints, like those of the fingers. However, it can also involve large joints like the knee. In rheumatoid arthritis the immune system attacks the joint lining thereby causing inflammation. Unlike with osteoarthritis, rheumatoid arthritis tends to occur more frequently in younger adults, typically before the age of 60 years.

Read more on rheumatoid arthritis.

Who is at risk?

  • Usually older than 40 years but younger than 60 years.
  • Women.
  • Family history.
  • Being overweight or obese.
  • Tobacco smoking.

Knee Posttraumatic Arthritis

Posttraumatic arthritis is a form of arthritis that arises following a knee injury. This can alter the biomechanics of the knee joint or damage the joint structures like the cartilage or bone. Due to these effects and in conjunction with everyday wear and tear on the joint, there is degradation of the joint structures similar to osteoarthritis. The arthritis may only become evident months or years after the initial knee injury.

Who is at risk?

Any person may be prone to posttraumatic arthritis as knee trauma may occur with a variety of injuries. It can arise with a fall, blow to the knee in trauma such as a car accident or with contact sports. Being overweight or obese causes greater strain on the already injured knee joint.


Pseudogout is not a common joint condition but most frequently affects the knee when it does arise. It is similar to gout in that it is due to a build up of crystals in the joint. However, gout is due to uric acid crystals with the big toe joint being commonly involved. Pseudogout is due to calcium pyrophosphate dihydrate crystals and this can cause joint inflammation. However, the presence of these crystals in the joint may not always cause inflammation and symptoms.

Who is at risk?

  • Abnormalities of mineral levels, such as hypercalcemia or hypomagnesemia.
  • Advancing age, particularly after the age of 75 years.
  • Genetics.
  • History of joint trauma.
  • Endocrine disorders, particularly of the thyroid and parathyroid glands.

Signs and Symptoms

The signs and symptoms of knee arthritis are usually isolated to the knee and largely overlap among the different types of knee arthritis. These knee arthritis signs and symptoms may include:

  • Pain in the knee and sometimes involving the thigh or lower leg. It may also cause difficulty standing or walking and lower limb strain may worsen the pain. A change in gait due to the knee arthritis can also cause hip pain over time.
  • Stiffness of the knee resulting in difficulty bending or straightening the leg. The limited range of motion may be temporary or permanent. Stiffness eases with movement in some conditions like rheumatoid arthritis while prolonged movement can cause additional strain and lead to further stiffness.
  • Swelling of the knee joint is another common symptom of the knee arthritis. The degree of swelling may vary depending on the severity of the arthritis as well as any recent strain or flareups. In conditions like rheumatoid arthritis, there may be nodules which are lumps that can make the joint appear enlarged.
  • Heat and redness of the skin over the knee joint are typically signs of acute inflammation. It is more likely to occur during an acute flareup or immediately after an injury or episode of joint strain. These symptoms are less likely to occur with knee osteoarthritis as it is a degenerative rather than an inflammatory joint condition.

Treatment of Knee Arthritis

The treatment for knee arthritis depends on the cause and type of arthritis. Treatment options usually involve medical therapy but surgery may also be reuired in some advanced and severe cases. Exercise, supportive devices like braces and physical therapy may also be helpful in the treatment and management of knee arthritis. Most of the common causes of knee arthritis are chronic and requires long term treatment and management.

Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used medication for managing the inflammation and to ease pain as well as other symptoms, irrespective of the type of knee arthritis. Analgesics and corticosteroids are other commonly used drugs among the different types of knee arthritis. However, beyond these drugs the treatment may be highly individualistic for each type of knee arthritis.

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