Knee Arthritis

Edited by Nick Hernandez, M.D., Assistant Professor, UW Orthopaedics & Hip & Knee

What is Knee arthritis?

Knee arthritis occurs when the joint surface cartilage (also called hyaline cartilage or articular cartilage) becomes worn away leaving the raw bone beneath exposed (See Fig 1). The cartilage normally serves as a “pad” or a bearing in the joint and under normal conditions the cartilage bearing is even slicker than a hockey puck on ice. When the bearing wears away the result is a rough joint surface that causes the pain and stiffness that people associate with osteoarthritis (See Fig 2 and Fig 3).

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Figure 1 - Arthritic Knee
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Figure 2 - Normal Cartilage
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Figure 3 - Defect in
joint surface cartilage

"Osteoarthritis" is the most common kind of Knee arthritis of the more than 100 kinds of arthritis some other kind include Rheumatoid Arthritis and Post-Traumatic Arthritis

Facts and Myths about Knee arthritis

Who usually gets Knee arthritis and what are the causes?

There is no certain answer to the causes of knee arthritis – particularly “Osteoarthritis”. However studies show aging and women have more “doctor-diagnosed” arthritis.

There are also some risk factors that may increase the likelihood that knees will become arthritic. These risk factors include:

  1. Genetics. Arthritis often runs in families.
  2. Severe trauma. Fractures (broken bones) and total removal of the supporting cartilages of the knee (meniscus) both increase the likelihood of knee arthritis.
  3. Obesity. This is associated with arthritis of the knees.

What are the symptoms of Knee arthritis?

Pain swelling and stiffness are the main symptoms of knee arthritis. When it becomes more advanced joint deformity (knock-knees or bow-legs) can occur.

What tests show if Knee arthritis is present?

The simplest test to diagnose osteoarthritis of the knee is the x-ray. Taken with the patient standing up plain x-rays can diagnose the condition with great accuracy. In addition a physician will also take a thorough history and perform a thorough physical examination.

What is the treatment for Knee arthritis?

For most patients who have only mild arthritis the pain can be managed with simple things such as ice rest activity modifications pills arthritis brace or joint injections.

However when the knee arthritis becomes severe (See Fig 4 and Fig 5) and the pain does not respond to those kinds of interventions joint replacement surgery can be beneficial. There are two kinds of join replacement surgeries:

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Figure 4 - X-ray showing
arthritis of the knee

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Figure 5 - Joint deformity
from knee arthritis
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Figure 6 - Model of a
knee replacement prosthesis

What are the risks with surgical treatment?

The risks of knee arthritis surgery include but are not limited to the following: infection injury to nerves and blood vessels fracture stiffness or instability of the joint loosening or wear of the artificial parts pain and the need for additional surgeries. There are also risks with anesthesia and blood transfusion (although transfusions are not always necessary). An experienced knee replacement team that does many such procedures each month will use special techniques to minimize these risks. 

Can patients regain all of their knee function and how long would it to fully recover after the surgery?

A knee replacement can never be as good as a normal knee. However in most cases a technically sound surgery coupled with a good rehabilitative effort on the part of the patient will lead to a major improvement in comfort and function. The first goal of rehabilitation is to restore range of motion. Once this is achieved the focus shifts to strength and endurance. While improvements may be evident soon after surgery gains in strength range and coordination may continue for up to a year after surgery.

Watch a video about knee arthritis replacement surgery:

Dr. Seth Leopold demonstrates minimally invasive knee replacement surgery and discusses the benefits to patients. The program follows a patient through the whole process from pre-op to post-op.

Minimally Invasive Total Knee Replacement Surgery Part 1


Minimally Invasive Total Knee Replacement Surgery Part 2