To understand why and how a joint is replaced, it’s important to first know what a joint is and what it does. The most basic definition of a joint is the point where two bones in the body come together. The adult body has about 206 bones and, depending on how they are classified, roughly 300 joints.

Different joints are designed for different jobs. Some make movement possible — like the bending of a knee. Others make sure that movement doesn’t happen — like the fixed joints that hold together the bone structure of the skull. A third type of joint connects bones while allowing only slight movement — like the vertebrae of the spine.

• Synovial joints- Joints designed for free movement are called synovial joints because they are lubricated by synovial fluid, which reduces friction and makes movement smoother and easier. There are six different types of synovial joints. They are classified based on the movements they allow, like bending, straightening, rotating, pivoting, swiveling or gliding.
• Ball and socket joints - The most familiar joints — and those most commonly replaced surgically — are ball and socket joints, and hinge joints. Ball and socket joints can move in multiple directions. Movement is possible because the ball-shaped end of one bone moves inside the cup-shaped end of another bone. The shoulder and hip are ball and socket joints.
• Hinge joints - Like the hinge on a door, hinge joints can close and open (bend and straighten), but only in one direction. The elbow and knee are hinge joints. 

Before recommending surgery, an orthopaedic surgeon will suggest you first explore other treatment strategies, including:

• Weight loss to lessen the burden on the joint
• Exercise or physical therapy to strengthen surrounding muscles, or to address repetitive movements that may be worsening symptoms
• Non-steroidal medications like ibuprofen or acetaminophen to reduce swelling and pain
• Steroid injections like cortisone to lubricate and cushion the joint

If your symptoms do not improve after trying these strategies, the joint may have deteriorated to a point where surgery is the only option for long-term relief.

The potential benefits of replacing an injured joint are significant, and can be life-changing:

• Pain is largely reduced and, in many cases, eliminated
• Mobility is greatly improved and, in many cases, completely restored
• In most cases, the replacement joint will continue to perform as intended for several years

The vast majority of joint replacement patients return to full activity with little or no pain and are glad they chose joint replacement surgery.

However, with any surgical procedure, there are risks to consider as well:

• There is a low risk of a medical complication resulting from surgery, including a cardiovascular event such as a stroke or heart attack, or an infection, blood clot, nerve injury or unintended movement of the artificial joint.
• A more common risk is that the procedure does not entirely resolve the symptoms and discomfort continues. (For example, about 15 percent of knee replacement patients continue to experience enough pain, “clicking” or stiffness to feel they may have traded one type of discomfort for another.) 

Call 734-936-5780 to speak with a representative in our Orthopaedic Surgery Call Center to learn more or make an appointment for a consultation.

Below are educational resources for a variety of musculoskeletal conditions available to orthopaedic surgery patients for pre- and post-surgical care. This contains helpful information for patients as they start their surgical journey.

• U-M Online Patient Education Library - Orthopaedic Surgery