The knee is the largest joint in the body, and it’s often affected by osteoarthritis (OA). OA causes knee pain when cartilage in the knee wears away over time and the joint can’t move as easily as before. People with osteoarthritis that is confined to one section of the knee may be candidates for a minimally invasive partial knee replacement.

Anatomy of a Partial Knee Replacement

The knee is divided into three main compartments that work together:

• Medial or inside part of the knee
• Lateral or outside part
• Patellofemoral or front of the knee between the kneecap and thighbone

A partial knee replacement is typically recommended only after other nonsurgical treatments, such as activity modification, strengthening exercises, medications, cortisone injections, or use of a cane while walking, have not been effective in providing relief for arthritis symptoms.

In partial knee replacement, only the damaged compartment is replaced with a metal and plastic implant while the healthy cartilage and bone in the rest of the knee is left in place. Before the procedure, the doctor examines the knee, tries to identify the location of the pain, and tests the knee for range of motion and ligament quality. Imaging tests, such as X-rays or magnetic resonance imaging, may be done to see the pattern of arthritis or better assess the cartilage.

Minimally Invasive Knee Surgery

In a minimally invasive partial knee replacement procedure, an incision of about three to five inches is made to allow for insertion of the knee replacement. This results in minimal damage to surrounding muscles and tendons around the knee. Compared to conventional surgery with a larger incision, benefits of minimally invasive surgery include:

• Less discomfort, swelling and blood loss
• Shorter hospitalization and rehabilitation
• Ability to return to work sooner

During the operation, the surgeon checks all three compartments of the knee for cartilage damage and to make sure the ligaments are intact. The affected cartilage is then removed and the ends of the femur and tibia are capped with metal coverings that are held in place to the bone with cement. A plastic insert is placed between the two metal parts to ensure a smooth gliding surface.

Patients can start to put weight on their knee immediately after surgery. They usually can walk without a cane several weeks after surgery, but may need physical therapy for a few months. Not surprising, patients who are most likely to experience positive outcomes from the surgery are those who follow recommendations for rehabilitation. 

Most types of exercise are allowed after surgery, including walking, swimming and biking. However, patients should avoid high-impact activities such as jogging. Patients typically experience less pain than they did before surgery and can resume most regular activities by six weeks after surgery. For more information about minimally invasive partial knee replacement, talk with your doctor.