OrthoVirginia Blog

What is a partial knee replacement?

by Ryan Robertson, MD 

Key Points

  • The knee is made up of three compartments: medial, lateral and patellofemoral
  • Partial knee replacements are a joint replacement for arthritis of one or two parts of the knee isolated to those affected joint compartments
  • Smaller surgery leads to less pain, quicker recovery
  • Similar longevity to total replacement if done correctly and for the right indications with modern implants

Introduction

partial-knee-replacement-xray-2.pngArthritis is a common problem, affecting 91 million Americans. 31 million Americans, or about 1/3 of people with arthritis, have osteoarthritis. Arthritis is the breakdown of the cartilage (the tissue that cushions the ends of the bones between joints), bony changes of the joints, deterioration of tendons and ligaments, and various degrees of inflammation of the joint lining (called the synovium). Arthritis can occur in all the joints of the body but commonly affects the knee. Lifetime risk of developing symptomatic knee arthritis is 45%.

The knee is made up of three compartments: medial (inside of the knee), lateral (outside of the knee), and patellofemoral (in front of the knee between the knee cap and thigh bone). Any one of these compartments or a combination of them can be affected by arthritis.

Osteoarthritis is the most common form of arthritis. It mainly effects middle age and elderly patients but can occur at all ages. Osteoarthritis is the most common cause of disability in the elderly.

Cartilage is tissue that goes between bones in a joint and acts as a shock absorber. As the cartilage breaks down, the joint experiences more stress and strain; as a result, the bone gets bigger (also called osteophytes) to decrease the pain from the increased stresses seen at the joint. The goal of treatment is to decrease pain and improve function. At the moment, there is no cure for arthritis but some treatments are aimed to try and slow the progression and help manage symptoms.

Common symptoms:
  • Joint pain and stiffness
  • Swelling and bony prominences (results of the osteophytes)
  • Cracking and grinding with movement of the joints
  • Decreased range of motion or function

Treatment

Non-surgical treatments are the most common types and are the first treatments doctors will give to help people with arthritis. These include: Patient Education, Activity Modification, Exercise/Periarticular Strengthening, Weight Loss, Assistance Devices, Heat or Cold Therapy, Medications, and Intra-articular Injections.

partial-knee-replacement-xray-1.jpgSurgical treatment consists of Joint Offloading, Fusion, or Replacement Procedures. Replacements are the most common and consist of partial or total knee replacements. In a total knee replacement all three compartments are replaced. In a partial knee replacement only one or two of the compartments are replaced.

Benefits of Partial Replacements

  • Quicker recovery
  • Less pain after surgery
  • Less blood loss
  • Feels more like a normal knee
  • Bends better
  • Better patient satisfaction
  • Fewer complications

Disadvantages of Partial Replacements

  • Slightly less predictable pain relief
  • Inability to completely correct alignments and effect motion like a total knee replacement
  • Potential need for future surgery. Total knee replacement is the most common procedure in the future if one develops arthritis in the nonreplaced compartments of the knee.

Candidates for Surgery

A good candidate for partial knee replacement surgery is someone with
  • Advanced arthritis with pain that is no longer adequately relieved with conservative (non-surgical) measures
  • Arthritis that is limited to one or two compartments
  • A lack of inflammatory arthritis, ligament damage, or significant knee stiffness or deformity.
Globally only about 8% of people with knee arthritis receive partial knee replacements, but up to 47% of people with knee arthritis could be candidates for partial knee replacement.

Surgical Procedure

The surgery for a partial knee replacement lasts 1-2 hours.

Surgery starts with an incision in the front of the knee and then inspection of the knee to ensure arthritis is isolated to the compartments to be replaced. The inspection also makes sure that the ligaments are intact.

If the knee is not appropriate for a partial replacement the surgeon may proceed with a total knee replacement if this option was previously discussed with you before surgery.

If the knee is in the right condition for a partial replacement, the procedure starts with preparing the bone by removing damaged and diseased bone and cartilage from the compartments to be replaced. Next, the metal implants are positioned and held to the bone with cement, a type of bone glue. Finally, a plastic spacer is placed between the metal components to allow for a smooth gliding joint surface.

Longevity

Previously, partial knee replacements were not as successful as they are now. They were seen as a temporary measure before you received a total knee replacement. However, when done correctly and in the right patients, a partial replacement can last as long as a total knee replacement. We expect these replacements to last 20+ years as studies have shown up to 90% of partial knee replacements still working at 20 years.

Next Steps

If you have joint pain and are concerned that you have arthritis you should see a doctor. Contact your primary care physician or call the OrthoVirginia office closest to you to schedule an appointment.
 
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