In knee replacement surgery, your doctor will remove damaged bone and cartilage from the knee and replace it with a new artificial knee.

Most knee replacement surgery is done because of osteoarthritis, a condition that causes the joint to break down (degenerate). Osteoarthritis affects mostly middle-aged and older adults.

At OHSU, the latest cutting-edge research is helping us bring you new treatments and cures for bone and joint injuries and disease. OHSU offers a variety of treatment options, from ACL-sparing total knee replacement to unicompartmental (partial) knee replacement, in which only a portion of the knee is resurfaced. Our knee specialists will work with you to determine the best treatment option for your condition.

Learn more about knee replacement

The following videos are provided for general information about a type of surgery or condition. They may not represent the surgery performed by your provider or the appropriate surgical option for you. Please talk with your provider about the recommended approaches for your specific case.

• Anatomy of the knee
• Knee arthritis
• Total knee replacement
• Mini incision total knee replacement

Knee cartilage overview

Cartilage is a rigid yet flexible connective tissue found in many areas of the body, including your joints. Articular cartilage coats areas of bone that are in close proximity to each other. It is found at the ends of your femur (thigh bone), tibia (leg bone) and on the underside of your patella (kneecap).

Articular cartilage is important because it provides a smooth surface for your bones to guide, acts as a shock absorber and protects bones from the pressure of your body weight. However, it does not have its own blood supply and must rely on the fluid in your joint (called synovial fluid) for its nutrients. Because of this, articular cartilage has limited ability to heal itself if damaged.

Knee cartilage injury

Cartilage injuries are common. In fact, more than half of people who undergo knee surgery for an unrelated injury are found to have cartilage injuries as well. Athletes who participate in twisting and pivoting sports such as football, soccer and basketball are particularly at risk. A cartilage injury can occur along with another knee injury, such as an anterior cruciate ligament (ACL) tear or it can occur on its own. Cartilage can also be injured from years of accumulated wear and tear. Symptoms of a cartilage tear may include pain, swelling, locking, catching and decreased range of motion.

Treatment of cartilage injury

There are a number of treatment approaches to cartilage injuries including nonsurgical, minimally invasive surgery (arthroscopy) and open surgery (arthrotomy). The approach your doctor recommends will depend on the size of your injury and your activity level. Nonsurgical treatment may include physical therapy, knee bracing, anti-inflammatory medication and injection into the joint with cortisone or hyaluronic acid.

Surgical options available at OHSU range from minimally invasive arthroscopic surgery to larger open surgeries to replace the damaged cartilage. The type of surgery recommended will depend on a number of factors including the size of your injury, your expectations and goals, the overall condition of your knee, and if there is any damage to the underlying bone.

If you have been given a diagnosis of osteoarthritis, cartilage repair surgery will likely not be recommended as this damage is often too extensive to be repaired. In other words, we are able to treat small potholes in the road, but if the whole road needs re-paving, knee replacement surgery may be a better option.

Common cartilage surgeries performed at OHSU

Arthroscopic chondroplasty

Two small incisions are made just below your kneecap and a thin fiber optic camera is inserted. This allows us to visualize the inside of the knee joint, then trim and smooth the damaged cartilage. Removing the damaged tissue allows for healthy cartilage to potentially fill in the defect.

Arthoscopic microfracture

Microfracture surgery is also done arthroscopically. First, the damaged cartilage is removed. Then, small holes are poked into the bone below, bringing new cells to the area which will eventually go on to grow new scar cartilage. Though this new type of cartilage is not quite as strong as your normal cartilage, it does serve to put a cover on the “pothole” which helps to improve many people’s symptoms.

Autologous chondrocyte implantation (ACI)

Another approach to cartilage repair involves replacing damaged cartilage with new cartilage that essentially matches the other cartilage in your knee.

ACI is a two-step procedure. In the first step, new cartilage cells are grown. During the second step, these new cartilage cells are implanted in your body.

First, healthy cartilage tissue is removed from a non-weight-bearing area of your bone. This step is done as an arthroscopic procedure. This tissue, which contains healthy cartilage cells, or chondrocytes, is then sent to the laboratory and the cells are cultured and increase in number over a three- to five-week period. During the second step, an open surgical procedure, or arthrotomy, is then done to implant the newly grown cells.

Neocart clinical trial

OHSU is one of a few hospitals around the country involved in the Neocart clinical trial, now in its third and final phase of investigation. This study seeks to compare microfracture surgery to a novel approach to cartilage restoration called Neocart. In this clinical trial, patients are randomly assigned to receive either microfracture surgery or Neocart. Neocart is a bio-engineered cartilage patch that is grown from your own cartilage cells.

First during an arthroscopic procedure, a small sample of cartilage is taken and sent to a lab to grow. The cartilage is grown over six to eight weeks in a matrix and arrives at OHSU as a patch that can be trimmed and customized to fit inside your knee through a small open incision.

DeNovo NT allograft cartilage transplant

Unlike ACI and Neocart, DeNovo surgery implants new cartilage that comes from a donor. There is no need for an arthroscopic procedure to harvest cartilage beforehand . Through a small incision “mini arthrotomy,” tiny new pieces of cartilage are adhered to your knee using a fibrin glue. Over time, these new pieces of cartilage will grow and fuse with your normal surrounding cartilage.

Osteochondral allograft transplantation

If a cartilage defect is too large for the above surgeries to be effective and/or if there is damage to the underlying bone, we may recommend use of donor cartilage and bone to replace your injured cartilage and bone. This is done through a small open incision in your knee. A thin piece of bone with the overlying cartilage attached is press-fit inside your knee. We work with an excellent tissue bank to ensure we have access to high-quality grafts screened for diseases and contamination.

In arthroscopic knee surgery, your surgeon uses a tiny camera and small instruments to diagnose and fix problems inside the joint. Arthroscopy can help us diagnose and treat many problems, including torn cartilage, torn ligaments and unstable joints.  It can also help us decide if knee replacement is a good option for you.

At OHSU, the latest cutting-edge research is helping us bring you new treatments and cures for bone and joint injuries and disease.

Reconstructive knee surgery can help repair bones, ligaments and muscles damaged by injury, arthritis or deformity. In this type of surgery, your doctor might put bones back in alignment, adjust ligaments, reconstruct other tissues or use small screws and rods to hold bones together.

Doctors at the OHSU Sports Medicine Clinic offer a full range of treatments for injuries of the knee, including ACL tears.

The best treatment for you depends on several factors including how recently your injury occurred, what concurrent injury you may have sustained and what your goal are for post treatment function. Our goals are to treat your pain, improve your function, reduce your newly acquired risk of degenerative joint disease and prevent additional future injuries.

Overview

The knee is a complex joint made up of principally three bones which are stabilized with several ligaments that interact to hold these bones in close proximity and dissipate stress. These ligaments work to allow you to turn, pivot and jump while protecting your cartilage (meniscus and hyaline). In concert these structures protect us from gravity. Four ligaments act to stabilize the knee joint while performing both simple tasks like walking down stairs and complex tasks like gliding over moguls while skiing. One of these ligaments, the ACL, is particularly vulnerable to injury while landing from jumps, twisting or hyper extending your knee.

Injury of the ACL is often associated with immediate pain, swelling and instability, but not in all cases. After a week or so of recovery and proper rehabilitation, some people may not notice many symptoms. However, untreated or improperly rehabilitated ACL injuries can become associated with chronic joint instability and an increased likelihood of further injury, particularly damage to cartilage and meniscus. This can occur even in the absence of symptoms.

Pre-Treatment Plan

At your first appointment, your doctor will have reviewed your history, including any past and current injuries, obtain images and review your personal expectations. Your answers give the doctor detailed information about your goals and the potential to return to full function, as well as the risk of further injury. This helps determine how urgent and what types of treatments will be most likely to get you back to a pre-injury level.

Conservative (Non-Surgical) Treatment

Treatment of a torn or injured ACL depends on your degree of injury, symptoms and activity level. Non-surgical treatment for an ACL injury includes rehabilitation exercises and education to reduce swelling and restore motion. This often includes a program of physical therapy and instruction on how to strengthen the area and your core muscles to reduce the risk of future knee instability.

Surgical Treatment

Surgery for ACL injuries involves replacing the torn ACL, as this ligament will not heal on its own even if the ends are sewn together. Minimally invasive techniques for ACL reconstruction can include replacing the ligament with a tissue graft. Several graft options are available and recommendations on graft types are based on a variety of factors  such as your age, activity level, goals and health history.  OHSU provides all graft options available and our surgeons have extensive experience with ACL injuries and the appropriate treatment required. We specialize in repairing ACL injury in patients with repeat injury, sometimes called “revision” ACL surgery.

After surgery and rehabilitation, your risk of re-rupturing a reconstructed ACL should be equal to injuring a normal ACL. Exercises to reduce the risk of ACL injury to either knee will be part of your post-surgery rehabilitation recommendations and physical therapy prescription.