Partial Knee Replacement

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Partial Knee Replacement

If your knee is severely worn, with arthritis or damaged from an injury, it may be getting hard for you to perform simple activities, such as walking or climbing stairs. You may even begin to feel pain while you are sitting or lying down.  If nonsurgical treatments like medications, injections or using a cane or walker are no longer helpful, you may want to consider knee replacement surgery. Knee replacement surgery is a safe and effective procedure to relieve pain, correct leg deformity, and help you resume normal activities.

When it comes to knee replacement surgery, there are generally two options to consider.  Total knee replacement and Partial knee replacement.  Partial knee replacement is  also called unicompartmental – or “one compartment” knee replacement.  This a great option for patients with arthritis limited to one side of the knee.  A partial knee replacement addresses the worn out part of the knee, and preserves the healthy parts of the knee, including the ACL ligament.  This means a less invasive procedure, with a quicker recovery, and most importantly a knee that feels more like a normal knee.  In spite of these advantages, only a small percentage of orthopaedic surgeons are experienced in performing partial knee replacements and perform them on a regular basis.  As a fellowship trained joint replacement surgeon, Dr. Latteier specializes in this procedure.

Knee Anatomy

The knee is the largest joint in the body, and is used in performing most everyday activities.

The knee is made up of the lower end of the thighbone (femur), the upper end of the shinbone (tibia), and the kneecap (patella). The ends of these three bones where they touch are covered with articular cartilage, a smooth, slippery rubber-like layer that protects the bones and enables them to move easily.  This cartilage allows the knee to move smoothly without resistance.

The most common cause of chronic knee pain and disability is arthritis.  Over time, and with wear and tear, injuries or increased inflammation from other arthritic conditions, the cartilage surface deteriorates and becomes rough.  Bone spurs can form along the edges of the joint. The cartilage can even wear all the way through and such that the under lying bone begins to rub bone on bone, like sand paper on wood.  This is very irritating to the joint and causes inflammation, pain and reduced function.  This wear and tear can occur throughout the knee joint or just in a single area  or compartment of the knee.  Your knee is divided into three major compartments:

  • Medial compartment (the inside part of the knee)
  • Lateral compartment (the outside part)
  • Patellofemoral compartment (the front of the knee between the kneecap and thighbone)

Healthy Knee. Notice the space between the bones on the x-ray on the right. Though not seen on x-ray, cartilage is between, and cushioning the bones.

Isolated medial compartment arthritis is the most common, involving over 30 percent of knee arthritis.  Isolated lateral and patellofemoral compartment arthritis also occur.

Medial Osteoarthritis
(Left) Osteoarthritis that is limited to the medial compartment. (Right) This x-ray shows severe osteoarthritis with "bone-on-bone" degeneration in the medial compartment (arrow).

Medial unicompartmental arthritis on the left;  Normal knee in the middle. Tricompartmental arthritic knee on the right.

Worn cartilage does not heal and cannot regenerate.  The debilitating symptoms of severe knee arthritis can be relieved by knee replacement surgery.  A knee replacement can be a long term solution, providing new smooth bearing surfaces in the joint and eliminate friction and inflammation.  Partial knee replacement is an alternative to total knee replacement for patients whose arthritis is limited to just one area of the knee.

Partial (Unicompartmental)  Knee Replacement Surgical Procedure

Knee replacement procedures (also called knee arthroplasty) might be more accurately termed a knee "resurfacing" because only the surface of the bones are actually replaced.  A partial knee replacement operation typically lasts between 1 and 2 hours and consists of:

  • Inspection of the joint. The three compartments of your knee to verify that the cartilage damage is, in fact, limited to one compartment and that your ligaments are intact.
  • Prepare the bone.  The worn cartilage along with a small amount of underlying bone is removed from the damaged compartment of your knee.
  • Position the metal implants. The removed cartilage and bone is replaced with metal coverings that recreate the surface of the joint. These metal parts are typically held to the bone with cement.
  • Insert a bearing. A plastic bearing is placed between the two metal components to create a smooth gliding surface.

During this procedure, the damaged cartilage in the one involved compartment is replaced with metal and plastic. The healthy cartilage and bone, as well as all of the ligaments, such as the ACL, throughout the rest of the knee are preserved.

X-rays of a good candidate for partial knee replacement. (Left) Severe osteoarthritis limited to the medial compartment. (Right) The same knee after partial knee replacement. A partial knee replacement implant.

Since only part of the knee needs to be resurfaced in partial knee replacement, it can typically be done through a smaller incision with less trauma to the knee and soft tissues.  Patients usually have less pain and return to normal activities sooner than total knee replacement patients. Most importantly, however, is that by preserving the healthy parts of the knee, and the ACL ligament, the knee feels more like a normal knee afterwards.

Advantages of Partial Knee Replacement

Multiple studies have shown that a majority of patients who are appropriate candidates for the procedure have good results with partial knee replacement.  The advantages of partial knee replacement over total knee replacement include:

  • Quicker recovery
  • Less pain after surgery
  • Less blood loss
  • Better knee motion and bend
  • Higher patient satisfaction rates compared with total knee replacement
  • The biggest advantage of a partial knee replacement is that it is more likely to feel like a normal knee.  Because the bone, cartilage, and ligaments in the healthy parts of the knee are kept, many patients report that a partial knee replacement feels more natural than a total knee replacement..

Disadvantages of Partial Knee Replacement

The disadvantages of partial knee replacement compared with total knee replacement include:

  • Slightly less predictable pain relief
  • Potential need for more surgery. For example, a total knee replacement may be necessary in the future if arthritis develops in the parts of the knee that have not been replaced.  However, since the overall alignment of the leg does not change with partial knee replacement, it is not common to see progression of arthritis in the other parts of the knee.

An advantage of partial knee replacement over total knee replacement is that healthy parts of the knee are preserved, which helps to maintain more "natural" function of the knee.



You will be allowed to put your full weight on your leg, and be able to be move around on a walker the same day.    With this kind of knee surgery most patients are able to go home the same day. We can do this procedure on an outpatient basis or an overnight stay in the hospital.

Recovery varies from patient to patient.  Plan for about 2-3 weeks on a walker and 2-3 weeks on a cane on average.  Typically a couple weeks earlier than for a total knee replacement. It still takes about 6 weeks for the incision and soft tissues to heal and for some of the tenderness to subside.   Although the arthritic pain in your knee will feel better, it is common to have some pain and swelling, especially after physical therapy and at night during this time. It is ok to increase your activity as you feel better.

Pain management.

After surgery, you will feel some pain. This is a natural part of the healing process. With partial knee replacement there is typically less pain.  We also use a multi-modal pain management approach including nerve blocks, non-steroidal anti-inflammatory drugs (NSAIDs), and local anesthetics and narcotic (opioid) pain medications. You will be prescribed a combination of these medications to improve pain relief, as well as minimize the need for pain pills.

Wound Care

Dr. Latteier uses a plastic surgery type of wound closure, where the sutures are under the surface, and will dissolve. There will be no clips staples or stitches on the outside.  The skin is sealed with skin glue. A water tight clear plastic dressing is used to protect the incision. With this closure there is rarely any drainage, but if you notice any increasing redness or bleeding under the dressing, be sure to let us know right away.  Showering is fine, but avoid soaking the wound in water until it has thoroughly sealed and dried.

Physical Therapy

We will set up a Physical therapy visit before surgery to teach you some exercises to help prepare you for surgery.  We also schedule a physical therapist to come to your house the day after you return home. They will help you get comfortable navigating your house, practice any stairs you may have, and go over some exercises to help you recover.  After 2-4 home visits, most patients can proceed to outpatient physical therapy for another 4-6 weeks. Physical therapy and home exercises are an important part of knee replacement surgery. If you do not work and exercise it, the knee it will stiffen up.

When is it time to consider Surgery?

People who benefit from a partial knee replacement often have:

  • Severe knee pain or stiffness that limits your everyday activities, including walking, climbing stairs, and getting in and out of chairs.
  • Failure to substantially improve with other treatments such as anti-inflammatory medications, cortisone injections, lubricating injections, physical therapy, or other surgeries
  • Severe wear and tear on X-rays
  • Quality of life is beginning to suffer due to you knee symptoms.

If your symptoms have advanced and nonsurgical treatment options are no longer relieving your symptoms, knee replacement surgery may be recommended.  With proper patient selection, modern partial knee replacements have demonstrated excellent medium- and long-term results in both younger and older patients.   Partial knee replacement is not a stepping stone to a total knee replacement down the road, but the long term definitive treatment for particular patterns of arthritis.

Orthopaedic Evaluation

If you are experiencing these knee symptoms, we recommend a thorough evaluation.  Will can determine whether you are a good candidate for a partial knee replacement.  This consists of:

  • Medical History
  • Physical Examination
  • X-rays / Imaging Tests

We will review the results of your evaluation with you and discuss whether a partial knee replacement is the best option to relieve your pain and improve your function. Other treatment options — including medications, injections, physical therapy, or other types of surgery — will also be considered and discussed. In addition, we will explain the potential risks and complications of knee replacement, including those related to the surgery itself and those that can occur over time after your surgery.


An important factor in deciding whether to have knee replacement surgery is understanding what the procedure can and cannot do.

More than 90% of people who have knee replacement surgery experience a dramatic reduction of knee pain and a significant improvement in the ability to perform common activities of daily living.  Feedback from patients shows that a partial knee feels more natural than a total knee, but it will not allow you to do more than you could before you developed arthritis.  A knee replacement is not the same knee you had when you were 20.  It may ache from time to time if you over-do it, or if the weather changes, but by and large, it is much better than the worn out knee you had.

With normal use and activity, every knee replacement implant begins to wear in its plastic bearing. Excessive activity or weight may speed up this normal wear and may cause the knee replacement to loosen and become painful. Therefore, most surgeons advise against high-impact activities such as running, jogging, jumping, or other high-impact sports after surgery.

Realistic activities following total knee replacement include unlimited walking, swimming, golf, driving, hiking, biking,  dancing, and other low-impact sports.

With appropriate activity modification, partial knee replacements can last for many years.  Currently, more than 90% of modern knee replacements are still functioning well 15 years after the surgery. Taking care to protect your knee replacement and your general health are important ways you can contribute to the final success of your surgery.

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