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What is a Partial Knee Replacement?

Partial Knee Replacement Options X Ray
X-rays of partial knee replacements by Dr. Buechel. Left to right: 1. Medial 2. Medial after ACL reconstruction 3. Lateral 4. Patellofemoral 5. Medial and Patellofemoral.

A partial knee replacement, also called a “resurfacing or arthroplasty”, is a surgical procedure that replaces (“resurfaces”) one or two of the painful, damaged, knee joint compartments.

Partial Knee replacements decrease or eliminate knee pain and swelling during weight bearing activity from the worn-out or damaged surfaces.

The compartments that can be replaced are:

  1. Medial (inner side and most common)
  2. Lateral (outer side and second most common)
  3. Patellofemoral (the kneecap compartment and least frequently performed)

The new surfaces called “implants” and they are made of cobalt chrome and titanium alloy metals, and a polyethylene plastic insert. These implants replace the damaged cartilage surfaces and the meniscus.

Partial Knee Replacement with Dr. Buechel’s Mini-incision Mako Robotic assisted technique is dramatically less invasive, preserving all the healthy functioning structures of the knee and allowing for a rapid return to activity.

Dr. Frederick Buechel with a knee joint model explaining a knee replacement procedure to a patient.

What are the keys to a successful Partial Knee Replacement?

  • Choose an experienced orthopaedic partial knee surgeon to perform your surgery. One who has done several hundred at least in the compartment you are looking to replace.
  • Choose an experienced surgeon to optimize and minimize your skin incision, be meticulous with the handling of your tissues, avoid cutting into the muscle, and provide a multilayered watertight closure with a cosmetic skin closure.
  • Choose a surgeon who uses advanced technology to optimize the preparation and installation of you implants. This is critical to success.
  • An experienced Mako Robotic Partial Knee surgeon would be optimal to achieve the reported low revision rates seen in the joint registry data for medial partial knee replacement (only 0.8% failure rate in the Australian Joint Registry Data, best in the world). Dr. Buechel was the launch surgeon for Australia providing all Mako Robotic Partial Knee training to the Australian surgeons starting in 2015.
  • Optimizing implant alignment, sizing, tracking, ligament balance, and bone preparation are keys to success and are possible using the Mako Robotic System on all cases.
  • Choosing a surgeon who uses Multi-Modal Pain management during and after the procedure to minimize the discomfort.
  • Your surgeon should educate you on why, or why not to do a partial knee replacement, so you are clear this is best choice for you.
  • Make the decision to optimize your health before and after your surgery to help healing.
  • Be dedicated to your recovery program protocol to optimize a successful and rapid return to activity.
  • Dr. Buechel’s 11-year robotic experience with thousands of partial knee procedures, meticulous attention to all details, use of robotic technology, comprehensive pre-surgery education and post-surgery protocols will optimize the chance of your successful partial knee surgery.
Dr. Buechel reviewing post-operative x-rays of his knee replacement patient.

What is a Patellofemoral Partial Knee Replacement?

X-Rays Images left to right:
1. Sunrise view (looking under kneecap) showing loss of space under the kneecap, (diagnosis is osteoarthritis).
2. Sunrise View of “Patellofemoral Replacement” installed. A polyethylene “plastic” implant is cemented under the kneecap and is invisible on x-ray, the “white” metal femoral implant is in the femur’s central groove.
3. Lateral view with a cemented patellofemoral implant in the patella and femur.
4. Lateral view with no cartilage space behind the kneecap indicating osteoarthritis that is severe.
5. Lateral view with a cementless patellofemoral implant in the patella, and a cemented femoral component.
6. Front view of the knee showing good medial and lateral compartment cartilage space.
7. Front view showing a cementless patellofemoral replacement with good medial and lateral joint spaces.
  • Patellofemoral Partial Knee Replacement is performed in the kneecap compartment called, the patellofemoral compartment. The “Patella” is the kneecap bone that normally has thick cartilage covering its undersurface. The “femoral” part of this compartment is the front groove of the femur between the two ends. This groove called the “trochlea”, is normally covered in thick cartilage as well.
  • When the patellofemoral cartilage surface wears down, the kneecap rubs against the front of the femur and this can cause pain, grinding, crunching, weakness and giving way when bending the knee.
  • Patellofemoral Partial Knee Replacement provides new surfaces that restores smooth painless motion under the kneecap in the front of your knee during knee bending activities and can last for decades.
  • Patellofemoral Partial Knee Replacement maintains the 4 main ligaments in the knee (ACL, PCL, LCL, MCL), keeps the healthy medial and lateral compartments and both menisci, and allows for a return of near normal knee motion and kinematics.
  • Patellofemoral Partial Knee Replacement allows patients to return to life’s normal activities, including walking, hiking, biking, swimming, dancing, running, climbing stairs, tennis, golf, deep knee bending and more.
  • Recovery time for near complete return to normal activities for patellofemoral replacements takes more time than medial or lateral partial knee replacements.
  • Patients with Patellofemoral replacements tend to feel stiffer for several months until the tissues mature and become more elastic again. Usually, full flexibility and resolution of the stiffness takes 6-12 months. However, you are walking and active from the day of surgery.
  • Dr. Buechel’s Patellofemoral partial knee replacements are performed along with the Mako Robotic Arm System to provide every patient a personalized precision implant installation.
  • Dr. Buechel has used the Mako Robotic Partial Knee System to install his partial knees for more than 11 years and nearly 2,000 cases in the USA and internationally.
  • Dr. Buechel uses the Mako Robotic Partial Knee System to:
    • Pre-operatively plan your patellofemoral surgery with precision sizing and initial anatomic implant positioning.
    • Intra-operatively, Dr. Buechel optimizes the patellofemoral implant tracking and the implant to cartilage transitions with the software.
    • The Robotic arm is then used by Dr. Buechel to prepare the bone surface to accept the implants exactly to plan.
Dr. Buechel performing physical exam

Who is a candidate for a Patellofemoral Partial Knee Replacement?

Image left to right: X-rays of patient with painful patellofemoral arthritis. 1. Sunrise view shows the kneecap on one side with little to no cartilage space. 2. The lateral view then shows the kneecap from the side with no space and rubbing against the femur. 3. The front view then shows the medial and lateral joint spaces well preserved with good space, indicating these compartments may not need replacing.
  • Deciding to have a patellofemoral partial knee replacement requires that your clinical history, physical symptoms, physical exam and imaging (x-rays and sometimes MRIs) point towards partial knee replacement.
  • This requires your surgeon to be experienced with partial knee replacement patients, so that you are given the proper recommendations, and you can make the best choice for you, between partial and total knee replacement.
  • Dr. Buechel is an expert in partial & total knee replacement who will ask you the right questions, perform a proper partial knee exam, and review with you the imaging to confirm where your problems are in your knee.
  • For isolated arthritis in just the patellofemoral compartment there is a huge difference between having a partial knee replacement versus having a total knee replacement.
  • Dr. Buechel will clearly teach you using knee models in the office how partial knee replacement works and the differences between partial and total knee replacement for isolated patellofemoral arthritis.
  • A patellofemoral replacement changes only the damaged kneecap part of your knee. The Medial and Lateral knee compartments are completely left alone, all your ligaments (ACL, PCL, MCL, LCL) are maintained allowing normal stability and knee motions to remain unchanged.
  • You can perform a total knee for the same condition, but you should be aware that with a total knee all the surfaces of the knee joint are cut off to accept the implants that cover all the surfaces, the menisci are removed, and one or both cruciate ligaments are removed changing the knee dramatically regarding balance feel and stability.

Clinical History that indicates a person is a candidate for a patellofemoral partial knee replacement can include one or several of the following:

  • Younger active adults, generally in the later 30s and beyond, who have anterior kneecap pain from arthritis when bending their knee, climbing stairs, getting in and out of seats, cars, and toilets.
  • Adults that have had a prior kneecap injury or fracture that has led to an arthritic painful patellofemoral compartment.
  • Patients that have failed one of the cartilage repairing operations for a worn down area of the kneecap or trochlea region.
  • Patients that no longer respond to injectable treatments like Hyaluronic Acid or cortisone.
  • Patients should not have a chronic dislocating patella. This resurfacing procedure does not correct patellofemoral malalignment, it provides only new smooth surfaces for the patellofemoral joint.

Symptoms that many people experience indicating they are a candidate for a patellofemoral partial knee replacement are:

  • Pain anterior in the knee when bending
  • Pain getting up from seated position
  • Pain walking up or down stairs
  • Dull aching pain, Sharp Pain
  • Swelling of the knee Joint
  • Stiffness in knee
  • Loss of motion in the knee
  • Walking distance has decreased
  • Limping
  • Decreased or stopped playing sports

Physical-Exam Findings people have indicating they are a candidate for a patellofemoral partial knee replacement are:

Dr. Buechel performing physical exam
  • Pain under the kneecap on examination with pressure applied to the kneecap when bending, or when rising or sitting.
  • Crepitus, crunching, or grinding under the kneecap when bending the knee.
  • The kneecap should track centrally and not dislocate off to the side.
  • No pain or tenderness in the medial or lateral compartments on the joint line.
  • The ACL and PCL ligaments should be stable on exam.
  • The collateral ligaments must be intact and have stable end points.

X-ray Findings people have indicating they are a candidate for a patellofemoral partial knee replacement are:

  • Sunrise or Merchant views show a decrease or total loss in the patellofemoral joint space of the knee. The patella should track close to centrally and not be dislocated. There may be bone spurs around the kneecap edges.
  • Lateral views show a decrease or total loss in the patellofemoral joint space. There may be spurs inferior and superior on the patella and anterior femur.
  • Anterior Posterior (AP View) and Flexion Weightbearing views (Rosenberg View) should show normal spaces in the medial and lateral compartments. There may be some small bone spurs.
X-rays Left to right showing isolated patellofemoral osteoarthritis of the knee.
1. Sunrise view: The joint space is almost gone on the right side of the kneecap rubbing against the femur
2. Lateral view: the kneecap is bone against bone with no cartilage space looking from the side.
3. AP Front view: The medial and lateral joint spaces are normal

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