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Knee Replacement Surgery Coding Challenge

knee replacement surgery coding
Total knee replacement was performed due to complications of rheumatoid arthritis.
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The Coding Challenge

Question: Patient with a long history of rheumatoid arthritis is admitted for a total knee replacement of both knees. The patient has significant bilateral knee joint pain, stiffness, and loss of function. Assign the CPT code(s).

A. 27447, 27447-50
B. 27446-50
C. 27447-51
D. 27487-RT, 27487-LT


A. 27447, 27447-50

The patient is having a total knee replacement, also known as a total knee arthroplasty, in bilateral knees.

Locate and Verify

Total Knee Replacement (Arthroplasty)

In the Alphabetic Index, look under Arthroplasty, knee, 27437-27447, 29879. You can also start by looking up Replacement, prosthetic, knee, 27447.

In the Tabular, we can verify the correct code as:

27447, Arthroplasty, knee, condyle, and plateau; medial AND lateral compartments with or without patella resurfacing (total knee arthroplasty)

There are guidelines listed at this code that state:

  • For revision of total knee arthroplasty, use 27487
  • For removal of total knee prosthesis, use 27488

Next, we need our modifier.


Adding a modifier to the CPT code not only gives it more specificity but also affects reimbursement. When a knee replacement is performed, we need to indicate laterality. Both knees were replaced in this case, so modifier 50 should be appended to the second CPT code, making it 27447, 27447-50.

Something to remember here: Some third-party payers want bilateral procedures submitted differently. Rather than reporting 27447, 27447-50, some payers may require -RT and -LT to be appended to 27447, making it 27447-RT, 27447-LT.

Still, others may want 27447 only reported once with modifier -50 appended, making it 27447-50.

Make sure to check with the individual payer to find out their requirements.

Modifier 50

Modifier 50 describes procedures or services that take place on identical, opposing structures, such as knee and shoulder joints, breasts, or eyes. Unless otherwise identified in the listings, bilateral procedures performed at the same session should be identified by adding modifier 50 to the appropriate 5-digit code.

Incorrect Answers

B, C, and D are incorrect. 

B. 27446-50. Code 27446 refers to Arthroplasty, knee, condyle, and plateau; medial OR lateral compartment. This is a partial knee replacement, also called a unicompartmental knee replacement. 

C. 27447-51. Code 27447 refers to Arthroplasty, knee, condyle, and plateau; medial AND lateral compartments with or without patella resurfacing (total knee arthroplasty). This is the correct CPT code but the wrong modifier. 

Modifier 51 is used for multiple procedures. When multiple procedures, other than E/M services, physical medicine, and rehabilitation services, or provision of supplies (e.g., vaccines), are performed at the same session by the same individual, the primary procedure or service may be reported as listed. The additional procedure(s) or service(s) may be identified by appending modifier 51 to the additional procedure or service code(s).

An example of the use of modifier 51 would be when a colonoscopy (45378) is performed during the same session by the same physician as an upper endoscopy (43200). They would be reported as 45378, 43200-51.

D. 27487, 27487-50. Code 27487 refers to Revision of total knee arthroplasty, with or without allograft; femoral, and entire tibial component. This is for a total knee arthroplasty revision, not for an initial total knee arthroplasty.  

Additional Information

Anatomy of the Knee

According to Johns Hopkins Medicine, the knee consists of the following:

  • Tibia (shin bone)
  • Femur (thigh bone)
  • Patella (kneecap)
  • Cartilage (tissue covering the surface of a bone at a joint)
  • Synovial membrane (tissue that lines the joint and secretes fluid around the joint to lubricate it)
  • Ligament (connective tissue that surrounds joint and limits movement)
  • Tendons (connective tissue that connects muscles to bones and controls joint movement)
  • Meniscus (curved portion of cartilage in the knees and other joints that absorbs shock)

The three main parts of the knee joint are the femur, tibia, and patella. The femur and tibia form the main knee joint. This joint is made up of medial (inner) and lateral (outer) compartments. The patella connects to the femur to make another joint.

Anatomy of the knee joint and coding for knee replacement surgery

Knee Replacement Surgery

Knee replacement surgery is a surgical procedure performed in patients who have severe arthritis or a severe knee injury. Various types of arthritis, such as osteoarthritis and rheumatoid arthritis, can cause damage and pain to the knee joint.

The damaged knee joint is replaced with an artificial joint called a prosthesis. The goal of surgery is to relieve the pain that has failed with other, more conservative treatments.

Artificial Joint/Prosthesis

A prosthesis is an artificial implant that is usually made up of 3 components. According to the U.S. National Library of Medicine, these components may be placed in the following areas in the knee joint:

  • Lower end of the femur (thigh bone)
  • Upper end of the tibia (shin bone)
  • Back side of the patella (kneecap)

During a total knee replacement, all three compartments of the knee are replaced. The replacement parts are usually made of metal, plastic, or ceramic.

artificial knee replacement

The Procedure

Once the patient is given general or regional anesthesia, the surgeon, often an orthopedic surgeon, will perform the following steps:

  • Knee area is incised (cut) to open it up. The incision is often 8 to 10 inches long.
  • Patella (kneecap) is moved out of the way to cut the ends of the femur (thigh bone) and tibia (shin bone) to fit the replacement part.
  • Back side of the kneecap is cut to allow for the new pieces to be attached there.
  • Two parts of the prosthesis are attached to the bones, one to the end of the thigh bone, and the other part to the shin bone. Bone cement or screws are used to attach them.
  • Underside of the kneecap is then attached with a special type of bone cement.
  • Muscles and tendons surrounding the new joint are repaired.
  • Surgical cut is sutured or stapled closed.
Three-minute video on a total knee replacement.
knee replacement surgery coding
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      1. I find your website very helpful and useful !! I will be sharing with colleagues on my team at work . Thank you so much !!

  1. Hi Debbie
    I recently subscribed to your blog. I am a new coder and still have much to learn. Thank you for sharing your knowledge.

  2. I am delighted that I stumbled upon your page. I am pursuing my degree in Health Information Management (HIM), and I must confess that your explanations are the best I have come across. I have taken courses in ICD-10, PCS, and CPT, and I am now taking a class to prepare for the RHIT test. The class has been stressful, but I find it exciting as well.

    1. Hi Theresa,
      Thanks so much for your nice comment. I try to help as much as possible and really appreciate hearing from my readers. Best of luck with your coding courses, and enjoy the challenge!

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