When considering surgical options for knee pain, two procedures often come up: Total Knee Replacement (TKR) and knee arthroscopy. TKR, also known as knee arthroplasty, is a comprehensive procedure reserved for people suffering from severe, debilitating arthritis that has destroyed the joint surfaces. In contrast, knee arthroscopy is a minimally invasive technique used to diagnose and treat localized, milder issues within the joint. A full Total Knee Replacement involves replacing the ends of the bones with metal and plastic implants and cannot be performed using traditional arthroscopic techniques. These procedures differ fundamentally in their goals, approach, and the extent of damage they are designed to address.
Why Total Knee Replacement Requires an Open Incision
The sheer scope and mechanical requirements of a Total Knee Replacement necessitate a large, open incision, making it incompatible with the small portals of arthroscopy. TKR is a complete resurfacing of the joint, not a repair of existing tissue, which requires extensive access and manipulation of the bone structure. The surgeon begins by making a long incision, typically 8 to 10 inches, down the front of the knee to fully expose the joint. This exposure often requires moving the patella, or kneecap, out of the way.
Once the joint is open, the surgeon must remove the damaged cartilage and a precise amount of underlying bone from the ends of the femur (thighbone) and tibia (shinbone). This step uses large, specialized cutting guides and alignment jigs to ensure the new joint will be perfectly straight and stable. These instruments are far too large and rigid to be inserted or maneuvered through small arthroscopic ports. The process of bone resection and shaping demands a wide field of vision and the physical space to use these complex tools.
Following the bone preparation, the metallic and polyethylene prosthetic components must be physically inserted, seated, and secured, often using bone cement. The artificial joint parts are substantial in size, designed to replace the entire weight-bearing surfaces of the knee, and cannot pass through the tiny incisions used for a camera and small instruments. A successful TKR relies on restoring the leg’s mechanical axis and achieving precise soft-tissue balance. This final assessment involves checking the tension of surrounding ligaments throughout the knee’s range of motion and requires the surgeon to have complete visibility of the entire joint space.
The Specific Uses of Knee Arthroscopy
Knee arthroscopy focuses on joint preservation and internal cleanup. This technique uses a tiny camera, called an arthroscope, inserted through one or two small incisions, each usually less than an inch long. The surgeon then uses specialized, slender instruments inserted through other small portals to perform the necessary work inside the knee.
Arthroscopy is effective for addressing localized internal problems that do not involve widespread bone-on-bone arthritis. A common application is treating a torn meniscus, where the surgeon can either trim the torn flap (meniscectomy) or repair the cartilage. The procedure is also the standard for reconstructing a torn anterior cruciate ligament (ACL) or repairing other damaged ligaments.
Other frequent procedures include the removal of loose bodies, which are small fragments of bone or cartilage floating within the joint that cause catching and pain. Surgeons also use arthroscopy to smooth out minor areas of damaged joint cartilage or to wash out the joint, a process known as debridement, to address early-stage arthritis symptoms. The goal is to repair or remove damaged soft tissue while leaving the overall bony structure of the joint intact.
Distinguishing Minimally Invasive Knee Replacement
The misconception that knee replacement can be done arthroscopically often arises from the development of Minimally Invasive Knee Replacement (MIKR) techniques. MIKR is an evolution of the traditional open TKR, not an arthroscopic procedure. Surgeons performing MIKR still make an incision and open the joint to access the bones, but the incision is shorter, typically reduced to about four to six inches.
The primary difference in MIKR lies in the surgical approach used to reach the joint, focusing on sparing soft tissue. Traditional TKR often involves cutting through or disrupting portions of the quadriceps tendon and muscle complex to gain maximum exposure. MIKR techniques, such as the quadriceps-sparing approach, use specialized instruments and retraction to work around the quadriceps muscle, causing less trauma to this important stabilizing structure.
This focus on soft tissue preservation is intended to translate into benefits for the patient, including less pain immediately following surgery and a potentially faster start to physical therapy and recovery. However, the fundamental steps of the surgery—the precise bone cuts, the removal of damaged surfaces, and the insertion of the large metallic and plastic implants—remain exactly the same as in a traditional replacement. While MIKR offers a smaller scar and less muscle disruption, it still requires an open procedure and a high degree of technical skill to successfully place the implants through the smaller working space.