Knee

Does your knee prevent you from performing and enjoying everyday activities?

Osteoarthritis affects nearly 350 million people worldwide.¹ It is a common condition in which cartilage breakdown around the joints causes your bones to rub together, and it is especially common in the knee joint, which carries most of the body’s weight. Symptoms include pain, swelling, and changes in appearance and function of the joint – which can contribute to loss of motion.

If other treatments, such as medication, therapy or injections, have proven ineffective, a total knee replacement may be the best way to get your life back.

What is total knee replacement?

Your knee joint is cushioned by cartilage that covers the ends of the thigh bone (femur), top of the shin bone (tibia) and the knee cap (patella), helping them to move smoothly against each other. But when this cartilage wears down and your bones begin to rub together, it can cause severe knee pain that reduces the function of your knee.

The goal of total knee replacement surgery is to replace this damaged bone and cartilage with smooth metal and high-grade plastic that recreate the surface of your knee joint. These new surfaces are designed to replicate the function and feeling of a healthy knee while also preventing the pain caused by damaged bones rubbing together. Total knee replacement is one of the most successful treatments to restore knee function and stop pain.

Is the implant important?

Traditional knee replacements have been shown to feel unstable and move in an unnatural way². Medial-Pivot knee implants were designed to address these limitations, providing patients with a natural-feeling implant that works like a healthy knee³.

Traditional implants are shown to decrease stability by sliding forward during everyday activities.^2-3But a normal knee pivots on its inner (medial) side. And when the knee bends, the outer (lateral) side rolls back, while the medial side rotates in one place⁴. Figure 1.

This is precisely how a Medial-Pivot Knee implant was designed to move, and how it received its name – by replicating the bending, rotating and twisting of a healthy knee³. This ball-in-socket design maximizes stability throughout range of motion, and allows patients to walk down stairs, and complete other daily activities with confidence⁸. Figure 2.

Stability you can count on

Studies have shown that instability is the leading cause of early revisions.^5-6 Traditional implants cause instability during everyday activities like walking down stairs, bending, and squatting due to the limitations in their design.

The stability of a Medial-Pivot knee achieves higher patient satisfaction when resuming everyday activities.⁷In fact, clinical studies have shown that patients prefer the design of a Medial-Pivot knee over traditional knee implant designs.⁷

Medial-Pivot Knee Replacement: a function enhancing implant!

In addition to the intrinsic stability of a Medial-Pivot knee, patients receiving this type of implant can perform activities easier than recipients of a traditional implants, since less muscle strength is needed to perform these activities.⁸

The quadriceps muscle is a large muscle group that includes the four prevailing muscles on the front of the thigh. Also called quadriceps complex, it is crucial in daily life activities such as walking, running, jumping and squatting, since it is mainly responsible for the knee extension.

Quadriceps muscle strength and function after a replacement surgery is a complex multifactorial issue, in which several parameters can play a role, the implant being one of them. With lower forces required for its function, the quadriceps muscle fatigue in bent knee activities and strength-
related tasks is lowered, resulting in better knee function with the potential for less pain.⁹

In comparative research, the Medial-Pivot knee implants have shown to be much more efficient in the activation of the quadriceps muscle. Recipients of a Medial-Pivot knee have shown to require half the muscle strength to perform every day activities compared to traditional knee designs.⁸

References:

1. Arthritis and Total Knee Arthroplasty: Knee Implant Procedures. Link to page. Mark McBride, MD ; Prakash Thulasimani. Nov 3, 2009. Accessed: Feb. 22, 2010

2. Dennis DA, Komistek RD, Mahfouz MR, Haas BD, Stiehl JB. Multicenter determination of in vivo kinematics after total knee arthroplasty. Clin Orthop Relat Res. 2003

3. Schmidt R, Komistek RD, Blaha JD, Penenberg BL, Maloney WJ. Fluoroscopic analyses of cruciate-retaining and medial pivot knee implants. Nov 2003, (416):37-57.

4. Komistek R. In vivo fluoroscopic analyses of the normal human knee. Clin Orthop Relat Res. 2003;410:69-81

5. Firestone T. Surgical management of symptomatic instability following failed primary total knee replacement. J Bone Joint Surg; 2006, 83(4): 80-4

6. Blaha D. Kinematics of the knee and total knee prosthesis design. J Bone Joint Surg Br 2002 Vol. 84-Bno. SUPP I 75-i-76

7. Pritchett JW. Patients prefer a bicruciate-retaining or the medial pivot total knee prosthesis. J Arthroplasty. 2011; 26(2): 224-8.

8. LaMontagne M, et al. Quadriceps and Hamstring Muscle Activation and Function Following Medial Pivot and Posterior Stabilized TKA: Pilot Study – EFORT, Prague, Czech Republic, 27–29 May 2015

9. Greene KA, et al.Quadriceps Muscle Function in Primary Total Knee Arthroplasty. J Arthroplasty 2008; 23(7 Suppl):15–19

Patient Disclaimer

Individual results and activity levels after surgery vary and depend on many factors including age, weight and prior activity level. There are risks and recovery times associated with surgery and there are certain individuals who should not undergo surgery. Consult your doctor to determine if surgery is right for you.

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