Newer materials are now available. One company has developed a method of converting a thin portion of the surface of the femoral component to a hard, smooth zirconia ceramic—which causes less wear against the plastic. We expect these components to wear roughly twice as well against the polyethylene insert as standard cobalt chrome components.

Polyethylene is also changing. UHMWP now can undergo a process called “crosslinking,” which converts the parallel strands of polyethylene molecules into a crosslinked “weave,” adding durability to the polyethylene. Although the crosslinking process causes the polyethylene to become more brittle, other methods for treating the polyethylene to reduce this affect, such as adding vitamin E to the polyethylene, are being evaulated.

With these and other new developments in materials, we should expect total knee replacements to last much longer than 20 years now and in the future.

Oxinium – The Science behind Ceramic Knee Replacements (PDF)

Controversy still exists regarding the efficacy and safety of performing bilateral total knee replacements under a single anesthetic versus performing them under separate anesthetics separated by some arbitrary period of time. Some studies suggest that the bilateral procedure is safe while others show a disproportionately high risk of complications when both knees are replaced at the same surgery.

In order to shed more light on the subject, a literature search was performed looking at all studies published in the English literature over the past 10 years addressing the efficacy and safety of simultaneous (2 surgeons operating at the same time, 1 on each knee) or sequential (1 surgeon operating on 1 knee, then directly on the other knee under the same anesthetic) compared to staged total knee replacements (2 knees replaced, each under a separate anesthetic separated by some arbitrary period of time between the two).

Although some literature suggests that bilateral total knee replacements under a single anesthetic is safe, particularly in young, healthy patients, the preponderance of the literature casts some doubt on the safety of the bilateral procedure, particularly if the patient is elderly or has any pre-existing health issues, most notably cardiac, pulmonary, or neurological problems.

Given the body of literature available, it is my opinion that except in rare circumstances, it is in most patients’ best interest to perform bilateral total knee replacements in a staged fashion. The minimum time between procedures has not been well established. Some studies suggest 4-7 days is adequate while others suggest waiting 3-4 months. I typically suggest waiting a minimum of 4-6 weeks, although there is not much science yet to support this somewhat arbitrary number.

Keys to a Successful Knee Revision (PDF)

Sports Recommended By The Knee Society

(*) Recommended only to experienced patients

No conclusion was reached among the members of The Knee Society as to the following sports:

ARTICLES

The Knee Society: Total Knee Replacement—Recommended and Discouraged Activities

American Academy of Orthopedic Surgeons: Knee Replacement Exercise Guide

A comprehensive assortment of early post-op knee replacement exercises including illustrations

Exercise Net: Knee Articulations

Knee muscle anatomy described and illustrated with still pictures and videos

“Stresses on Your New Knee Joint”

An illustrated overview from Total Joints—a noncommercial site posting from Sweden, in English translation, as a public service to patients:

“…In a total knee prosthesis, the stresses are concentrated on smaller areas than in normal knees…What matters is the stress on the polyethylene [PE] surface of the tibial component…PE has only limited resistance against high stresses. If the stresses exceed a limit, the PE will be damaged.”

Noble PC et al.: Clin Orthop Relat Res. 2005; Feb(431): 157-65 ”Does total knee replacement restore normal knee function?”

Authors’ conclusions: “Our data show that many of the limitations reported by patients after total knee arthroplasties are shared by individuals with no previous knee disorders. However, only approximately 40% of the functional deficit present after a total knee arthroplasty seems to be attributable to the normal physiologic effects of aging. Patients who had total knee replacements still experienced substantial functional impairment compared with their age- and gender-matched peers, especially when doing biomechanically demanding activities. This suggests that significant improvements in the procedure and prosthetic designs are needed to restore normal knee function after a total knee arthroplasty.”

Kuster MS et al.: Am J Sports Med. 2002; 32(7): 433-45 ”Exercise recommendations after total joint replacement: a review of the current literature and proposal of scientifically based guidelines”

Summary: The author of this review study recommends that TKA patients remain active but stick to “low joint load” activities for routine physical fitness, such as swimming, cycling, and “possibly” power walking (on flat ground). Skilled hikers and skiers can participate in those sports occasionally, for fun, but patients should avoid unfamiliar sports after joint replacement. TKA patients also should avoid activities that place a high load on the knee when it is bent at 40-60 degrees (such as in hill hiking), because it places high stress on the polyethylene component.

McGrory BJ et al.: Mayo Clin Proc. 1995 Apr;70(4):342-8 “Participation in sports after hip and knee arthroplasty: review of literature and survey of surgeon preferences”

Summary: The authors searched the scientific literature on the topic and surveyed 28 orthopedic surgeons—about half of them young residents and “fellows” and half staff consultants—at the Mayo Clinic. For an activity to be designated as either “recommended” or “not recommended,” 75% of surgeons had to agree. Young surgeons were more cautious than staff surgeons about allowing a return to cross-country skiing. Otherwise, survey responses were similar: “Recommended sports included sailing, swimming laps, scuba diving, cycling, golfing, and bowling after hip and knee replacement procedures and also cross-country skiing after knee arthroplasty. Sports not recommended after hip or knee arthroplasty were running, waterskiing, football, baseball, basketball, hockey, handball, karate, soccer, and racquetball. “

Note: Recommendations about sports after TKA differ slightly with respect to specific activities, but consensus exists in favor of low-impact activities that avoid twisting the knee.

BOOKS

“Exercise beats arthritis”, by Valerie Sayce et al

“Healing Hip, Joint and Knee Pain” by Kate S. O’Shea

“The Complete Waterpower Workout Book” by Linda Huey, et al

“The Egoscue Method of Health Through Motion: Revolutionary Program That Lets You Rediscover the Body’s Power to Rejuvenate It” by Pete Egoscue

GOLF

Rothman Institute “Playing Golf and Knee Replacement Surgery”

The seven tips in this short article explain how to resume golfing in a way that avoids overloading or twisting an artificial knee.

1. Start slowly with chipping and putting before progressing to playing 9 or 18 holes.
2. While walking exercise is important for your heart, resume your golfing career by using a cart. Eventually you can walk the course. At that time use a caddy or a roller for your bag. Carrying your bag increases forces across your knee joint and may excessively stress your new knee.
3. Use spikeless shoes. Spiked shoes fix your stance during the golf swing and will increase rotational stress on your artificial knee. As most courses now require spikeless shoes, this advice may be superfluous.
4. Avoid playing in wet weather where the chance of slipping or falling during a golf swing is increased.
5. Learn to play more “on the toes”. Swinging flat-footed increases stresses on the joint replacement. On the backswing, the left heel should come off the ground and on the downswing, the right heel should come off the ground. (Note- This recommendation is for right-handed golfers and the terms “right/left” need to be reversed for left-handed golfers. This advisory was added by Dr. Hozack who plays as a lefty.)
6. Right-handed golfers with a right total knee replacement may benefit from “stepping through” their swing with their right leg. The right leg comes off the ground during the downswing and follow-through, and actually steps toward the target. This will effectively unload a right total knee replacement; however, no golfer with a left total knee replacement should attempt this, as it may result in excessive loading of the left knee.
7. Right-handed golfers with a left total knee replacement may benefit from an open stance. This may make the backswing a little more difficult, but if the player allows his left heel to come up, he should still be able to accomplish a full turn. The open stance has the golfer facing the target, and the hips do not need to turn as drastically to the left in the impact zone, thereby reducing the stress and torque within the left knee.

HORSEBACK RIDING

The Knee Society lists it as “slightly more risky,” and “Exercise Recommendations after Total Joint Replacement” advises avoiding repeated full loading of the knee (with all your weight on it) in 40-60 degrees of flexion.

TENNIS

Mont MA et al.: Am J Sports Med 2002; 30:163-166 “Tennis after Total Knee Arthroplasty”

Summary: A questionnaire was sent to United States Tennis Association members who had undergone a total knee arthroplasty (TKA). The study group included 28 men and 5 women (46 knees) with a mean age of 64 years. Only 21% of the patients’ surgeons approved of them playing tennis, and 45% of surgeons recommended only doubles. All patients were satisfied with their TKAs and tended to play at a high level—about three times per week, which does not reflect the level in the general population. Future studies should try to determine the effect of tennis on the general population of patients with knee arthroplasty, particularly the effect after 15-20 years. Until such studies are performed, the authors recommend that physicians advise caution in tennis after TKA.

EXERCISE EQUIPMENT

Walkaerobics.com In-home walking video

Kangoojumps.com Low impact rebound shoes

Study of Impact Shock during Jogging

SPORTS MEDICINE

The American Journal of Sports Medicine

American Physical Therapy Association

Research on Advantages of Minimally Invasive Hip Replacement (Read PDF)

While the wear rate with ceramic-on-ceramic total hip replacements is negligible and other problems (including fracture) extremely rare with the use of well-designed components and accurate surgical technique, squeaking in total hip replacements has recently become an issue. Squeaking in total hip replacements is thought to be caused by roughening of the ceramic surface of one or both components, or the presence of 3rd body debris in the space between the ball and socket.

Any impingement between the neck of the femoral component and the ceramic liner of the socket can generate particles of ceramic and/or metal that may lead to squeaking. Partial shucking of the head in and out of the socket may also cause damage to the ceramic surfaces stripe wear. Avoiding these problems is highly dependent on accurately positioning the acetabular and femoral components.

Recently, it has been noted by several authors, including myself, that a particular design of ceramic liner (where the ceramic is protected from chipping by a metal ring which extends past the ceramic) used with a specific femoral component manufactured by the same company has lead to an extremely high risk of squeaking. The squeaking likely occurs due to impingement of the metal femoral neck against the protective metal ring, generating metal debris which enters the interface between the ball and socket and causes a vibration that we hear as a squeak. In my practice, the incidence of significant squeaking in designs without the protective ring is less than 1/2% while the incidence of squeaking in a small group of ceramic hips with this protective ring is >10%, a 20-fold increase. Therefore, many surgeons, including myself, have quit using this acetabular component design.

Ceramic hips require very precise placement of the components to prevent impingement between the femoral and acetabular components. However, if done well, a ceramic hip should wear extremely well without chipping, breakage, or squeaking, and also without the theoretical risks that metal-on-metal hips carry.

Because implant positioning is absolutely critical to the success of a ceramic-on-ceramic total hip replacement, be sure to ask your surgeon how much experience he has with ceramic-on-ceramic hip replacements. Done well, these hips may last your lifetime, even if you are young and active.

Additional reading on squeaking ceramic hips:

• Influences of Prosthetic Design on Squeaking after Ceramic-on-Ceramic Total Hip Arthroplasty AAOS 2009 Poster
• Influences of Prosthetic Design on Squeaking after Ceramic-on-Ceramic Total Hip Arthroplasty AAOS 2009 Handout
• “The Squeaking Hip: A Cause for Concern-Disagrees.” Yang CC et al Orthopedics. 2007 Sep;30(9):739-42
• “Squeaking in a Ceramic on Ceramic Total Hip” Eickman TH et al Proceedings of the 8th BIOLOX Symposium 2003.
• “Squeaking in Ceramic-on-Ceramic Hips; Incidence, Causes and Solutions.” Toole, G. et al 2008.

Research on Causes of Squeaking Ceramic Hips (PDF)

Since use of the “Capsular Noose” procedure, developed by Dr. Swanson in 2002, and the use of larger femoral heads and lateralized offset stems, dislocation of the artificial hip is very.unlikely. However, during the early post-operative period while soft tissues are healing, you should be careful to avoid extreme positions, especially turning the knee inward when your hip is flexed (such as bending forward while sitting down with crossed legs). Always remember, as long as you can see the inside of the knee on the operated side, dislocation is extremely unlikely, even while bending over.
The physical therapist will teach you stretching exercises to help cross your ankle over the opposite knee for handling shoes, socks, clipping toenails, etc. Always keep the knee rotated outward when you bend the hip past 90 degrees (such as reaching for something on the floor when sitting in a chair).

As a general rule, it is safe to flex the hip past a 90 degree angle if the knee is rotated outward and you can see the inside of the knee—keep this rule in your mind at all times; it will eventually become automatic when you bend over. Additionally, you will be given specific exercises by a Physical Therapist to help strengthen and stretch the muscles around the joint. Do these exercises regularly, at least 3 times daily, during the first 6 weeks after surgery. Stretching exercises are also important, particularly rotating the knee outward. You will be taught to sit in a chair with your feet together and press the knees outward while bending forward a bit. You will also begin to slide the operated ankle up the opposite leg with the knee rotated outward to eventually enable a “figure-4” position to allow easy access to your feet. Remember, as long as the knee is rotated outward, it is very difficult to dislocate the hip.

For more information about the Capsular Noose Repair read Dr. Swanson’s Publications and Presentations

To see a demonstration of post-op exercises and stretches read the Patient Brochure

Research on New Surgical Method to Reduce Dislocation Risk (PDF)