Wait…So Running Isn’t Bad for My Knees?
In another “counterintuitive conclusion” researchers from some recently published studies are not finding a clear correlation between running and bad knees. In fact, runners may actually be at lower risk for developing 
osteoarthritis compared to non-runners. Go figure. Then go running….
Read more About This Story Here
Weight Gain After Knee Replacement?
A recent study out of the University at Delaware found that patients actually gained weight following knee replacement surgery. Conventional wisdom was that after suffering years of debilitating pain, formerly sedentary arthritis sufferers would resume activity and exercise following their knee replacement. However, researchers found that patients actually gained an average of 14 pounds after a two year follow up period…
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Patellar Clunk Syndrome: Complication Following Knee Replacement Surgery
In general, 
Total knee replacement (TKR) is a highly successful procedure. However, complications, although relatively rare, can sometimes occur. One such complication is known as 
Patellar Clunk Syndrome.
To understand this condition, it helps to first understand a little bit about knee anatomy and function (Figure 1). During knee flexion and extension, the patella (knee-cap) rides within a groove in the femur (thigh bone).
Figure 1: Basic Knee Anatomy
In knee replacement the worn ends of the bones are “resurfaced” with metal and plastic implants. The patellar groove is part of the metal femoral component that is implanted onto the prepared femur during the total knee replacement procedure. At the end of this groove there is a transition between the metallic implant and the native bony surface.
Following knee replacement, scar tissue can sometimes form at the top or “superior pole” of the patella. During particularly deep flexion, this scar tissue may move below the end of the groove in the femoral component and then “catch” on the end of the groove as the patella moves back with knee extension. It is this catching and then forceful release with extension that results in the “clunk” and pain characteristic of this condition.
This condition is more prevalent in a type of knee replacement known as Posterior Stabilized, or “PS” knee replacement, although it has also been reported in Cruciate Retaining (CR) knee designs as well. 1 In PS knee designs, where the posterior cruciate ligament is removed, the patellar groove tends to be shorter to avoid contact (in extension) between the end of the groove and a plastic post on the tibial component found in these types of designs. Consequently, the patella can come off the end of the groove during lesser degrees of flexion.
The publication cited at the end of this article provides more detailed information and a review of some of the literature on patellar clunk.
1 Niikura T, Tsumura N, Tsujimoto K, Yoshiya S, Jurosaka M, Shiba R. Patellar Clunk Syndrome After TKA with Cruciate Retaining Design: A Report of Two Cases. Orthopedics. 2008: 31:90
Joint Stiffness: Complications Following Knee Replacement Surgery
In a relatively recent article 1 published in the Musculoskeletal Journal of Hospital for Special Surgery, Dr. Alejandro Gonzalez Della Valle et al reviewed the origins of and treatments for early onset stiffness, a common complication following knee replacement surgery. We’ll present a brief summary of the article here.
How Prevalent is Stiffness after Knee Replacement?
In a review of the literature, the authors state that stiffness occurs in roughly 6% of cases, making it the most common knee replacement surgery complication.
How is Stiffness Defined?
The researchers reveal that what is perceived as “stiffness” following knee replacement has evolved over time. Several years ago, a knee was considered stiff if the patient could not extend their knee beyond 25 degrees of flexion (that is, a flexion contracture of 25 degrees) or if the full arc of motion was less than 45 degrees. More recently, as surgical technique and implant design have improved and as younger, more active patients receive implants, expectations have changed. Today, stiffness has been defined as a 
flexion contracture equal to or greater than only 10 degrees or an arc of motion less than 95 degrees. The authors note that this degree of motion is what is required for common activities of daily living (walking, sitting, stair climbing). Practically speaking, a joint can be considered “stiff” when it limits the patient’s ability to perform such activities.
What Causes Stiffness after Knee Replacement?
The authors place the causes of stiffness into three broad categories:
Preoperative – These include things like post-traumatic osteoarthritis, patients with prior high tibial osteotomy and patient whose preoperative range of motion (ROM) is limited.
Intraoperative – Included here are what the authors termed “technical errors” during the procedure. Things like, improperly sized implants and poor “balancing” of the joint through improper bone preparation fall into this category. The researchers explain these as well as other technical errors in detail.
Postoperative - Following surgery, stiffness can be caused by additional factors. Some examples are by patient behavior (“poor patient motivation”) deep infection and inadequate pain management.
How is Stiffness Treated
The authors then outline the various ways in which stiffness can be treated following knee replacement. Manipulation of the knee by the surgeon under anesthesia is generally successful when used within the first three months after surgery. After this period, more aggressive surgical options should be considered since manipulation can result in fracture or soft-tissue damage. Some surgical treatments described are arthroscopy, tibial insert (or spacer) exchange and revision surgery (i.e. exchange of the femoral component typically to correct imbalance in the spacing between the thigh and shin bone created at the time of surgery). The authors also stress the importance of proper rehabilitation following knee replacement.
The original article is available online through PubMed Central.
1. Gonzalez Della Valle A, Leali A, Hass S: Etiology and Surgical Interventions for Stiff Total Knee Replacements. HSSJ 2007, 3: 182-189
What do Cherries and Seaweed Have in Common? They Both May Help Your Osteoarthritis
Osteoarthritis (OA) is joint inflammation caused by the breakdown and eventual loss of articular cartilage. It is characterized by pain, stiffness, and swelling. Recent reports suggest that two natural substances could help reduce pain and improve function in patients suffering from this often debilitating disease.
Researchers at the Baylor Research Institute 1 conducted a pilot study where patients took pills made from tart cherries. This particular group of patients suffered from osteoarthritis of the knees. The scientists found that more than half of the patients had significant improvement in pain and function after taking the pills for eight weeks. These encouraging preliminary results have prompted the researchers to embark on a broader study. It will be interesting to see if the favorable results continue.
In a separate study 2, the use of a supplement made from seaweed was examined. In this study, patients were given a pill derived from a seaweed rich in calcium, magnesium and other minerals. The authors noted that earlier studies have shown that mineral supplements may improve OA symptoms. In this particular study, patients who received the pill were able to walk farther in a controlled test and experienced a small improvement in range of motion when compared to a group receiving a placebo. The study is available online through PubMed Central.
1 “Can Cherries Relieve the Pain of Osteoarthritis.” www.baylorhealth.com 31 Mar. 2009. http://www.baylorhealth.com/About/NewsRoom/BaylorNews/Pages/03182009Cherries.aspx
2 Frestedt JL, Kuskowski MA, Zenk JL. “A Natural Seaweed Derived Mineral Supplement (Aquamin F) for Knee Osteoarthritis: A Randomised, Placebo Controlled Pilot Study” Nutrition Journal, 8:7, 2009
Is Knee Replacement in Your Future?
Most knee replacements are performed for the treatment of osteoarthritis where the smooth cartilage in the knee joint breaks down resulting in pain, stiffness and swelling. The x-ray below is of a knee where osteoarthritis is present. Note the close proximity of the upper (femur) and lower (tibia) bones. In this knee the cartilage, which is not visible on an x-ray has worn away. If this had been a healthy knee, there would be a distinct gap between the two bones.
Osteoarthritis is usually progressive. It often begins mildly, but over time, wear in the cartilage starts to result in an uneven distribution of weight across the knee joint; often with more damage observed on one side versus the other. This in turn causes even more force to pass through the affected side, resulting in even faster degeneration of the joint.
This localized damage is most commonly found on the inside or “medial” part of the knee (
medial compartment), but it can also occur on the “lateral” or outside part of the knee (lateral compartment). When it occurs on the medial side, the patient may have a varus or “bow-legged” deformity. When lateral osteoarthritis is present, a distinct “knock-kneed” or valgus deformity is observed.
These deformities are usually corrected at the time of 
knee replacement surgery.
It is interesting to consider what, if anything, may initiate this cycle of uneven wear, worsening load distribution, and further wear. Is it possible that some folks may be predisposed to this condition due to their bony anatomy? A presentation at this years AAOS meeting looked to answer this very question. 1 The researchers examined the anatomy in patients receiving knee replacements whose pre-operative varus and valgus deformities were significant. In those patients, they found that key functional axes in the knee were not aligned normally. Specifically, they found that the alignment of the “mechanical axis” of the lower limb to the 
epicondylar axis in the knee was not normal. To understand these axes and their observed relationship, a review of basic knee anatomy is required.
In the normal lower limb, the mechanical axis is defined as an imaginary line originating at the center of the femoral head (the “ball” on the “ball-and-socket hip joint) passing through the center of the knee and ending at the center of the ankle. When the hip, knee and ankle line up in this way, the lower limb and knee joint alignment are considered “normal”. In a varus or valgus knee, the center of the knee is no longer on this line and is pushed “outward” in varus and “inward” in valgus.
The epicondylar axis is an imaginary line connecting the femoral (thigh-bone) origins of the medial collateral and lateral collateral ligaments (MCL and LCL). One can think of these ligaments as the “ropes” or “chains holding a swing. In this analogy, the epicondylar axis is like the top bar of the swing. The tibia or thigh bone is the swing which rotates about the bar (epicondylar axis) during knee flexion and extension.
In their study, the authors observed that in patients with severe varus or valgus deformities, the epicondylar axis was “misaligned” relative to the mechanical axis in the same direction (albeit smaller in magnitude) as in the knee joint deformity. For example, if a patient had severe osteoarthritis in the medial or inside part of the knee, a significant bow-legged or varus deformity was observed and the epicondylar axis was “tilted” in the same direction. In other words, the inherent bony anatomy appeared to predispose certain patients to uneven loading across the knee joint (a “crooked swing”), which, in turn appears to have made them more susceptible to the resulting osteoarthritic deformity. The results were not statistically significant, but a noticeable trend was observed. So to answer the question “is knee replacement in your future?” one may not have to look much further than one’s own bony anatomy.
1. Beyers-Thering MT, Krackow KA, Mihalko WM. “Relationship of the Femoral Epicondylar Axis to the Mechanical Axis in Deformed Osteoarthritic Knees.” 2009 AAOS Annual Meeting, Poster No. P201
MIS Knee Replacement May be Linked to Early Failure?
A high incidence of 
knee replacement failures performed using a Minimal Incision Surgery (MIS) technique was noted in a paper presented at the 2009 annual meeting of the American Academy of Orthopaedic Surgeons (AAOS). 1
In total knee replacement, the worn ends of the bones that make up the knee joint are resurfaced with metal and plastic implants. The surgeon must carefully align the implants relative to the bones and must restore the proper alignment of the bones to one another. If proper alignment is not achieved, excessive wear and premature loosening of the implants may result.
In “Minimal Incision” or “Minimally Invasive” Surgery, exposure of the surgical site is limited. Often the landmarks used in standard total knee replacement surgery may be obscured. The surgeon must rely on experience and sophisticated instruments to properly align the components. Although MIS knee replacement has grown in popularity in recent years, the possibility of issues arising due to the limited exposure has remained a primary concern.
In their paper, Dr. Derek Miller et. al. examined a series of revision cases performed by five surgeons at three different centers between 2004 and 2006. Excluding revisions due to infection and re-revisions, 236 first time revisions were recorded. Of those, 43 were originally performed via MIS, and 193 were revisions of implants first implanted using a “standard” knee replacement technique. In comparing the two groups of revisions, the findings were dramatic. On average, the time to revision was 14.8 months in the MIS group compared to 80 months for the standard group. Thirty-seven percent of the MIS group were failures less than 12 months after surgery compared to only 5% in the standard group. More than eight out of ten of the MIS revisions were in total knee replacement patients that had their implant in for less than two years.
Although MIS knee replacement may lead to quicker recovery and less scarring, this study suggests that the long-term performance of these procedures may be compromised. It remains to be seen whether continued advances in the technique and surgeon experience can counteract this trend.
1 Miller DW, Barrack RL, Barnes CL, Clohisy, JC, Maloney WJ, “Minimal Incision Surgery As A Risk Factor For Early Failure Of Total Knee Arthroplasty?” 2009 AAOS Annual Meeting, Podium No. 272
Knee Replacement Allergies – Nothing to Sneeze At?
Knee Replacement Allergies – Nothing to Sneeze At?
Each year, hundreds of thousands of knee replacements are performed. In knee replacement, the worn ends of the bones that make up the knee joint are replaced with metal and plastic implants. In most cases, results are excellent, however in rare cases, an immune response may arise and can become problematic. That is, the patient may suffer from an allergy or hypersensitivity to the metallic components of the implant. Symptoms may include warmth or swelling at the knee, a skin rash and even loosening of the implant.1
This phenomenon is so rare, that its very existence has been debated. But at this year’s annual meeting of the American Academy of Orthopaedic Surgeons, a paper was presented documenting what appear to be allergic reactions to knee replacements.2 Dr. Alvin Ong et. al. recorded 19 cases from 2005-2008 where total knee replacement failures were attributed to metal sensitivity. The authors ruled out all other possible causes of implant failure and then performed a special test, the lymphocyte transformation test (LTT) which looks at a patients sensitivity to certain metals. Seventeen of the nineteen patients with failed knee replacements were tested. Ten patients recorded high sensitivity while the remaining seven indicated mild sensitivity.
Following the sensitivity testing, 16 of the patients had a second procedure where the traditional metal knee replacement was removed and replaced with a non-metallic implant (the ceramic Oxinium implant from manufacturer Smith and Nephew). Following this knee replacement, the authors reported good results and elimination of the inflammation that was present with the traditional metal implant.
So although an allergic reaction to metal knee replacement implants may be rare, it is not unheard of. Unfortunately, diagnostic tests like LTT are relatively expensive and persons testing positive are not always symptomatic.1 In their article, Dr. Ong et. al. suggest that surgeons be mindful of the possibility of metal hypersensitivity especially when failures of implants are noted and cannot be attributed to other factors.
1 Rabin SI, Graf CN, Hopkinson, WJ, Hallab NJ “Immune Response to Implants.” emedicine.medscape.com. 08 Mar. 2009. <http://emedicine.medscape.com/article/1230696-overview>
2 Jafari SM, Della Valle CJ, Orozco F, Ong AC. “Metal Hypersensitivity Following Total Knee Arthroplasty: A Real Phenomenon?” 2009 AAOS Annual Meeting, Poster No. P134
“Total Knee Replacement: Get it While You Can”
Each year, the American Academy of Orthopaedic Surgeons (AAOS) holds its annual meeting. This year, two presentations highlighted a pending “perfect storm”: the demand for total knee replacement (total knee arthroplasty) will increase dramatically while the supply of Orthopaedic Surgeons trained to do them will decrease sharply.
In a paper entitled, “Joint Replacement Access in 2016: A Supply Side Crisis,” 1 Dr. Thomas K Fehring et. al. stated that “demand for arthroplasty is expected to double in 10 years.” By 2016, this translates into an annual demand of 1,046,000 knee replacement procedures. At the same time, the expected supply of Orthopaedic surgeons is expected to fall such that if they were to work at current rates, they will only be able to perform 287,759 knee replacements, leaving many “waiting in pain”.
In a related presentation, “National Projections of Younger Patient Demand for Primary and Revision Joint Replacement,” 2 Dr. Steven Kurtz, et. al. explained the “demand side” of this equation. Overall demand for knee replacement is growing, but not just because the population is aging (i.e. a greater number of people over 65), but also because the demand for knee replacement in folks under 65 is growing as well. That is, it will become increasingly more common for folks under 65 to be total knee replacement recipients.
Hip replacement was also highlighted in both studies; however the shortfall is not estimated to be as severe. Ultimately, both papers warn that something must be done to alleviate this pending crisis.
References:
1 Odum S.M., Iorio R., Fehring T.K. “Joint Replacement Access in 2016: A Supply Side Crisis” 2009 AAOS Annual Meeting”, Poster Presentation P043
2 Kurtz S., Lau E., Ong K., Kelly, M.P., Bozic K.J. “National Projections of Younger Patient Demand for Primary and Revision Joint Replacement”, 2009 AAOS Annual Meeting, Podium No. 183
Arthritis, Osteoarthritis and Osteoporosis….What’s the Difference anyway?
In this post we will provide some simple definitions for similar sounding terms that are related to the knee joint and overall bone/joint health.
Arthritis
The term 
arthritis simply means an inflammation (-itis) of a joint (arthro-). There are over 100 kinds of arthritis. A joint is an area in the body where two bones meet. In the knee, there are actually three bones which come together. There is the mating of the femur (thigh bone) and tibia (shin bone) forming the tibio-femoral joint and the mating of the femur with the patella (knee cap) forming the patella-femoral joint. Either one or both of these joints can be inflamed and, therefore, be arthritic.
Osteoarthritis
Osteoarthritis is a specific type of arthritis caused by the breakdown and possibly eventual loss of articular cartilage. Articular cartilage is a special kind of cartilage that covers the ends of the bones where they meet or articulate. In the knee, articular cartilage is found at the mating ends of the femur, tibia and patella. When this cartilage begins to wear down (which can be caused by a number of things such as age and obesity), pain, stiffness, and swelling (arthritis), can occur. This type of arthritis is also called degenerative arthritis, and as the name suggests, usually worsens over time. If it becomes severe enough, Total Knee Replacement may be indicated. For more information, see our section on Osteoarthritis.
Osteoporosis
Unlike arthritis and osteoarthritis, 
osteoporosis is not related to the joints or joint degradation. It is a change in the actual structure of bone itself. Our bone is a living, dynamic tissue that changes over time. It has a complex structure specifically designed to serve its weight bearing function. Within a long bone like the femur, for example, there are two types of bony structures. Cancellous or spongy bone is found in the interior near the ends of the bones. This type of bone is porous, hence the name. This porous interior is covered by a layer of dense bone known as cortical or compact bone. This bone also forms the hallow shaft of long bones. The picture below shows a cut away view of bone and it various structures.
In osteoporosis, the major impact on bone is that the porosity of the spongy bone increases. That is, the pores or holes in the “sponge” get bigger. This leads to an overall weakening of the bone and can result in fractures. Common sites for such fractures are the vertebrae, hips and forearm. For more information on Osteoporosis, visit our dedicated section on that topic.
Hopefully these descriptions will clarify some confusion related to these similar terms and conditions.
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Introductory Topics
Introduction - Home Normal Knee Anatomy The Diseased Knee: Osteoarthritis The Knee Replacement Procedure
Surgery Overview > Total Knee Replacement Surgery Video Knee Replacement Complications Minimally Invasive Knee Replacement Unicompartmental Knee Replacement Computer Assisted Knee Replacement Knee Replacement Implants
The Parts of a Total Knee Replacement Mobile Bearing Knee Replacement Knee Implant Wear Knee Implant Manufacturers Related Topics
Knee Arthroscopy Total Hip Replacement Osteoporosis -
- To Retain or Sacrifice the PCL…That is the Question
- The Impact of “High-Risk” Sports in Knee Replacement Patients
- Video Showing a Traditional Total Knee Replacement Surgery
- Mobile Bearing Knee Replacement Offers no Benefits vs. Fixed Bearing
- Press-Fit Total Knee Replacement: Working to Prevent Loosening and Bone Loss
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