Knee Replacement

By: Christopher Lynch, M.D.

Painful arthritis of the knee affects up to 10% of the general United States population over 65 years of age. As a result, data estimates that approximately 350,000 total knee replacements are performed each year in the United States. In the past, knee replacement was typically reserved for the elderly, more sedentary patients with significant disease throughout the entire knee. Increasing demand from younger, more active patients with variable amounts of knee disease has prompted advances in knee replacement designs and techniques and has led to expanded use of total and partial knee replacement. In patients with severe arthritic disease affecting only one compartment, it may not be necessary or wise to replace all three joint surfaces.

total-knee-replacement.jpgIn joints that rely on more than one cartilage interface, like the knee, arthritis may not significantly affect all of these opposing cartilage surfaces. Therefore, it is not always necessary to replace the minimally diseased surfaces nor is it necessary to sacrifice, as extensively, essential stabilizing ligaments, muscles or tendons. Knee replacement replace individual diseased compartments while leaving healthy joint surfaces and normal knee stabilizing ligaments intact.

normal-knee.jpgThe knee joint consists of three equally important and separate cartilage interfaces. The medial(inside) and lateral(outside) compartments are used while walking. The opposing smooth and slick cartilage. The stability and distribution of weight within these compartments is aided, in each, by the meniscus. Stability is further maintained in these compartments by the anterior and posterior cruciate ligaments(ACL and PCL) and, with assistance from both menisci and the knee cap, are responsible for antero-posterior (front to back) stability of the knee. The medial and lateral collateral ligaments control side to side stability. The interactions between normal medial and lateral cartilage surfaces and surrounding ligaments, muscles and tendons are essential for optimal knee stability, mechanics and function.

The undersurface of the knee cap, the patello-femoral joint, is the third joint in the knee. With the hamstrings, the knee cap and attached ligaments are the stabilizers preventing “buckling” of the knee and assisting in maintaining optimal knee motion. The relatively small cartilage at the patello-femoral joint experiences extremely high pressures. It functions to improve the strength and efficiency of the extensor mechanism (kicking muscles). These pressures are higher when rising from chair and stair climbing. It is not surprising that pain behind the knee-cap frequently accompanies the development of painful arthritis in other compartments in the knee.

ligament-diagram.jpgIn patients with disease affecting two or three compartments (ie: medial, lateral and patello-femoral), the most predictable long-term pain relief is achieved with a total knee replacement (TKR). TKR involves a measured removal of all cartilage and a small amount of its underlying bone from the distal femur, proximal tibia and the undersurface of the patella. Each surface is “capped” with polished and extremely smooth metal and/or plastic to replace, as equally as possible, the diseased and surgically removed bone and cartilage. The MCL and LCL are left intact and the extensor mechanism is repaired during closure.


Single compartment knee replacement, is most commonly performed for knees with isolated pain medially (inside). The typical patient is a moderately active patient who does not engage in extensive heavy labor activities who complains of isolated medial knee pain. History, physical examination and radiographs should isolate the symptoms to an individual compartment without the involvement of the other two compartments. Patients complaining of medial joint line pain, medial pain with ambulation and particularly with stair climbing or squatting should be absent. The exam should show well maintained joint spaces and absence of pain in both the lateral and patello-femoral compartments. In addition, although the indications for UKR are becoming more controversial, many surgeons believe that significant bentknee deformities (>10 degrees fixed flexion), uncorrectable bow-legged (varus) or knock-knee (valgus) alignment at the joint, loss of motion (

The benefits of UKR design are the ability to retain important structures necessary for optimal stability and function in the knee. The ACL, PCL, collaterals, opposite compartment meniscus and cartilage surfaces at the opposite and patello-femoral compartment are not violated in UKR. This allows improved post-operative stability and more normal knee mechanics than that achieved with a TKR. In addition, the synthetic surfaces utilized in knee replacement do not reproduce the smooth, resilient, lowfriction surfaces of healthy intact cartilage on healthy intact cartilage. Two of the three compartments in UKRs retain these optimal opposing healthy joint surfaces. A final benefit of performing a UKR is a more limited exposure. The incision into the quadriceps tendon(thigh muscle) is smaller than a standard incision for a TKR. This limited exposure theoretically decreases post-operative thigh weakness and incisional pain, leading to a more rapid rehabilitation course. 

bone-knee-diagram.jpgThe benefits of UKR are numerous and include a less invasive surgical technique, maintenance of stabilizing structures, improved post-operative knee mechanics, improved.rehabilitation and variable postponement of a more involved TKR. However, UKR has particular indications and may be unsuccessful and ultimately detrimental if utilized in the wrong patients. While all patients with isolated single compartment disease are candidates for UKR, each candidate must be evaluated on an individual basis taking lifestyle, patient expectations, weight, cause of arthritis, stability and deformity into consideration. In those patients with expectations to return to heavy labor activities, overweight patients, ACL deficient patients, patients suffering from inflammatory arthritis and those with fixed deformities should consider alternative treatments including proximal tibial or distal femoral realigning osteotomies or total knee replacement. Remember, the best results occur only when the surgery matches the problem at hand.

Computer Navigated Total Knee Replacement

Computer Navigated Total Knee Replacement
By Christopher B. Lynch, M.D.

Total Knee Replacement (TKR) continues to be one of the most successful medical interventions performed today. This procedure allows patients with painful arthritic knees to return to a more active lifestyle and achieve an improved quality and, in many cases, quantity of life. In general, ten-year knee replacement survival studies average > 90%, 15- year @ 85% and 20-year @ 75% survival. These numbers are certainly an improvement over previous survival studies reporting on the use of earlier implant designs and surgical techniques. Rates of survival continue to improve with advances in technology and techniques. Recent advances such as the incorporation of computer navigated systems promises to improve outcomes and long-term survival of currently implanted TKR’s.

Initial early implant techniques incorporated “eyeballing” the essential bone cuts without the use of guides or jigs. Failures using this technique were attributed to poor attention to achieving optimal lower extremity alignment (excessive knock-knee or bow leg), and failure to balance ligaments (too loose or too tight on the inside or outside of the knee). Malalignment and instability causes abnormal stresses on the implant and the bone leading to increased risk of premature failure in TKA.

In an effort to improve outcomes by achieving better alignment, current generation surgical techniques involve the use of jigs and guides that are designed to allow more predictable and reliable bone cuts. Updated techniques have also been developed to allow for appropriate and equal balancing of the ligaments to prevent the knee being too tight or too loose. The use of these jigs and guides has certainly improved the overall alignment of total knee replacements. Alignment and ligament balancing are among the most important aspects of a surgically successful total knee replacement. Optimal alignment , unfortunately, is not a guarantee with any current technique. In fact, several recent studies have determined that optimal alignment is not achieved in 8-25% of patients, even in the hands of the most skilled surgeons, with current cutting systems.

Computer Navigated Knee Systems are the latest tools designed to aid the surgeon in more predictably and reproducibly achieving optimal alignment and in addition, assist in achieving appropriate and necessary ligament balancing. The computer navigation system that I currently use (Ci System, DePuy) involves the use of a “computer eye” that uses infrared beams to read the position of shiny spheres attached in a specific pattern to the thigh and shin bones. The computer “eye” also reads a wand that I use to “register” the outline of the bones at the knee and generate an image of the patients’ knee and entire lower extremity on the computer screen. Using this image and guides specific for the computer, appropriate cuts of both the thigh and shin bones can be made with up to a 0.5 a degree of accuracy in all planes. 0.5 degree is well within the 3 degree safe zone for alignment. The computer may also make suggestions regarding ligament balancing and sizes of implants which I may, or may not, choose to use based on my experience.

Although we joint replacement surgeons do not necessarily “need” the computer, studies from around the world have repeatedly determined that the accuracy of the computer is significantly better than the current techniques at achieving optimal alignment and avoiding outliers of the lower extremity during total knee arthroplasty. The accuracy of the computer navigation system produces optimal alignment in >95% of cases and reduces the risk of any significant outliers. Technology continues to improve and as surgeons we need to remain current. This recent advance promises to be the standard of care in the (near) future improving long-term outcomes. Eventually this technology may allow us to safely reduce incision size and minimize peri-operative soft tissue trauma potentially speeding up post-operative rehabilitation. So far, clinical results in the short term have been excellent and x-ray results have indeed proven that the computer is extremely accurate.

Approximately two years ago, I was the first surgeon in the New Haven area to utilize this technology. I had not used the computer on all my patients over the course of the last two years, but my early personal results after my first 100 selected computer navigated total knee replacements have been extremely encouraging. As a result of my continued success utilizing the computer during knee replacement, currently all potential knee replacement patients are considered candidates for computer navigated knee replacement. Currently, I continue to incorporate this technique for many total knee replacements at both Milford Hospital and The Hospital of St. Raphael.

© 2008 The Orthopaedic Group, LLC Not to be reproduced without the express permission of the author

Total knee replacement - Please be a patient PATIENT

John F. Irving, M.D.

Total knee replacement has been proven to be one of the best reconstructive procedures offered to patients suffering with debilitating arthritis over the past 30 years.  It is expected that close to 750,000 total knees will implanted in the United States in 2014 with millions having been implanted in the last decade.  The operation is primarily performed for pain relief.  Secondary benefits include improvement in ability to perform activities of daily living such as dressing oneself, return to physical activities, ability to socialize, and maintain one’s independent living.  Surgery will increase mobility, stability, and safety.

Total knee replacement is a very different operation than a total hip.  The knee joint is very superficial,  covered only by skin and ligaments whereas  the hip  is deep in the groin and protected and covered  by large muscle groups.  We demand more from the knee than the hip.  The knee must move through a greater arc or range of motion than the hip during some activities such as stair climbing.  The expectations of a rapid recovery from a total hip and total knee are different.   The post-operative course from a total knee can be long, frustrating and requires consistent rehab.

Though the ultimate excellent result for a knee replacement is achieved in most patients, the speed and duration of the recovery process is quite individualized.  Most of the time, the FUNCTIONAL recovery is quite rapid.  Patients will progress from a walker and/or crutches to a cane in about 2 weeks’ time.  Many patients, depending on their age and severity of the arthritis and disability  before surgery, will not need any ambulatory assistance by a month or so after surgery.  However, the biggest impediment to recovery and patient satisfaction is the biological healing process called INFLAMMATION.  This is persistent SWELLING, ACHINESS, STIFFNESS and WARMTH.   Patients may not feel the operation to be a success and worthwhile, feel like the knee is their own, for even 1-3 years after surgery even though they are FUNCTIONING AT A HIGH LEVEL.

Often,  patients considering  a total knee replacement  may  know someone who had this operation and is walking around and active without pain 3 weeks after surgery.  Of course,  this is the exception and not the rule.  The majority of individuals take 1-3 months to recover enough from surgery to get back to many of the their former living, work and recreational activities.

The INFLAMMATORY response takes a long time to recede. This process may be frustrating to the patient, therapist and surgeon…..but you can’t rush Mother Nature!  In general the swelling-stiffness-achiness –warmth is only 50%(1/2) resolved by 6 weeks after surgery, 75%(3/4) resolved by  3 months, with complete resolution taking a year and sometimes even longer.  ( Please see link to New York Times article by Jane Brody from 6/5/08 on our web site,

Despite the sometimes prolonged course to recovery for a Total Knee, it is a great life changing operation.  You, as the patient have to be an active participant in the recovery and rehabilitation program!  The final result is about 33% surgeon, 33% physical therapist and 33% patient effort.

If you are planning on having a total knee, please expect to work hard after the surgery to maximize your result and please be a patient PATIENT!

The Truth About Peri-Operative Anesthesia for Modern Joint Replacement Surgery

By Christopher B. Lynch,  M.D.

Although surgery itself can be a significant source of stress for patients about to undergo a joint replacement, many patients seem to have more apprehension about the anesthesia than any other aspect of the procedure. The fear of going to “sleep”, trusting they will ultimately “wake up” and not having control of the situation during the procedure weighs heavy on some patients.

Most patients still believe, however, that anesthesia for routine total joint replacement involves general anesthesia. This is a method of anesthesia, still utilized in many other surgeries, that involves receiving one or more of several potent sedatives, a complete body paralytic (paralyzes the entire body including the diaphragm which allows you to breathe on your own) and placement of an endotracheal tube through your mouth and throat into your lungs so a machine can breathe for you during the procedure. Fortunately for the majority of routine joint replacement surgeries, general anesthesia is no longer required, nor is it recommended.

One of the greatest advances in joint replacement surgery in the last few decades has been the utilization of regional anesthesia rather than general anesthesia. Regional anesthesia involves the isolated “numbing” of specific nerves and nerve distributions that receive pain sensations from the lower extremities (legs), allowing the surgery to be performed without “going to sleep”. No intubation is required.

For hip replacements my standard anesthesia protocol includes a small amount of pre-operative “relaxation” on the way to the operating room and a spinal performed by our team of anesthesiologists once in the operating room. A spinal is a single injection of a local anesthetic into the spine that very quickly and completely numbs, and temporarily paralyzes, the lower extremities from the waist down. This block typically wears off after about 3hrs or so. This allows me time to prepare and position you for the procedure, perform the surgery and get you to the post-op care area pain- free. Motor and sensory function to your legs will return while in the post-anesthesia care unit, and when it does, we move you up to the floor to start you walking with all your weight on your new hip.  

For partial and total knee replacements, in addition to the protocol mentioned above, patients also receive an injection into the upper thigh called an adductor canal block that additionally “numbs” only the sensory (not motor) pain fibers of the thigh and knee.  A fishing wire- thin catheter is also placed at the same time into this adductor canal by the block team. This is currently done in the pre-operative holding area prior to heading into the operating room. Placement of the catheter allows for 24-48hrs of continuous dosing of pain controlling anesthetic to the knee and tissues surrounding the knee. During the procedure two additional long acting local anesthetics are injected into the areas around the bone, tissues and skin as an additional way for me to help control the early post-operative pain. Like the anesthesia utilized in the hip, the spinal wears off after 3hrs or so,  and at that point we begin to get you mobile on the orthopaedic floor.

Although, there are still situations in which general anesthesia is recommended or required in joint replacement surgery, such as an extended lumbar spine fusion where there is no access to the nerves in the spine, this use of regional anesthetic has all but made the use of general anesthesia obsolete in joint replacement surgery.  Patients are given the option of receiving sedation during the case and literally taking a nap or, if they wish, being completely awake and aware of everything that’s taking place in the operating room.  Currently most patients are choosing the “nap”.

Theoretic benefits of the regional blocks also include less post-operative nausea and grogginess, decreased blood loss, decreased risks of blood clots, decreased use of narcotics in the early post-op period and quicker recovery due to decreased pain.  It is my opinion that the best thing to happen to joint replacement surgery in the last 2 decades has less to do with custom implants or instruments, navigation or surgical technique, but more to do with these continued advances in peri-operative anesthesia and immediate post-operative pain management.

You’ve had a total joint replacement…Now What?

By Shannan Hardy MSN, APRN

You have had your surgery, you have undergone rehabilitation and you’re back on your feet. When and how will your life begin to resemble your pre-surgical life?  You will soon be able to begin to resume many activities that were too painful before surgery. Recovery from total hip replacements and total knee replacements is different in several ways. Hip replacement patients recover more quickly than knee patients.  This includes the length and type of rehabilitation, how quickly you will return to your desired level of functioning and the activities that are in the realm of possibility for you in the years after your replacement.

The first few weeks or months can be frustrating and uncomfortable, with the reality of just having had surgery.  This is especially true if you have preconceived notions of how fast you should be independent that might not be true.  Continue to follow the directions of your surgeon and your therapists. This stage is time limited and the more effort you put into your immediate recovery, the more you will get out of it.  If a single joint is replaced you probably will be done with a walker, crutches or cane by a month give or take after your surgery.

During the first year, you should steadily regain strength and flexibility in your total joint. If you adhere to your exercise program and stay active, your artificial hip or knee will show steady and ongoing improvement. Just as every person is different, every recovery is different. Don’t compare yourself to your spouse, your friend or a co-worker that had a similar surgery. It’s important to have realistic expectations about your new total joint. You shouldn’t expect your total joint to function exactly the same as it did earlier in life, before you had arthritis. They are good joints, not normal joints.  For example, knees may not bend as much as original knees and it may not be as comfortable to kneel. Hips may not be quite as flexible as they once were or be able to withstand extremes of rotation. 

Some experts say that high impact activities such as running, jogging, court sports, and contact sports should be avoided. Most surgeons say that what a patient can do after surgery is directly related to their level of functioning prior to surgery, their exercise or sports history and how vigorously the patients participate in rehabilitation.  Realistic activities following total knee replacement include unlimited walking and gym exercising, swimming, golf, hiking, biking, ballroom dancing, and other low-impact sports. However patients who work hard with physical therapy, especially on muscle strengthening and mobility, can ski, skate, play hockey, do extreme yoga and play doubles and even singles tennis!

The goal of a total joint replacement is to relieve pain and increase mobility thereby improving safety, lifestyle and independence. Successful patients are compliant, have a strong desire to continue to lead an active life and will make short term sacrifices for long term gain.  Please remember, it takes at least a year for your body to completely heal and rehabilitate from a total joint!  Occasional discomfort, clicks, pops, stiffness and swelling can continue for a time after surgery.  You will have more good days than bad days, as time goes on. If you have questions regarding your joint replacement or are thinking about having a joint replacement but are concerned about activity afterwards, please don’t hesitate to ask your surgeon or the staff.

Commonly asked questions about total joint recovery

Q: How long do I have to wait to drive?

A: If your left hip or knee was replaced and you have an automatic transmission, you may be able to begin driving in 1-2 weeks or so, provided you are no longer taking narcotic pain medication. If your right hip or knee was replaced, avoid driving for at least 3 weeks. Remember that your reflexes may not be as sharp as before your surgery.

Q: When can I have sex after total joint surgery?

A: Sexual activity can be safely resumed approximately 2 - 4 weeks after surgery. Some caution and creativity is recommended.

Q How soon can I fly after surgery?

A: As soon as you are comfortable with sitting down, you can fly.  Usually, 1 -2 weeks is the depending on your mobility. You will be on a blood thinner for 3 weeks after surgery.  During flying or driving on long trips, exercise your calf muscles and ankles frequently.  Also, get out of the seat and walk the aisle of the airplane, and stop to walk around your car every hour to avoid the possibility of blood clots.  Take the blood-thinners prescribed after surgery to reduce the risk of blood clots and wear your white anti-embolism stockings.  If you can take aspirin, consider taking 325mg daily if traveling long distances by car or airline for the first 3 months after your total joint.