News Category: Knee

Science has answered many questions about knee osteoarthritis (OA). Here’s a brief list of what is known:

Braiding. We’ve seen it in hair, rope, and yarn. Now doctors are using it in tendon grafts. If you tear the anterior cruciate ligament (ACL) in your knee, it might be replaced by a piece of tendon from your hamstring muscle. In the past doctors have folded the tendon in half to make a stronger graft. This makes the hamstring graft shorter, but stronger. Braiding the tendon graft was the next step.

Braiding changes the shape of the tissue, but does this actually increase the strength of the graft? Researchers from Harvard Medical School say no. Braiding may actually put the tendon fibers in a position that weakens the tendon’s strength. They don’t recommend braiding tendon grafts at all.

How did they come to this conclusion? They took hamstring tendons from human cadavers. Half of the grafts were braided. The other half weren’t. A special machine was used to test the strength of the grafts. Stiffness was measured. Maximum load handled by the graft was also recorded.

The authors report a 35 percent reduction in strength in braided tendons. Stiffness was decreased by as much as 45 percent. The use of braiding was first based on the thought that braiding ropes and cables increased their strength. In fact, braiding materials improves flexibility, not strength.

Braiding hamstring tendon grafts decreases stiffness and the amount of force the graft can handle. Researchers are going to keep testing the braided method of grafting. The next step is to try different types of braiding. Testing in live tissue may also make a difference.

When a patient’s symptoms last longer than expected, doctors take notice. Most muscular or soft tissue injuries heal within six to eight weeks. If symptoms last beyond that time, it could be something more serious.

That’s the case for this 21-year-old male soccer player with severe thigh pain and numbness. Playing soccer made the symptoms worse. Ten months earlier, he had received a direct blow to the upper right thigh where the pain and numbness were now centered.

A careful review of his history and examination led to the diagnosis of meralgia paresthetica. Meralgia means pain in the thigh. Paresthetica refers to the numbness. This condition occurs when the lateral femoral cutaneous nerve of the thigh gets pinched by something.

This young man had surgery to fix the problem. When the doctors looked inside his thigh, they found a band of fibrous tissue cutting across the nerve. After cutting the band of tissue, the patient was symptom-free. He eventually went back to playing soccer without any more problems.

There are many possible causes of meralgia paresthetica. Sports injury is an uncommon cause. The doctors report this case because of its rarity. They remind other sports medicine doctors that meralgia paresthetica can be caused by tumors pressing on the nerve. Diabetes can also cause nerve damage and symptoms of thigh pain and numbness as described here.

Sports doctors who recognize a nerve entrapment syndrome quickly can save the player time and money. Surgery to release the nerve is advised for high-level athletes.

Many people in rural areas depend on the Mayo Clinic in Rochester, Minnesota, for information on how and when to treat unusual health problems. Joint infection in both knees after a total joint replacement is one of those conditions.

There are no studies so far on how to treat this problem. What works best? Doctors at the Mayo Clinic reviewed the charts of 21 patients treated between 1976 and 1999 to find out. Two-thirds of the patients had an increased risk for infection because of other health problems such as diabetes, kidney disease, and cancer.

Many infections occur within the first three weeks after a joint replacement. In fact, half of all infections occur in the first week after the implant operation. There are different ways to treat this problem. Sometimes the doctor tries to save the new joint. They do this by cleaning out the infection and replacing part of the implant.

In some cases the infected implant is removed, and a temporary spacer is put in its place. A new implant is inserted when the infection is under control. Other patients need a new joint replacement right away. In all patients an antibiotic is used to kill the bacteria. The medication is given intravenously, by mouth, or painted on the parts put in the knee. To be on the safe side, most patients are also put on long-term oral antibiotics.

The authors found that keeping the infected implant always had a poor result. Waiting too long to replace an infected implant was equally bad. Removing the implant and clearing up the infection before putting in a new implant seems to work the best.

However, not all patients can be treated this way. Some patients have other health concerns that get in the way. The best treatment takes place during two separate operations. The patient may not be able to handle that much time in surgery. Options are fairly limited in these cases.

Since this study included patients from 1976 on, the researchers think results today may be better. They recommend removing all hardware and cement. The joint should be cleaned carefully. Treatment with intravenous antibiotics is advised next. Any spacer or implant reinserted should be painted with antibiotics or held in place with antibiotic-treated glue.

Are you the kind of person who tests the water one foot at a time, or are you more likely to jump in with both feet? This is the kind of decision people who need both knee joints replaced have to make. They can choose to do one knee at a time or both at the same time.

Before making a decision like this, a little more information is helpful. What are the risks and problems with each choice? How often do patients die after having knee replacements? Are you more or less likely to die after a single or double (bilateral) knee replacement?

Doctors at Dartmouth Medical Center took a look at these questions. They reviewed the records of two groups of total knee patients. One group had a single joint replacement. The other group had both knees replaced at the same time. They found no difference between the two groups in terms of blood clots, internal bleeding, or knee infections.

The only real difference was in the number of patients who had a heart attack after the operation. In this study, patients over the age of 70 treated with bilateral knee replacements had a greater risk of heart attack. The bilateral group also needed more blood transfusions. Very few patients died in either group. The risk of death is no greater for patients having a single or double knee replacement than someone the same age without surgery.

The authors think older patients are willing to accept more risk by having a bilateral procedure. They do this to reduce the amount of time in the hospital. The time in recovery afterwards is also less. A bilateral approach is still safe with few problems for most patients.

Patients with patellofemoral pain syndrome (PFPS) know a thing or two about knee pain. In their case, it’s often the sideways tilt of the kneecap (patella) that causes pain and other symptoms. Teenagers, athletes, and soldiers are the most likely to suffer this condition.

PFPS can be diagnosed with imaging studies such as CT scans or MRI. X-rays don’t always show it because the knee has to be completely straight or just slightly bent to see the problem. But X-rays cost much less than CT or MRIs. X-rays are also easier and faster than other methods of imaging.

Canadian researchers tried using a new X-ray system to look at the knee. Measures of patellar tilt, position, shape, and height were made using a specific type of X-ray system. This new machine is designed to show as little distortion as possible. The knee was X-rayed in 35 degrees of flexion.

Two groups of military subjects were X-rayed. One group had PFPS. The other group was similar in age, years of military service, and gender, but had no knee problems. The authors report no difference in X-ray measurements taken between the two groups. It didn’t matter if the quadriceps muscle was contracted or not.

The authors conclude that the new X-ray system isn’t a useful tool to diagnose PFPS when the knee is flexed at 35 degrees. The knee is bent too much to show any alignment problems. Further study is needed.

A 76-year old woman in England isn’t getting the most out of her total knee joint replacements. She had both knees replaced six years ago. Her left kneecap (patella) was getting way off track, but not quite dislocating. This is called subluxation. In fact, both her patellae have this problem. The left subluxes most often, but the right actually dislocates.

She’s had several falls right onto her knees. Both knees hurt, and she’s having trouble getting up and down stairs. Her doctors found the case interesting enough to write it up as a case report. There are no other reports like this in the medical journals. After a thorough exam and X-rays, here’s what the doctors found.

When the new joints were put in, the upper half of the implant probably wasn’t rotated quite enough. This set the woman’s patellae slightly off track. She had an operation to cut a band of fibrous tissue along the outside (lateral side) of her knees. This procedure, called lateral release, often helps even out the pull on the patella and helps them track more in the middle.

The lateral releases didn’t help. The patella subluxation got worse. The doctors used an arthroscope to look inside her knee joints. They found the patellae had come apart. When the knee replacement is done, sometimes a plastic insert is attached to the back of the patella. The insert had separated from the patellae. This is called patellar dissociation.

The doctor removed the insert but left the patellae in place. The undersides of the patellar bones were covered with fibrous tissue and cartilage. This is a normal finding, so nothing more was done to them. The patient had a rapid recovery from the operation. She was much better after rehab was done to strengthen the muscles and improve patellar tracking.

The doctors who wrote this case report say this case really shows the benefits of arthroscopic surgery. Using this tool to look inside the knee joint helped them find and fix the problem.

The doctors in this study are the first to take a long look back on knee surgery for meniscus tears. The meniscus is one type of cartilage inside the knee joint. It’s located on both sides of the joint and divided into two parts: medial and lateral. The medial meniscus (MM) is on the inside edge of the knee. The lateral meniscus (LM) is on the outside edge.

This study compares the results of MM removal to LM removal. Meniscus removal is called meniscectomy. In all cases, only part of the meniscus was removed. The patients were followed for at least 10 years. X- rays were used to look at the joint as a means of measuring results. The researchers were also looking for ways to tell which patients would have the best outcome.

The researchers found that patients having a lateral meniscectomy had a second operation on the same meniscus twice as often as patients with medial meniscus problems. They also report that the joint space narrows quite a bit wherever the meniscus is removed. The authors didn’t find any factors in the LM group to predict the result. On the other hand, there were many predictors in the MM group. The three most important were age at the time of surgery, type of tear, and whether or not the cartilage was damaged.

Taking a look back in the cases of meniscectomy will help guide future treatment. Removing the cartilage puts the joint at risk for faster degeneration. The meniscus plays an important role in knee motion. These French researchers believe a 10-year follow-up study is too short. Watching what happens over time after a partial meniscectomy requires longer study.

Even with all of today’s technology, doctors still rely on their feelings — literally — to diagnose some problems. For example, there are 20 special tests to diagnose tears of the meniscus in the knee. But one of the oldest and best known tests is just to feel the joint for tenderness. The doctor feels along the joint line on the inside or outside of the knee. Tenderness along the inside points to a tear of the medial meniscus. Pain along the outside is more likely to be a tear of the lateral meniscus.

One doctor in Turkey compared the joint-line test to results of arthroscopic exams. Arthroscopy allows the doctor to look inside the knee with a special tool. The condition of the meniscus is clearly visible with this test. More than 100 young men, ages 18 to 20, were tested. All were injured as members of the Turkish army.

The doctor found that tenderness along the joint line gave the correct diagnosis in about two-thirds of the cases. This is called a true positive result, meaning that the joint line was tender and a tear was confirmed with the arthroscope. A false negative result is when there’s no joint tenderness, but a tear is found in the meniscus. Another possible result is a true negative result, in which there is no tenderness and no tear.

The author reports that joint-line tenderness is more accurate for lateral meniscal tears. He was more likely to have false negative results with medial meniscal tears. In this study, there was a high false positive rate. A false positive means there is joint-line tenderness, but the arthroscope shows nothing wrong with the meniscus. The author thinks this may have been caused by recruits who had nothing wrong with them but who wanted sick leave.

Putting in a new knee joint can be tricky. It’s something like trying to hang a picture in just the right spot. The implant can be placed too far up or too far over. Since there are at least two major pieces to the implant, multiply the possibilities of mistakes by two. This will give you some idea of how many wrong spots there are for the knee implant!

Every surgeon has one key goal in mind when putting in a knee joint replacement: accuracy. Each piece must be set in the correct spot. The right angle and just the right amount of rotation are also needed. Scientists say there are almost five million possible choices for placement for each part of the implant. When we add size of the implant into the equation, the number of choices increases even more.

Right now, doctors make all these decision just by looking at the patient’s joint and the nearby anatomy. The chance for error is great with this method. That’s why doctors at the State University of New York in Buffalo are suggesting computers to help. Computers are fast, remember everything, and make all the math calculations. Imaging equipment to show the position of the implant can be combined with computers for the best fit.

Computer assisted orthopedic surgery (CAOS) can reduce errors to a range of 0.1 to 1.0 mm. This is much, much better than the “eye-balling” method. However, CAOS is only as good as the software that guides it. Detailed graphics and accuracy are very important.

The authors of this report think both hardware and software will continue to improve. Greater accuracy and convenience will be possible. CAOS will be simpler, easier, and less costly. It remains to be seen if CAOS will be present in every doctor’s office or only in large surgery centers.

Surgeons who do more of a certain surgery become more skilled at it. The same is true for hospitals. Many insurance companies and HMOs would like patients to go to these surgeons and hospitals. The idea is that patients who go to more skilled surgeons and surgery staff will have fewer problems after surgery. This means less cost–and it’s better for the patient, too.

These authors wanted to see how this theory held up in the case of total knee replacement (TKR) surgery. They used a nation-wide database to track more than 50,000 patients after TKR. They used records from all kinds of hospitals in all parts of the United States. They grouped surgeons and hospitals by the number of TKRs they did in a year. The researchers also looked at data about the patients, such as their age, gender, health, and income. They crunched quite a few numbers:

Doctors have found the ideal patient for a unicompartmental knee replacement (UKR). But first, what’s a UKR? It’s half of a knee replacement. In a UKR, usually only the inside (medial part) of the joint is replaced. It isn’t always necessary to replace the entire joint when only one side is worn out or damaged. Unicompartmental implants work quite well for some patients with an uneven wear pattern.

Who are these patients? In other words, who is the ideal patient for a UKR? Someone over 65 years of age with a fairly quiet lifestyle. Doctors call this a lifestyle with low physical demands. The patients must have good knee motion and knee alignment.

What if you’re not the right age, but you still need the operation? This is the focus of this study. This is only the third study to report the results of UKR in “younger” older adults (60 or younger). Patients were followed for an average of 11 years, so this is a long-term study. The study showed that height, weight, and body-mass index (BMI) didn’t affect the results. The authors report a 93 percent success rate for UKR.

This means that this younger range of patients has more treatment options. In the past, a tibial osteotomy was the only real choice. Tibial osteotomy is the surgical removal of a wedge-shaped piece of bone from the lower leg bone (the tibia). The osteotomy is done where the tibia meets the knee. Taking out this piece changes the weight-bearing angle of the bone and joint. The goal is to change the force on the joint by shifting the pressure to the opposite side.

This study suggests that UKR may be useful for active middle-aged adults. It may eventually replace the need for tibial osteotomy procedures. These results are as good as with a total knee replacement.

Patients with severe arthritis in both knees often start out with a single knee joint replacement. Only replacing one knee may not be a good idea. The other knee’s loss of motion and strength can affect the side with the new joint. Rehab is harder and longer. The results are often less than optimal.

Doctors at the Pennsylvania Hospital in Philadelphia have a suggestion. They think doing both arthritic knees at the same time is a good idea. And if you’ve had one knee done that needs to be redone (revised), go ahead and get a new joint on the arthritic side that’s never been done before. Yes, that means you’ll be having both knees operated on at the same time. The first knee will get a revision, while the second knee will get a new joint.

They tried this at their own center and found the patients were very pleased with the results. In fact 99 percent of the patients said they would “do it over again.” The doctors were especially surprised to find that the patients thought the revised side was the better knee. They were delighted with how much better they were. The improvement in their revision made all the difference.

The authors of this study advise one operation to fix the implant in need of revision and replace the other knee at the same time. The best time to do this is when the patient has severe arthritis and damage on both sides. The loss of motion, decreased strength, and deformities on one side will affect the knee on the other side.

“Snip snip” in the world of surgery means that something is about to change. Sometimes the changes make things better–sometimes not. Doctors release a muscle by snipping or cutting it at the tendon. Snipping the quadriceps tendon in the knee may need to be done in some surgeries.

This study reports the results of three patients who had a complete rupture of the quadriceps tendon. The rupture took place in the first eight weeks after surgery to replace the knee joint. All three were heavy, active men who’d had their knee joint replaced. Each one had a snip, or proximal release, of the quadriceps tendon.

The doctors reporting these cases hope to increase awareness of possible problems with this type of tendon release. They conclude that the tendon snip may lead to complete tendon rupture. The treatment method is safe, but the patient must be followed carefully.

Knee flexion may have to be limited to 45 degrees the first week after surgery. Motion can be increased carefully in the weeks after that. Since there was no obvious cause for the ruptures, doctors don’t know how to prevent them. Fortunately a quadriceps rupture is rare after total knee replacement, even with a tendon release.

People needing both knees replaced can have both done at the same time (one-stage). Or they can enter the hospital two separate times (two-stage). The two-stage method has a much shorter wait between operations than ever before.

But what about the costs? Is it less expensive to do a one-stage or two-stage knee replacement for people who need both knees done? It makes sense that the one-stage method would have a shorter total hospital stay and lower costs.

A recent study from Stanford University School of Medicine looks at cost issues. They compared 91 one-stage patients with 32 two-stage patients. They looked at both the hospital costs and costs after discharge. All patients had both knees replaced.

The researchers found that hospital costs for a one-stage knee replacement are almost 25 percent less than for a two-stage operation. But the costs go up afterwards when the one-stage patients go to a rehab unit for up to nine days.

Most of the two-stage patients went directly home. Some had home health services, but this was much less costly than in-patient rehab services. The authors conclude that what happens after surgery is more important in comparing costs of one-stage to two-stage knee replacements. One-stage patients are more likely to need a longer stay in a rehab unit.

Any surgery has complications. One of the problems after knee replacement surgery is blood loss. Most of the blood is lost after surgery, while patients are still lying in bed. Most patients und up needing blood transfusions, a procedure with its own set of risks. It would be better to avoid blood transfusions if possible.

These authors tested the use of a special pillow after knee replacement surgery. It was designed to help prevent blood loss. The pillow is placed under the knee, keeping the knee and hip bent at a 90-degree angle. The pillow was tested in 20 patients. They used the pillow for the first 24 hours after surgery. Their blood loss was compared to 20 patients who did not use the pillow. Blood loss was recorded at different times over the 48 hours after surgery.

Patients who used the pillow had less blood loss over the whole 48 hours. On average, they lost a total of 550 ml (about 18 ounces) less blood–a significant amount. None of the patients who used the pillow needed a blood transfusion. Three patients in the control group required transfusions.

There were concerns that using the pillow would make knees stiffer after 48 hours. But both groups had about the same range of motion. The pillow showed great success. The authors recommend using this special pillow after all knee replacement surgeries.

Every coin has two sides. Total knee replacements (TKRs) are a lot like that, too. On one side are the results of advances and improvements over the years. This side shows TKRs as a good and reliable operation for arthritic knees. On the other side are the reports of complications after the operation. These include infection, fracture, blood clots, and loss of muscle control. On more rare occasions this side of the TKR coin also includes heterotropic ossification (HO).

HO is the formation of bone in and around soft tissues such as muscles. HO can develop along the front of the thigh above the knee joint after TKR. But how often does it really happen? And what are its effects? These are the questions Japanese researchers studied. Sixty-three TKRs for rheumatoid and osteoarthritis were included. X-rays were taken before and after the operation to compare the changes in bone.

The researchers were surprised to find HO present in nearly 40 percent of the patients. The changes were seen within four weeks of the operation. However, the changes went away over time for two-thirds of these patients. HO was more common in the patients with osteoarthritis in this study.

The authors suspect one of the reasons HO isn’t seen after TKR has to do with the X-rays. Doctors reading the X-rays are looking for signs of infection or implant loosening. They may not see the small changes in the shadows of the bone that occur with HO.

If a coin could have three sides, here’s what the TKR coin would show. HO after TKR takes care of itself over time. By the end of 12 months, motion in the joint is the same in patients with and without HO. Treatment for the HO may not even be needed.

Poor wound healing, infection, loosening, fracture, nerve damage, dislocation, loss of motion, stiffness. This is just a small list of things that can go wrong with a total knee replacement (TKR). It sounds worse than it is. Only 0.2 percent of the adults having this surgery actually have implant failure. One rare cause isn’t even on the list–having an implant put in that’s too large for the knee.

The doctors of this report tell about two cases of oversized implant on the femoral side (upper half of the implant). In both cases, pain and loss of motion after surgery brought the patients back to their doctor. X-rays were used to diagnose the problem.

The large implants were taken out and a smaller implant was put back in. The result was a success for both patients. The authors conclude the success of any joint implant is based on preventing complications. The doctor’s knowledge of implant design and operative technique are part of this success.

These doctors offer some advice to avoid the problems that come with an oversized implant. First, the implant must be properly sized. If the patient is between sizes, the doctor should choose the smaller one. Next surgeons are cautioned to make sure there is equal room in the joint for bending and straightening the knee. Finally if the patient ends up with an oversized implant that is causing problems, it may be best to replace it with a smaller one.

X-rays and MRIs don’t always show the doctor everything. However, when it comes to damage to the cartilage after a kneecap (patella) injury, arthroscopy is quite helpful.

When the patella dislocates, there can be damage to the cartilage in several places. First, the cartilage behind the patella itself can get cracked. And the cartilage covering the end of the thighbone (femur) can take a beating.

Previous studies used X-rays after a patellar dislocation to look for damage to the cartilage. It wasn’t until an arthroscope was used to look for cartilage damage that doctors realized how often this happens. The arthroscope is a slender instrument with a tiny TV camera on the end. It can be inserted right inside the knee joint to show the doctor what’s going on.

The authors of this study report a 95 percent chance of cartilage damage after patellar dislocation. They describe the type and location of the damage. This will alert other doctors where to look and what to look for.

They also report that the cracks may look small or very fine. However, the cracks move and get larger with any movement. The researchers conclude that high contact forces from patellar dislocation can cause cracks in the cartilage of the knee. It’s more common than previously thought. Arthroscopy is the test of choice to look for cartilage damage after patellar dislocation.

An injury to the anterior cruciate ligament (ACL) doesn’t have to mean the end of an athlete’s career. Advances in surgical treatment have made it possible for many athletes to return to their former level of play. They may just have to sit on the sidelines for six to eight months.

There are several choices in ACL surgery. One is to replace the torn ligament with part of the patellar tendon and an attached piece of bone from the tibia (the shinbone). Bone-to-bone contact gives faster healing. The second is to use a strip of tendon from the hamstrings to reconstruct the torn ACL.

Many doctors favor the hamstring method. It gives good graft strength and only requires a small incision. Unlike the patellar tendon method, the hamstring graft doesn’t normally come with connected bone plug. Doctors in Italy tried a new method of grafting. They used the hamstrings tendon with an added piece of bone. The graft they used is called a semitendinosus graft with a bone block (STB).

STB gives a faster bone-to-bone healing much like the method using the patellar tendon graft with bone plug. It also has a low rate of donor-site problems. Just how well does it work?

Eighty active athletes with an ACL injury were included. All participants got their muscle strength back within a year. They could return to high-risk sports activities by six to eight months. There were some cases of pain with kneeling and numbness from nerve damage.

Even with good motion and strength, some athletes were unable to return to their preinjury level of play. The authors think this might be due to the fear of a new injury. Some athletes changed their focus and moved away from sports participation.

This newer method of ACL grafting gives good knee stability. Patients generally regain strength and can often return to active sports. And patient satisfaction is high. The authors conclude that their STB method of reconstructing a torn ACL has merit.