News Category: Knee

If you injure your anterior cruciate ligament (ACL) in Maine do you get the same treatment and advice as if you injure it in Arizona? Researchers routinely survey doctors across the natio about their practices for various conditions and illnesses. ACL injury is one of those conditions.

Surveys are updated every five years or so to see if anything has changed. This study looked at the use of bracing for patients after ACL surgery and for patients with an ACL injury who don’t have surgery.

Ongoing research still can’t show enough evidence to support the use of bracing for ACL injuries. And managed care has decreased payment for bracing. Many patients are paying for the braces out of their own pockets. For these and other reasons, fewer doctors are prescribing braces after surgery.

Doctors are still bracing patients with an unstable knee who don’t have it fixed. In these cases, doctors are worried about damage to the joint because of the injured ligament. A torn knee ligament that isn’t repaired or braced often leads to early knee arthritis. Many doctors think it’s worth it to spend the money bracing if there’s any chance these problems can be prevented.

Most doctors decide whether to brace and which brace to use based on the patient’s sport or activity level. Overall they are using bracing for ACL injuries and after ACL surgery less often. This is true in every geographical region in the United States.

People in need of a new knee joint often wonder how far their knee will bend after surgery. Researchers have new insights. They found that a major influence on how far you can bend your knee after knee joint replacement is the amount of knee bend you have before surgery.

These researchers studied 4,727 knees before, during, and after knee joint replacement. They measured the amount of bend (flexion) in each patient at six months and one, three, five, and seven years after knee replacement. Increases in knee motion stopped after three years. This finding supports results from other studies.

No matter what kind of arthritis the patient had or how badly the knee was lined up, the amount of knee flexion before surgery was still the number one way to tell how much knee bend would be present after the surgery. Patients with less than 90 degrees of knee bend before surgery were more likely to have a poor result.

Know that if you’re in need of a new knee joint, you have an edge in telling how far your knee will bend after surgery. This research makes it clear. A powerful predictor of how far a knee will bend after knee joint replacement depends on how far the knee bends before surgery.

Both steroid and hyaluronic acid (HA) shots are commonly used to treat the pain of knee osteoarthritis (OA). Each has been well tested. But few studies have compared the two directly.

This study tested these shots in 50 patients with painful knee OA. One group got a single steroid injection in the painful knee joint, with the possibility of having one more if needed. (About half of the group received a second injection.) The other group got three HA shots over three weeks.

The patients’ pain and knee function were measured using three different scales before treatment and again three and six months after treatment. Overall, pain and function scores improved modestly in both groups. However, women showed much less improvement than men for both types of injections. Women’s poor outcomes didn’t seem to be related to age or to more severe OA. The authors recommend further research to help understand this result, which could have major consequences for how doctors treat knee OA in women.

The authors found the results of the HA unimpressive, especially considering that it was 100 times more expensive than the steroid. The steroid group got similar results with fewer shots, which means they had less pain and less risk of infection. The authors recommend that steroid shots should be the first-line injection to treat the pain of knee OA.

What do you do if you need a new knee joint, but you’re too young? Tibial osteotomy may be one option. The tibia is the shinbone in the lower leg. In a tibial osteotomy, a wedge of bone is taken out and the bone realigned. The goal is to change the areas of stress on the joint during weight bearing.

During the healing process the bone must be held in place. There are many ways to do this. Research has not been done to show which method is best. This study compares two commonly used devices: a plate with screws and a blade staple. The plate fits over the freshly cut bone and is screwed in place. The blade staple is pointed on both ends so it can be tapped in place to secure the bone.

Synthetic (manmade) bones were used to test both types of fixation devices. A machine put each bone to the test by stressing it over and over. Compression and tension loads similar to normal walking were applied. The plate and staple were subjected to more than 200,000 cycles of motion. This is equal to the number of walking steps taken by the average patient before healing is complete.

The researchers found the plate fixation lasted past 200,000 cycles. The blade staple did not. Only one of the nine blade staples lasted the full distance.

Holding the healing bone together after an osteotomy is important. The patient needs early knee motion without disturbing the new joint alignment. A secure fix at the osteotomy site will help healing. The authors advise using a plate and screws instead of a blade staple.

Having a total knee replacement? Expect to be given an anticoagulant to prevent blood clots. Most doctors start patients on warfarin (a drug that slows blood clots) either the night before or the night after joint replacement surgery. Patients usually continue this drug for six weeks after the operation.

There are risks with taking this drug. Infection and poor wound healing are the most common problems. Stomach upset and gastro-intestinal (GI) bleeding are also possible. Are the side effects from the drug worse than getting a blood clot?

Doctors at Kaiser Orthopedics in California studied this question. They reviewed the charts of a large number of patients. One group received warfarin after the operation. The other group didn’t get any preventive treatment — no drugs, compression devices, or special stockings.

Patient results were tracked for 90 days. No one died from a blood clot in either group. However, the group that received the preventive drug had twice as many problems as the group that didn’t. The biggest problem was areas of swelling under the wound, called wound hematomas.

Researchers in this study point out that some doctors are questioning the routine use of drugs to prevent blood clots after an operation. They suspect the drugs may do more harm than good. More research is needed to solve this question before completely stopping the practice.

Has pain from osteoarthritis of the knee gotten you down? Tried everything? Doctors report that hyaluronate (HA) therapy is a safe and effective treatment. HA is injected into the knee joint when drug or other therapies haven’t worked.

HA mimics a substance normally found in the joint. It helps keep the joint moving smoothly. In the past 15 years, about 10 million injections have been given worldwide. The Food and Drug Administration (FDA) has approved three types of HA for use with osteoarthritis.

Studies such as this one are trying to find out if HA is safe for use. There are reports of knee pain and swelling after injection. Usually problems occur after a second or third injection. The symptoms often go away without treatment. In rare cases, an allergic reaction or more serious problem develops.

The authors of this review report that HA is a good treatment option for some patients. Doctors may want to use HA in cases of drug failure or sensitivity to drugs. With three different HA products available, more studies are needed to compare the safety and effectiveness of each one.

A torn meniscus in the knee is the most common knee injury in athletes. But athletes are not the only ones who suffer meniscal injuries. Two-thirds of all meniscal tears occur outside the sports arena, in nonathletes.

For patients with a torn meniscus, surgery is often needed to take out the piece of injured tissue. The doctor does this with an arthroscope. This tool allows the surgeon to enter the joint with only a small puncture hole, rather than using an open incision. Some patients have knee swelling, pain, and loss of motion after the operation. Physical therapy has been shown to help patients recover faster. Some studies suggest that exercise programs may be helpful for muscle weakness after a meniscectomy.

This study looked at two groups of patients early after a meniscectomy. Both groups were given written and verbal directions. Group one had six weeks of physical therapy, three times a week. Group two had only a home program without a physical therapist to guide them.

Patients were selected from a wide range of clinics and doctors in London, England. The researchers measured knee range of motion, knee function, and patients’ quality of life. They also looked at how long it took for each patient to return to work. Patients were measured four days after the operation and again six weeks later.

There were no differences in results for the two groups. The authors conclude when a partial meniscectomy is done without problems, physical therapy is not needed afterward.

A torn anterior cruciate ligament (ACL) in the knee can start a chain reaction of problems in that knee and leg. Recent research has suggested that an ACL injury can also cause problems in the other leg. Somehow a neurological response called the gamma loop becomes interrupted. The gamma loop controls normal muscle tension and assists in muscle activation–in this case, in the quadriceps muscles in the thigh.

These authors studied quadriceps strength in two groups of people. One group had a torn ACL, and one group had healthy knees. The uninjured leg was tested in the group with the torn ACL. Quadriceps strength was tested. Then the subjects went through 20 minutes of vibrations to the leg. Vibrations are known to interfere with the gamma loop, causing decreased strength. As expected, the healthy group showed decreased strength after vibration. But the group with injured ACLs had no reduction in strength, a clear sign that the gamma loop was not working properly.

No one is sure why the quadriceps in the opposite leg would be affected by an ACL tear. These authors suggest ways that nerve signals from the injured ACL could be applied to both legs by the nervous system. They recommend that larger studies be done to support these findings. Understanding how the body reacts to ACL tears would help doctors and therapists develop more effective rehabilitation plans for patients who have a torn ACL.

Knee joint replacements aren’t just for adults. Children with rheumatoid arthritis can have disabling knee problems. A joint replacement may be a good treatment option. This option is so good, some children have both knees replaced.

A study from the Mayo Clinic in Rochester, Minnesota, reports the results of knee replacements in children. Twenty-five knees were replaced in 13 children with rheumatoid arthritis. The patients were all under the age of 20.

Doctors don’t usually recommend knee implants for children. They’re concerned that the implant won’t last. They don’t want children to have multiple operations before mid-life. Things are changing, though, because many studies show good results (in adults) with today’s modern knee replacements.

The authors of this study looked at pain and function as measures of success. Before the operation, some of the children couldn’t even walk, while others could only walk indoors or for short distances outside. After surgery, only one patient had to use a wheelchair. All others could walk varying distances.

Pain was lower after the knee replacement, but range of motion was not restored. The loss of motion caused many other problems. The doctors think this is true because the soft tissues around the joint are also affected by the arthritis. They may have become too damaged for the joint replacement to help.

The authors conclude that joint replacement is an option for children with rheumatoid arthritis. They advise trying to save the joint first with every other treatment possible. Parents and patients can expect less pain and improved quality of life, but motion may not be restored.

When osteoarthritis affects the knee, uneven wear and tear can occur. One side of the joint can wear down more than the other. The knee may angle to one side, causing either a knock-kneed (valgus) or bow-legged (varus) problem. A valgus knee puts more pressure on the inside edge of the knee. A varus knee puts a greater load on the outside. This transfer of load can actually make the arthritis worse.

Someone who is young and active with arthritis only on one side of the knee may not want or need to have the entire joint replaced. Treatment options include removing a piece of the thighbone just above the knee (femoral osteotomy), replacing just one side of the knee joint (partial knee replacement), or replacing the entire knee joint (total knee replacement).

Doctors try to choose the treatment that will save the joint for as long as possible. Sometimes an osteotomy is the best short-term option, but a joint replacement is needed later. This study reviews the results of 11 knee joint replacements in nine patients who had a past femoral osteotomy.

Most of the patients (seven out of 11) had excellent to good results. The success was based on improved range of motion, decreased pain, better function, and better alignment of the knee. The four patients who only had a fair result had knee pain or an unstable knee.

The authors make several summary statements:

When a knee joint has been fused in place, doctors can sometimes convert the fusion and restore the hinge motion at the knee by implanting a new knee joint. The authors of this study review 36 cases of fused-knee conversion. Most of the patients were young (ranging from 23 to 58) and had a fused knee for many years.

The study took place in Korea, where childhood tuberculous arthritis is more common. More than half the patients studied were in this category. The rest had infectious arthritis. Some knees had fused naturally, while others were fused surgically.

The joint replacement used in this group of patients was different from the implant normally recommended. A constrained total knee is advised when collateral ligaments along the sides of the knee are absent or weak. However, doctors at the Joint Replacement Center of Korea used a nonconstrained, posterior stabilized total knee replacement.

Results were good. Sixty-one percent of all patients were free from pain, and the rest noted only mild pain after a long walk. The knees were stable, and all patients were pleased with the result. They all said they would do it again if given the choice.

There were some problems with muscle weakness and skin infections. The authors think that even with these problems, total knee replacement in fused knees is a good idea. More than one kind of joint implant can be used.

A total knee replacement (TKR) is a common way to stop the pain and loss of motion from arthritis or other conditions affecting the knee. Occasionally problems occur, and the leg has to be removed or amputated. The loss of limb isn’t always related to the TKR. Other problems such as tumors or poor circulation are sometimes at fault.

How often does this happen? Until recently the answer to this question was unknown. Doctors at the Mayo Clinic read the charts of over 18,000 patients from the last 30 years. They report that 0.36 percent of the patients receiving a new knee joint later had the leg amputated above the knee.

The amputations were done an average of eight years after the knee replacement procedure. For some patients, removing the leg had to be done as early as eight days afterward. For another patient, it wasn’t until almost 24 years later.

Most of the amputations (nearly 65 percent) were for causes other than the TKR. Only 25 of the 18,443 patients had the amputation for reasons directly linked to the TKR.

When a TKR fails, the doctor can usually revise the implant in a second operation. But when chronic infection sets in or severe bone loss occurs, the leg may have to be removed. Amputation is always a last resort. And the results of this large study show that amputation after TKR doesn’t happen very often.

A total knee replacement can help people with painful knees walk and do other activities with greater ease. But walking can put uneven forces on the new joint implant, causing wear and tear. The joint replacement can even fail altogether.

One major factor on implant wear and tear is the way the joint is placed in the knee. Lining up the implant with the bones and soft tissue is very important. Poor alignment is probably the number one cause of uneven wear.

Designing and making a long-lasting implant is the focus of current research. Researchers at the Orthopedic Research Labs in Cleveland, Ohio, studied four total knee implants. Only the bottom half of the joint was studied. This half of the implant is inserted into the lower leg bone (tibia). The scientists were interested in stress on the tibial implant during the toe-off phase of walking.

The authors found that implants with matching edges limit contact stress during walking. However, with this design, rotation is limited. As a result, the torque, or twist, is increased where the implant meets the bone. The chance that the joint implant will loosen increased with this type of implant.

Less conforming implants allow for more rotation. However, they showed increased stress on the edges of the implant. The stress was even worse if the muscles weren’t in balance. Surgeons attempt to balance the muscles and soft tissues during surgery because uneven pulling of the muscles is enough to cause uneven wear and tear.

The results of this study give design engineers information for implant improvement. Managing contact stress is an important key to solving the problem of damage patterns to the tibial insert.

More and more people are having total knee replacements (TKRs). The demand for new joints is pushing the market. Companies making joint implants are working with doctors to improve product design. Wear is an important feature now that younger and more active patients are getting implants.

TKRs aren’t as good as the human knee. Motion is never quite the same. The stress on the new joint is also greater than on the human knee. These two factors typically result in greater wear and tear.

A moveable joint may offer some help. A moveable joint straightens and bends the knee, but it also slides and twists to mimic normal knee rotation. The moveable implant is called a rotating platform TKR. This new implant design might result in less wear and a lower chance of coming loose. Range of motion may be better, with improved motion of the kneecap.

This study looked at knee motion in healthy adults compared to motion in volunteers with knee pain who were waiting for a TKR. The results were compared to three million cycles of simulated motion in mechanized joint implants in a lab. This means that a machine moved the replacement implant through the motion. Three types of implants were tested: the fixed-bearing, rotate only platform, and translate-rotate platform.

The authors conclude that the new moveable implant designs are impressive, but that they aren’t really any better than the old fixed style of implant. There did not appear to be any difference in range of motion, function, or complications after surgery.

So far, the newer implants haven’t solved the old problems of contact stress and wear and tear on the knee joint replacement. More studies are needed to find a longer lasting implant.

There are no two ways about it: the knee joint is meant to rotate during motion. Studies show that as much as 12 degrees of knee rotation occur during everyday activities. And when total knee replacements (TKRs) don’t allow rotation, they may get loose and fail.

Constraint describes the fit where the top and bottom of a new knee joint meet. TKRs must have a balance between joint looseness (low constraint) and reduced motion (high constraint). Too much constraint limits the needed rotation. The design of the implant has a lot to do with how much constraint is present.

Implants have different designs for a reason. For example, some implants are made for patients who still have the posterior cruciate ligament (PCL) in place. The PCL connects the tibia and femur. It is a key stabilizer of the knee. The implant must fit around the PCL, which means that less knee rotation can occur.

Implants with closely matching halves (top half and bottom half fit together well) have more resistance to rotation. TKRs that don’t match as well have less resistance and more rotation. Another cause of decreased motion is called box-post impingement. In this case, the side walls of the upper half of the implant come in contact with the central post of the lower half of the implant. The pinching causes increased constraint (less rotation).

In this study, two kinds of TKRs were examined in the lab. The goal was to find out how much rotation is limited by the design of two different knee implants. The bottom half of each implant (called the tibial component) was attached to a special table. During movement, rotation of the top half (the femoral component) over the tibia wasn’t stopped.

A repeated load of 450 pounds was applied to each implant. The load was kept steady while rotating the joint. Details of how each implant responded to the forces are reported. The authors determined that rotation of a TKR is a key factor in the function and stability of the joint.

The researchers found that small changes in rotation can more than double the force on the implant, depending on its design. Current implant designs give a trade-off. Implants with less constraint may allow for more knee motion, but this can lead to extra wear that causes the implant to break down earlier. High constraint implants provide better stability, but the forces that happen with knee motion (especially rotation) can take a toll on the spot where the implant is fixed inside the bone. When this happens, the fit of the implant can loosen, leading to problems and the possibility of needing another surgery.

It’s true that exercise after knee replacement surgery is important. But can you do these exercises on your own or do you need a clinic-based program? A group of researchers in Canada studied this question.

They divided 160 patients into two groups. They were all knee patients who had the meniscus removed or an anterior cruciate ligament (ACL) repair. One group had a clinic-based rehab program. The other group followed a home-based exercise program. The home group was monitored by telephone calls from a physical therapist. All patients had a total knee replacement and did the same exercises.

There weren’t any differences between the two groups. Results were the same at 12 weeks and at one year after surgery. Researchers looked at pain levels, walking ability, range of motion, and number of stairs climbed in 30 seconds. The same findings have been reported for other patients.

Not everyone needs physical therapy after a total knee replacement. Home exercise programs may be a good plan. A physical therapist can set up the program and follow the patient by phone. This gives the patient a level of care after the operation, but it limits the number of visits to a clinic.

Studies are needed to show which patients need a clinic-based rehab program from the start. The authors think certain psychosocial or other factors may help point out patients who need more supervision during rehab.

Replacing a painful knee with a new knee joint may not be the end of a patient’s problems. Particles from the implant can flake off and end up in the joint lining. The body then sets off an immune response that can cause bone loss and loosening of the implant.

The build-up of particles from wear and tear on the implant is one of the most important factors in how long an implant will last. Researchers must think about this as implant design is changed or improved. A study of knee joint fluid (synovial fluid) from 17 patients with no problems after knee replacement offers some useful information.

Synovial fluid was collected one year after surgery. All of the patients had a joint that was working quite well. Half of the patients had an older kind of implant (posterior stabilized) and half had a newer type (medial pivot). The researchers found that the size and shape of the particles didn’t make a difference. It’s the total number of particles that can bring on bone changes and implant loosening. And the medial pivot implant had fewer wear particles than the posterior-stabilized model.

Future studies are needed to see what if any effect early particle wear has on how long the implant lasts. The authors think it’s important to look at implant wear in new joint designs before they are used in many patients. Early studies like this help compare older implant wear to the newer, updated designs.

Not all total knee replacements (TKRs) are alike. Studies to compare them are ongoing. Tests done in the lab measure the effect of muscles, tendons, and ligaments on joint implants. This gives scientists information about joint laxity (looseness) and stability. Tests to measure the wear and tear on joint implantss are also done this way.

In this report, the authors look at how and why testing implants in the lab is not the same as testing them in human knees. Even so, they say that there is value in knowing what the joint can and can’t do before putting it in a human knee. This report also reviews many of the studies on TKRs done by others. Included are comparisons of different machines used in the lab to move the joint implant.

Researchers have only begun to scratch the surface in studying TKRs. There are many factors to measure and compare. Besides comparing one implant to another, scientists also look at many other issues. For example, the joint can be tested at extreme motions or with different muscle forces. Changing the tightness of ligaments and testing during activity rather than at rest are just a few of the other conditions tested.

The authors conclude by saying that the way a joint moves depends on several factors. These include the shape of the joint surfaces, how much friction is created, and the overall design of the TKR.

Senior citizens in the United States, Asia, and the Middle East agree on at least one thing. After having a knee joint replaced, they all know that bending the knee fully is the key to many, many daily activities. Getting a new knee joint isn’t enough. Full knee flexion is also needed.

Researchers at the Biomotion Foundation in Palm Beach, Florida, are doing their part to help seniors with this problem. They studied 121 patients with 16 different types of joint replacements. Fluoroscopy, a special type of X-ray, was used to show the patients’ knee motion on a TV screen.

The researchers found that there is more knee flexion when the thighbone (femur) rests more toward the back of the lower leg bone (the tibia). This position is called posterior femoral position.

The type of implant and its shape decide this position. Some implants allow the femur to move freely forward and back during knee flexion. Others push the femur forward during flexion. One implant forces the femur backward during knee flexion. This is the posterior-stabilized arthroplasty. The posterior-stabilized implant generally gives patients the most knee flexion.

The authors conclude that doctors’ surgical skill and methods may not be the only factors in getting knee flexion back after a total knee joint replacement. It seems that the implant design is also linked to how much knee flexion patients gain.

Many doctors are busy in the operating room fitting patients with brand new knee joints. At the same time, doctors at the Rocky Mountain Musculoskeletal Research Laboratory in Denver, Colorado, are studying the motion of these new knees.

Doctors and engineers are working together to compare normal knee movement with the motion of a total knee joint replacement. They also compare joint implants to one another. The goal is to find ways to mimic normal knee motion in the implants. Younger patients with early knee replacements need the implant to last 20 years or more. Uneven wear, knee laxity (looseness), and loss of full motion can cause implant failure.

In this study, two types of total knee replacements were studied. Motion during walking and deep knee bends were measured using high-frequency video fluoroscopy. This technique produces video X-rays that can be viewed on a TV screen. Normal knee motion is recorded during actual movement using fluoroscopy and a computer program. This study is the first to show contact points between the femur and tibia in three dimensions.

The researchers looked at contact points between the the tibia and femur bones of the knee. They analyzed the sliding and gliding motions of the knee implants and noticed when the bones separated without touching. Notably, the implant sometimes moved in an opposite pattern from a normal knee. This is called paradoxical movement. The authors think this may be a possible cause of implant failure and should be studied further.