News Category: Knee

Total knee replacements (TKRs) are designed to restore normal knee function. However, there’s one slight problem. TKRs today rarely allow patients to bend the knee beyond 120 degrees. Normal knee flexion is around 120 degrees. Most people have more than 120. In some people, the knee is actually able to bend as much as 160 degrees.

Knee flexion is increased by a movement called femoral rollback. This gliding motion occurs inside the knee joint as the upper leg bone (femur) rolls backward on the lower leg bone (tibia). Femoral rollback improves muscle function around the knee and helps increase knee flexion. It does this by keeping knee structures from getting pinched at greater angles of flexion.

Researchers are asking, “What’s the best way to get full range of knee flexion?” This study looked at the effect of the posterior cruciate ligament (PCL) on femoral rollback. The PCL is a key ligament inside the knee joint. A robotic testing system was used to measure femoral roll back after a TKR. Cadavers (human bodies preserved for study) were used for the study. The knee joint was tested with a PCL and again after the PCL was cut.

The authors report that femoral rollback occurs at different times in different degrees for the entire range of knee flexion. This is true for the normal knee as well as the knee with a TKR. Femoral rollback in a TKR is increased when the PCL is intact. However, the authors found that normal knee motion needs more than just a healthy PCL. The ligament must be well balanced and the tibia must rotate inward during knee flexion. The other soft tissues that allow or control tibial rotation are important, too.

Improving the design of TKRs is a goal of this research. The hope is to consistently increase knee flexion beyond 120 degrees. Improving posterior femoral translation may be the key to this result. TKRs of the future will need to restore normal joint motion with and without the PCL for this to happen.

Imagine that after years of painful knee symptoms, you have a total knee replacement (TKR). Ahhh, relief at last! But within a couple of months, the knee starts making a loud “clunk” every time you straighten it from a fully bent position.

The problem could be the patellar clunk syndrome. This syndrome occurs when a fibrous nodule develops on the back of the kneecap (patella). When the knee bends, this fibrous bump gets trapped within a notch in the surface of the thighbone (femur). (The bottom of the femur meets the top of the tibia in the lower leg to form the knee joint.) As the knee straightens, the bump moves out of the notch. Knee pain and a “crunching” sound occur as the patella moves against the femur. At the same time, a “clunk” is usually heard.

Doctors think that two factors cause the patellar clunk syndrome: the design of the joint implant (on the femoral side) and the patient’s knee-flexion angle. Generally, only patients with more than average knee flexion get this problem.

The authors of this study report this may be a problem of the past. The newest implant design offers a longer and deeper groove on the back of the kneecap. With this new implant, it takes much more knee flexion for the patella to drop into the notch in the surface of the femur. The chances of getting a nodule and a clunk are much lower with the design of the new implant.

TKRs have gone through many design changes over the years. Starting in 1978, there have been a series of changes that affect the kneecap. The second generation of implants was released in 1989. Another design made its way onto the market in 1995. The newest implant and next generation appears to have eliminated patellar clunk syndrome.

Patients with arthritis sometimes have both knees replaced at the same time. This is called a bilateral operation. In general, there are no more major problems than when only one knee is replaced. However, doctors are concerned by how much blood is lost when a patient has both knees replaced in one operation.

New ways to save blood and donate your own blood before surgery are in use. The program is called blood management. The goal is to reduce blood loss and the need for transfusions. Transfusions are generally safe, but using someone else’s blood does carry the possibility of transferring diseases such as HIV and hepatitis.

One way that blood loss can be limited is with the cell saver system. It collects the patient’s blood and gives it back during the operation. This is called blood recovery. Yet even with this method, patients may have hidden blood loss that can’t be measured. When this happens, a blood transfusion may be needed during surgery. To ensure that enough blood is available, the patient can predonate his or her own blood (autogenic blood) or receive a donation from someone else (allogenic blood).

Doctors can’t tell how much blood a patient will lose during a bilateral total knee replacement. The authors conclude that blood recovery is a good way to manage blood loss during this operation. The patient can still donate one or two units of blood for personal use. Combining the cell saver system with autogenic blood donation reduces the volume of blood that would otherwise need to be donated by the patient.

Viscosupplementation is a relatively new treatment for knee osteoarthritis (OA). When the pain of knee OA doesn’t go away with conservative treatments or even steroid injections, injections using a special ingredient called hylan G-F 20 often help. These treatments involve removing synovial fluid from within the knee joint and replacing it with hylan. The hylan acts like hyaluronan, which is normally found in synovial fluid and helps lubricate and cushion the cartilage. Most knees with OA have low levels of hyaluronan.

Knee lavage, on the other hand, is a treatment for knee OA that has been around for some time. Lavage involves injecting saline into the joint to “wash” it. Doctors think that lavage works by removing debris and other factors that can cause irritation and inflammation. Lavage also seems to help relieve the pain of knee OA.

These doctors tested whether lavage and hylan treatments worked well together, and for which patients. Patients were allowed to pick which treatment they wanted. The first group of patients got knee lavage in the first week, followed by an injection of hylan each of the next three weeks. The second group only got the three injections of hylan over three weeks. The results were followed over an average of one year. The outcome was considered successful when pain was cut in half and patients rated the outcome as good or excellent.

In group one (lavage plus treatment), the outcome was successful in almost 80 percent of patients. In group two, only 54 percent of patients had a successful outcome. However, the authors note that patients with the worst OA saw much less improvement in both groups — 58 percent in group one and 36 percent in group two.

The authors suggest that the treatments of lavage and hylan be combined unless MRI findings show especially bad OA or certain degenerative changes in the knee. They emphasize that proper technique is needed for a good outcome and that this method of treatment is not helpful when total knee replacement is obviously necessary.

The anterior cruciate ligament (ACL) of the knee is up to eight times more likely to be injured in women athletes than in men. No one knows exactly why this is true, although many factors have been tested–everything from increased joint laxity and weaker thigh muscles, to hormones and inadequate shoes. Many of these factors may be involved, but none has been identified as the primary cause of increased ACL injuries in women.

These authors tested the role of the hip muscles. Nine male and nine female Division I college athletes did single-leg squats. Single-leg squats were chosen because the movement is common in sports and it requires body control on a fixed leg. Electrodes over the thigh muscles were used to measure the athletes’ muscle activation, while cameras recorded the movements.

There was a great deal of difference in the way men and women did the squats. Women tended to further bend their ankles, tilt their feet inward, bend at the hips, and rotate the hips out. Women also tended to start and end the squat a bit bowlegged, which the men never did. The women also activated their quadriceps muscles (in the front of the thigh) more than the men.

The authors thought the results suggest that women have a harder time controlling the muscles of the hips, so they rely more on the quadriceps muscles to control the knee. This puts the knee in a less stable position, which could help explain why women are more prone to ACL injuries.

The results were not conclusive, but the authors believe they are onto something. They are doing follow-up studies with more athletes to determine how differences in hip muscles affect women’s chances of ACL injury.

Reconstruction of the anterior cruciate ligament (ACL) of the knee is a tricky business. Many factors affect the success of the surgery. One factor is how well the graft material attaches to the bone after surgery. However, there is limited information on when this happens or how surgeons can tell when it occurs.

These doctors from Japan followed the way hamstring tendon grafts attached to the bone after arthroscopic surgery to repair a torn ACL. They studied 64 patients, most of whom had injured their ACL during sports activities. All surgeries were done in the same way and by the same surgeon. The authors used MRI scans and physical exams to figure out how well the graft had attached. These tests were done frequently, from two weeks to two years after surgery.

Arthroscopy (in which a tiny camera is inserted into the joint) and X-rays using contrast dye were done at an average of two years after surgery to confirm how well the graft had attached. Almost all of the patients had good results from surgery. Two years later, 97 percent of patients were participating in their normal sports activities. About 90 percent had full range of motion of the knee.

Despite these good results, there were differences in knee stability and stiffness. The authors grouped patients into four different categories according to the way knee stability and strength had developed over the follow-up period. The authors used the test data to determine that one group of patients had early graft attachment, which allowed the best possible healing and rehabilitation. The authors think that one group may have had good attachment only on the tibia (the lower leg bone), but that still allowed a strong, stable knee to develop. The other two groups had poor or no graft attachment, resulting in stretched-out graft tendons–and less stable knees.

The authors note that certain findings from MRIs and physical exams can give doctors clues about how well the graft is attaching to bone. They recommend that patients who seem to show poor graft attachment should go more slowly through rehabilitation to give the graft more time to attach. The authors recommend further research on how to rehabilitate ACL grafts that are not attaching well to the bone.

This study shows that surgical treatment of one particular knee injury is worth it, even years later. Seventy-two patients were included in a study at the Steadman-Hawkins Sports Medicine Foundation in Vail, Colorado. All subjects had an injury of the articular cartilage in the knee. Articular cartilage is the smooth covering over the surface of the bone inside the knee joint. Articular cartilage allows the parts of the knee to glide smoothly during movement.

In all the patients, there were no torn ligaments or a damaged meniscus in the knee. However, the cartilage was torn all the way down to the bone. This is called a full-thickness tear. Everyone in the study was treated arthroscopically. This means the doctor didn’t cut the joint open. Instead, a long, slender tool called an arthroscope was inserted through small puncture holes in the skin. A tiny TV camera at the end of the scope allows the doctor to see the inside of the joint on a screen.
In this procedure, all defects in the cartilage are removed. A special tool called an awl is used to make holes in the bone around the edge of the healthy cartilage. This technique is called arthroscopic microfracture. Pain and swelling eventually decrease with this treatment. Activity level and function improve or at least stays the same. The authors report that patients under age 35 generally do better than patients over 35.

Even seven years after the surgery, 80 percent of the patients rated their results as “improved.” Most of the positive changes took place in the first year. Many patients continued to improve up to three years after the operation. The authors conclude that microfracture combined with rehab therapy gives the best results for full-thickness cartilage tears. Age is a factor that should be considered.

Most studies agree that using the patient’s own tissue to repair an anterior cruciate ligament (ACL) tear is the way to go. When the tendon is taken from patellar tendon in front of the knee, many in the medical world consider it the “gold standard.”

Despite the good results with this method, there are problems. Muscle weakness, pain, tendonitis, and kneecap fracture are just a few of the possible problems. Researchers are looking for a better way to repair the ACL with fewer complications. This study of ACL repair compares the use of two sources of tendon material in combination with a special way of adding stability to the knee, called iliotibial band tenodesis.

An autograft is tissue taken from the patient. Allograft is the term for tissue donated by someone else. A tenodesis is the use of a tendon from a muscle by moving one of its ends to a different place. In the case of iliotibial band tenodesis, the doctors use a portion of the iliotibial tract, a broad, fibrous band of tissue along the outside of the thigh. One end of the iliotibial band is cut and moved from the outside of the lower leg bone (tibia) to the outside of the thighbone (femur). The goal is to make the knee joint more stable. Moving the iliotibial tract above the joint helps keep the tibia from sliding or shifting forward.

Results were measured by asking patients questions about:

One of the ongoing mysteries of sports medicine is why women athletes suffer so many more anterior cruciate ligament (ACL) injuries than men. The ACL is a ligament in the knee that is commonly injured during stop-and-go running, cutting, and jumping during sports. Basketball, soccer, and volleyball players are especially prone to ACL tears. Recovery from ACL tears can be difficult. They sometimes end the sports careers of athletes. Women athletes would work hard to prevent ACL tears–if only they knew how.

These authors wanted to test the idea that women athletes can’t consciously activate the knee muscles to the same extent as men. Men and women basketball, volleyball, and soccer players from Division I athletic programs were recruited for the study. So were men and women athletes who bicycled, rowed, and ran. This group was included to see how the knee muscles worked in athletes who didn’t put such high demands on their ACLs.

All the athletes sat with their knees bent at 30 degrees and then again at 60 degrees. A machine put a certain amount of force on the outside of the foot. This mimics the forces on the knee when landing from a jump on one foot. Knee and leg movements and muscle activation were measured while the athletes were passive. Measurements were taken again while the athletes resisted the force with all their might.

Results showed that the women’s knees rotated much more than the men’s knees. Also, men increased their knee stiffness significantly more than women did when they were told to resist the force (218 percent for men compared to 178 percent for women). All athletes had less knee rotation when the knee was bent to 60 degrees. For the most part, athletes who took part in bicycling, rowing, and running had more knee rotation and less knee stiffness than the basketball, soccer, and volleyball players.

Surprisingly, the women basketball, soccer, and volleyball players showed the least amount of increase in knee stiffness between the passive and active tests. The women’s knee muscles seemed to be fully activated, but they could not generate the same increase in knee stiffness. The authors don’t know why this is true, but they believe this leads to less muscle protection around the knee and may play a role in why women have more ACL injuries.

Further research with more athletes is needed to make complete sense of this mystery. However, this study does point to some new directions for training and strengthening programs for women basketball, volleyball, and soccer players.

Injury to the proximal tibiofibular joint is rare, or perhaps just rarely reported. “Proximal” describes the place where the two bones of the lower leg (the tibia and the fibula) meet at the knee. This article reviews injuries at this joint.

There are strong ligaments around the joint to hold the bones together and reinforce the joint. Several different injuries can occur to disrupt this joint. One of the ligaments or muscles can be torn. The joint can be dislocated. Nerve tissue can be stretched or injured.

Some injuries are caused by trauma. Others occur without trauma or injury, such as when there is overall tissue looseness (called laxity). Two other risk factors increase the chances of a proximal tibiofibular injury.

When the knee is bent, one of the protective ligaments is more relaxed. A twisting force when the knee is in this position is more likely to cause injury than when the knee is straight. The natural shape and angle of the joint from birth can also increase the risk of injury.

Since this injury is rare, it can be easily missed. The symptoms include pain and a bump or swelling along the outside of the knee. Putting weight on the leg is painful, especially when climbing stairs. Some patients only have trouble during sports movements that require a sudden change in direction.

Doctors must sort out a tibiofibular injury from damage to the knee joint or soft tissues around the knee. A careful examination of the ankle, tibiofibular joint, and knee usually brings about a correct diagnosis. X-rays can give some extra information.

This condition may get better in children as they mature. For children, teens, and adults, treatment can include changing the way activities are done, using supportive straps, and doing muscle strengthening. For a chronic problem that doesn’t go away, surgery may be needed.

Total knee replacement surgery (called total knee arthroplasty, or TKA) is becoming quite common these days. New and improved designs for the implants make the TKA a good choice for many patients with knee pain. The new joint or implant is known as a prosthesis.

There are many different styles of knee prostheses. The basic surgery to remove the damaged or diseased joint and replace it with an implant is the same for all knee prostheses. However, there are some small differences.

One of these important differences has to do with the kneecap, or patella. The patella moves up and down over the front of the knee joint. This is called patellar tracking. Maintaining good patellar tracking after a TKA is the subject of this study.

A single orthopedic doctor used two methods to retain good patellar tracking. All patients got the same prosthesis. In one group, the fibrous tissue alongside the patella was severed (released). This band of tissue is called the lateral retinaculum (LR). Cutting the LR is thought to keep the kneecap from pulling too much to the outside edge of the knee.

A new method was used with the second group. Instead of cutting through the LR, it is instead “peeled” off the patella in a way that keeps the correct tracking pattern. Not cutting into the LR prevents bleeding. It also stops a painful snapping when the cut edge of the retinaculum passes over the bone underneath it.

Keeping the kneecap on track after a TKA may depend on the surgeon’s skill. Small changes in how the surgery is done may make a difference in the final result. LR release may be replaced by the peel method with the new prosthetic designs.

Loss of knee flexion can be a big problem after knee surgery or a knee injury. Loss of flexion is usually caused by scar tissue formation, called fibrosis. Fibrosis spreads over or replaces normal tissue during the healing process.

Fibrosis occurs most often after a knee fracture or injury to knee ligaments. Sometimes, the surgery to repair a torn ligament results in more loss of knee flexion. In some cases, the natural shape of the bones becomes flat or distorted from injury or disease. This can also cause a loss of knee flexion.

In this study, patients with loss of knee flexion had physical therapy (PT). The goal was to improve knee motion without further surgery or injury. If PT alone didn’t work, home mechanical therapy was added. A special machine was used to provide mechanical therapy. The program is called a patient-activated serial stretch (PASS). While sitting in a chair, the patient places a foot in a holder. The machine loads the knee through the foot using a hydraulic device. The patient controls the load and the stretching.

The device is used for 15 minutes, four to eight times each day. The knee is bent into full flexion for one to five minutes. Then the joint is straightened (extended) for the same amount of time. Finally, the knee is stretched back into full flexion again for another one to five minutes.

The authors report that patients using PASS regained knee flexion without further damaging tissue. When used often, this form of stretching seems easier on the knee joint. In cases where knee flexion hasn’t improved, patients may benefit from the use of mechanical therapy to regain functional range of motion.

The muscles and joints of our legs work together in complex ways that aren’t completely understood. Knee problems in particular can lead to problems in other joints or muscles. If the underlying knee problem is not treated, reinjury or further problems are likely.

These doctors report two cases of injuries to the vastus lateralis muscle located in the outer thigh. The vastus lateralis muscle is one of four muscles making up the quadriceps muscle of the thigh.

Both patients were injured while playing softball. Both patients went to a doctor for severe thigh pain, and both reported having generalized pain in the front of the knee for at least a year before their thigh injuries.

The type of pain they described in the front of the knee is called patellofemoral pain syndrome, or PFPS. This condition is common, especially among runners. It usually comes on slowly and causes low levels of knee pain, especially during activities such as going up and down stairs. PFPS may happen because of injury to the cartilage behind the kneecap or because the kneecap isn’t tracking correctly as the knee bends.

These doctors think changes caused by PFPS led to the muscle injury in these two patients. The quadriceps muscle attaches to the kneecap. The kneecap gives the quadriceps muscle a lever for added force. It is possible that the presence of PFPS lead to an imbalance in the quadriceps muscle, setting the stage for muscle injury.

Both patients responded well to treatment for the muscle strain. The authors conclude that it is important for doctors to look for possible underlying causes of knee strains.

Knee pain from arthritis is often the reason for having a knee joint replacement called total knee arthroplasty (TKA). The TKA reduces pain but at a price. The quadriceps muscle along the front of the thigh straightens the knee. Control of this muscle is reduced after TKA.

This problem can persist a year or more after surgery. Poor muscle performance has been linked with increased risk of falling, reduced walking speed, and difficulty getting up out of a chair.

Many studies have shown that a loss of knee extension is common after TKA. This study goes beyond that and looks at the cause for the decrease in muscle force after TKA. Rehab suggestions are offered.

The key problem is failure of voluntary activation. This means that the patient is trying hard to straighten the knee, but the muscle isn’t contracting fully. Pain, swelling, and joint damage may be part of the cause. However, simply reducing knee pain doesn’t improve muscle contraction.

This study shows the importance of special muscle training to get back full muscle force. Traditional exercises may not be enough for many patients. Electrical stimulation to the muscles and biofeedback for the patient are useful tools. The patient learns how to maximize muscle contraction.

According to these authors, decreasing knee pain with a TKA is not a good enough measure of success. Restoring full force during knee muscle contraction is important after TKA. The authors think restoring muscles to their full capacity may prevent falls and lengthen the life of the new knee implant.

When you turn 80 years old, you become an octogenarian. You may live another 10 or even 20 years! Studies show that on average people who reach 80 live another seven or eight years. At this stage of life, arthritis may affect the knees and hips, requiring joint replacement. More and more octogenarians are having total knee replacements. This makes it possible for researchers to study long-term results of joint implants in older adults.

A doctor at the Texas Bone and Joint Center looked at 110 patients who were 80 years or older. Everyone in the group had a total knee arthroplasty (TKA). After five years, 99 percent of the patients were still alive. The early results were good, with pain relief and improved motion for everyone.

Knee function after TKA is better in this age group compared to younger patients. There are several reasons for this. Older patients probably start out with more knee problems and are more likely to have other health problems. Thus, the improvements are measurably greater.

In octogenarians, the new joint implant holds up better with fewer problems than in younger patients. The authors of this study think low use and low demand on the TKA in octogenarians are the major reasons for the good results. However, 10 years after the operation, only 20 of the original patients were still alive.

The authors conclude that a standard TKA that lasts 10 to 15 years can be used in older adults. Newer, more expensive implants that are designed to last longer aren’t needed. Less use of the knee and the potential for dying within 10 years makes the use of newer, more costly designs unnecessary for this age group.

Most patients don’t think much about the design of their new knee joint replacement. But doctors give this much thought and study. These implants don’t last forever. The typically only last from 10 to 20 years. That’s why researchers are trying to find ways to make implants last longer.

The author of this report reviewed the results of 16 studies. Each study looked at the final outcome of knee replacement surgery, also called total knee arthroplasty (TKA). The hope is to find what makes an implant last without breaking down or coming loose.

Recent changes were made in the design of implants. A way to stabilize the implant from the backside of the joint was added. This improves stair climbing ability and increases range of motion. A metal backing was also added to help distribute the load more to the front of the lower leg bone (the tibia).

According to this study, these changes did not increase the life of the implant. Lower contact stress and reduced wear weren’t any lower. All implants lasted at least 10 years in all patients. This was true whether metal or polyethylene (manmade plastic) was used in the implant.

The author reports that these are short-term findings. No studies beyond 10 years were reported. Findings are fairly limited. For example, only one study comparing all-polyethylene with metal-backed implants was published. More studies are needed to find out which implant lasts the longest and why.

The kneecap (patella) has some important functions. One is to move up and down over the knee joint during motion. This is called patellar tracking. If the ligament along the outside edge of the patella is too tight, the kneecap gets off center. This can cause painful problems.

This tracking mechanism can get uneven when a knee joint is replaced. The procedure to replace the knee joint is called total knee arthroplasty (TKA). Doctors must be very careful when using a tourniquet during this operation. It has been shown that the pressure from the tourniquet can put a strain on the patellar ligament.

Likewise, the tourniquet can put tension on the quadriceps (thigh) muscle where it attaches to the patella. Too much pressure can be a problem. When the tourniquet is released, the patella may pull too far to the side, affecting patellar tracking.

In this study, researchers looked at the stress on patellar tracking during TKA. Two different ways to perform the operation were compared. In one method, the incision is made alongside the kneecap (through the patellar ligament). This is called the parapatellar approach.

In the other method, the opening to the knee is made above the kneecap (through the quadriceps muscle). This method is called the midvastus approach. When the tourniquet was taken off after this surgery, stress in the outer portion of the knee went down. The authors conclude that patellar tracking must be rechecked after deflation of the tourniquet when a midvastus incision is made for TKA.

Stress on the patellar ligament was much less after the parapatellar approach. This was true for all angles of knee flexion. The authors emphasize that tracking of the kneecap should be rechecked after releasing the tourniquet, regardless of the surgical method used.

How do you know if a total knee replacement is successful? Is it measured by the amount of knee range of motion (ROM)? Function? Patient satisfaction and quality of life? Actually, researchers use all three measures. ROM may be the most important because it affects the patient’s ability to use the knee.

This study looks at the role of knee ROM one year after knee replacement. The procedure used to replace the knee joint is called total knee arthroplasty (TKA). Patient satisfaction and quality of life (QOL) are also included as important measures of success.

Patients in 12 centers from the United States, United Kingdom, and Australia were included. This was the first TKA for each patient. Everyone had knee osteoarthritis and received the same type of replacement implant.

Studies show that people use 45 to 105 degrees of knee flexion for daily activities. The authors report that patients unable to bend their knee more than 95 degrees have worse function than those patients who can flex more than 95 degrees.

In this study, however, patient satisfaction and QOL are based on the ability to use the knee. Actual knee flexion didn’t seem to matter as much. Patients with problems in the other knee or the hip on the same side had less knee motion in the TKA knee. Notably, patients with a stiff knee can compensate better than those with a stiff hip.

The authors conclude that success after a TKA can be based on the patient’s report. Actual knee flexion doesn’t seem to be as important as getting around during daily activities.

Total knee joint replacements have two parts: the femoral component and the tibial component. The femoral part fits up into the thighbone and forms the upper half of the new joint. The tibial implant has a plate that meets the femoral side and a stem to hold it into the tibia (lower leg bone).

This study compared the use of full versus partial cement on the tibial component. Just the underside of the plate is covered with cement in a partial, or surface, cement approach. Full cement covers the plate and the stem as it fits into the long shaft of the tibia.

One other variable was added in this study. Two different shapes of tibial stems were compared using just surface cement. Some of the tibial stems cemented in place were I-shaped, while others were more rectanglular, or cruciate, in shape.

Tibial bones from cadavers (human bodies preserved for study) were used. Today’s modern equipment and computer systems make it possible to measure the effect of stress on the implant. The bone and tibial implant were exposed to 6000 cycles of stress. The machines put three times the average body weight on the implant, as if the person were standing on the leg during walking.

The authors found that the location of the cement isn’t as important as the amount of cement used. Tiny motion sensors measured any movement of the implant inside the tibia. There is no difference in implant motion when the depth of cement is 3 to 5 mm. There was also no difference in motion between the I-beam and cruciate stem with surface cement.

The authors conclude that since knee joint replacements may have to be revised or replaced, surface cement should be used. With less cement, the implant may come out more easily if it needs to be removed. Less bone damage improves the chances of success for a second implant.

Chances are you know someone who’s had an anterior cruciate ligament (ACL) tear. The ACL is one of two ligaments that cross inside the knee joint. The second ligament is called the posterior cruciate ligament (PCL).

ACL tears are far more common than PCL tears. Both types of tears can cause major problems. Treatment decisions are based on understanding of the injury and what can happen years later. The goal of this study was to find out if a PCL tear increases the risk of cartilage damage in the same ways as damage to other ligaments.

Doctors in Germany studied 181 patients with PCL injury that was not surgically repaired. Two areas of cartilage (inside the knee joint and behind the kneecap) were viewed with an arthroscope. An arthroscope is a tool used by doctors to look and work inside the joint.

X-rays showed that changes in the cartilage are present within a year after a PCL tear. The two injuries together (PCL tear and cartilage damage) also result in early arthritis. Even more problems occur if there is an old injury of the meniscus, the protective cushion between the knee joint. The authors of this study suggest that surgery to repair a torn PCL may be needed to prevent worse damage to the knee.

It appears from this study that two-thirds of all patients with a torn and unrepaired PCL will develop damage to the knee joint cartilage. Half of the changes occur on the inside edge of the knee joint. Another third affect the kneecap or patella. A smaller number cause damage to the outside edge of the knee joint.

The authors of this study hope the new understanding of PCL tears and their effect on knees will help doctors make better treatment decisions. The risk of joint damage increases when the ligament isn’t repaired. The outcome is worse if the meniscus was torn previously. For these reasons, early surgery to repair a torn PCL may be necessary.