News Category: Knee

Injury to cartilage in the knee, called the meniscus, is the most common reason for knee surgery. The meniscus on the inside edge of the joint is the medial meniscus. Medial meniscus tears can cause painful popping and swelling. The knee joint can get stuck or locked in one position.

Sometimes what looks like a medial meniscus tear turns out to be something else that doesn’t need surgery. This is a report of three such cases. All three patients had a history and symptoms just like the doctor would see with a medial meniscus injury. The three patients injured their knees in various ways. One 24-year-old postal service worker fell from a curb, twisting his left knee. A 24-year-old rugby player twisted his right knee during a game, and a 19-year-old hurt himself without knowing it while surfing. In each case the doctor used an arthroscope to look inside the joint. This device has a tiny TV camera on the end and helps make an accurate diagnosis.

The arthroscope showed that none of the three patients had a medial meniscus tear. The medial meniscus was just fine. Instead, all had a torn coronary ligament. The coronary ligament fits around each meniscus like an apron. It loosely holds the meniscus to the lower leg bone just below the meniscus. When torn or ruptured, this ligament heals by itself over a few months. Surgery isn’t needed unless something else is also damaged.

The authors point out that these cases show how damage to the coronary ligament in the knee can mimic a torn medial meniscus. It’s important to get the correct diagnosis to avoid unnecessary surgery.

What is causing so many women to have anterior cruciate ligament (ACL) injuries? Female athletes are at especially high risk. In fact, they are up to eight times more likely to have an ACL injury than men in the same sport. Soccer, basketball, and volleyball players injure the ACL most often.

The most obvious place to look is hormone levels. Women have far more estrogen and progesterone than men. Studies have shown estrogen changes the structure of the ACL. Most injuries occur when estrogen levels are the highest. This is usually during ovulation (days 10 to 14 of the menstrual cycle).

In this study researchers looked at the role of another hormone called relaxin. Relaxin is present throughout the body. It’s found most often in the breasts, uterus, and prostate. In pregnant women it loosens the ligaments around the groin and pelvic areas. It’s unclear what (if anything) it does to the ACL.

The level of relaxin was measured in ACL specimens. These were taken during total knee replacement surgery or ACL reconstruction. The ACL specimens came from four men and eight women. The level of relaxin was also measured in tissue samples collected from the uterus and from the knee meniscus. Uterine samples came from women having hysterectomies. Meniscal tissue came from patients having a total knee joint replacement.

The results of these three groups were compared. Relaxin was found in all uterine and ACL samples. Very little to no relaxin was found in the meniscal tissue. Young women had the highest amounts of relaxin. This shows that relaxin does bind to the ACL. How relaxin interacts with or changes the ACL remains unknown. This will be the subject of future studies.

Notice any changes in your balance as you get older? Are you less stable when reaching for objects? Afraid of falling? An exercise form called Tai Chi may be the answer. Tai Chi is an Asian mind-body exercise. Millions of Chinese have used this form of exercise for hundreds of years.

This study measured the effect of Tai Chi on knee joint sense of position and overall body balance. Two groups of older adults (60 years old and older) were tested. One group had practiced Tai Chi for at least three years. The control group had never done Tai Chi, but some were active in walking and stretching.

Tai Chi stresses exact joint positions, speed of movement, and directions. Each movement is repeated slowly and smoothly. When doing Tai Chi movements, the body is required to shift weight in all directions. Smooth, coordinated motion is the goal.

The researchers found adults practicing Tai Chi have much better sense of knee joint position. This is called proprioception. They have faster reaction times when leaning toward eight different target positions. When it comes to balance and falls, Tai Chi participants in this study were more stable than the control group.

The authors conclude Tai Chi practice can improve balance when shifting weight in different directions. By improving balance, the adult becomes more stable. Increased stability makes it easier to climb stairs, get on and off a bus, and perform other daily activities. Better stability also makes it less likely that you will lose your balance and fall.

Severe knee osteoarthritis (OA) often leads to pain and inactivity. Many people with this condition go on to have a knee joint replacement. But how different is their knee function from adults their own age who don’t have OA? This is the subject of a study from the University of Toronto. Physical therapists did the research.

Subjects were put into two groups. One group was scheduled for a total knee replacement (TKR) in one week. The other group never had knee OA or other knee problems. Each group was tested one time only. Measures used to compare the two groups included physical activity, function, strength, and endurance.

The researchers found many differences between the two groups. The TKR group climbed fewer stairs and shopped less often. They almost never joined in sports activities. Swimming and golf were the only sports activities listed for the TKR group. This is compared to cycling, kayaking, Tai Chi, rowing, and tennis for the other group. The TKR group also walked slower and took longer to complete all activities.

Women in the TKR group had less muscular strength and endurance compared to women in the group without OA. No difference was measured between the two groups for men in these areas. Both men and women in the TKR group said that physical activity wasn’t limited by pain as much by capacity. In other words, even when the pain was under control, they didn’t have enough strength or the ability to perform the activity.

The authors conclude that these findings support the need for different exercise programs for men and women with OA awaiting a TKR. A rehab program is needed before the joint is replaced. Improved physical capacity and function before TKR could improve the outcomes of surgery. Being fit and ready for surgery could improve patient’s ability to do normal tasks. This would give patients greater independence and less isolation. Patients might even be able to delay surgery and decrease how long it takes to recover.

The human knee can bend up to 160 degrees. This much motion allows us to easily do activities like getting in and out of the bathtub. It also makes it possible to squat down to check the line for a putt on the green while playing golf. Others use this amount of flexion to kneel or to squat while gardening, praying, or doing work tasks.

The knee rarely bends this far again after a knee joint replacement. The average patient has between 100 and 115 degrees of knee bend. Knee flexion after total knee replacement (TKR) rarely goes beyond 120 degrees. The reasons for this limit in motion are many and varied. Researchers report factors present before, during, and after the operation that can affect knee flexion. In this article, doctors from Harvard Medical School outline each of those factors and discuss them.

The doctors say that to increase knee flexion, we must first know how the healthy human knee works. Then limiting factors can be changed to mimic the normal knee. Three TKR implants on the market are designed to increase knee flexion. A total knee system is proposed as one solution. Every surface shape, angle, space is studied. So is how each of these factors changes as the knee flexes. The results are then put to use in these new and improved knee implants.

One way to test how well these new knee systems work is through the use of robots. The first such robotic studies are underway at the Massachusetts Institute of Technology (MIT). Engineers from MIT and doctors from Harvard Medical School are teaming up on this. They are studying all three implants. The results of this ongoing study will help guide future implant designs. Increasing knee flexion is the goal. The outcomes of this study will be reported here as the information is published.

Can a better knee joint replacement be designed? The author of this report thinks so. There is a problem getting full flexion after total knee replacement (TKR). A new implant design tries to address this issue. The high-flex knee implant gives better bend, but more bone must be taken off to do it. This is a problem if the patient needs another operation on the same knee later.

The high-flex design has been on the market for about five years. It’s the first knee to allow flexion up to 155 degrees. Other knee implants give patients 110 to 125 degrees of flexion. Daily activities such as walking, climbing stairs, and getting on and off the toilet require about 110 degrees.

Patients who want to kneel for long periods of time, sit cross-legged, or squat need more flexion. The high-flex design makes it possible. This is important for some religious groups and for some jobs. There are problems with this much flexion. The kneecap gets off track more easily. The result is more pain and excess wear. The kneecap can even break or come loose.

Many studies show that the patient’s knee motion before a TKR determines the outcome of the surgery. Good motion means a good result after TKR. The patient with poor flexion isn’t likely to get full flexion after the implant is put in. The author suggests that the high-flex implant should only be used with patients who have full motion going into surgery. He concludes that a better design is needed that gives full motion to all patients without forfeiting so much bone during surgery. He also envisions an implant that reduces knee pain and instability when the knee is fully bent.

Anxiety and depression have been linked to pain after total knee replacement (TKR). Doctors at the Northwestern Orthopedic Institute in Illinois are looking for ways to reduce pain after TKR. They studied 116 patients before and after surgery to find risk factors that predict pain. If they can tell who might be affected and why, they may be able to prevent the pain.

The researchers measured pain, stiffness, and physical function. They also took X-rays. Another test showed symptoms of anxiety and depression. They asked each patient about current life stress. Results showed a typical pain pattern after TKR. Most patients reported that pain intensity was cut in half three months after the surgery. About 25 percent still had significant pain after three months. By one year, one in eight patients had pain despite normal test findings.

Patients who had pain that lasted beyond the expected time after TKR tended to have symptoms of depression and anxiety before the operation. Patients with the most depression beforehand had the worst pain a year after surgery. How does knowing this help doctors and patients? Simple screening can be done with every patient before TKR. Anxious patients can learn coping skills before the operation. A class in relaxation is advised. Physicians can follow patients who have high distress scores more closely.

The authors suggest that patients with a high stress profile see a psychologist to deal with depression before having TKR surgery. They say doctors should treat pain sooner in patients with anxiety or depression. Taking steps to reduce psychologic stress before TKR surgery may result in less pain and better function after the operation.

About one-third of people with arthritis of the knee have the problem in both knees. This can be a big problem when it’s time for knee replacement surgery. In the past, the only option was surgery on one knee at a time, with several months in between. But two separate surgeries double the risk of complications. Two surgeries mean more time in the hospital and more time in rehab. Two surgeries also increase costs.

In the past 10 years or so, some surgeons have been doing both knee replacement surgeries at the same time. This is called bilateral total knee replacement. (Doing just one knee is called unilateral surgery.) Many studies are being done to determine how safe and effective bilateral knee replacement surgery really is.

This study compared 92 patients who had bilateral knee replacement with 92 patients who had unilateral knee replacement. All the knee replacements used the same types of implants. The bilateral surgeries were done with two teams of surgeons. Both knees were worked on at the same time to shorten the time under anesthesia. Shorter anesthesia times usually mean fewer complications.

All patients were followed for at least three years after surgery. Some patients were followed for seven to eight years. Researchers looked for complications and asked questions about satisfaction with the surgery. Researchers also looked at the patients’ health records from before surgery.

There were some interesting comparisons:

What effect does knee bracing have on muscle control for patients with a damaged anterior cruciate ligament (ACL)? Bracing is often prescribed for athletes who want to keep playing sports but who have a weak ACL. The players say the brace gives them needed support and improved performance. No one knows how this works.

Researchers at the Mayo Clinic Sports Medicine Center studied the effects of bracing on muscle control. They tested 10 subjects with chronic ACL problems. All of the subjects in this study had been wearing a brace for at least 30 months. Each one hopped on one leg with and without a brace. Muscle activity for the hamstrings (back of thigh), quadriceps (front of thigh), and gastrocnemius (calf) muscles was measured by electromyography.

Research has shown that the normal muscle-firing pattern is hamstrings first, then quadriceps, and finally the gastrocnemius. According to this study, the order of muscle firing is the same for most patients using a knee brace. The timing changes somewhat. There may be a delay before the muscle starts to contract. This delayed response is measured in units of time and is called latency. Onset latency is common among brace wearers.

Without the brace, the order of muscle-firing changes, but not all the time. Each person seems to have his or her own pattern. The authors of this study think there are several reasons for these findings. Electromyography measurements for the same muscle performing the same activity varies widely. There may be other factors to blame such as age, gender, brace fit, and muscle strength. It’s possible that the effect of bracing lessens over time. Perhaps bracing works better early on, right after the leg is first injured.

The researchers also suggest it’s possible that bracing works for other reasons than preventing a delay in muscle firing. Maybe the brace changes the entire leg’s function and that, in turn, helps stabilize the knee. Until it’s known how bracing works, doctors will have to continue prescribing them according to their own experience and observations.

Some tears of the meniscus in the knee don’t have to be removed. They can be repaired. Sometimes the same meniscus is torn and repaired more than once. This study reports the results of repeat repairs in 18 torn menisci.

Research has shown that removing the meniscus leads to increased force on the joint surface. Taking out as little as one-third of the inner meniscus increases contact stress on the joint by 65 percent. Scientists think the loss of cartilage and increased stress is what causes osteoarthritis in knees that have had part or all of the meniscus removed.

The meniscus is so important doctors still try and save it when it tears a second time. What are the results of a second (or third) meniscal repair? In these 18 cases, repeat meniscal repairs were 72 percent successful. The average follow-up was seven years. Range of motion, function, and X-rays of the joint space were measured in all cases.

Repeat tears often occur in the same place as the first tear. Sometimes the repeat repairs can’t be fixed a third time. If the tear is too long, too deep, or goes in too many directions, repair may not be possible. Removing part of the meniscus is the next step.

The authors conclude that repairing a torn meniscus a second time can give the patient relief from pain. Most patients can eventually return to strenuous levels of activity. Doctors aren’t sure if the repeat repair protects the meniscus as well as the first repair. More studies are needed to compare knee function and results after the first meniscus repair to results after the second meniscus repair.

Something needs to be done to prevent injuries to the anterior cruciate ligament (ACL) in the knee. About 100,000 people injure their ACL in the United States each year. One billion dollars is spent every year to surgically treat torn ACLs.

Scientists agree that the first step is to find risk factors for ACL tears. It would be best to find factors that can be tested for easily. The next step is to reduce the risk. The hope is to find risk factors that can be changed. These are called modifiable risk factors.

Physical therapists at West Point have some information to offer. They studied 859 West Point cadets over a period of four years. The study included 739 men and 120 women. Researchers were particularly interested in noncontact ACL injuries. During the four years of this study, there were 24 noncontact ACL tears in 16 men and 8 women.

Doctors, physical therapists, and athletic trainers tested each freshman cadet. They looked at knee stability and ligament laxity. They also measured joint motion, muscle strength, and muscle flexibility. Measurements from X-rays showed ligament size in relation to the bone. The space or notch inside the joint for the ligament was also measured. Previous studies have shown a link between small notch width and ACL tears. There are some researchers who think smaller ACLs are more likely to be torn in noncontact injuries.

Therapists conducting this study were unable to find the cause of noncontact ACL injury in men. Notch width, ACL size, and joint laxity predicted some, but not all, injuries in men. It’s likely there are many factors at work.

Risk factors for women were easier to find. The authors report that weight and body mass index (BMI) were the only modifiable risk factors. The risk of injury increased in women who also had a greater than normal joint laxity and a narrow femoral notch. These risk factors didn’t account for all injuries. The authors conclude there are other factors at work as well. Future studies may be able to identify them.

Patients with both osteoarthritis (OA) and a torn meniscus in one area of the knee are faced with a new problem. Will the OA get worse if the meniscus is removed? What if the painful symptoms are really from the OA? Will taking the meniscus out make any difference?

Researchers at the National Health Service in England set out to answer these questions. Doctors searched their data banks to find cases of both knee OA and a torn meniscus. Over eight years, 3,000 patients had arthroscopic knee surgery. Of those 3,000, researchers found 126 patients who had both problems. This group was compared to a smaller control group of 13 patients. The control group had severe arthritis with exposed bone, but the meniscus was fine. Researchers compared factors including pain, effect of symptoms on work or recreation, and amount of medication used to control symptoms.

The group with severe OA and a torn meniscus had arthroscopic surgery to remove the cartilage. The smaller group just had any frayed cartilage smoothed out and the area cleansed. Everyone was rechecked and examined one year later. Most patients were followed for four years.

The authors report that removing part of the meniscus in patients with severe OA doesn’t speed up damage from the arthritis. These patients’ symptoms improve in the short term. In fact, patients in the control group ended up having more joint replacements than the group with meniscus problems. On the other hand, the meniscectomy didn’t improve the OA symptoms.

In patients with both severe OA and a torn meniscus, doctors can’t tell which problem is causing the pain until after the operation. According to this study, it’s okay to remove the meniscus. It doesn’t seem to make the OA worsen later, and the patient gets relief of symptoms right now.

Researchers can’t always find the answers they need in one study. Sometimes it takes a series of studies performed step-by-step. Scientists at the University of Tokyo in Japan are doing studies on the strength of the quadriceps muscle. The quadriceps muscle covers the front of the thigh. Its job is to straighten the knee.

The first study done by these researchers injected a numbing agent (lidocaine) into the knee cavity of subjects with healthy knees. They measured the strength of the quadriceps before and after the injection. They found that injecting a local anesthetic into the knee joint reduces the strength of muscle contraction.

This tells them that signals coming from the knee joint affect the strength of the quadriceps muscle. It doesn’t tell exactly which structure inside the joint is affected. It could be cells lining the joint, ligaments inside the joint, or some other soft tissue.

Next, the study was repeated with one difference. The subjects all had a torn anterior cruciate ligament (ACL). Once again, muscle strength was measured before and after lidocaine was injected into the knee joint. There was no difference in muscle strength. This led the researchers to conclude that a loss of quadriceps strength happens because signals from the ACL somehow affected the muscle.

These findings help explain why patients with a torn ACL have quadriceps muscle weakness when nothing is wrong with the muscle. The ACL has sensors that receive and send signals. These sensors are called mechanoreceptors. The next step may be to find out which mechanoreceptors are affected most by damage to the ACL and show how this results in lost muscle strength. The final step is to find a way to treat it.

Patellofemoral pain, also called PF pain, is the name for pain in the front of the knee around the patella (the kneecap). It is a common disorder. PF pain is especially common in adolescents and young adults. Many athletes suffer from PF pain, and more women have it than men. However, the condition is not well understood. Doctors think that many factors may be involved in PF pain. Weak muscles around the knee, an off-center patella, and a flattened arch (foot pronation) may all contribute to PF pain.

Weak hip muscles may also help cause PF pain. These authors tested that theory. They checked hip strength in 15 adolescent girls and young women who had PF pain. They compared the results to 15 girls and young women with healthy knees. All subjects took part in sports. Hip strength was tested while lying on the side (hip abduction) and while sitting (external rotation).

Results showed that subjects with PF pain had much lower hip strength than subjects who had healthy knees. Subjects with PF pain were 26 percent weaker in hip abduction and 36 percent weaker in external rotation. The authors feel the weak hips were related to PF pain in these young women. Weak hips can allow the kneecap to move out of alignment during exercise. Over time, PF pain develops.

The authors recommend training programs to strengthen the hips for patients with PF pain. They note that this study has one major limitation: they can’t tell which came first, the PF pain or the hip weakness. It could be that the hip muscles became weak because the women were protecting a painful knee. No matter which came first, other studies have shown that exercises to strengthen hip muscles can help get rid of PF pain.

Doctors are looking for a way to prevent bone fractures after total knee replacement (TKR) surgery. Researchers in Taiwan may have found the answer. It may have to do with low bone density, which is problem for aging adults. And the same group is most likely to need a joint replacement.

Many studies have shown that bone density drops even more after hip or knee replacement. It shows up as early as one month after the surgery and often lasts for years. Alendronate, known to most patients as Fosamax®, has been used with good results for osteoporosis and fractures related to this disease. Now it’s been shown to boost bone density around the knee after a joint replacement.

Researchers studied two groups of women who were getting a TKR. The study group took a daily dose of Fosamax® for six months. The control group did not. The study group had a significant increase in bone mineral density in the bones on either side of the knee implant. Their bone density increased 10 percent. The control group lost bone in the same area. They lost about 14 percent of their bone density. The greatest changes took place in the first six months for both groups.

All the patients got the same knee implant with cement. Everyone had the same rehab program. Except for the Fosamax®, the researchers treated and followed the two groups exactly the same. Bone mineral density was measured at one, six, and 12 months. A special imaging machine called dual energy X-ray absorptiometry (DEXA) was used to take the measurements.

This is the first study to show the effects of Fosamax® after TKR. The long-term effects of taking this drug after joint replacement are unknown. The short-term effects are significant enough to make it worth finding out what happens with long-term use. Researchers are also looking for the best doses to use and when to use the drug.

Imagine 50,000 parts. More than 500 unicompartmental knee implants. Twenty-three surgeons. Ten years. These numbers may not mean much to us, but they show 10 years effort and cooperation for the doctors of the HealthEast Hospital system in St. Paul, Minnesota.

In 1991 these doctors started a community-based registry to track the results of total joint implants. Type of implant, failure rate, cost, and patient data was collected on all patients getting a joint replacement.

Researchers recently looked at the results for unicompartmental knee replacements (UKRs). A unicompartmental implant replaces one side of the joint when arthritis has worn down the joint unevenly. The results show more than 90 percent of the UKRs were for the medial compartment (inside edge) of the knee. Most UKRs were cemented in place. Nine different designs were used. Hospital stay was about five days. Doctors were able to use this information to track which type of implants held up the best.

The most common cause of UKR failure was worsening of the arthritis. Loosening of the implant was the second reason for implant repair or removal. Overall results showed that 88.6 percent of the UKRs lasted at least 10 years. The authors say this isn’t as good as the 94.8 percent results for total knee replacements in the same study.

The authors suggest that every community start a local registry. Pooling the numbers gives the local doctors a snapshot of his or her results compared to other doctors in the same area. The goals are to improve implant success and reduce costs of implant failure.

Doctors are getting good results with a new method to keep the kneecap on track when doing total knee replacement surgery. This new method is called a mesh expansion release of the lateral patellar retinaculum. The patella is your kneecap. The retinaculum is a fibrous band on either side of the patella. Lateral means it’s along the outside edge of the patella.

If the quadriceps muscle along the front of the thigh pulls too much to one side, the patella starts getting off track. The result can be a painful loss of knee motion. One treatment method for poor patellar tracking is to release the lateral retinaculum. The doctor does this by cutting through the retinaculum.

But problems can occur with this operation. Blood vessels and nerves can be damaged. The patella can get broken. Tenderness over the bone, numbness of the skin, and loss of strength are also possible problems. Anyone getting a knee replacement needs a patella in good balance and without extra problems. A traditional lateral release may not be a good choice for these patients.

This is where the mesh expansion release comes in. Instead of cutting through the retinaculum, the surgeon makes several slashes through the fibrous band. The cuts are staggered in several rows side by side. There are two or three slash cuts in each line. As the knee moves, the retinaculum stretches or expands. The result is that the patella stays more in the middle, where it belongs.

In this study, doctors at an orthopedic surgery center used the mesh expansion method in 13 patients getting a total knee replacement. All 13 patients had good results with pain relief and improved function. Even after two years, there were no problems from the mesh expansion.

The authors conclude the mesh expansion is safe and effective. This treatment method to balance the patella can be used during total knee replacement surgery. The advantage is less damage to the joint capsule and faster healing than a full retinaculum release. It probably shouldn’t be used for patients with severe joint deformity or severe retinaculum tightness.

It used to be that torn cartilage (meniscus) in the knee was removed. Doctors know better now. For the past 50 years, researchers have studied the meniscus. We now have a much better idea what this C-shaped piece of cartilage does in the knee. As it turns out, it’s very important to the long-term health of the knee. Taking out the meniscus affects the joint’s ability to bear loads, hold steady, and absorb shock.

Whenever possible, doctors try to save a torn meniscus. The cartilage is still removed when it’s crushed or damaged beyond repair. The surgery to remove a torn meniscus is called a meniscectomy. In this study, doctors at a sports medicine center looked at the results of the worst tears ever repaired. They wanted to see if repair or removal had a better long-term outcome.

The patients studied were young and athletically active. Each patient had at least half of the meniscus torn. Each patient also had a tear of the anterior cruciate ligament (ACL) in the knee. All patients had an ACL reconstruction. The first group also had a meniscal repair. The second group had a meniscectomy. Each patient was followed on a yearly basis for an average of six to eight years.

The rehab program after surgery varied over time, depending on the latest research. For example, in the early 1980s, patients were told to limit how much weight they put on that leg for two to four weeks. In the late 1980s, patients were told to put as much weight on the foot and leg as they could handle. In the 1990s, activity was limited for the first week to keep the swelling down.

The researchers were expecting to see better results in the patients who had a meniscal repair. What they found was no difference between the two groups. When they looked a little closer they also found less patient satisfaction for athletes with degenerative tears. A degenerative tear in the meniscus usually goes in two directions: up and down and from side to side. These types of tears heal but don’t seem to work the same after repair. They often tear again.

The authors conclude that degenerative meniscal tears can heal, but they don’t always function. The current trend to repair all meniscal tears may need to be restudied. A larger study over a longer period of time is advised to confirm this new finding.

Most research after total knee replacement (TKR) reports knee function one or two years after surgery. These authors wanted to see how the replacement knees fared over a longer time. They checked on patients’ knee function for seven years after TKR. They also wanted to see how patients’ health affected knee function.

Sixty-four patients were followed. They all had the same type of joint replacement, done in the same way. The patients’ average age was 65. Almost 85 percent of them had problems only in one knee. About five percent had problems in both knees. The other 11 percent had other health problems, such as arthritis in other joints.

Results showed much better function over the whole seven years compared to pre-surgery scores. The overall function decreased from the first year after surgery to the seventh year, but not by much. However, patients who had other health problems saw their knee function decline much more than the average.

Also, over the course of the study, many patients became reclassified as having health problems. Only 11 percent had other health problems at the time of surgery. Seven years later, 31 percent of the patients were in that group. The authors also found that women had much lower function scores both before and after TKR. The authors don’t know why. Age and weight at the time of surgery did not seem to be related to function.

This study reminds doctors that knee function declines over time. It also reminds doctors that aging and other health problems can affect knee function. The authors note that it is important to consider health ratings in studies of TKR outcomes.

Total knee replacement (TKR) can greatly improve knee function. But in the weeks right after surgery, TKR patients can have a lot of pain and problems moving. Part of recovery from TKR is taking it slow until the knee is ready.

One activity that doctors tell patients to avoid right after TKR is driving. Driving too soon after TKR can be dangerous. The knee is just not ready to do the quick, forceful movements of braking. Doctors usually tell TKR patients to wait at least eight weeks before driving.

However, this is not based on much research. These authors tested braking time in 31 patients before TKR. They tested the same patients again three, six, and nine weeks after surgery. The authors compared the results before and after surgery. The braking times were not much different even three weeks after TKR. The authors found much quicker braking times for all patients six and nine weeks after surgery. The authors found that men had much faster brake times than women at all times tested.

Results were also compared to data from people of the same age who did not have TKR. The men had times that were average when compared to people with no TKR. The women who had a TKR, while showing dramatic improvement, still didn’t have even average braking time.

The authors also found that brake times didn’t seem to depend on which knee had been replaced. This was surprising. They expected to find that patients who had a TKR in the right knee would have more problems braking.

The authors conclude that doctors can allow patients to drive six weeks after TKR, as long as there are no other health or function issues.