News Category: Knee

What determines the result of knee surgery? Is it how well the body heals? Is it how well the patient can get around? Researchers say it’s something called the health locus of control.

This refers to the patient’s beliefs about themselves and others. They may believe that other people (doctors, therapists, trainers) control what happens. Some patients think that the final result is left to fate, luck, or chance. These people have an external locus of control. Others hold to the belief that their own actions decide the outcome. This is an internal health locus.

Researchers used a group of patients who had surgery to repair the anterior cruciate ligament of the knee as study models. They found that patients who believed their outcome after surgery was under the control of others had a poorer result. Those patients who thought fate, luck, or chance were responsible for their result had the same reduced result with more pain, less function, and more limitations. Patients who believed that their own actions and attitudes made the difference had less pain, could do more, and weren’t as limited.

Before surgery, it may be a good idea to do an attitude check. A positive internal drive, rather than reliance on other people, luck, or chance may be all it takes to have a better result.

If you tear your meniscus, or knee cartilage, current practice suggests fixing the tear rather than removing the damaged cartilage. Meniscal repair preserves the knee and prevents more problems down the line. But how do surgeons repair tears of this kind?

In the last decade, new devices have replaced simple sutures in knee surgery. One of these is the meniscus arrow. Shaped like an arrow, this device has barbs to hold torn cartilage in place. The meniscus arrow is bioabsorbable and dissolves in the body over time. Even better, the arrow can be inserted using an arthroscope. This tool lets surgeons work under the skin without making big incisions. This reduces surgery and healing time.

A number of studies show that meniscus arrows are strong and effective. This study echoes those results. Thirty patients had meniscal repairs using two or more arrows. Most of the patients also had anterior cruciate ligament (ACL) repairs at the same time to stabilize the knee.

About two years later, 83 percent of the patients had good or excellent results, no matter what the size of the tear. In two cases the surgery was said to have failed. These patients went on to have more surgery.

There were no major complications from surgery. A few patients had skin irritation from the arrow tips. These symptoms went away with injections or on their own. Skin irritation may be avoided by choosing arrows of the right length, so that the tips do not stick out.

The authors feel that meniscus arrows are safe and effective for meniscal tears. Meniscus arrows must be inserted properly, so that the barbs are engaged. The authors recommend bracing and four weeks of no weight-bearing activity after surgery. More movement and weight bearing may be okay, but more research is needed to say for sure. Finally, ACL damage must be addressed to get the best results from meniscal repair. If the knee is unstable, it is only a matter of time before the meniscus repair fails.

Technology using heat has made it possible to tighten injured joints. Heat shortens the tissue that holds the joint together. When heated tissue cools down, it contracts and tightens. This is called thermal shrinkage.

Radiofrequency is a new way to apply heat without damaging the joint. It has been used successfully on the shoulder. Now doctors are trying it on the knee.

When the ligaments holding the joint together are torn or stretched, the joint can become loose. This condition is called joint laxity. In the knee, the anterior cruciate ligament (ACL) is most often affected. Surgery may be needed to repair or replace the ligament.

Doctors have tried using radiofrequency treatment on patients with ACL laxity. The new heat treatment has not been successful for most patients with knee problems. Although the heat can shrink the ACL, the ligament must have good blood supply to heal. In the case of old injuries or ligaments that have already been operated on, there isn’t enough blood for healing to occur.

Heat is being studied as a way to treat ACL injuries. This treatment may be useful for new knee injuries. However, it is not as helpful for patients with old knee injuries or those that have had a past knee surgery.

Women are eight times more likely than men to injure the anterior cruciate ligament (ACL) of the knee. New research suggests that hormone levels may have something to do with women’s ACL injuries. In other words, women may be more prone to ACL injuries during certain times of the month.

Scientists measured hormone levels in 65 women with recent ACL tears. Hormones were measured with urine samples taken within 24 hours of injury and again at the start of the next menstrual cycle. More injuries occurred at the time of ovulation (release of egg) than any other time of the month.

Twenty-four hours before ovulation, there is a sharp increase of  luteinizing hormone in the blood. This hormone triggers the release of estrogen in preparation for reproduction. This lasts about five days. During this time, women are more likely to injure their knees. Interestingly, women taking birth control pills are less prone to knee injury.

Women are more likely to injure the ACL during the ovulation phase of the menstrual cycle. This is especially true for women who are not taking birth control pills. Birth control pills appear to have a protective effect against ACL injuries. The exact reason for this remains unknown.

Many people suffer from arthritis behind the kneecap, called patellofemoral osteoarthritis. This kind of arthritis causes knee pain when going up or down stairs. Patients also have pain after sitting with the knee bent, or when standing up after sitting.

About 80 percent of adults with this condition are helped by nonsurgical treatment such as medication, special exercises, and avoiding painful activities. Other patients may get relief from a simple surgery called lateral retinacular release.

With this procedure, the surgeon cuts the retinaculum. This is a dense, fibrous band of tissue along the outer edge of the kneecap. The arthritis doesn’t go away with the release of the retinaculum. However, pain relief is reported by many people who have this surgery.

Retinacular release can delay major surgery such as total knee replacement. Patients who are too young for joint replacement or too sick for major surgery may choose this easy operation for arthritis relief.

Did you know that it’s possible to break your kneecap? This is called a patellar fracture. This type of fracture sometimes happens without the patient even knowing. Doctors became aware of this problem while taking X-rays after knee replacement surgery. About half of the patients with patellar fractures didn’t have any pain or symptoms. Only a small number of patients had moderate to severe pain from fracture.

It’s not clear what causes these fractures after knee replacement surgery. Patellar fractures could result from the condition of the bone or the amount of bone removed during knee replacement surgery. Fractures could also result from poor alignment of the kneecap and the leg bone.

The treatment depends on the type of fracture. Patellar fractures are Type I, II, or III, depending on the condition of the bone and attached muscle, and the presence of loose pieces. Type I can be treated without surgery. This is called nonoperative treatment. Types II and III usually require surgery to repair or remove the bone.

Less than one percent of patients have patellar fractures after knee replacement surgery. However, more adults are having this surgery. This means more patellar fractures will probably be seen in the future.

The cartilage in the knee doesn’t heal very well. The cells just don’t seem to be able to repair themselves. If the damage is deep enough to go clear to the bone, there are cells in the bone marrow that can help. Doctors have tried to stimulate the bone marrow to make cells that will become cartilage. They’ve tried drilling, sanding, and putting small cracks in the bone to release these healing cells.

Different kinds of cells make up cartilage, ligaments, and tendons. These are called collagen fibers. Some collagen fibers are harder and stronger than others. Likewise, some collagen tissue is softer and has limited durability. Treatment to stimulate bone marrow is more likely to form tissue that is softer and less stable.

With this in mind, researchers have explored other sources of cartilage cells to promote healing. Animals were used in the 1980s to see whether injecting cartilage cells helped the healing process. Studies are now being done on humans. In one study, cartilage cells were shaved from the patient’s injured knee, washed and cut up, and then injected back into the damaged area. Rehabilitation took place over the next eight weeks. Each patient was followed for five years or more.

Good to excellent results were reported in almost all of the patients. Failures were the most common in patients who had damage to the cartilage and the ligaments of the knee at the same time. Some failures were the result of patients not following the prescribed exercise program.

The use of cartilage harvested from a person’s own knee is a new treatment developed over the last 10 years. It is a much better method of repair in some cases compared to sanding, drilling, or fracturing the damaged area. The repaired cartilage is stiffer and more stable after two years. Patients are able to return to full activities. These good results are present in more than half of all cases, even years later.

Patients must use caution with activities after total knee replacement in order to protect the artificial joint. Older, active patients may need to be especially careful with the new knee joint.

Can patients return to sports and activities after total knee replacement? The answer to this question isn’t fully known. Studies show that more than half of all adults who are active in sports before knee replacement return to activities afterward. However, they tend to choose activities with less impact such as golf or bowling.

How about higher-impact activities like tennis? Researchers studied 35 tennis players with an average age of 64 who had total knee replacement. After one year, patients were playing singles and doubles tennis. They played three times per week. Patients were able to compete within six months of surgery. All of the patients reported improved skills. They could run faster, stop easily, and change directions quickly.

Older adults are staying active longer. Doctors are concerned about how new knee joints will hold up with high-impact activities like tennis. Most doctors think artificial joints will loosen with too much activity. More long-term studies are needed on this issue.

Total knee replacement is a popular kind of surgery–and for good reason. This surgery successfully relieves pain and improves function in arthritic knees. From 1999 to 2000, the number of knee replacements went up by 23 percent. As the United States population gets older, the demand for this surgery will continue to grow.

The cost of knee replacement is also on the rise. This is a problem for the federal government, which pays for about two-thirds of all knee replacements through the Medicare program. Is there a way to reduce the cost of knee replacement without compromising patient care?

These authors thought so. They looked at the effects of a two-part cost-reduction program. First, the authors set a clinical pathway, or standardized routine of care, to take patients from surgery to rehabilitation. The pathway was designed to improve care, reduce hospital stays, and reduce hospital costs.

Second, a program was started to reduce the money spent on knee implants. Under the new program, implant selection was based on the amount of stress patients were likely to put on their new knees. This was decided on the basis of patient age, weight, activity, and health. Patients who were likely to put a lot of stress on implants could have a variety of implants, including more expensive models. Patients who were likely to put less stress on implants got less expensive models that worked just as well.

Patients who had knee replacements with the new cost-reduction programs were compared to those who had knee replacements before these programs were in place. Five to eight years after surgery, there were no differences in the results of the two groups. Both groups had excellent relief from pain. They had more knee movement and were better able to do activities. Both groups were very satisfied with treatment. Neither group was more likely to need more surgery or medical care.

The quality of patient care stayed the same, even though the cost of the procedure (adjusted for inflation) went down 19 percent. This was due to the fact that patients spent only four days in the hospital with the cost-reduction program, versus seven days before the program started. Patients were able to spend less time in the hospital after surgery because they were discharged to rehabilitation facilities. Costs were also reduced with the use of less expensive implants called “all-polyethylene tibial implants.”

The authors feel that the cost of total knee replacement can be reduced while maintaining excellent standards of care. Orthopedic surgeons will continue to put patients first, even under pressure to cut medical costs.

Sometimes surgery to reconstruct the anterior cruciate ligament (ACL) fails. Another surgery, called revision knee surgery, may be needed. Because this is rare, doctors haven’t decided the best way to approach a second or third surgery to repair the ACL.

Two orthopedic doctors kept track of failed ACL repairs, which numbered 11 out of 2,264 cases. The 11 patients with failed surgeries had each had at least two ACL repairs. Each repair was done using a piece of tendon at the knee called the patellar tendon. This piece of tissue was taken from the patient’s own knee and used in place of the torn ACL.

When operating for the third time, the doctors faced a difficult decision. Could they take more tissue from the patellar tendon? They had already taken tendon and a small piece of bone from both knees. Would the “recycled” tissue hold up? Could patients afford to lose more patellar tendon tissue? Would the injured knee be restored to its full strength and stability? What about the muscle that attaches to the patellar tendon (the quadriceps)? Would the quadriceps on the donor leg regain its normal strength?

The doctors rolled up their sleeves and got to work. They collected information over a 10-year period. They read every report that came out on this subject and compared results. They put together two separate rehabilitation programs: one for patients who had grafts retaken (reharvested) from the ACL-injured knee, and one for patients with grafts taken from the uninjured knee.

As part of the testing before surgery, MRI (magnetic resonance imaging) was used to look at the donor tissue. Each patellar tendon was examined carefully. This made it possible to use the healthiest part of the patellar tendon.

The results of this study showed that reharvesting donor tissue from the injured knee is not as good as taking normal tissue from the uninjured knee. There were more complications and less use of the knee joint with reharvested tissue from the injured knee.

Sometimes surgery is needed to revise a previous ACL surgery. When this occurs, an MRI scan of the opposite knee can be used to find healthy donor tissue. Doctors can take a portion of the patellar tendon from the uninjured knee and use it in place of the torn ACL. This results in a strong and stable knee with normal muscle strength in both legs.

The meniscus or knee cartilage performs many important functions. It helps absorb shock and lubricates the joint. It holds the joint steady, and it takes some of the load off the knee. Without this little pad of cartilage, arthritis can develop.

For over 100 years, doctors took out the meniscus whenever it was torn or damaged. Today, the knee meniscus is saved whenever possible.

What if the meniscus can’t be saved? In 1984, doctors in Germany tried a new solution to this problem. They transplanted meniscus from human donors to replace the torn cartilage in 23 patients.

Two different methods were used to prepare the tissue. In one group, the donor cartilage was frozen quickly and then dehydrated, meaning the water was removed. In the second group, the tissue was deep-frozen.

Patients were followed for 14 years after surgery. Patients who received deep-frozen meniscal tissue had better results than the quick-freeze group. Even after 14 years, the transplanted tissue that had been deep-frozen was in good condition.

In comparison to the deep-frozen meniscus, the quick-frozen and dehydrated tissue was smaller. It was also smaller than normal tissue. This led to more arthritis in the knee.
 
Saving the meniscus is the best way to preserve the knee joint. When this isn’t possible, tissue can be transplanted to the injured knee. Deep-frozen meniscal tissue works best because it functions more like normal, healthy tissue.

The meniscus, or knee cartilage, is commonly torn in athletic injuries. Often, one of the ligaments inside the knee is torn along with it. Ten years ago, this kind of injury would have resulted in surgical removal of part or all of the meniscus. Now, improved methods are available to hold the meniscus in place. Sutures or stitches are being replaced by devices called arrows. These fasteners have barbed shafts that help hold the knee cartilage together.

There are many advantages to these arrows. They are bioabsorbable, which means the body absorbs or dissolves the material once the area has firmly healed. Operating time is cut in half because of the ease of inserting the arrows. And there are fewer cases of additional operations or serious complications with arrows.

Possible problems include arrows moving or sticking out of the skin, arrow breakage, and symptoms at the repair site. There may also be knee pain or tenderness, skin irritation, and bruising under the skin.

When a new technique is introduced in the world of orthopedic surgery, it takes a while to decide who can and can’t have that procedure. For example, certain types of tears don’t heal well with arrows. Irritation of the skin and knee pain or tenderness occur in one-third of all patients. However, these symptoms usually go away in the first year.

More and more people are choosing to repair a torn meniscus rather than remove it. This is partly because of the improved equipment used in surgery. One-third of all meniscal repairs are performed with the new bioabsorbable arrows. Doctors continue to look for ways to improve the design and use of arrows. The size of arrows and the location and angle of arrow insertion are all under careful study.

Painful swelling in the leg after surgery may signal a blood clot. Blood clots aren’t always dangerous. They may dissolve without any further problems. The real concern comes when a blood clot doesn’t shrink and disappear. The clot can get larger and damage the blood vessel. Swelling and blockage of the blood vessel can keep the clotted arm or leg from getting enough blood.

Worse than that, a blood clot can break away from the wall of the blood vessel and travel in the bloodstream to the lungs, heart, or brain. Death or stroke can result. What are the chances of this happening? The risk is much less with medications called anticoagulants. Anticoagulants such as aspirin and heparin prevent blood clots.

The chances of blood clots increase under certain conditions. Open surgery of the abdomen or pelvis, hip, or knee has been connected to blood clots. Anyone can develop blood clots after surgery, but adults over 40 years are at greater risk. Anyone with a previous history of blood clots is at risk. People with heart disease are closely monitored for blood clots after any of these surgeries. Finally, the longer the operation, the greater the chance that blood clots will form.

What are the chances of blood clots after arthroscopic surgery? The arthroscope is a surgical instrument that allows doctors to operate without opening the body. Doctors can insert a thin tube with a tiny TV camera on the end into a body cavity or joint. The arthroscope guides doctors during surgery. Only a small hole or incision is required. Other surgical tools can also be inserted through this site.

Until recently, no one knew how often blood clots occurred after arthroscopic surgery. Medication to thin the blood and prevent blood clots hasn’t been given routinely to these patients. A group of physicians in Switzerland studied patients who had arthroscopic knee surgery. One group of patients received medication to prevent blood clots. A second group did not take this medication. Patients in both groups were carefully examined before and after surgery.

There were many more cases of blood clots in the group who did not take the blood-thinning medication. In this group, 15 percent had blood clots. Meanwhile, only 1.5 percent of patients who took the medication had blood clots.

The risk of blood clots after arthroscopic knee surgery is high. Medications to prevent this problem should be taken for at least two weeks after surgery. Most doctors recommend a 30-day period of medication to give patients the best protection against blood clots.

The lining or cartilage of a joint heals better if it is damaged clear to the bone. Damage that only goes through part of the cartilage doesn’t heal nearly as fast or as well. Scientists think this is because cartilage needs the healing cells that are on the surface of the bone. An opening all the way through the cartilage allows those cells to come to the injured site.

With osteoarthritis, cartilage loses its normal structure and function, causing rough, irregular joint surfaces. At first, the individual fibers of the cartilage get damaged. As the disease gets worse, cracks or fissures develop. These fissures go deeper and deeper through the cartilage and then into the bone.

Doctors are looking for ways to prevent this loss of joint surface. In the meantime, they are looking for ways to repair the bone. Some surgeons are trying to shave the joint down to the bone to promote repair of the damaged surface. One group of Japanese physicians looked at the effect of surgery to “realign” the leg bones. The purpose of this surgery is to redistribute the weight on the joint more evenly. This kind of operation is used in patients with osteoarthritis on only one side of the joint.

This group of doctors found that even with the corrected leg alignment, the cartilage still couldn’t repair itself. Once the damage is done, it is very hard for cartilage to repair itself. Repair of injured cartilage requires the healing cells under the bone. However, surgery to correct alignment did prevent further joint damage.

Researchers have new information about the joint damage that comes with osteoarthritis. Cartilage can’t repair itself unless the damage goes clear to the bone. Then cells from the blood and tissue under the bone come to the rescue of the cartilage. Realigning the bones with surgery does not help the repair process, but it does keep the damage from getting worse. This information has led researchers to look for ways to stimulate the joint to repair itself. This may involve cell transplantation, growth factors, and tissue transplants.

What do badminton players, basketball players, weight lifters, long-distance runners, and hockey players all have in common? Any of them can develop a condition called medial tibial stress syndrome (MTSS). With MTSS, there is pain in the lower leg that gets worse with exercise. This condition can occur in one or both legs. The bone affected is the tibia, the larger of two bones in the lower leg.

No one knows for sure what causes this problem. It could come from inflammation or a tiny fracture. With continued advances in medical technology, researchers hope to find the cause of MTSS. Two breakthroughs in testing bones are bone scans and bone density tests. A bone scan involves a special camera and radioactive substance that show “hot spots” in the skeleton due to over-activity of bone cells. Bone density tests are a special type of X-ray that measures mass within bones. When researchers applied these imaging methods to the tibia, they made some interesting discoveries.

Athletes with medial tibial stress syndrome were compared to two other groups. The first group included athletes of the same sex and age who did not have MTSS. The second group had volunteers of the same age and sex who were not athletes but exercised at least two hours a week.

There were three important findings: (1) athletes with MTSS had lower bone density in the problem area, (2) bone density was decreased in both tibia bones even when symptoms were only present on one side, and (3) athletes with MTSS had higher bone density overall than the nonathletes, but not as high as athletes who did not have MTSS.

Which came first–the tibial stress syndrome or the decreased bone density? For now, researchers can only guess. Loss of bone density may occur as a result of exercise or from a problem with bone development in the growth years. Exercise may simply trigger a reaction to a problem that’s already there.

Researchers hope that, by studying athletes with low bone density in the lower leg (but no symptoms), the cause of MTSS will be found. Bone scans and bone density tests may help researchers see how changes develop and whether bone density improves when symptoms disappear.

Ever looked at some part of a gadget and thought: I wonder what this little gizmo does? Remove it and find out! Maybe nothing happens at first. But wait a few years and the importance of that piece becomes all too clear. Such has been the case for removing knee cartilage, or the meniscus.

If you tore your meniscus 20 years ago, the surgeon would probably just take it out. But studies since then have shown the importance of the meniscus to the knee. Without it the space between the two leg bones that form the knee joint gets narrow. There is less cushioning for the joint. Eventually the joint starts to wear down.

Now, improved methods in surgery allow doctors to save as much of the cartilage as possible. New research has focused on the results of this type of surgery, called tissue-conserving therapy. As part of this ongoing research, researchers in Sweden rechecked a group of patients who had either partial or total removal of the cartilage, called a meniscectomy.

Fourteen years after surgery, patients had X-rays and physical exams. Knee function, range of motion, and muscle strength were measured. X-rays were used to look for flattening of the bones, narrowing of the joint space, and hardening of the tissues.

Physical exams showed that range of motion was less on the operated side when patients had the whole meniscus taken out (total meniscectomy). Range of motion was not changed when patients only had part of the meniscus removed (partial meniscectomy). Muscle strength was the same for both groups. Also, knee function was the same before and after surgery for both total and partial meniscectomies. There was a decrease in physical activity in both groups, but overall, there were no major problems in either group. X-rays showed that patients had much greater changes in the joint after total meniscectomy compared to the partial procedure.

How much of the meniscus is removed determines the final result. There are very few long-term changes with a partial meniscectomy, even years later. However, a total meniscectomy increases the risk of changes in the joint. Joint space narrowing seems to be the biggest change, though knee function appears to stay the same. With continued improved methods, doctors will be able to save more of the torn tissue. This will give patients a healthier knee years later.

There’s more to a kneecap than meets the eye. Located over the knee joint, it seems to move up and down easily enough. But if the kneecap gets off its track, the cartilage behind the knee can get torn and frayed. This causes pain behind the kneecap called patellofemoral pain (PFP). People who have this condition really appreciate just how much the kneecap does during walking, climbing stairs, and squatting.

With PFP, there is a tendency to avoid standing on the affected leg or using the muscles around the kneecap. This results in a slower walking pace and changes how much the knee joint moves. The knee bends and straightens less. There is a tendency to lean forward when going up stairs. These are the ways the body reacts to pain of PFP. It compensates by taking as much pressure off the knee as possible.

One way to treat PFP is to tape the kneecap. This holds the kneecap in its proper place and decreases pain. Climbing stairs becomes easier. The body returns to a normal posture, with a more upright trunk. Patellar taping improves kneecap tracking, or the ability of the kneecap to stay on its track. Taping also improves the ability to stand on the leg. This restores the normal pattern and speed of walking.

Taping helps people with patellofemoral pain by holding their kneecap in place. One thing that doesn’t change with taping is the activity of the quadriceps muscle around the knee. Researchers who study the effects of taping on the knee suggest additional treatment for this problem. Once the kneecap has been taped and realigned, muscle retraining can begin. This is another important part of the rehabilitation process.

Try to make this out: “A guide pin is drilled from medial to lateral exiting at the tibial posterolateral corner and it is then overdrilled with a cannulated 6.5-mm diameter reamer. A Beath needle is passed from medial to lateral, pulling the semitendinosus tendon to the posterolateral aspect of the knee.” Knee! Now there’s a word we can recognize!

This sounds like a manual for an auto mechanic. But it’s really a technical note from a surgeon explaining a new method for knee surgery. Doctors, like mechanics and other workers, report to one another methods that work and how to do them. The above instructions are part of a step-by-step guide for an uncommon knee problem in orthopedics.

Knee injuries that produce too much looseness in the back, outer rim of the knee joint are challenging to repair. This condition is called “posterolateral instability.” Injuries to the knee during contact sports are the most common cause of this type of instability. Typically, two ligaments deep within the joint tear. These are the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL). Sometimes only one ligament is torn, along with other supportive structures.

To make this diagnosis, the doctor must carry out a very detailed exam. It is necessary to study the way the patient walks and performs many special tests. Which tests are positive tells the doctor where the injury is located. Imaging studies are needed to make a final diagnosis. These may include X-rays and magnetic resonance imaging (MRI).

Surgery for this type of knee instability is long and complex. Sometimes it isn’t possible to finish the job in one operation. The surgeon may repair the PCL, along with the structures around the back of the knee. The ACL is repaired at a later date.

“A guide pin is drilled in the anatomic insertion of the popliteus and lateral collateral ligament, the tendon is folded over itself, and a firm stump with the 2 components of the fold is made with a nonabsorbable suture.” Let’s leave joint repairs to the experts. At least they can read the manual!

Baker’s cyst of the knee is a fairly common problem. It was originally described back in 1877–by Dr. Baker, of course! Modern medicine has been able to use ultrasound to view Baker’s cysts. Updated surgical methods have allowed doctors to find out what causes this condition.

At first, it was thought that a Baker’s cyst was a problem unto itself. But using a special instrument with a tiny TV camera on the end (called an arthroscope), doctors have been able to see inside the joint. An actual connection can be seen between the cyst and the backside of the joint. There is an open channel between the cyst and the joint through which fluid can pass.

What causes this channel to form? In almost all cases, there has been some damage to the joint. The most common cause of a Baker’s cyst is either a tear in the knee cartilage (the meniscus) or damage to the bone from trauma or arthritis. Once doctors figured this out, they wanted to know if treating the cyst was necessary. Perhaps just treating the underlying problem would be enough to get rid of the cyst.

It turns out that this approach works in some cases. The cyst does go away when the meniscus is repaired. But cases of bone damage have a different outcome. Mild damage can be successfully treated with surgery, and the cyst disappears. But more extensive damage to the bone or cartilage means that surgery will not eliminate the cyst.

Doctors now know that Baker’s cysts are caused by some other damage in the knee joint. This new information has changed the way doctors treat this problem. Instead of removing the cyst, doctors attempt to repair the damage to the bone or joint. When the injury isn’t too great, the cyst goes away. Patients with severe joint damage may end up with a cyst that won’t go away. And they also tend to have more pain and poor results.

It’s a well-known fact that women athletes injure the anterior cruciate ligament (ACL) of their knees more often than men. Many explanations have been suggested. Perhaps the training of men and women is different enough to increase risk for ACL injury in women. There are gender differences in hormone levels, knee structure, hip width, and the angles at which muscles attach around the knee. However, no single cause or combination of factors has been proven.

One of the functions of the ACL is to keep the larger bone in the lower leg (tibia) from sliding forward of the upper leg bone (femur). This movement of the tibia at the knee is called tibial translation. The ACL keeps forward tibial translation in check. Contracting the muscles around the knee increases the stiffness of the knee. This also reduces forward tibial motion and offers additional protection to the ACL.

Since scientists haven’t been able to pin gender differences on anything within the joint, they decided to test the muscles around the joint. Researchers measured how much tibial translation occurs in men and women with and without the muscles around the knee contracted. In this way, researchers could tell how much of the knee stiffness was from muscles contracting and how much came from other structures in the knee. They found that men were able to produce more stiffness in the knee than women. Women could double the stiffness of the knee by contracting the muscles, but men could more than triple the knee stiffness.

There were no significant differences in actual muscle strength between men and women. There were no differences in knee stiffness based on height or muscle strength. The only difference was by gender. One more interesting observation was noted. Women used the quadriceps muscle (front of the thigh) more than men did. Meanwhile, men activated the hamstring muscle (back of the thigh) more than women did.

Men and women achieve different amounts of knee stiffness by contracting the muscles around the knee. Men and women also activate different muscles to stiffen the knee–hamstrings for men versus quadriceps for women. Can these patterns be changed by muscle training or conditioning exercises? That’s the next question for researchers to answer.