FAQ Category: Knee

A very good question. First of all, only a piece of the hamstring tendon is removed. At least half or more of the tendon is left intact. The postharvest strength of the graft tendon must be strong enough for early rehab and daily activities.

If the graft doesn’t hold it usually pulls away from the bone with a little piece of bone attached. This is called bone avulsion.

Before these grafts were ever used on patients, scientists used animal and cadaver studies to test the strength of the tendons before and after grafting. This is how they know which tendons will hold up after a piece is removed for use as a graft.

They also found that ACL tensile strength decreased over 50 percent between age 20 and 50. This isn’t true of the patellar tendon. During this same time period, tensile strength of the patellar tendon doesn’t change. That makes the patellar tendon a good graft choice.

Fortunately there is more than one tendon available for grafting. And if you don’t use your own tissue, it may be possible to obtain tendon grafts from a donor bank.

In the case of an ACL repair, the surgeon will inspect the damage first in order to decide what has happened and what to do next. The previous graft will be examined for partial or full-thickness tear. In some cases a revision or repair of the graft is possible.

If that’s not the case then the knee is reconstructed again. If your surgeon used the hamstring tendon last time, then the patellar tendon is the next logical choice.

Scientists are also looking at the use of the very strong quadriceps tendon. They found that even after taking a piece of the quadriceps tendon for grafting, the quadriceps tendon is still stronger than the patellar tendon was before a piece was removed to use as a graft.

Discoid refers to a round-shape. Lateral means outside or away from the body. Meniscus (single) or menisci (plural) refers to a type of cartilage found most often in the knee.

The normal meniscus is a mature crescent-moon shape. A discoid meniscus is usually a very early crescent moon shape but thicker in depth. It’s more common to find a discoid meniscus in the lateral edge of the knee joint.

The problem with this is that the discoid shape makes a barrier to normal contact between the articular surfaces of the knee. This unusual anatomy develops before birth. OCD a fairly rare problem but a discoid lateral meniscus is even more rare, affecting people of Japanese origins more than any other group.

It can result in mechanical deformities and a condition called osteochondritis dissecans or OCD. In OCD the cartilage and a thin layer of bone pulls away from the joint. It sounds like this may be what you are describing happened to you.

The kind of test you’re describing sounds like the normal joint gap that’s present when pressure is applied. Usually there is slightly more movement on the outside edge of the knee joint compared to the inside. There’s also more motion when the knee is bent compared to when it’s straight.

When the knee is fully straightened, it’s called the closed-pack joint position. That’s the most stable position of the joint so it makes sense the joint gap or laxity is the least in this position. The opposite is true for the open-pack joint position (flexion).

You didn’t say what kind of operation you’re having. If you’ve torn the ligaments and you’re having a ligament repair, then the surgeon will try to restore your normal joint laxity. With a joint replacement sometimes the ligaments inside the knee are kept and sometimes they are removed. The kind of implant you get depends on whether or not you still have your ligaments. Again, the surgeon tries to balance joint movement to mimic normal as much as possible.

This would be a good question to ask next time you have the chance.

You may be describing the anterior drawer test. This is a test for ligament laxity or looseness. The lower leg bone (tibia) slides or glides forward underneath the thighbone (femur). A certain amount of slide or glide is normal. Too much sliding around is a sign that one of the ligaments inside the knee joint may be torn or damaged.

There is a series of tests for knee ligaments. If you’ve had the anterior drawer test, you’ve probably also been tested for side-to-side and rotational motion. All of these movements are needed for normal motion. Too much or not enough joint “play” or laxity can cause problems and put you at risk for future injury.

Joint laxity refers to how tight or loose a joint is. Laxity is determined naturally by your genetic makeup. Sometimes people are naturally loose or tight. In other cases one or more ligaments has been stretched or even torn with use and age. This can increase the joint laxity causing problems. Uneven wear and tear on the joint is one such problem. It can lead to degenerative arthritis and the need for a joint replacement.

The surgeon tries to mimic the normal knee as much as possible when putting in an artificial joint. Matching your natural laxity is the goal but can be difficult.

A recent study of knee joint laxity before and after total knee replacement made some interesting discoveries. The researchers found that the lateral or outside edge of the knee joint is more lax than the medial or inside joint line. On testing, this is called the joint gap. They also reported less lateral laxity after joint replacement.

There’s no way to change joint laxity without surgery. Muscle strengthening helps protect the joint when the ligaments don’t hold the joint stable. It sounds like you’re already working on that. Your surgeon will balance the joint laxity during the operation.

There probably isn’t a direct link between the Rocky Mountain Spotted Fever and your new knee pain. A doctor would need to tell you for sure. Sometimes there is a residual arthritis that crops up after RMSF or Lyme disease. Both conditions are infectious diseases spread by the bite of a tick.

There are two other possible factors. One is weight loss. If you lost a major portion of body weight during your illness, you may have lost muscle bulk and strength as well. Bones are at increased risk of fracture without the protection of strong muscles around the joints.

The second is your training schedule. Many athletes jump right back into training where they left off instead of building up gradually. Many stress injuries occur when training frequency and intensity are too much too soon.

See a medical doctor before continuing your training program. If you’re cleared to go ahead, then step back a few notches and build up your strength first then endurance for the triathlon. If you were off for three months, you can expect it to take three months to regain your former training level.

It’s been clear for a long time that bone stress injuries occur from overuse. Not only military recruits but also athletes are at risk. More recently it has been observed that healthy adults starting a new or intense physical activity or exercise also suffer from stress fractures.

There may not be one single factor for everyone. Women seem to be at higher risk than men. This may have hormonal reasons or it could be biomechanical. For example women have a shorter stride length during marching. They may compensate by lengthening their stride and hitting the ground harder with their heels.

In a recent study from Finland military recruits who had been running before beginning military training had fewer stress fractures. This suggests gradual training may be a way to avoid stress fractures. Other possible factors include genetics, type of exercise, and terrain.

Diagnosing stress fractures isn’t easy. As you know they don’t show up on X-rays in the early stages. This is called a false negative. In other words, the X-ray was read as normal when there really was a problem.

Bone scans have the opposite problem. They often indicate there is a problem when there isn’t one. This is called a false positive. False positives are more common with children and teenagers who are still growing or remodeling bone.

MRIs seem to offer the best results when looking for bone stress injuries. In a recent study of military trainees with exercise-induced knee pain, two separate radiologists read the patients’ MRIs. They did this without knowing the patient’s symptoms or history. They didn’t consult with each other. There was good agreement between the two physicians and an accurate result with the MRI.

MRIs can’t show the difference between bone bruises and bone stress injuries because bone marrow edema is present in both. In such cases the physician must rely on the history.

Problems with motion, strength, and balance occur in up to 20 percent of the patients who have a total knee replacement. The reasons vary and sometimes are never fully understood. In cases where the cause of the problem is clear, the therapist can apply a specific treatment to regain motion.

Aggressive physical therapy (PT) is often needed when problems persist as much as seven months from the surgery. There’s not much danger that anything will happen to the implant with hands on PT. Besides stretching the muscles the therapist may also us a technique called joint mobilization to improve motion.

In mobilization one half of the joint is moved or glided along the other side. During stretching or mobilization you may be put in positions with strong pressure applied. This is necessary to avoid a second operation to surgically manipulate the joint.

Don’t be afraid to ask the therapist to explain what he or she is doing. Express your concerns so that you can understand your own treatment.

You may have what’s called a contracture. Muscle or joint tightness keeps the joint from moving to the end of its range. If you can’t straighten it out, it’s called a knee flexion contracture because your knee is stuck in flexion.

There are other causes for contractures. Sometimes there’s swelling in the joint. The muscles on either side of the joint may be imbalanced and fighting against each other. In other cases the implant is not aligned properly. Scar tissue can also pose a problem.

By six months you should have all of your motion back. It’s best to discuss this with your orthopedic surgeon. A short course of physical therapy may be needed. If that doesn’t work then sometimes a second operation is needed. Don’t wait because the problem isn’t likely to go away on its own. Early treatment usually results in better and faster results.

There may be some cause for concern. Temperature increases in the joint can cause cell death and fibrous tissue to form. These changes can lead to pain and implant loosening.

A recent study at the University of Washington (Seattle) compared the temperature inside three types of knees. They measured the knees of normal adults, adults with arthritis, and patients with total knee replacements. The normal knees increased temperature by about one-degree after 20 to 40 minutes of activity (biking, walking).

Some of the implants had 2 to 3-degree changes. Knee replacements made of cobalt-chromium seem to generate the greatest amount of heat. Find out what kind of implant you have and what’s normal for that replacement. Make sure you go to your follow-up appointments with the surgeon. X-rays can be used to detect any early problems with the implant. Warmth can also be a sign of infection, which should be evaluated by your doctor.

No, many patients report warmth or heat in their replaced knees. It’s more likely to happen or to be noticed in the first two years after getting the new knee joint.

Research has shown there are normal knee temperature increases in the knee. Using temperature sensors we know there’s a one-degree increase with activity like walking or biking. Many joint implants heat up the synovial tissue around the joint by two to three degrees.

The cobalt-chrome with polyethylene implant has higher temperature increases (five to seven degrees). The rotating hinge knee implant has as much as a nine-degree increase after 40 minutes of activity. This suggests that friction from exercise is not dispersed right away.

Tell your orthopedic surgeon about your symptoms. You may need closer follow-up if the heat continues. There’s some concern about the life of the implant, too. Over time the increased heat may prevent new cell growth needed for strong bones around the implant. Bone loss or bone resorption can lead to loosening of the implant.

It’s true that heat can build up inside a joint replacement from friction during activity. It doesn’t always go away fast enough. The temperature goes up with use. Half the increase occurs during the first five to six minutes of exercise (walking or biking). The maximum temperature occurs after the first hour.

Blood supply to the joint helps cool any temperature increases. The patient’s size, activity level, and type of training affect temperature. Synovial fluid in the joint helps transfer the heat to nearby tissues.

Right now there are more unknowns than knowns about this problem. For example doctors don’t know if age makes a difference. It seems like younger (more active) patients would have greater temperature increases. Studies haven’t proven this yet.

Activity and exercise are important though. So until doctors have an answer to this question, it’s best to keep a consistent level of activity and exercise. Keep your regular follow-up appointments with the surgeon to check your implant each year, too.

The box heel touch is an exercise used to improve active control of the knee. The goal is to avoid letting the standing knee collapse inward while stepping down off a 12-inch box. As the athlete stands on the box with one leg, he or she lowers the other leg to touch the heel to the floor and come back up. The supporting leg must hold steady without angling in or out.

Once the athlete can do this exercise using neutral knee alignment there is a next step. Place a foam pad on top of the box. The balance pad decreases the stability of the supporting surface. The athlete must maintain balance while completing this exercise. Be sure and use a mirror to help monitor the position of the knee. Any time the knee collapses inward, correct the position before going on. Different size and density of foam pads can be used to offer more or less of a challenge.

ACL injuries are common in athletes who jump, pivot, twist, or make sudden cutting movements. Girls are four to six times more likely than men to injure the ACL. Scientists aren’t sure why but they are studying this problem closely.

The latest findings suggest a problem with neuromuscular control. Any muscle weakness, loss of power, or failure to activate the muscles can lead to increased knee load. When the load is too much for the muscles, the ligaments tear or rupture.

One thing to watch for is a difference in strength from side to side. If one leg is 20 percent (or more) stronger than the other leg, there may be a neuromuscular imbalance. An athletic trainer or physical therapist can test you on a variety of hopping tasks. Any differences from side to side may help identify areas of weakness. Neuromuscular training for specific deficits is recommended.

When athletes perform a tuck jump, they start in the “athletic position” with feet shoulder width apart. From a slight crouch the athlete swings the arms behind and jumps straight up. The knees are pulled up as high as possible and tucked under the bottom.

There are several common mistakes athletes make when completing the tuck jump.

There are many factors involved in choosing the right implant for each patient. The goal is to use the implant that can give the most motion and function without losing stability. Some implants have more constraint or limits than others.

The condition of the soft tissues in and around the joint is a big factor in implant selection. The surgeon must try and balance these structures to allow as much flexion and extension as possible.

Sometimes the ligaments are torn or the cartilage is damaged. The surgeon may try to save these structures. Or it may be necessary to remove them. Certain knee implants are designed based on whether the ligaments are present or absent.

The patient’s activity level can also make a difference. Implants with greater constraint puts more stress and load on the implant-bone interface. A very active person may experience implant loosening and failure with this type of joint replacement.

There are other things the surgeon must think about. It makes a difference if the patient is bow-legged or knock-kneed. If the kneecap must be removed (or has already been taken out), the load on the ligaments increases. Choosing the right implant is a challenging and important task for any surgeon.

Actually, no. You can probably thank your surgeon for being so careful. A recent study from the Anderson Orthopaedic Research Institute has shown that implants with a longer shelf life are also linked with greater amounts of osteolysis.

Osteolysis is the bone loss that comes when bits of bone and debris from the implant flake off. Not only does this cause bone loss but it can also weaken the implant so that it can come loose. Osteolysis can also weaken the bone leading to fracture.

The risk of osteolysis increases by a factor of 1.5 for every year the insert stays on the shelf. It’s thought that the quality of the plastic components is less with time. This can contribute to implant failure and other complications.

Osteolysis is a term to define bone loss. It’s not uncommon after total knee replacements (TKRs). Bits of bone and debris from the back of the implant fleck off over time. The tibial plateau is referring to the lower leg implant. It’s more of a flat surface (hence the term ‘plateau’) compared to the round end of the femoral (thigh) side of the implant. The medial side is the inside edge of the joint.

Scientists are studying this problem. They are trying to reduce the amount of osteolysis. So far they’ve found three risk factors. These include polishing the back of the implant (where it joins the bone). The second is using a different method of sterilization. The one risk factor that can’t be changed is gender. Men are much more likely to have osteolysis after TKR compared to women.

With mild osteolysis you’ll want to keep making regular visits to your surgeon for follow-up. X-rays taken over time will help make sure you get further treatment when it’s needed sooner than later.