FAQ Category: Knee

Full-thickness cartilage defects (down to the bone) in the knee come with two major problems. First, cartilage doesn’t heal well. Second, treatment often results in failure. One of the newer treatment options is autologous chondrocyte implantation (ACI).

In this procedure, chondrocytes (cartilage cells) taken from normal, healthy joint tissue are used to make more chondrocytes. The new cells fill in the hole where the defect exists in the damaged cartilage. It works well, but it has been limited mostly to younger patients. Older adults (45 years old and older) have been excluded from this approach.

Studies on the use of autologous chondrocyte implantation (ACI) among older adults are very limited. And there’s a basic philosophy that by age 45 or older, the patient would do better to have a total knee replacement instead of ACI. Recovery is faster with fewer problems. But a new study reports that cartilage implantation was just as successful in older patients as it is in younger ones.

And, in fact, comparing results of ACI in younger versus older patients in this study showed similar results. The success and failure rates were about the same between the two groups. Young or old, the same types of exclusions should remain in effect. These include the presence of inflammatory joint disease, metabolic or crystal disorders, ligament instability, and poor knee joint alignment. ACI is not an option in such cases or if X-rays show 50 per cent (or more) loss of joint space in the knee.

ACI may be extended to older adults who are healthy and active and who don’t want a total knee replacement just yet. They may find that pain relief and improved joint function available after ACI makes it possible to return to their previous social and recreational activities.

Careful patient selection (young or old) remains a key factor in the success of the ACI procedure. Age does not have to be an immediate strike against you. Obesity, noncompliance with the rehab program, tobacco use, and loss of joint space are major risk factors for failure. Such patients must be screened for and excluded from this type of surgery.

The orthopedic surgeon gets a lot of diagnostic clues from the history of what happened, how it happened, and the signs and symptoms you developed after the accident. There are some specific tests that can be done to identify which ligaments might have been injured and/or whether or not there was cartilage (or other soft tissue) damage.

In fact, there are actually dozens of tests that can be done. But the surgeon will be able to narrow it down to the most important clinical tests for your particular situation. For example, the clunking that you mentioned is a red flag for possible knee instability. This could be caused by a tear of the anterior cruciate ligament along with injury to other knee structures.

Diagnosing knee problem can be difficult due to the complexity of the structures and anatomical differences from patient to patient. There isn’t one test that provides the answer for each patient.

Scientists studying this problem have new tools and new technology to explore the normal and pathologic biomechanics of the knee and tests for knee instability. In the future, computer systems with the ability to measure and analyze movement will make it possible to identify types and degrees of joint instability. The hope is that it will be possible to plan ACL reconstruction surgery with each individual patient in mind.

For example, knowing the amount and direction of excess rotational movements (not just forward and back instability) is significant. These findings are important for the athlete who needs to jump, stop suddenly, pivot, shift, and cut quickly. Just repairing or reconstructing the torn ACL will not restore stability in the movements that require rotation. All other soft tissue injuries and imbalances must be identified and corrected.

It sounds like you had an acute lateral patellar dislocation. This means the kneecap moved off the midline of the knee and ended up along the outside of the knee. When this happens, the medial patellofemoral ligament (MPFL) is usually injured. Studies have shown that half the restraining force holding the kneecap in place comes from the MPFL. Successful treatment must address the condition of the MPFL. If it’s torn and is not repaired, then the chances of recurrent patellar dislocation increase dramatically.

Successful outcomes may depend on the type of surgery performed. Arthroscopic repair reduces the risk of injuring blood vessels and nerves in the knee. And any loose fragments of bone, cartilage, or meniscus can be removed easily.

But complete rupture of the MPFL at its femoral attachment may not be seen and cannot be restored fully by arthroscopic surgery alone. There may be other soft tissue injures that remain unidentified with arthroscopic repair. The surgeon relies on MRIs to help identify the location and extent of soft tissue damage.

You may find out more with an orthopedic re-evaluation. See your surgeon for a follow-up appointment. You’ll be able to find out what factors are involved and what are your treatment options. You may need additional imaging studies with CT scan and/or MRIs to find out for sure what else might be going on that’s hindering your complete recovery.

Muscle weakness is common with knee osteoarthritis. At first, scientists thought this was just linked with pain. Pain leads to inactivity, which leads to muscle atrophy and weakness. But further studies have shown there may be more to it than that.

A specific mechanism referred to as arthrogenous muscle inhibition (AMI) may be a key factor. This refers to an inhibition of motoneurons in and around the affected joint. Efforts to restore strength are unsuccessful even for people who don’t have joint pain.

Research is now focused on finding ways to interrupt or inhibit the firing of these signals that inhibit muscle function. One of those ways may be with static magnetic field (magnet) therapy. The results of a recent study from Taiwan showed that a magnetic knee wrap for patients with osteoarthritis is safe, effective, and low cost.

Using measures of strength, pain, and function, the patients who used the magnetic wrap showed significant improvement over the control group who wore a placebo wrap. The main focus of the study was the effect of magnetic knee wrap on quadriceps strength. In particular, isokinetic strength was measured.

Isokinetic refers to strengthening the muscle throughout the range of motion. Patients included had mild-to-moderate knee osteoarthritis with chronic knee pain. Everyone wore the knee wrap daily during their waking hours for 12 weeks. If they had arthritis in both knees, the wrap was worn on the more painful knee. If both knees were equally painful, the wrap was placed on the nondominant leg. Patients were advised not to exercise or participate in strength training of any kind during the 12 weeks period of time.

Strength improved in the magnetic wrap group right from the start. And strength continued to improve until it peaked at the end of the 12th week. On the other hand, the control group showed no improvement and even a mild decrease in strength. Patients in both groups were equally compliant (cooperative to wear the wrap as directed).

The authors believe this was the first scientific investigation into the effect of a magnetic knee wrap to improve quadriceps muscle strength. They concluded that there may be a role for static electromagnetic field in recovering lost strength in patients with painful knee arthritis.

In fact, they suspect the way the magnetic therapy works to improve strength isn’t by direct strengthening of the quadriceps muscle. They suggest that a static electromagnetic field may help turn the quadriceps muscle back on after being inhibited by changes in the nerve messages set up in response to pain signals.

The next step in exploring the use of static electromagnetic field for knee osteoarthritis is to conduct a similar study with patients who have more advanced (severe) arthritis. And a longer follow-up period for this study (and any future studies) would be helpful to see if the effects of turning off muscle inhibition associated with osteoarthritis are long-lasting.

It would be helpful to know if a short course of magnet therapy is all that’s needed to get the muscle action turned around. Strengthening programs would be more effective with better results than when conducted alone. And this added information might help explain why rehab to improve motor control and function has not helped improve quadriceps strength.

Slipping knee most likely refers to an unstable knee from injury of important ligaments or other soft tissues. For example, without the anterior cruciate ligament (ACL) to hold the lower leg stable, the tibia (lower leg bone) slips forward underneath the femur (thigh bone).

If it’s a severe enough injury, the person may feel a definite clunk as the bone shifts (subluxes). This type of injury is actually diagnosed by using clinical tests that reproduce this clunk. The two most commonly used tests are the Lachman test and the pivot-shift test.

The orthopedic surgeon or sports medicine specialist is able to grade the severity of the injury using these tests. That directs treatment. With athletes, the ability to jump, stop quickly, change direction (pivot and shift) is critical and must be restored.

Moderate-to-severe injuries (higher grades) may require surgery to reconstruct the knee. Milder injuries (lower grade) may respond to conservative (nonoperative care) with rest, activity modification, and antiinflammatory medications. Physical therapy to restore normal motion and strength is an important part of the return-to-sport equation.

It helps to have a working knowlege of the anatomy and pathophysiology (what happens on a cellular level after injury) when managing muscle injuries. At the microscopic level, muscles are arranged in small units or bundles. They are surrounded by protective layers of tissue and satellite cells. The satellite cells are a type of stem cell that stand by in case of injury. They start the healing response when it’s needed.

Muscle injury occurs when the muscle fibers are stretched too far, too fast. The strain or tear usually starts at the weakest part of the contractile unit. The weakest point of the muscle (where a strain is most likely to occur) is at the myotendinous junction. This is the transition zone between the muscle fibers and the tendon that attaches the muscle to the bone. The muscle is soft and pliable. The tendon is more like tough connective tissue and less resistant to sudden force.

Once an injury has occurred, the body responds quickly. First, it mobilizes inflammatory cells and sends them to the area of injury. That’s when we get pain, swelling, and a warmth or even hot feeling around the injured site. That’s the acute phase (first 24 to 48 hours).

Then, the satellite cells are activated to create new muscle fibers. They help knit the torn area back together over the next six to eight weeks. In the last phase of muscle healing, the body spends some time remodeling the tissue.

An early or acute injury is usually managed with the RICE principle (rest, ice, compression, elevation). The goal is to reduce swelling and pain while restoring motion. Over-the-counter drugs such as Tylenol for pain relief or ibuprofen (nonsteroidal anti-inflammatory drug or NSAID) may be presecribed during the early phases of healing and recovery (seven to 10 days).

Long-term use of NSAIDs is no longer advised. Animal studies have shown that muscle force and function can be inhibited with prolonged NSAID use. These drugs may reduce the number of satellite cells available for tissue regeneration.

Resting the injured muscle is a good idea at first but long-term immobilization should be avoided. At first, the pain prevents movement. And during the acute phase, keeping the muscle and joints still helps protect the injured area from further damage. Scar tissue formation is also less likely if the strained muscle is given a short rest from a repeated contract-relax sequence.

Gentle movement should be resumed within 48 hours. Usually, this coincides with a natural decrease in pain and swelling. The task now is to regain motion and eventually full strength. For athletes, a physical therapist or athletic trainer can be very helpful during this phase of rehab and recovery. Sports experts recommend waiting to resume sports activity until the injured side has at least 80 per cent of strength when compared to the uninjured side.

Muscle injury occurs when the muscle fibers are stretched too far, too fast. The strain or tear usually starts at the weakest part of the contractile unit. And the injury is most likely to occur during an eccentric contraction.

Eccentric contraction means the muscle is shortened or already contracted and is now lengthening. An example of this is the biceps muscle in the upper arm. Making a fist and bending your elbow as much as possible is a concentric contraction of the biceps muscle. Now, as you lower your hand and straighten the elbow, the biceps muscle is contracting eccentrically (lengthening or stretching out).

The weakest point of the muscle (where a strain is most likely to occur) is at the myotendinous junction. This is the transition zone between the muscle fibers and the tendon that attaches the muscle to the bone. The muscle is soft and pliable. The tendon is more like tough connective tissue and less resistant to sudden force.

Some muscles are more prone to injury because of the location or fiber type. For example, muscles that attach across two different joints are under increased force from different joint angles and movement. The hamstrings behind the thigh cross the hip and knee. The gastrocnemius (calf) muscle crosses the knee and ankle.These are two of the most commonly injured two-joint muscles.

Athletes with muscle strength imbalances appear to be at increased risk of a primary (first) muscle strain. That’s one reason why a preseason screening program is advised for all competitive athletes. Training errors and poor biomechanics are two other possible risk factors for muscle imbalances that can lead to a muscle strain.

For older adults who are active in sports or other physical activities, muscle atrophy and loss of tendon flexibility (contractility) are major risk factors. There’s some evidence that stretching before physical activity may help prevent muscle strains. But this is currently a controversial area with some studies showing no preventive effect of stretching before exercising.

It makes sense that warm muscles are more flexible and possibly less prone to strain injury. Warm-up activities and stretching are still advised by some as part of strain injury prevention. Until further studies can clear up confusion around this subject, it can’t hurt to include warm-ups in any training program and it may help.

You may be referring to hyaluronic acid, a substance that is present in the fluid structure outside, around, and between cells. It is a thick substance that is sometimes referred to as a goo molecule. It’s found in the synovial fluid that lines and lubricates the joints. It is also the protective coating around each cartilage cell.

Hyaluronic acid has the ability to suck up and water needed to cushion joints from the shear stresses and compression they are subjected to. It seems to have many roles. Besides remaining elastic under high shear forces, it also makes it possible for the joint to withstand the heat that develops within the joint even with low shear stress.

Hyaluronic acid can store mechanical energy for release later when needed. It bathes the cartilage cells with fluid and keeps them nourished. It even has antiinflammatory properties to reduce joint inflammation and an ability to reduce pain — or at least the perception of pain.

Although the treatment works well for some people, it doesn’t have the same effect on everyone. Some patients obtain no relief whatsoever from their painful symptoms. Up to one third of the patients treated with viscosupplementation experience some type of negative side effect. Reports of temporary effects such as pain, warmth, swelling at the injection site have been noted.

It’s not clear yet which patients are the best candidates for this treatment. Your father was lucky to be one who responded well. More time and larger studies will eventually help us sort out who can benefit from this treatment and who should try something else.

Core training refers to a strengthening program of muscles in the trunk, which includes the abdomen, pelvis, and low back. More and more studies are showing the positive benefits of doing these lumbopelvic stabilization exercises. They have been shown to benefit people with problems in the lower quadrant. This can include low back, hip, and knee problems.

The relationship between patellofemoral pain syndrome (PFPS) and weakness of the core muscles has been demonstrated in the last few years. As a result, more studies are focusing on the benefit of doing these exercises to decrease knee pain and improve function in patients with PFPS.

The exact reason for the link between lumbopelvic stabilization and PFPS isn’t completely clear. One theory is that the body is a dynamic functional unit. Anything that affects one area has the potential to affect other regions along the kinetic chain. In the case of knee problems, the foot and ankle below and the hip and spine above can impact what happens at the knee.

Treatment that takes into consideration the biomechanical links between the foot, ankle, knee, hip, pelvis, and spine seem to be most effective in treating PFPS. The results of numerous studies support the idea that PFPS occurs as a result of multiple interactions (dysfunctions) between these regions.

When done properly, core training can’t hurt and it may be very beneficial — for the knee as well as other areas of the body. If you have been diagnosed with PFPS and have not received any treatment for this problem, you may want to try a couple of different treatment options combined with Core training.

This approach seems to have the kind of results (decreased pain, improved function, faster return to sports) most athletes are looking for. A physical therapist can help you with this kind of program. An individually prescribed program is recommended based on your particular alignment, areas of weakness, and/or loss of motor control and proprioception (joint sense of position).

You can do most of the exercises at home on your own with occasional direction from the therapist. The program will be progressed according to your responses measured by pain and function.

Physical therapists often treat athletes with patellofemoral pain syndrome (PFPS), a common cause of knee pain when squatting, kneeling, running, and going up and down stairs. There isn’t one individual test that can confirm the diagnosis of PFPS. And there isn’t one best way to treat the problem either.

That puts therapists in a bit of a quandary when it comes to choosing the right way to treat patients with this problem. Many studies have been done to sort out what works best. Is it taping? Taping with exercise? Exercise alone? If exercise helps, what kind of exercise is advised?

It is believed that PFPS occurs because of altered biomechanics between the patella (knee cap) and the femur (thigh bone). The patellofemoral joint is where the kneecap moves up and down over the lower end of the femur. It makes sense that restoring normal patellofemoral biomechanics should reduce pain and improve function. But a one-size-fits-all type of treatment program has not been found.

Studies show that taping the knee to improve patellar tracking (movement up and down over the femur) can be helpful. But the proper (most effective) method of taping is still under investigation. Other studies have shown that strengthening the quadriceps muscle over the front of the thigh and/or hip muscles can alter the symptoms of PFPS. Exercising these muscles seems to improve proprioception (sense of joint position) in the leg. The result is decreased pain and improved function.

Yet another direction in treatment has been the use of manual therapy techniques for PFPS. In this approach, the therapist uses nonthrust or thrust manipulations of the hip, knee, and/or patella to relieve pain and improve movement. There is support that this method is successful.

Using multiple treatment techniques at the same time to affect the entire kinetic chain (foot to spine) may work for PFPS because it addresses the biomechanical links between the foot, ankle, knee, hip, pelvis, and spine.

The results of studies so far support the idea that PFPS occurs as a result of multiple interactions (dysfunctions) between these regions. Treating the lower extremity as a functional unit may respond no matter what combination of specific interventions are used.

Any kind of surgery, no matter how simple, can have its problems. Postoperative complications can include infection or poor wound healing. In the case of autologous chondrocyte implantation (ACI), there are some additional unique problems that can occur.

ACI is a two- or three-step process. The procedure is done by taking normal, healthy cartilage cells from the patient. They use these cells to grow more cells and then reimplant the new batch of cells in the damaged area of the knee joint. The new cells usually adapt well to the new environment. That’s the three-step process. In a two-step procedure, a patch of healthy cells large enough to cover the defect is harvested and transplanted. This leaves out the middle step of growing extra cartilage cells in the laboratory setting.

Until recently, reports on the long-term results of this procedure and any complications have been limited. Small studies with only a few patients were reported on. But a group of three surgeons from Europe pooled their cases together and analyzed and reported on the results. They were specifically interested in looking at complications from the ACI procedure.

Three different ACI techniques were used. The three methods used were: 1) periosteum-covered ACI, 2) Chondrogide membrane covered ACI, and 3) a three-dimensional matrix-associated ACI. A group of over 300 patients who had one of these ACI procedures were followed to see which patients had the most problems after ACI and what those problems were.

They found four major problems after ACI: 1) hypertrophy, 2) disturbed or inadequate fusion, 3) delamination, 4) graft failure. Hypertrophy refers to overgrowth of the transplanted tissue. Insufficient fusion describes patients where the transplant just didn’t regenerate like it should. The edges between the healthy, normal tissue and the implanted cells don’t meld together to form a solid, smooth surface. Delamination is the separation of the cartilage layer from the bone underneath.

In a few cases, there was osteonecrosis (death of the bone underneath the cartilage transplant). In all cases, patients were diagnosed on the basis of pain and/or loss of function after the surgery. Symptoms occurred anywhere from the first six months up to three years later.

Right now, the treatment approach in revision surgery is to remove the damaged, dead, or insufficient tissue and regraft the defect. This usually results in a good return of function, but there are no studies yet on the clinical outcomes of revision surgery for failed ACI.

Persistent pain, loss of motion, and decreased function still present six months after the first surgery are not normal responses. It’s probably time for a follow-up phone call to your doctor’s office (if not a follow-up visit).

Your symptoms could be a sign of a failed implantation. An MRI may show abnormal cartilage or bone signals in the area that was operated on. Sometimes arthroscopic surgery is the only way to find out what’s going on. If there is a failure of the tissue to regenerate or fuse, then a revision procedure may be needed.

Sometimes the transplanted graft shifts away from the underlying bone. This is called delamination and requires repair as well. A second (revision) operation may be needed. Right now, the treatment approach in revision surgery is to remove the damaged, dead, or insufficient tissue and regraft the defect. This usually results in a good return of function, but there are no studies yet on the clinical outcomes of revision surgery for failed ACI.

But before making any assumptions or predictions, see your surgeon for a follow-up appointment. There may be a simple solution to the problem. Early diagnosis and intervention is always advised to prevent further long-term complications.

The tibial plateau is the flat top of the upper portion of the tibia (lower leg bone). This type of fracture was once called a bumper or fender fracture. During a car accident (fender bender), force directed from the femur (thigh bone) down onto the tibial plateau, results in fracture of the plateau. Car accidents aren’t the only way this type of injury occurs. Falls, industrial accidents, and getting hit by a car as a pedestrian are also possible ways to sustain a tibial plateau fracture.

Surgery to repair unstable fractures is usually done by open reduction and internal fixation (ORIF) using a plate and screws. Bone graft material is used whenever there’s a need for extra bone to support a fracture site or defect in the bone. It’s easily available (taken from the patient’s pelvic bone) and inexpensive. And it is bone inductive (fosters bone growth) to provide structural support to the damaged area.

The downside is that the graft site can be painful for a very long time. In some cases, infection can delay recovery. Patients often report difficulty walking due to the pain. And the combination of pain and impaired walking result in loss of function.

To avoid the major and minor complications of bone graft, scientists are exploring the use of bone substitutes. At the present time, bone graft is considered more risky with a greater chance of complications compared with bone substitutes. But bone substitutes are still considered somewhat experimental.

Studies so far have shown that there is a higher rate of subsidence in the bone graft group. Subsidence refers to the sinking or collapse of bone into itself. Bone substitute is an acceptable replacement for bone graft material. It may be a better choice. It is stiffer, offers more support, and holds up better under load compared with autogenous bone graft. There is also less sideways shifting or subsidence of the healing bone with this type of bone substitute.

Talk to your surgeon about this decision. He or she may have some additional thoughts or comments. It’s always wise to go with whatever the surgeon is most comfortable or more experienced with. The main goal is to use a graft material that will prevent collapse of the joint surface and underlying bone.

The ACL, the anterior cruciate ligament, is a major ligament of the knee. It is one of four ligaments that allow you to move your knee as you do.

The reason it is a common injury among certain types of athletes is because of the movements the athletes make. Certain sports, like basketball, have a high risk of ACL injury. It’s the stopping and starting, and turning that can put the strain on the knee and injure the ligament.

Of course, you don’t have to be an athlete to injure your ACL. Many people are injured doing every day things but they fall or turn the wrong way, causing the ACL to tear.

The ACL, or the anterior cruciate ligament is one of four ligaments that help support and stabilize the knee. Without the ligaments, there would be nothing that could help you control the knee’s movements. The ACL is responsible for pulling on the tibia, or shin bone. When you straighten your leg, the ACL pulls on the muscles to stabilize the tibia, preventing it from moving too far. If you have a ruptured or torn ACL, that stability isn’t there and your knee may tend to give way all of a sudden.

Researchers have documented the beneficial effect of physical therapy after severe trauma such as your son experienced. A special study called the Lower Extremity Assessment Project (LEAP) project has collected data on patients at eight level I trauma centers in the United States.

Analysis of the information collected shows that patients who are identified as needing physical therapy don’t always get these services. Those who do, have better overall results as measured by range-of-motion, physical activities, daily self-care, and walking or climbing stairs.

Why doesn’t everyone get this kind of treatment? There may not be one single reason. First, there are always reimbursement issues to consider. Patients with adequate health insurance are more likely to get the help they need. Those who don’t have health care coverage and have to pay expenses out-of-pocket may bypass the services.

Second, there isn’t a standard measure to help orthopedic surgeons or primary care physicians identify who needs therapy. Third, some patients are just more likely than others to seek additional services. This idea is referred to as patient self-selection.

The benefits of physical therapy for various health care problems are currently under investigation. Studies show positive effects of physical therapy for patients with total hip replacements, chronic low back pain, whiplash injuries, strokes, and hip fractures. As more studies are done, further information will be added to help insurance companies and self-paying patients see the long-term benefit of this valuable service. In the end, early and adequate rehab can save third party payers and patients money.

Degenerative joint disease (also known as osteoarthritis or OA) is a common problem in the aging adult. Two out of 10 people over the age of 60 develop OA. Knee arthritis is especially common. Pain and loss of motion from this condition can really limit your activities and lead to increasing disability.

At the same time, surgeons are able to replace the knee joint with a perfectly functioning implant called a total knee replacement (TKR). In fact, TKRs have become so successful their number has increased over 80 per cent in the past 10 years.

Scientists collecting data on TKR patients have noticed a very important trend. As you have noticed, once the first knee joint is replaced, it seems there is a predictable pattern of deterioration in the opposite (nonoperated) knee. It’s not uncommon for patients with one TKR to end up having a second joint replacement on the other leg.

Is this a coincidence or is there a reason for this pattern? A recent study from a Biomechanics and Sports Medicine Laboratory at the University of Tennessee was able to shed some light on this. They looked at the angle of the knee in the operated and nonoperated knees of 18 patients and compared it to with an equal number of knees in healthy adults (the control group).

They found an increase in the first peak knee adduction moment of the nonoperated leg (compared to healthy controls and even compared to the operated leg). The adduction moment is the angle formed by the femur (upper leg or thigh) as it connects at the knee with the tibia (lower leg). The measurement is taken in the frontal plane. That means from the front of the patient rather than from the side or from the back. The first peak moment occurs as the person steps onto the foot (stance phase).

The increase in angle suggests there may be some change in the biomechanics of the knee and leg during the stance phase of walking when the patient puts weight on the leg. It’s also possible that the patient has a new knee but still walks with the abnormal gait pattern that was present before surgery. This effect could speed up deterioration of the other knee leading to osteoarthritis and the need for a second knee replacement.

So for now, it looks like your observation may be correct. Since researchers have just started looking for reasons why, we don’t know if changes present before the first knee replacement are a factor or if knee angles, uneven loads placed on the knees, or some other factors are the cause. And it’s not clear yet if surgeons can predict who will develop problems on the opposite side based on these findings. More studies are needed to sort out all the effects and factors.

Knee arthritis affects a large number of older adults each year. Risk factors are not completely understood. Recent evidence points to loss of hip strength as a possible contributing factor. Foot mechanics such as toeing-in or toeing-out has also been suggested as having an important role in the start of knee osteoarthritis.

Hip abductor muscle weakness changes the alignment of the leg (and knee) when a person is standing upright. The hip abductor muscle moves the leg away from the body. Weakness of the hip abductors causes the pelvis to drop on the contralateral> (other side). This occurs as the contralateral leg swings through when walking.

As the leg swings through, there is a shift in the body’s center of gravity toward the swing contralateral leg. The result is an increased force or load on the medial knee joint of the standing (supportive) leg. Medial refers to the side of the knee closest to the other knee. This idea explains kinetic forces from the top down that contribute to the development of knee degeneration leading to osteoarthritis.

On the other hand, there are equally important forces from the bottom up. And that refers to the foot position and biomechanics of the foot and lower leg acting on the knee. A toe-out position of the foot actually reduces the force of excessive abduction. It turns out that people who turn out may have less risk of knee deterioration compared with people who don’t toe out or who toe out less.

Pain or other symptoms experienced at a site remote from the cause of the problem is called referred pain. It is a fairly common problem that physical therapists are trained to watch out for. For example, knee pain can occur as a result of low back, hip, sacroiliac, or ankle impairments.

With any musculoskeletal problem, therapists conduct a thorough screening exam to make sure the problem has a musculoskeletal origin and is within the scope of their practice. To do this, they use a screening model that includes past medical history, risk factors, clinical presentation, and associated signs and symptoms.

An understanding of the clinical presentation comes from a broad exam referred to as a regional interdependence exam. By expanding the exam to include a broad region (not just a single joint), problems like this can be identified quickly and treated appropriately. This helps prevent delays and the extra cost of treating the wrong thing.

There is some convincing evidence that altered kinematics is a major factor in patellofemoral pain syndrome (PFPS). Kinematics refers to patterns of movement — specifically how the patellofemoral joint and the knee joint rotate and glide in relation to one another during motion.

The patellofemoral joint occurs where the patella (kneecap) glides up and down over the femur (thighbone). Increased pressure from contact between the patella and the femur can lead to PFPS. This is called retropatellar stress — it means behind the kneecap.

Stress on the patellofemoral joint is made worse by rotations of the lower leg during weight-bearing activities. And repetitive actions with weight-bearing load during running and jumping increase retropatellar stress. The result is PFPS.

The mechanical factors that cause PFPS are likely present when you do the particular activities you are practicing. So doing more of them can make the problem worse. Altered hip and knee motion during weight bearing activities seems to be the main culprit.

Studies show that in athletes with PFPS (especially female athletes), there is an external rotation movement that occurs in the knee during single-leg squats and jumps. Evidently, this motion is not present in athletes who don’t have PFPS.

A closer look at the dynamics of movement has shown that when it comes to PFPS, changes in hip motion may be just as important as what the knee is doing. It appears that athletes who adduct the hip (knee moves toward the other knee) during single-leg squat motions have a greater tendency to develop PFPS. PFPS is more likely to occur if the knee externally rotates at the same time. The overall pattern of motion is one of medial collapse, sometimes referred to as dynamic knee valgus.

Training to stabilize the hip and retrain the knee to reduce the amount of external rotation during weight-bearing activities may be the answer. Physical therapists are actively studying this problem and looking for a solution. Someday, it may even be possible to identify athletes at risk for PFPS and put a stop to it before it even starts.