Knee-Deep in Research

Helping Hands for Hurting Knees

When it comes to research on knees, Terry Grindstaff, Ph.D., has plenty of helping hands — from Creighton students. More than 20 have helped him as research assistants since 2009, one reason why Grindstaff’s been able to catalogue more than 1,000 tests. Marcus Palimenio, a graduate assistant enrolled in Creighton’s three-year Doctor of Physical Therapy program, has worked in Grindstaff’s lab since 2013.

“It’s been nice to be exposed to this side of PT. It’s a unique opportunity,” says Palimenio, a former baseball player at Garden City Community College in Kansas, who, himself, has undergone knee surgery.

Learn more about Creighton’s knee research and the opportunities it offers students in this video.

Knee-Deep in Research

With a split-second shock, Nick Cerveny’s entire body jumps involuntarily as if he just experienced a body-wide hiccup. The 26-year-old, nine months removed from major reconstructive knee surgery, feels some discomfort. But he just laughs it off.

“The stimulus can be somewhat uncomfortable,” says Terry Grindstaff, Ph.D., assistant professor of physical therapy and researcher in the Rehabilitation Science Research Laboratory at Creighton. “But it does provide us and the patient with some very valuable information.”

Grindstaff has applied the same stimulus to himself many times — all in the name of science. Specifically, in search of the neuromuscular consequence of knee joint injury.

Grindstaff’s work covers a range of knee injuries — anterior cruciate ligament (ACL) tears, cartilage damage, osteoarthritis and more — among people of all ages and abilities. Visitors to his lab have included amazing athletes and sedentary seniors.

He’s trying to discover how knees go bad, how they can get better and ways to mitigate pain in what is the body’s largest and most injured joint. His work is getting noticed. Grindstaff and his colleagues have received more than $1.2 million in grant funding, and, in 2014, he received a New Investigator Award from the American Physical Therapy Association.

“He is, without a doubt,” says Deborah Givens, Ph.D., chair of the Department of Physical Therapy, “the most productive clinical researcher that I have encountered in my 20 years of experience in academic physical therapy.”

Knee Matters

Grindstaff’s research matters not just to Creighton student-athletes, with whom he’s worked since coming to campus in 2010. It’s also important for the middle-aged electrician who tore his meniscus but has to regularly climb a ladder as part of his job. It matters to the 65-year-old grandmother whose arthritis prevents her from walking with the grandkids in the park.

It matters to lots of folks.

Yes, to athletes, whom we most often associate with knee injuries. Overall, knee injuries make up about 55 percent of all sports injuries. Grindstaff has seen plenty of those. The Creighton University professor was an NAIA national-qualifying wrestler at Dakota Wesleyan University in Mitchell, S.D., where he earned an undergraduate degree in sports medicine. He also is among the medical staff for USA Wrestling and has traveled with its teams on trips to Russia, Eastern Europe and elsewhere.

But athletes are only part of the story. According to a National Ambulatory Medical Care Survey, there were 18.6 million visits to physicians in 2010 for knee issues. That’s up from 12.5 million in 2000. Of those visits, 10.7 million were made by people 45 and older.

In 2011, there were nearly 650,000 total knee replacements, one of the most common and costly musculoskeletal surgical procedures performed in the United States. That’s more than double the number of surgeries most often associated with older people — hip replacements. By 2030, according to one study, total knee replacements are expected to grow an astonishing 673 percent to 3.5 million.

What’s going on? Increased sports participation, especially among youth, certainly is a factor. But an increasingly obese and older population also contributes to the spike. The heavier we are, the more stress we put on our knees. The older we get, the more likely knees are to degenerate. Even diet can come into play. Poor biomechanics, too.

No matter the cause, people with bad or injured knees typically share a common consequence — loss of muscle function in the quadriceps femoris, the large muscle group covering the front of the thigh that helps straighten your knee and flex your hip when you walk or run. That’s what Grindstaff is studying.

But where most clinicians and researchers focus on this muscle group to help the knee, Grindstaff looks elsewhere — to the spine and brain.

“The classic approach for knee injuries — or, more broadly, the management of musculoskeletal injuries — is to focus on the injured area,” Grindstaff says.

The direction Grindstaff takes — an approach only a decade or so old — is more comprehensive, asking, “What’s the contribution from the brain?”

It’s All in the Head

Grindstaff’s primary investigations center on “quadriceps inhibition.” It’s an exploration of why the quadriceps muscle seems to not work as well after knee surgery. It’s not a matter of the quadriceps instantly losing its inherent strength, he says.

“The day before you have surgery, you can make your thigh muscle contract,” Grindstaff says. “The day after or even hours after surgery, you cannot contract the muscle at the same capacity. That’s driven neurologically, and I think that’s where we kind of miss it sometimes from a rehabilitation perspective. Clinically, we tend to only focus on strength.”

Quadriceps inhibition is a reflexive response, beyond our conscious control. The body’s nervous system, in a protective effort, stops or “inhibits” the quadriceps muscle from fully contracting. And quadriceps inhibition happens with a variety of knee injuries, whether it be a torn ACL, meniscus tear or osteoarthritis. It happens even if a saline solution is injected into a healthy knee, mimicking joint swelling or injury.

“Quadriceps inhibition is almost ubiquitous,” Grindstaff says. “It occurs with almost any knee injury.”

Once shut down, the quadriceps group weakens and atrophies. Efforts to strengthen the quadriceps muscle are limited and the quadriceps may never fully regain strength despite surgery or resolution of knee symptoms.

To see why this is so, Grindstaff and his staff have performed more than 1,000 tests on subjects. He estimates 70 percent of them were physically active who suffered a knee injury during or as a result of physical activity.

One test explores the role the spine reflexes play in quadriceps inhibition.

Most people are familiar with a knee-jerk reflex, in which the knee extends after the patellar tendon is hit with a reflex hammer. The reflex Grindstaff measures is very similar.

Grindstaff has subjects lie on a table and then attaches electrodes over three portions of the thigh muscle. The electrodes are connected to a machine that measures electrical activity in the quadriceps muscle. Another electrode, placed near the top of the thigh muscle, is used to elicit the reflex. A brief electrical stimulus is applied, activating the femoral nerve, which results in a quadriceps muscle contraction. A series of weak impulses are provided at first. Then the stimulus is increased. Subjects feel a brief but intense stimulus, and their thigh muscle contracts.

Another test explores the role the brain plays. Grindstaff and his student research assistants seat subjects in a chair, which looks like a high-tech version of a leg-extension machine found in most fitness facilities. Next, a coil is placed on the head. It is used to apply a magnetic stimulus to the motor cortex, which activates the thigh muscle. Muscle activity is measured with the same electrodes as in the previous test.

Terry Grindstaff, Ph.D., assistant professor of physical therapy, left, uses sophisticated technology to test the
response of the thigh muscle when a stimulus is applied to the brain’s motor cortex in patient Nick Cerveny.

A seven-inch-long scar tattoos the side of Cerveny’s left leg, a lifelong reminder of the January 2014 rugby match during which he tore his ACL and LCL (lateral collateral ligament) and partially detached his hamstring. That required two grafts, surgeons using the Achilles ligament from a cadaver to replace the torn ligaments. He’s back to running and lifting weights, but as Grindstaff’s tests show, his leg is not 100 percent.

Once seated in the chair and connected to the electrodes, Cerveny is asked to kick his lower leg as hard as he can to establish his maximum strength. Increasing levels of stimuli are then applied.

In people with knee injuries, the more intense stimuli register more activity in the quadriceps muscle than when the subject is kicking as hard as possible without any stimuli. That tells Grindstaff that Cerveny and other injured people like him aren’t using all of their thigh muscles.

Why does this matter?

Post-injury, people have to put more planning into how they walk, run, jump or skip. “It kind of steals resources available to do other things,” Grindstaff says. “If an athlete has to think a lot harder to get the thigh muscle to contract or think a lot harder on jumping mechanics or where her body is in space, now she can’t dedicate resources to the person in front of her trying to take the ball away. The ability to dual-task is compromised.”

And vice-versa. If the athlete is only thinking of the ball, he’s not dedicating enough thought to what’s going on with his leg, increasing the odds of another injury due to faulty mechanics.

How might that be overcome?

“I think cognitive thought or mental imagery has some really good potential there,” Grindstaff says. “Adding tasks to rehabilitation that require both cognitive thought and physical exertion are good options.”

The Brain and Pain

Another look at how the brain influences the knee comes with the work of Thomas Guck, Ph.D., a psychology professor and director of behavior science in Creighton’s Department of Family Medicine. A psychologist, he works in the area of pain perception and the psychology of pain, mostly chronic pain.

He’s working with Grindstaff specifically in an exploration of kinesiophobia, the fear of movement, and catastrophizing, the belief that something is worse than it actually is.

Individuals with higher levels of kinesiophobia and catastrophizing tend to have greater deficits in quadriceps strength, decreased physical function and report lower levels on quality-of-life measures. This further highlights the interaction between pain behavior and physical function.

Guck and Grindstaff are currently studying how health care providers can influence patient perceptions of pain. One group is told that treatment received will reduce pain and improve strength. A second group is told the treatment may or may not reduce pain and improve strength. The results of this study will better inform clinicians on how presentation of treatment options can influence patient outcomes.

Before an injury, athletes with healthy knees move without thinking. After an injury, though, many fear to move the same way they once did — even if they’re physically healed. “That’s a tough step for them to make, even though they may have recovered fully from an anatomical point of view,” Guck says. “One of the big issues is trust and harm.”

Also, rehabilitation often is accompanied by pain. But if damage isn’t being done to the injured knee, that pain is just part of the process and must be endured. If patients don’t rehabilitate as well as they can because of the pain, recovery can be delayed.

“That distinction is a tough one for some,” Guck says.

It helps to have a good physical therapist who knows the difference, helping patients get past the pain to “new levels of function.”

“If the patient believes they’re doing harm or damage anatomically, they’re not likely to do as well going forward,” Guck says. “If they come to believe that they are not doing harm or damage to their anatomy, they’re more likely to challenge their fear of pain and move forward.”

Also, it’s important to distinguish between acute pain — something that happens with tissue damage or an injury — and chronic pain, where the anatomy is healed, but pain persists.

“The question,” Guck says, “is, How well am I functioning even in the presence of pain? Am I doing all the things I want to do — dancing or walking or doing things important to me?”

It’s All in the Hips

Where Grindstaff and Guck turn to the spine and brain to find answers about the knee, colleague Dimitrios Katsavelis, Ph.D., turns to the hips.

Katsavelis, assistant professor in Creighton’s Department of Exercise Science and Pre-Health Professions, is most interested in how fatigue can lead to injury. In one of his tests, Katsavelis brought subjects to fatigue by having them run at various speeds — including all-out. What he found is that when the legs tire, proper flexion at the hip can’t occur. That prevents proper flexing at the knee and, thus, makes a knee injury more likely.

Also during fatigue, the shock-absorbing function of the knee doesn’t work as well.

“You cannot really absorb the shock, the forces you’re receiving from the ground, very well,” Katsavelis says. “That’s a lot of internal forces acting on the body.”

That force works against the tibia and the femur, causing bone-on-bone contact, which can lead to arthritis. The quadriceps muscle can help dissipate these forces.


Grindstaff has tested different interventions for people with knee pain, including manual therapies such as joint mobilization and manipulation, electrical stimulation and ice. So far, two interventions show the most promise.

The first is old-school and low-tech: ice.

The other is Transcutaneous Electrical Nerve Stimulation (TENS). That’s done via low-level electric current applied through electrodes.

“By altering some of the sensations at the knee, we can have a positive impact on muscle function,” Grindstaff says. “It’s kind of a common intervention used for pain relief, but we are using it in a different way than most clinicians would consider.”

Grindstaff has subjects wear the TENS unit throughout the day. “It kind of feels like your knee is falling asleep,” he says. The goal is to reduce pain.

Initial findings indicate patients with anterior knee pain and meniscus injuries can immediately increase quadriceps function by 5 percent. “That’s pretty exciting,” Grindstaff says. “Even if they do not have pain, if we are able to override the reflexive inhibition, it will help them to more effectively use their quadriceps muscle during rehabilitation.”

And TENS may be a better option than ice given that subjects can wear the TENS unit all day, even while exercising.

“I think it’s giving us options to help improve or augment our existing approach to knee injuries,” Grindstaff says. “Right now, we are very focused on looking at some of the causes of quadriceps inhibition and looking at preliminary ways we can have an initial impact. I think our future research will further examine these interventions by incorporating them with existing physical therapy programs and studying people for longer periods of time.”

Grindstaff mentions that he has a couple ideas in particular he hopes to test. He and his student researcher look at each other and smile. Grindstaff isn’t ready to say what they are.

Who knows. He and his Creighton students might discover an intervention that shocks us all.