Playing for Pain: Athletes and osteoarthritis

The high school basketball star lies on the operating table, his damaged meniscus about to be arthroscopically removed. The orthopedic surgeon, most of his face hidden by his mask, turns to the camera.

"He'll have a higher incidence of arthritis as he gets older than you or I would," the surgeon says. "But in terms of his basketball career, he has a good chance of performing fine."

Watching the basketball documentary Hoop Dreams on a movie screen in 1995, members of the biomechanics mainstream heard those words and cringed.

When that film was being made, it was already common knowledge among biomechanics practitioners that meniscectomy was associated with an increased risk of osteoarthritis, particularly in athletes. More than a decade later, however, researchers are less inclined to blame osteoarthritis in former athletes on a particular method of treating joint injury than on the injury itself. And although athletes involved in certain sports may be predisposed to such injuries, researchers have also found that former participants in high-impact sports have an increased risk of osteoarthritis that is independent of any history of injury-raising the frightening possibility that the increased risk of osteoarthritis in former athletes is in fact attributable to their participation in a sport.

Epidemiology

Given the spectrum of different sports associated with increased risk of developing OA, it is difficult to identify any particular sport-specific characteristics that are common to all of them.

Soccer is one of the biggest culprits, particularly in European research. As early as 1993, researchers from Sweden found that the prevalence of knee gonarthrosis in former soccer players was four times the prevalence in age-matched controls.¹ Finnish researchers found that the odds of hospital admission for OA of the hip, knee, or ankle were twice as high among former soccer players as among controls.² Two separate British studies found that the prevalence of knee OA in retired soccer players ranged from 32% (study subjects with an average age of 47.6 years) to 49% (average age 56.1 years), significantly higher than the 20% prevalence previously reported in the general British male population between the ages of 45 and 54.^3,4

"Soccer is not a sport. It is a knee killer," said Alwin Jaeger, MD, chairman of orthopedic surgery at the University of Frankfurt in Germany, who said that soccer players accounted for one-third of the 50 former athletes with knee OA in his 2002 study.⁵

European researchers have also identified an increased prevalence of OA in former track and field athletes. In 1995, Swedish investigators found that arthrosis of the hip was four times more prevalent in 114 male former track and field athletes (including long jumpers, triple jumpers, hurdlers, javelin throwers, and shot putters) than in 355 age-matched nonathletes.⁶ The link between javelin throwing and hip arthrosis was underscored by researchers from the University of Heidelberg, in Germany, who in 2004 reported hip arthrosis in 22 of 38 hips in 19 male former javelin throwers but just seven of 38 hips in age- and size-matched nonathletes;⁷ they also found evidence of osteoarthritis in the dominant elbows of all 19 former javelin throwers.⁸ The same group found that hip arthrosis in male former high jumpers was slightly less prevalent (15 of 44 hips) than in javelin throwers but still significantly higher than in matched nonathletes (six of 44 hips).⁷ In a separate study they found that the extent of degenerative changes in the ankles of 40 former high jumpers was not significantly different from age- and size-matched controls.⁹

Team handball, a sport that rivals soccer for incidence of anterior cruciate ligament injuries, perhaps not surprisingly also yields a high incidence of hip osteoarthritis, according to researchers from the University of Rouen in France. In the January issue of the British Journal of Sports Medicine, they reported hip OA in 12 of 20 male former elite handball players (60%), compared to 13% of 39 age- and weight-matched male control subjects.¹⁰ And in another ACL-ravaging sport, volleyball, Swiss investigators found degenerative ankle disease in 19 of 22 former elite athletes but only two of 19 controls.¹¹

On this side of the pond, the sport most commonly associated with osteoarthritis is American football; National Football League Hall of Fame quarterbacks Joe Namath and Joe Montana, among others, have spoken publicly about their struggles with OA. Documentation of that relationship, however, has been in short supply. A 1976 clinical and radiographic assessment of 51 former professional football players found no evidence that participation in the sport contributed to knee OA.¹² And a 1984 study of former North Carolina high school football players reached the same conclusion-although the high school study did find that a history of football-related injury was positively associated with knee OA.¹³ It wasn't until 2002 that retired players' advocates had some data to back up their observations, when researchers from the Center for the Study of Retired Athletes at the University of North Carolina at Chapel Hill found that 37.6% of 2488 former NFL players (average age 54.4 years) had been diagnosed with OA by a physician.¹⁴ That study was presented at the 2002 meeting of the American College of Rheumatology but has not yet been published in full.

Barriers to treatment

As alarming as these statistics are, equally disturbing is the probability that researchers do not yet know the true extent to which former athletes suffer from OA, given the emphasis in competitive sports on playing through pain and the tendency for that mindset to persist even after athletes have retired.

"Most of the former handball players with hip OA accept the pain," said Maxime L'Hermette, a sports sciences researcher at the University of Rouen and lead author of the January BJSM study.

Some former elite athletes maintain the close communication with practitioners that they had during their playing days. But others tend to be stoic about their injuries, said Andrew L. Chen, MD, an orthopedic surgeon with Littleton Orthopaedics in Littleton, NH, and lead author of a 2005 review article on management of the aging athlete published in the Journal of the American Academy of Orthopaedic Surgeons.¹⁵

"There are a lot of athletes who essentially say, 'I've been living with pain my entire life, and I'm not going to seek treatment until I can't walk,'" said Chen, who is also a team physician for the U.S. ski team.

The UNC study found that only 58.6% of former NFL players diagnosed with OA were actually receiving treatment for it. Lead author Leigh F. Callahan, PhD, a professor of orthopedics, medicine, and social medicine at UNC-Chapel Hill, suggested that practitioners who treat former athletes may be as likely as the players themselves to downplay the significance of osteoarthritis relative to other conditions the patient may have.

"We have found in studies looking at health status in family practices that individuals and physicians tend to focus on other conditions such as diabetes, cardiovascular disease, etc. They think arthritis is just a part of aging and that you cannot do that much for it," Callahan said.

Adding insult to injury

In Hoop Dreams, the first surgery performed on high school basketball player William Gates was an (ultimately unsuccessful) attempt to repair his torn meniscus, rather than remove it. At the time, researchers and practitioners were suspicious of a possible link between meniscectomy and osteoarthritis in athletes that had been reported during the 1980s.^16,17 Their suspicion grew as the indemnifying evidence mounted in the 1990s.^18-20 But a 2002 German study of 50 athletes (soccer players, skiers, basketball players, and volleyball players) who had undergone meniscal repair found osteoarthritic changes in all 50 athletes an average of 6.3 years after surgery.⁵ This suggests that meniscal repair would not have improved Gates' chances of developing osteoarthritis even if the procedure had succeeded.

Lead author Jaeger suggested that the prevalence of OA in his study subjects resulted from meniscal repair techniques that did not effectively eliminate persistent anterior knee instability.

"Athletes with repaired menisci are still at risk for osteoarthritis if there is persisting instability," he said. "One also has to stabilize the knee, otherwise the meniscus will not heal."

Instability is also likely the reason why conservative management of anterior cruciate ligament tears has been linked to an increased risk of knee OA in former athletes. In the June issue of Arthroscopy, researchers from Dusseldorf reported grade 4 chondral lesions in 13 of 18 former Olympians who had suffered ACL tears during competition 20 years earlier. The athletes had not undergone reconstruction, even though all had returned to competition after six to 14 weeks of rehabilitation.²¹ Ten of those athletes ultimately underwent total knee replacement. And ACL reconstruction may not spare an athlete from osteoarthritis if the knee becomes chronically unstable, as investigators from Goethe University in Frankfurt found in a study of semiprofessional athletes who underwent revisional ACL reconstruction.²² Fifteen of the 24 demonstrated an increase in osteoarthritic changes an average of 36.9 months postsurgery.

And although an athlete with a reconstructed ACL is generally thought to face a lower risk of osteoarthritis than an ACL-deficient athlete,^23,24 recent research suggests that choice of treatment may not be the determining factor. In a 2004 study of male former soccer players 14 years after an ACL injury, Swedish investigators found no difference between surgically treated and conservatively treated athletes with regard to radiographically detected OA.²⁵ And in the same year, findings from the same institution also suggested that surgical reconstruction did not affect prevalence of knee OA in female soccer players 12 years after ACL injury.²⁶

"If surgery encourages a continued athletic career, it may fulfill the wishes at that moment of the patient (and sports injury specialist/team physician), but it does not necessarily serve the long-term interests of the knee," said Stefan Lohmander, MD, PhD, professor of orthopedics at University Hospital in Lund and lead author of the study of former female soccer players.

The sport's the thing

The notion that a history of injury predisposes an athlete to developing OA later in life makes sense from a biomechanical perspective, particularly if one accepts that current surgical techniques have not yet achieved perfection with regard to stability and alignment. What's more puzzling is the growing body of evidence that suggests even athletes who have not sustained injuries are more at risk for OA than are nonathletes.

A 1999 Danish study of 39 former elite soccer players found that, although signs of arthritis were more prevalent in the knees and ankles of 42 subjects with previous injuries to those joints than in uninjured subjects, the prevalence in 17 uninjured former athletes (26% in the knee, 18% in the ankle) was still higher than one would expect to see in the general population.²⁷ In the French study of former handball players,¹⁰ none of the study subjects had a history of lower extremity injury, yet 60% had radiographic OA in at least one hip joint. And the 2002 study of former NFL players¹⁴ found that the lineman position was significantly associated with a diagnosis of OA independent of injury history, despite the fact that linemen are thought to experience more knee injuries than players at other positions. The risk of OA for linemen was also independent of body mass index, despite those players often weighing more than 300 pounds.

In addition, more and more researchers are finding that long-distance runners, whose lower extremity joints are subjected to repetitive pounding over miles and miles and years and years, do not appear to share the same increased risk of OA as their counterparts in other sports. In 1985, American investigators found only a 2% incidence of severe knee and hip pain in 504 former collegiate cross-country runners; only 0.8% of all runners had surgery for osteoarthritis a mean of 25 years removed from competition.²⁸ Ten years later, a Finnish study found a 14% prevalence of knee OA in former elite runners, compared to 29% in soccer players and 31% in weight lifters; half of the runners with knee OA had previous injuries that were likely contributors.²⁹ Researchers from the University of California at San Francisco found no significant differences between 28 members of a senior running club (age 60 to 77) and 27 age-matched nonrunners with regard to radiographic OA of the knee or hip.³⁰ And a Stanford University study presented in November at the annual meeting of the ACR found that OA-related radiographic changes in 53 senior distance runners (average age 76 at study's end) after a 14-year period were not significantly different from those seen in 99 control subjects.³¹

Quirks of cartilage

Researchers from Central Queensland University in Australia and the University of Munich in Germany believe that experienced runners have undergone mechanical adaptations that allow their joints to withstand loading more effectively than inexperienced runners. Using magnetic resonance imaging, they documented joint effusions in all but one of seven beginners following a marathon run; no effusion was seen in six experienced recreational runners or two professional runners following the same run.³² In a separate study, they used 3D MRI to assess cartilage volumes in 48 runners following 5-, 10-, and 20-km runs with a three-minute rest in between. They found that the patella, tibia, and meniscus experienced significant reductions in volume following the 5-km run but that further reductions following the longer distance runs were seen only in the medial meniscus.³³

"During running most likely fluid is expressed from the extracellular matrix," said Erik Hohmann, MD, director of the Musculoskeletal Research Unit at Central Queensland University and lead author of the marathon study. "The fast recovery of volume certainly indicates that the matrix is not damaged by the repeated impact loading."

The question of why cartilage responds to loading differently in some athletes than in others is shaping up to be something of a holy grail for researchers in this field. Leading the charge is Joseph A. Buckwalter, MD, a professor and the head of orthopedic surgery at the University of Iowa, whose theory revolves around a process called chondrocyte senescence.

Chondrocyte senescence describes the gradual loss of function in chondrocytes (components of articular cartilage that synthesize new molecules in response to changes in the cellular matrix), which in the aging patient leads to osteoarthritis. Buckwalter and colleagues believe chondrocyte senescence may be accelerated following a traumatic joint injury, or even-importantly-following microtrauma to the joint that may not be easily detectable.³⁴ According to this theory, former athletes who develop osteoarthritis likely experienced impact loading during competition at a level significant enough to accelerate chondrocyte senescence, even if no ligaments were torn or other visible injuries sustained.

"What we think is that oxidative damage is one of the important causes of the age-related decline in chondrocyte function and that joint injury accelerates this process," Buckwalter said.

In laboratory tests on articular cartilage specimens, the Iowa researchers confirmed that shear stress and oxidative stress both trigger cellular mechanisms that are associated with chondrocyte senescence; they have not yet conducted similar tests on human subjects, but ultimately plan to do so, Buckwalter said.

The key will be to identify the point at which joint loading exceeds the articular cartilage's ability to repair itself, a point that appears to lie somewhere between loads experienced during normal walking and those experienced during an ACL tear. As suggested by the Queensland and Munich studies, the Iowa researchers believe long distance runners should end up closer to the walking end of the joint loading spectrum, Buckwalter said.

"Joint use should not affect chondrocyte senescence," he said.

Intervention and prevention

As difficult as it can be to manage osteoarthritis in any patient, treating OA in former athletes presents its own set of challenges.

"Once OA develops in the postathlete phase, it's a difficult clinical problem," Lohmander said. "You have a young person with an old knee."

Experts generally agree that currently available OA therapies-including bracing, orthoses, weight management, viscosupplementation, and exercise-should be as effective in former athletes as in the general population.

"Athletes should be educated that there are things that can be done for arthritis, and they should be encouraged to seek treatment and interventions," Callahan said.

But some barriers to treatment are unique to former athletes. There is the inherent stoicism, to be sure. But there are other concerns as well.

Former NFL players, who are almost universally covered by worker's compensation, don't have to worry about their OA treatment being paid for as long as the joint in question has been treated continuously since the player's retirement from football, Chen said. But if years without treatment go by between the player's retirement and the onset of OA, it can be difficult-despite the evidence in the medical literature-to convince insurers that the pain stems from years of playing football.

"If they were being treated all along, then that's a no-brainer," Chen said. "But if 15 years later they all of a sudden say they have OA, then the insurance company might ask, 'How do you know you didn't do that riding your horses out on your ranch?'"

Then there is the question of knee replacement surgery. A reasonable option in an elderly person, arthroplasty may not make sense in a young patient who will likely outlive several implants, particularly if that young patient is a 300-pound former lineman. In such patients, an osteotomy that can relieve pain by helping to correct joint alignment may be an alternative, Chen said.

"We also use more aggressive arthroscopy to 'clean up' the joint. That's not something you would normally do in a 78-year-old person," he said.

One obvious way to minimize an athlete's risk of OA is to minimize that athlete's risk of injury. The widespread focus in sports medicine research on preventing noncontact ACL injuries, particularly in women, will also likely result in decreasing the prevalence of OA in athletes. Maintaining proper technique is also important to injury avoidance, according to both L'Hermette and Chen.

The more difficult question involves treatment of the injured athlete, whose risk is already elevated.

"In light of our inability to prevent OA developing in the postinjury knee, we need to focus on injury prevention and postinjury knee care," Lohmander said.

In Iowa, Buckwalter and colleagues are looking at ways to counteract chondrocyte senescence in injured joints. Antioxidants may be able to minimize oxidative damage, joint distraction may provide an optimal mechanical environment during rehabilitation, and immature chondrocytes transplanted into the injured joint shortly after injury may be able to pick up where the native chondrocytes have left off. These preventive measures would not be limited to athletes with visible injuries, Buckwalter said.

"We are developing a method of assessing cartilage injury that does not involve visible disruption of the surface," he said.

With further research, biomechanical analysis may be able to identify those athletes who will be unable to withstand high-impact loading following an injury, suggests Nancy E. Lane, MD, director of the Center for Healthy Aging at the University of California-Davis and lead author of a 1998 study on OA in runners.³⁰

"We need to get these athletes tested for gait," Lane said. "If athletes can handle a high-impact load to their joint, then they may be able to compete again. But if they cannot, then even walking will increase their risk of OA."

Urho Kujala, MD, PhD, professor of sports and exercise medicine at the University of Jyvaskyla, and colleagues also are studying the genetics of OA, raising the possibility that eventually an aspiring athlete will have the advantage of knowing whether he or she is genetically predisposed to OA before choosing a sport.

"Someday in the future we will know more about who has a higher risk of developing primary OA," Kujala said. "Those with very high familial risk should perhaps not participate in sports like soccer."

Priorities

The real issue may be getting athletes, especially young athletes, to think realistically about osteoarthritis as a consequence of sports and sport-related injury.

In Hoop Dreams, as high school sophomore Gates reflects on his failed attempt to come back from his first meniscal procedure, it's clear he isn't thinking about life after basketball.

"A lot of people say I shouldn't have played, shouldn't have come back at all," he says. "Coach kept sayin' it's really up to me. And if you leave it up to me, I'm goin' back out there on the court."

Jordana Bieze Foster is a freelance writer based in Massachusetts and the former editor of BioMechanics.

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