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Joint Injuries and What You “Kneed” to Know


By Scott LaFee   |   April 22, 2014

While sports, exercise and physical activity are essential to good health, there’s a potential downside as well: getting hurt. Each year, millions of Americans visit their doctors with musculoskeletal complaints and impairments, often involving sports- or activity-related joint injuries.

knee replacement Wahl  
Knee problems are most frequent (an average of 2.5 million visits to emergency rooms annually). It has been estimated that one in 3,500 Americans will suffer damage to their anterior cruciate (ACL) ligament – one of four major ligaments in the knee – each year. That’s roughly 95,000 significant knee injuries annually from just one type of damage, one that frequently requires surgical reconstruction. Shoulder injuries are the second-most common complaint.

We asked Christopher J. Wahl, MD, an associate professor and chief of sports medicine in the UC San Diego Health's Department of Orthopedic Surgery, to diagnose the current situation.

Q: Are there inherent factors that predispose some people's joints, specifically the knee and shoulder, to become unstable or more susceptible to injuries?

A: There are myriad factors, some of which we understand well and others we don't, that may predispose an individual to injury. The shoulder is perhaps the best example. It is the least inherently stable joint in the body –a trade-off of incredible mobility at the expense of stability.  There is enormous variation from individual to individual in the degree of elasticity of the connective tissues that make up our joints. It is a genetically inherited trait. We sort of “inherit” or adopt our interests or activities as well – the manner in which we've been given the encouragement or opportunity to participate in certain activities that involve movements known to put the shoulder at high risk for dislocation, such as surfing or kayaking.

So you can imagine that a person who genetically has very elastic connective tissues and who has taken an interest in activities that can predispose one to shoulder dislocation is at a much higher risk than a person without this elasticity or who doesn't participate in “at risk” activities.

Q: Why is the incidence of female athletes suffering from ACL injuries rising?  Is it a result of more women in sports or something particular to their physiology?

A: The increased incidence of ACL injury among females is probably a combination of several factors. The number of women competing has grown exponentially with the emphasis of organized competition at every level from junior club sports to professional athletics. 

Second is what I like to call the “Just Do It” effect:  the intensity of practice and play today is far increased over what it was 20 years ago.  Even among recreational athletes, there is a huge emphasis on speed and power (high-energy injuries), endurance (overuse/fatigue injuries) and precision (more practice increases the chance of injury). 

Finally, there is sound scientific evidence that there are modifiable and innate, sex-specific factors that predispose to ACL injuries. Differences between males and females in the way they tend to jump, change direction and land can be addressed. Anatomic differences play a huge role. I recently published a study looking at differences in knee joint shape between males and females and the association with cruciate injury. The findings indicated that people who suffered ACL injuries had relatively smaller, highly curved joint surfaces on the outer aspect of the knee. Interestingly, the majority of females studied shared this anatomic trait while only a minority of males did. However, males with the shorter, more curved joint surfaces were the ones who suffered ACL tears. 

Q: Have we reached a point where the demands of sports, particularly those of collegiate or professional athletics, are more than human joints can safely bear over time?  Is the likelihood of becoming seriously hurt or suffering some sort of chronic disability becoming inevitable?

A: While there is no question that the demands of sports have increased, there has also been an unprecedented focus on performance, training, and injury prevention.  In fact, the former cannot happen without the latter because no coach, no team, and no sport benefits if players are always injured or their careers end prematurely.

It is the competitive nature of elite and recreational athletes to push limits. It is the responsibility and challenge of leagues, organizations, coaches, parents, physicians and trainers to work together to find ways to minimize the risk. Equipment advances, rule changes that encourage safe play, preparation and proper training and advances in injury treatment are all continually addressing this challenge.

Still, we should never take for granted the tremendous physical and mental health value of athletic and team participation and an active lifestyle. These benefits, which are nearly universal to participants, far outweigh the risk of disabling injuries, which are fortunately uncommon.

Q: How has the treatment of joint injuries changed in recent years?  What's ahead in terms of preventive measures or surgery?

A: It would be far easier to ask “what isn't changing!” From an orthopedic surgeon's perspective, we have been able to better define what constitutes “normal joint function” and develop minimally-invasive techniques to more accurately reproduce the anatomy and function of the joints with our repairs, with minimal trauma to the rest of the joint. We also have a better understanding of the factors that make one procedure more or less successful than another given an individual patient's anatomy, their activities, age, sex and other variables. Clinicians now have a vast and growing armamentarium of tools and techniques that can be used in combination to meet the specific demands of the individual.  

From the perspective of injury prevention, there is a better appreciation for what populations are at risk for particular injuries (like women and ACL tears) and specific prevention and training programs are utilized to minimize the chance of injury.  Advances in conditioning, strength and preparation have an enormous protective effect for the athlete.

Q: Do you think it's possible to create an artificial joint capable of allowing athletes to resume their careers?

A: That's going to take some time, mainly because our bodies set such a high standard. Given the incredible demands we put on our joints, the function and durability of the human joint is astounding and far exceeds the longevity and resistance to breakdown of artificial materials and joint designs.

Some of the most exciting innovations are happening at the cellular level – research that will someday allow us to regenerate injured tissues or structures or grow replacement tissues, like cartilage. The science is promising but at present scientists and clinicians are only capable of growing the cell types found in the joints. We have not yet been able to engineer and orient these cells into the architectural tissues that function like original joints. Imagine the joint cartilage as a beautiful building with columns and arches and windows and doors. At present, we can make piles of bricks and mortar; we're still working on the architecture.

Related Specialties

Sports Medicine