By Jeffrey B. Driban, PhD, ATC, CSCS; Brian Pietrosimone, PhD, ATC; Nicole M. Cattano, PhD, ATC; Matthew S. Harkey, MS, ATC; and Brittney A. Luc, MS, ATC
A knee injury can have painful and disabling long-term repercussions, such as the early onset of knee osteoarthritis (OA) or accelerated knee OA. Injury prevention and effective interventions may help reduce the risks, but patient education and monitoring after an injury are also warranted.
Many patients and clinicians focus on immediate outcomes following a knee injury, such as decreasing pain and disability, as well as restoring muscle strength, physical function, and preinjury activity levels. However, the long-term implications following a knee injury are becoming increasingly apparent, and there is a need to educate patients about long-term risks.
A patient with a history of knee injury is three to six times more likely than those without such a history to develop knee osteoarthritis (OA),1 one of the leading causes of disability.2,3 Furthermore, a patient with a history of joint injury tends to be diagnosed with OA approximately 10 years earlier than individuals without a history of joint trauma.4 For example, Frobell et al found that 26% of individuals aged an average of 31 years had radiographic knee OA just five years after an anterior cruciate ligament (ACL) injury, regardless of initial treatment strategy.5 Within 10 to 15 years following an ACL injury, individuals have a 50% chance of developing knee OA, especially if the meniscus was compromised at the time of the injury.6-9 In fact, individuals who undergo an ACL reconstruction and a meniscectomy are 3.5 times more likely to have knee OA approximately 10 years after an ACL injury than those without a meniscectomy.9 Accordingly, individuals with a history of joint trauma may be burdened by OA for more than half of their life, leading to a greater risk of developing comorbidities,10 as well as significant psychosocial and economic consequences (eg, healthcare expenses, work loss).
The early onset of OA should not be an acceptable outcome for our young patients, and we need to take steps to protect the long-term health and wellness of those younger patients. Moreover, we need to recognize that knee injuries can have dramatic long-term implications for older adults, as well.
Knee injuries may also be a catalyst for the onset of accelerated knee OA among adults older than 45 years. Accelerated knee OA is characterized by a rapid progression from a normal appearance to end-stage disease within four years, and sometimes progresses to end stage in as little as 12 months.11 A recent study evaluated the relationship between injuries and accelerated knee OA using data from the Osteoarthritis Initiative, a large cohort study of individuals older than 45 years with or at risk for knee OA.11 The accelerated knee OA study found that individuals who developed end-stage disease because of accelerated knee OA were three times more likely to report sustaining a knee injury within the preceding four years than those who did not develop knee OA. Furthermore, individuals who developed accelerated knee OA were nine times more likely to report having sustained a knee injury in the year before they presented with end-stage knee OA compared with those who did not develop knee OA.
Thus, certain acute injuries may initiate a dramatic, accelerated deterioration in joint health in patients older than 45 years within a period as short as one year. The first year after an injury within this population may be a critical time period to monitor a patient’s joint health to determine who is most susceptible to developing accelerated knee OA.
Another possible interpretation of these findings could be that the onset of accelerated knee OA increases the risk of an additional knee injury. Hence, we hypothesize that there could be a vicious cycle in which an injury could lead to the development of accelerated OA, which increases the risk of a subsequent knee injury (see Figure 1). An additional knee injury consequently causes further progression of knee OA.
All of this highlights the importance of listening to our older patients when they report a knee injury. We cannot afford to ignore the warning sign of a patient reporting a knee injury, and we should be prudent in determining the nature of the injury, including its type and severity. Subsequently, we should monitor changes in the patient’s joint health by scheduling frequent follow-up appointments to monitor changes in joint symptoms and function, as well as performing periodic radiographic assessments for at least 12 months. Hopefully, in the next few years we will gain a better understanding of how the type or severity of injury, as well as the subsequent treatment, may modify the risk of OA.
The high risk of early onset OA and accelerated knee OA following a knee injury in both younger and older patients demonstrates that it is vital for clinicians to take steps to ameliorate these risks. But how can clinicians prevent knee OA? The first line of defense may be implementing primary injury prevention programs, which could reduce the risk of an acute injury (see Figure 1). We could prevent 15% to 25% of symptomatic knee OA cases if we could prevent knee injuries.12 Fortunately for our younger, physically active patients, we know that primary injury prevention programs can prevent more than 40% of lower extremity injuries.13-19 Therefore, we need to encourage youth sport leagues and schools to implement primary injury prevention programs for young, physically active people. In addition to preventing injury, injury prevention programs could save healthcare costs,20,21 improve performance,22-24 and reduce the risk of long-term disability related to early onset OA.
More research is needed to see if primary injury prevention programs could be adapted for an older at-risk population. It is encouraging that exercise programs that incorporate balance, strengthening, or both can reduce the risk of falls.25-27 Older patients may also receive additional benefits from these supervised exercise programs beyond just a reduced risk of knee injuries (eg, reduced risk of falls, mental health benefits, improved cardiovascular function). For example, an exercise program for older adults that includes strength training, a common component of injury and fall prevention programs, can also help to improve muscular power and strength,28 walking speed,29 balance,29 blood pressure,30 body composition,30,31 cognitive reasoning,32 and reduce the risk of falls.33 Furthermore, mind-body exercise programs (eg, tai chi) that incorporate balance and neuromuscular control can help improve balance,29 reduce the risk of falls,34 decrease depression,35 and improve cognitive function.36 Supervised exercise programs can also be a great opportunity for older adults to socialize with peers, become more physically active, and improve their quality of life.
Intervention following injury
Unfortunately, we will not be able to prevent every injury. Therefore, we also need to understand how our current therapeutic interventions following an acute injury ameliorate or worsen the long-term outcomes after an injury. The first randomized clinical trial comparing individuals who received either an ACL reconstruction or conservative care with an optional delayed ACL reconstruction found that both groups of patients had similar rates of knee OA five years post injury.5 Recently, two systematic reviews also evaluated the long-term outcomes of patients who received an ACL reconstruction or remained ACL deficient. Harris and colleagues focused on four studies that directly compared 140 individuals with an ACL reconstruction and 240 individuals who remained ACL deficient.37 At an average follow-up of approximately 12 years, both groups had a high prevalence of knee OA, and there was no definitive evidence that surgical or nonsurgical treatment after an ACL injury could ameliorate the risk of knee OA.
Luc and colleagues assessed 38 studies that included more than 2500 individuals with an ACL injury. Among individuals with an isolated ACL injury, a higher percentage of those who had undergone an ACL reconstruction went on to develop knee OA (42%) than those who were ACL deficient (29%).38 However, among participants with a meniscectomy, individuals with an ACL reconstruction were slightly less likely to have knee OA (52%) than those who remained ACL deficient (59%). Luc et al found some evidence that graft type (eg, hamstring or bone-patellar tendon-bone autografts) and surgical technique may have been an important aspect of determining risk for knee OA. However, this remains a controversial topic, since some randomized clinical trials support this hypothesis39,40 and others do not.41-43
One of the main challenges in understanding the risk of OA after an ACL injury is that the surgical and rehabilitation strategies continually evolve at a pace faster than outcomes can be collected. The data from previous studies may not be applicable to today’s patients, since they are undergoing slightly different surgical interventions. Despite this limitation, it is crucial for us to explain to our patients their potential risk for OA. While we don’t know how the type or severity of injury may influence the risk of developing OA, patients should be encouraged to consider some general precautions.
Despite our lack of information about how our treatment strategies can ameliorate or exacerbate a patient’s risk for OA, there are some general steps that may be beneficial. During the rehabilitation process, we should identify neuromuscular inhibition and deficits, which could alter joint mechanics that could increase the risk of joint damage. The identified deficits can then be targeted in an attempt to restore normal neuromuscular function and proper movement patterns. Providing patients with strategies for reducing their risk factors for developing OA may be crucial. For example, we should encourage patients to maintain a healthy lifestyle and body weight, since high body mass index is a risk factor for accelerated knee OA.11 We should also highlight the importance of continuing to engage in therapeutic exercise programs even after patients are discharged from supervised care. We may even need to monitor these patients for aberrant neuromuscular function or movement patterns after they return to their regular activities.
While this may be a new approach to thinking about patients after an injury, it is not a dramatic departure from other health professions in which practitioners carefully monitor patients who present with risk factors for other chronic conditions, such as cardio- vascular disease. Using examples from other disciplines might also help us explain to patients why they should take steps to prevent OA, even though they may be currently asymptomatic. After all, they probably do not think twice about brushing their teeth to prevent tooth decay, or taking medication to manage high cholesterol or blood pressure along with having routine follow-up appointments with their physicians to monitor their health status.
In conclusion, a knee injury is more than a short-term problem. It represents an important catalyst that can lead to early onset or accelerated OA. The consequences of knee injury could be dramatic because it can greatly alter patients’ future function and quality of life. Many factors may influence who develops OA after their injury, such as type and severity of injury, treatment strategy, and patient characteristics (eg, body mass index). We still need to learn more about how to ameliorate the risk of OA after an injury, and there is currently no accepted intervention to slow, stop, or reverse OA progression.
Despite the limitations in our knowledge, we must recognize that we need to talk to our patients about the risk of OA after an injury, be prudent with our treatment strategy, and plan for the long term. Because many of our patients and their families and friends will be focusing on short-term goals–such as restoring function and returning to activities–we must also think about the patient’s long-term health and well-being. Educating our patients can only help in the long-term battle against OA by making the patient an informed participant in the process. Together, we can improve our understanding of OA risk after a knee injury and make efforts to improve long-term outcomes.
Jeffrey Driban, PhD, ATC, CSCS, is an assistant professor at Tufts Medical Center and Tufts University in Boston. Brian Pietrosimone, PhD, ATC, is an assistant professor at University of North Carolina at Chapel Hill. Nicole M. Cattano, PhD, ATC, is an assistant professor and athletic trainer in the Department of Sports Medicine at West Chester University of Pennsylvania. Matthew Harkey, MS, ATC, and Brittney Luc, MS, ATC, are doctoral students at the University of North Carolina at Chapel Hill.
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