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The old knee in the young athlete: knowns and unknowns in the return to play conversation
  1. Clare L Ardern1,2,3,
  2. Karim M Khan1,4
  1. 1Aspetar Orthopaedic & Sports Medicine Hospital, Doha, Qatar
  2. 2Division of Physiotherapy, Linköping University, Linköping, Sweden
  3. 3School of Allied Health, La Trobe University, Melbourne, Victoria, Australia
  4. 4Centre for Mobility and Hip Health, University of British Columbia, Vancouver, British Columbia, Canada
  1. Correspondence to Dr Clare Ardern, Aspetar Orthopaedic & Sports Medicine Hospital, P.O. Box 29222, Doha, Qatar; c.ardern{at}

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Twenty-year-old Sarah is a sport-obsessed amateur football player. She enjoys the social side of playing in a team sport, but most of all she loves the physical and mental challenge of game day. There is no better feeling than winning. She works hard on her skills and fitness, training twice a week with the team, and most other days on the cycle commute to the University and with her own gym programme. Maybe it was her young age1 and dodgy biomechanics2 that conspired against her. Perhaps it was the type of grass on her home pitch.3 But she winds up at your clinic clutching an MRI report that bears the dreaded diagnosis—she's ruptured her ACL.

Return to play is a fundamental concern for athletes and sports medicine clinicians—one important benchmark for judging treatment success. For many athletes with ACL injury, their most pressing concerns are about meeting their own expectations, or those of significant others (eg, coach, team mates, family), for returning to their pre-injury level or sports performance. Sarah will be faced with three options when she is ready to return to play—return to the pre-injury level sport, change sports participation (either change sport or change level) or retire.

What does Sarah need to know to make an informed decision?

Fact 1: Excellent physical function on impairment-based and activity-based measures can be achieved regardless of surgical or non-surgical treatment choice.4

Fact 2: Young athletes (under 25 years) are about twice as likely to return to their pre-injury sport as older athletes,5 and have up to six times increased risk of a new ACL injury on returning to pivoting sports.6

Fact 3: Regardless of treatment for ACL injury, up to 90% of people may go on to develop post-traumatic tibiofemoral or patellofemoral osteoarthritis,7 and symptoms are apparent 10–15 years after injury.8

Unknown 1: Does continuing pivoting sports heighten the risk for osteoarthritis? Meniscal or articular cartilage injury in combination with ACL injury is associated with a higher incidence of post-traumatic osteoarthritis compared to isolated ACL injury;7 it is reasonable to expect that further insult to the knee could amplify osteoarthritic changes.

Unknown 2: Does retiring from sport reduce the risk for osteoarthritis? The assumption is that with retirement comes a lower chance of further insult to the knee. However, new imaging technologies such as optical coherence tomography demonstrate subtle changes in the articular cartilage after knee injury that were not previously visible on imaging or with arthroscopy.9 Therefore, the apparently quiet knee could be hiding subtle and persistent pathological changes.

Unknown 3: How does changing sport or retirement affect an athlete's quality of life? The answer may depend on the reasons for changing or giving up sport. Sarah's quality of life may be diminished if she feels forced to give up sport because of physical disability.10 However, if she perceives that the decision is self-determined there may be no negative impact on quality of life.10 Athletes can enjoy many sustained physical and mental health benefits, provided their love of sport translates to life-long physical activity participation.10

Does the obsession with return to the pre-injury level sport as the benchmark for successful treatment do more harm than good?

If activity modification might help promote short-term and long-term knee health, what is stopping us from advocating it more often, and why do some athletes not follow activity modification advice?11 As clinicians, we need to be able to separate our own cognitive biases (eg, surgery is necessary to allow a return to pivoting sports; I only consider my treatment successful if the athlete returns to pivoting sports) from the information we present to our athletes,12 and listen to athletes’ own perceptions of treatment success.

Recommendation 1: Our patient is the boss of her return to play decision, but motivational interviewing might be helpful for exploring and possibly overcoming the barriers to activity modification.13 In addition to football, Sarah also actively participates in other more ‘knee-friendly’ physical activities—cycling and gym. Motivational interviewing could facilitate a dialogue about activity modification and the risks of returning to pivoting sport. Physiotherapists are perfectly positioned, as specialists in behavioural change, to help patients find the best activity so they can be active despite injury or illness. There are patellofemoral experts and temporomandibular experts; maybe it is time for activity modification experts? Conversations initiated early after ACL injury by physicians or orthopaedic surgeons may help the physiotherapist ‘sell’ activity modification advice during rehabilitation.

Recommendation 2: Shared decision-making may help present Sarah with the risks and benefits of returning to pivoting sports. Shared decision-making involves the clinician helping Sarah to understand the reasonable options; presenting and comparing options, weighing up the pros and cons, and understanding the risks, to arrive at a return to play decision.13 Combining shared decision-making with motivational interviewing could be a powerful way to empower Sarah to make an informed decision about her return to play that also satisfies her desire to be physically active.

Recommendation 3: When presenting risks, the information needs to be context specific and relevant to the athlete. For some athletes, factors such as salary and endorsements might be the strongest influence on the return to play decision; there is limited scope for the clinician to influence this decision. For other athletes like Sarah, the decision may be influenced by their sense of athletic identity;14 she may not want to change sport, and be prepared to play whatever the short-term or long-term consequences.15 Sarah needs to know that about 1 in 3 young female athletes who have had one ACL injury get another one if they return to their pre-injury pivoting sport.6 Whereas Sarah's cousin, Ben, a 35-year-old amateur rugby player with a combined ACL and medial meniscus injury, needs to know that if he goes back to playing rugby and has another meniscal tear, it is almost certain he will have an arthritic knee in 5 years.


Competitive sport and health are not synonymous.16 Sport is often about winning and achieving ‘the best’, whatever the cost. In contrast, health is related to quality of life; about sustained participation in society, free from injury and illness. Clinicians need to be aware of their own cognitive biases when presenting information to athletes, to facilitate a shared decision-making approach, helping athletes separate the notions of sport and health when making return to play decisions.


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  • Twitter Follow Clare Ardern at @clare_ardern

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.