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Introduction
A recent thought-provoking editorial1 suggested that the reported annual increase in hamstring injuries could in fact be associated with increased awareness rather than an actual increase in injury incidence. We share the author’s optimism on the improving knowledge on (musculotendinous) hamstring injuries, yet we still have concerns regarding awareness of its evil twin—the full-thickness hamstring tendon avulsion.
In this letter, we argue that there is a ‘blind spot’ when it comes to diagnosing these serious injuries.
Are clinicians more at risk or more vigilant?
Hamstring tendon avulsions mostly affect the proximal tendons, and are typically sustained during sports or slip and fall accidents involving a combination of forceful hip flexion and knee extension.2 Our ongoing prospective study raised concerns that medical professionals may be disproportionally affected by these injuries. We noticed that 20% (95% CI 9% to 37%) of included patients with a full-thickness proximal hamstring tendon avulsion were medical doctors and physiotherapists. In the Netherlands, medical doctors and physiotherapists make up approximately 0.8% of the adult population.3 4 This percentage is in sharp contrast with the significantly higher proportion of those medical professionals that we encountered in our cohort of patients with a full-thickness proximal hamstring tendon avulsion.
Interestingly, we observed that substantial diagnostic delay (ie, time between injury and MRI-confirmed diagnosis) did not occur in medical doctors and physiotherapists (figure 1). Delayed patients were typically diagnosed with a severe hamstring strain injury without further imaging and referred to a physiotherapist. Patients were subsequently referred to our centre when they did not progress as expected despite adequate treatment.
Time (in days) between injury and MRI-confirmed diagnosis.
This leaves us with the question: Are medical professionals at specific risk of proximal hamstring tendon avulsion or are they more likely to have their injury adequately assessed within a short interval after injury?
The blind spot
There is no evidence to support the idea that medical professionals are at increased risk; hence, we argue that our observation can be explained by heedfulness or assertiveness among medical professionals.
Considering that 0.8% of the Dutch adult population are either medical doctors or physiotherapists and assuming that clinicians and non-clinicians have similar risk of sustaining the aforementioned injury, for every eight medical professionals we can expect 992 non-clinicians. This is clearly not the case in our study population, suggesting that many non-clinician patients remain unseen or undiagnosed. Therefore, we hypothesised that there is a hamstring injury blind spot, meaning that this injury may be heavily underdiagnosed due to poor awareness. The over-representation of medical professionals is a reflection of this blind spot as it could indicate a selection phenomenon in which an overlooked diagnosis or misdiagnosis is less likely in clinicians. After all, clinicians have been known to demonstrate different illness behaviour due to their knowledge of the human body and medical system, resulting in deviation from regular care pathways.5 This could improve their chances of an (early) imaging-confirmed diagnosis.
The consequences
Missing a proximal hamstring tendon avulsion could have serious consequences, as poor clinical outcome has been reported if it is left untreated.6 The current body of evidence, despite its limitations, indicates that surgical intervention yields better subjective and functional outcomes than a non-operative approach and thus surgical consultation should be considered. Moreover, a delayed diagnosis can also affect chances of a good outcome, since delayed intervention (ie, later than 47 or 88 weeks after injury) is reported to result in inferior outcome, and is considered to be more difficult for the surgeon.2 In addition, even if the patient and the doctor were to make a shared decision in favour of conservative treatment, an adequate conservative treatment protocol would be expected to produce favourable results compared with a missed diagnosis.8
Clinical picture and pitfalls
The potential consequences of a missed or delayed diagnosis underline the need for a high level of suspicion of proximal hamstring tendon avulsion when certain clinical clues are present (box 1). If clinical evaluation is suggestive of a proximal tendon avulsion or leaves room for any doubt, imaging by means of ultrasound or MRI should be performed to confirm or rule out tendon avulsion injury.
Key clinical features
Typical clinical findings in proximal hamstring tendon avulsion injury
Trauma mechanism involves forced hip flexion combined with knee extension.
Tearing or popping sensation.
Severe pain, sitting is painful.
Severe loss of function, walking is difficult.
Extensive posterior thigh bruising appears within days (figure 2).
Pain on palpation of ischial tuberosity and over the area of bruising.
Palpable loss of bone-tendon continuity during resisted knee flexion.
Pitfalls
Trauma mechanism occasionally involves hip abduction rather than hip flexion.
Bruising can be subtle (figure 2) or even absent.
Loss of function (knee flexion) may not be complete, as it can be masked by intact gastrocnemius muscle function.
Range of motion (straight leg raise and active knee extension test) may be full or even more than the contralateral leg.
Main differences with acute hamstring strain injury
Trauma mechanism often involves high-speed sprinting.
Mild loss of function.
Bruising is limited if present.
Pain on palpation of muscle belly.
Range of motion is reduced.
Posterior thigh bruising in three patients presenting at 2 (top), 8 (middle) and 10 (bottom) days after injury. At 2+ weeks after injury, the bruising may be located exclusively around the back of the knee.
Conclusion
Proximal hamstring tendon avulsions are serious hamstring injuries that result in an unfavourable outcome when the diagnosis is missed or delayed. Our anecdotal observation could indicate that this injury is underdiagnosed. The aim of this letter is to improve clinical awareness of proximal hamstring tendon avulsions and to encourage clinicians to maintain a high level of suspicion in combination with a low threshold for the use of imaging when clinical evaluation is suggestive or leaves room for any doubt. We ask the readers of the British Journal of Sports Medicine to help enhance awareness by informing peers and referrers about this potential blind spot.
Footnotes
Contributors ADvdM, JLT and GR: writing and editing of the manuscript. RWP and GMK: writing and conceptual outline of the manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent Not required.
Provenance and peer review Not commissioned; externally peer reviewed.