This is part 1 in this month’s clinical theme: Hamstring Injuries in Sport.
Following on from our recent discussion on the classification of muscle injuries in sport, I thought it would be a good idea to look at a pretty common example in more detail.
Did anyone watch a football game on the weekend?
Did someone injure their hamstring?
The 2014 AFL Injury Report reported an average of 5.2 new hamstring injuries per club, which was the highest incidence of any injury in the AFL¹.
Actually, it wasn’t even close.
The next most common were ankle sprains, coming in at 3.2 new injuries per club, per season¹.
More importantly, an average of just over 20 games were missed (per team) in the 2013 season, due to hammys¹.
Mechanisms of Hamstring Injuries
The literature describes two main mechanisms of hamstring injury:
- High-speed running type injuries
- Stretch-type injuries
High-speed running type hamstring injuries
This type of injury is probably the more common type we will see.
Here’s a classic example:
Video courtesy of AFL.
These injuries typically involve the long head of biceps femoris, more commonly at the musculotendinous junction²,³.
The athlete usually describes a lot more pain with a high-speed running injury, as well as quite a lot more functional limitation³,⁴.
The recovery seems to be a fair bit quicker, though.
The athlete will often feel a noticeable improvement in pain, strength, and muscle length within 7 days, but it can give a false sense of security, as they are still in an early stage of healing³.
Stretch-type hamstring injuries
On the other hand, stretch-type injuries tend to occur with rapid hip flexion / knee extension, such as a high kick³,⁴.
The recovery is typically longer than running-type injuries, as it will often involve injury closer to the ischial tuberosity, including the proximal semimembranosis tendon³,⁴.
Feel free to refer back to the article on grading and classifying muscle injuries in this previous article, for more features of different types of muscle injuries.
What are the risk factors for hamstring injuries?
A systematic review by de Visser et al (2012) reported limited evidence for three factors in recurrent hamstring strains, and they were⁵:
- An initial injury of larger volume, confirmed on MRI (total volume, as opposed to cross-sectional area
- More often had a grade I initial strain
- More often had a history of ipsilateral ACL repair, irrespective of graft selection
Similarly, a meta-analysis by Freckleton and Pizzari (2013) explored a larger range of factors, and found the following three factors to be most commonly associated with hamstring injuries (muscle belly, not tendon involvement)⁶:
- Age (increasing with age)
- Previous history of hamstring injury, and
- Peak quadriceps torque
Many other risk factors have been reported by different authors, with variable levels of evidence (and often conflicting), including⁶:
- Hamstring strength and flexibility (however, eccentric strength deficit has been reported as a factor for injury recurrence by several authors⁸,⁹)
Reviewing the literature regarding hamstring injuries is definitely another example of differing reports by different authors and research groups.
Is there any way to clinically predict time to return to sport?
As mentioned above, the anatomical location of injury will be a preliminary guide in determining tissue healing timeframes.
From a predictive capacity, a recent study in the Netherlands by Moen et al (2014) analysed 74 athletes, and explored 28 clinical and MRI parameters in their measurement of return to sport⁷.
After sifting through the inclusion and exclusion criteria, and analysing their results, they only found the following two parameters as statistically associated with time to return to sport⁷:
- Self-predicted time to return to sport
- Passive straight leg raise
- There are two main types of hamstring injuries:
- High-speed running injuries
- Stretch type injuries
- Features of a hamstring injury with typically a better prognosis:
- Mid belly or musculotendinous junction
- Lower grade injury – little to no structural defect
- Mechanisms: running-type injury
- Minimal history of previous injury
- Features of a hamstring injury with a typically poorer prognosis (longer recovery):
- Injury closer to the ischial tuberosity
- Involvement of central or proximal hamstring tendon
- Mechanism: stretch-type injury
- Previous history of hamstring injury (ipsilateral)
- Previous ACL surgical repair (ipsilateral)
- Factors most associated with predicting return to sport:
- Self-predicted time to return to sport
- Passive straight leg raise
Peter Brukner recently published an open-access article in the British Journal of Sports Medicine and you can find this here:
In the next article, we’ll have a look at a summary of evidence based assessment to help in grading and classifying hamstring injuries.
As always, I’d love to hear from you.
Please share any experience you have with regards to hamstring injuries, and especially help share this with any recent grads that may be interested.
- Orchard et al 2014, ‘Australian Football League: Injury Report 2014. 23nd Annual Injury Report. [Link]
- Askling CM, Tengvar M, Saartok T, et al. Acute first-time hamstring strains during high-speed running: a longitudinal study including clinical and magnetic resonance imaging findings. Am J Sports Med 2007;35:197–206.
- Askling et al 2012, ‘High-speed running type or stretching-type of hamstring injuries makes a difference to treatment and prognosis’, British Journal of Sports Medicine, vol. 46, no. 2, pp. 86-87.
- Askling C et al 2007, ‘Acute first-time hamstring strains during slow-speed stretching: clinical, magnetic resonance imaging, and recovery characteristics’, Journal of Sports Medicine, vol. 35, pp. 1716–24.
- de Visser H et al 2012, ‘Risk factors of recurrent hamstring injuries: a systematic review’, British Journal of Sports Medicine, vol. 46, no. 2, pp. 124-130.
- Freckleton G and Pizzari T 2013, ‘Risk factors for hamstring muscle strain injury in sport: a systematic review and meta-analysis’, British Journal of Sports Medicine, vol. 47, no. 6, pp. 351-358.
- Moen et al 2014, ‘Predicting return to play after hamstring injuries’, British Journal of Sports Medicine, vol. 48, no. 18, pp. 1358-1363.
- Brukner P 2015, ‘Hamstring injuries: prevention and treatment— an update’, British Journal of Sports Medicine, 0:1–4. doi:10.1136/bjsports-2014-094427.
- Brughelli M et al 2010, ‘Contralateral leg deficits in kinetic and kinematic variables during running in Australian rules football players with previous hamstring injuries’, Journal of Strength and Conditioning Research, vol. 24, pp. 2539-2544.
Another special thanks to Greg Mullings (Sports Physiotherapist, Fremantle Football Club), for his hamstring rehabilitation presentation in Perth, November 2014.
Creative Commons image courtesy of John Martinez Pavliga.