Hamstring Injuries in Sport
Dr. Ronan Kearney

Watch this video of Dr. Ronan Kearney, Consultant Sports and Exercise Medicine Physician at UPMC Sports Surgery Clinic, presenting on Hamstring Injuries in Sport

This video was recorded as part of UPMC Sports Surgery Clinic’s Online Public Information Meeting, focusing on Knee and Sports Injuries

Dr. Ronan Kearney is a Consultant Sports and Exercise Medicine Physician at UPMC Sports Surgery Clinic.

My name is Dr. Ronan Kearney I’m a Consultant Sports & Exercise Medicine Physician. I mainly work at UPMC Sports Surgery Clinic in Santry. However, I also work across a number of different sports predominantly at the high-performance centre in Sport Ireland looking after mostly athletes preparing for the Paris Olympics. I have also done some work in the past with European Tour Golf, International teams in the FAI and also club level rugby. I am from Louth and I have been involved with Louth GAA’s Men’s Football Senior Team. I am also Chairman of The Gaelic Athletic Medical Association. Addressing Hamstring injuries has formed a large part of my job both in the clinic and the sports I am involved in.

Just a quick overview of today’s talk, it Is important to understand the context and background of these injuries and to know the anatomy in order to assess, manage and prevent hamstring injuries.

This was Usain Bolt the fastest man in history entering his las race as part of the 4×400 metre relay. At the World Championships in 2017. It was a very unfortunate end to such an incredible career of sprinting. Sprinting is the typical mechanism of injury of hamstrings. I will now discuss how we assess manage such injuries in this presentation.

With the focus on team sport, hamstring injuries make up for 25% of all team sporting injuries. They make up 33% of all time lost to injuries also. A study carried out within the GAA saw that 26 days was the average loss per injury. If we consider a full intercounty GAA team how might this look for the season? On an average for each team 9 players suffer a hamstring injury per season. This will take a tole on not only the player health but also the team’s performance. As well as that re-injury rates are also reported to be often quite high. Some hamstring injuries involving the tendon can have an injury rate of over 60%. This would either indicate an assessment of the management strategies are incomplete or an athlete has potentially returned to play too early but in reality, it is probably a mixture of both.

How might the toll of injuries affect the team’s performance overall? This was an interesting study of the estimated league performance and financial cost of injuries for premier league teams. It showed that the more total days out injured corresponded to a drop-in league position and the authors calculated that 271 days out injured would cause a drop in final league position by 1 place. In premier league terms this corresponds to about 37 million pounds. Being a Liverpool fan, I will highlight Manchester United in 2016/17. Man Utd had a high injury toll compared to the other top 6 clubs and it had an associated correlation with their total league points lost. They had the most valuable team in the league but not even their manager Jose ‘The Special One’ Mourinho could counteract the impact of the injury toll. Obviously, there are many other factors affecting a league position but it gives us context on the impact of hamstring injuries within elite sport.

This is a busy slide and it in no means covers all the risk factors for hamstring injuries there are some factors that we just can’t control such as age and previous injury. However, it is essential to understand that those who have had a previous hamstring injury or even a lower limb injury are 3 times as likely to suffer a hamstring injury. It is obvious that it would be sensible to try and reduce the risk where possible on factors that are modifiable such as strength, biomechanics and training load. Wen know that reduced hamstring strength is a risk factor for hamstring injury as is a number of key biomechanical measures such as ankle and hip range of movement. We also know that a sudden spike in training load going from doing very little to a lot is increasing that risk. We also know that athletes that have gradually increased running at high speed exposure over time have a lower risk of hamstring injury. Other factors such as a new manager with the team, as well as poor communication between coaching departments within a team increases the risk of injury. Really think outside the box when trying to reduce the risk of injury

How do injuries happen? Sprinting is the most common cause of injury as we have just seen Usain Bolt’s video. However, there are a number of other reasons, this was an interesting study done at Leinster Rugby. Where we can see that both decelerating in the orange and rucking in the lighter blue colour both sit at 19%. I suppose this comes back to management and from a rehabilitation perspective its important to review the mechanism that caused the injury. This might involve a discussion amongst coaches regarding the rucking technique to see if there is any ways of reducing the risk a mechanism for causing another injury.

Understanding the anatomy of the hamstring is the key to be able to understand and assess the injury itself. The hamstring is made up of muscle and tendon but lets just focus on the muscle first that we have circles here. Muscle is made up of long muscle fibres both fast and slow twitch and when they become active they allow the limiting move, with strength training these fibres enlarge. If the muscle is injured a number of healing steps happen which we see on the right-hand side of the screen. The top of the screen we see the inflammatory cells fill the muscle defect and a blood clot or a haematoma form. The next very important step is the regrowth cells and they are called satellite cells and they stimulate the injured muscle tissue to repair with a scar. The final step is the muscle scars return to normal. If rehabilitation is not correct there is an incomplete healing and a chronic scar can form. This chronic scar generally is not as robust as normal muscle and can lead to an increase risk of injury.

Now we will focus on tendon, tendon is very different to muscle and tendon is made up of stiff collagen fibres which have a high tensile strength that have elastic property. They respond and adapt to mechanical loading the junction between the muscle and the tendon is often the weaker link in the connection of movement. Tendon healing takes a lot longer in muscle for numerous reasons including the lack of a regrowth cell that we spoke of, the satellite cell. It is slower to heal and requires a cell scaffold alongside a number of other gradual mechanical loading in order for it to adapt and regain its tensile strength. For this reason, a number of weeks rest which is not an uncommon management strategy often is the worst thing for hamstring tendon injuries. When we look on the right-hand side of the screen here it is the stages of healing. The first stage of hamstring tendon healing is similar to that of muscle where a blood clot or haematoma develops and inflammatory cells fill the defect. Platelets increase and release growth factors to kickstart healing. By week 5 a tendon scar has generally formed and it may take up to 8 weeks before it is stronger and robust. With appropriate loading, rehabilitation and exercise it gradually returns back to normal healed tendon tissue. We often see patients at Sports Surgery Clinic that have reinjured their tendon in this phase before it has fully bridged the defect of a knee injury. When a tendon that is reinjured becomes a trickier injury to manage.

We will just go through some of the hamstring anatomy itself. The video on the left, we see there is 3 main hamstring muscles, the semi tendinosis, the biceps femoris which has 2 different heads, this is the long head biceps femoris and it is the most commonly injured hamstring muscle. If we rotate around we can see there is the short head of the muscle that inserts further down. If we rotate back to the inside part of the leg we see that below the other two hamstring muscles lies the semimembranosus which is an uncommonly injured hamstring muscle. The picture on the right illustrates that the tendons of the hamstring muscles are not just insertion points onto bone, each of the hamstring muscles have long tendons that span most of the length of the thigh. This makes the diagnosis of the tendon or muscle injury difficult by just location of the pain.

Are we hamstrung by anatomy? We might be if we don’t fully appreciate a few key concepts. Mechanically, the hamstrings cross both the knee and hip joints this means that they have greater contraction velocity, greater capacity to change length and unfortunately, they have less capacity to withstand tension. We already know that tendons heal differently to muscle and this tendons healing phase also takes longer. If we don’t respect this we are most definitely hamstrung from the onset.

Can we tell if a hamstring injury is either a muscle injury, muscle tendon injury or a tendon injury? It is often difficult to tell just by taking a history and examining someone, some clues that may suggest a tendon injury can include a popping sensation, a severe loss of function or strength, bruising in the area or there may be some more subtle signs such as a higher up injury near the pelvis, or a lower down injury near the knee sometimes mean a tendon injury. More recently we know that rotational mechanisms seem to be at a higher risk of distal or closer to the knee tendon injuries or a recurrent injury that just does not feel right may be a tendon injury.

This was a study from the GAA, often the initial suspected grade of hamstring injury and the projected return to play time is very wrong. The initial projected time loss for over 4 weeks was only 2% of the actual time loss time was a quarter.

How do we get around this? MRI is vital at identifying the exact location of the hamstring injury. It shows us what structure is involved and it takes a lot of the guess work out of injury grade prediction. The MRI above shows the injury site in the tendon and as the tendon loses tension it becomes wavier further down. We also see tear into the muscle junction with a feather like appearance at the arrows. This would be classified as a very high-grade hamstring injury, a grade 4 C and depending on the clinical picture may want surgical repair.

We grade hamstring injuries with the help of MRI now, we no longer use the historic grading system of 1, 2 and 3. This has been replaced by the (BAMIC) criteria the British Athletic Muscle Injury Classification. This ranges from 0-4 and A-C. This is a busy slide so lets just simplify it a little bit.

Really to simplify the (BAMIC) classification, if it is a muscle only injury the it is a grade A. If it is an injury at the junction between a muscle and tendon then it is a grade B. If it is a tear to part of the tendon or all of the tendon it is a grade C.

Is this really relevant? Yes, it helps us to stratify the risk of re-injury, we know that grade C injuries where the tendon is involved will take a lot longer to heal and also has an increased rate of re-injury. Also, knowing the tissues involved in the injury with the help of the (BAMIC) plays an important part in rehabilitation. When a track and field athletics group follow the (BAMIC) graded rehabilitation protocol. The re-injury rate was dramatically reduced to 2.9% over a 4-year period which is very impressive when we look at the re-injury rates overall.

As well as that, not only has it helped to stratify the risk of re-injury and help guide rehabilitation principles. The (BAMIC) grade gives a good predictor of a return to play time. When working with athletes often the first question an athlete will as you is ‘When can I return to play?’ The grading system allows for an estimated return to play prediction. It is not a crystal ball, however, there are many other factors that will influence return to play time but it is as good a tool as we have currently to guide the prediction of the return to play. Often times, a re-scan with MRI at the 6-8 week mark can be helpful to assess structural healing and this often comes in helpful when dealing with a target of a short timeframe with return to play. It can give the athlete an objective marker of structure of injury at that time point and forms part of the evidence for which the risk/reward decision making comes in to play.

As a Sports & Exercise Management Consultant our assessment of hamstring injuries always start with a detailed history and clinical exam. We then find the mechanism and the clinical queues as well as prior history is upmost important. Knowledge in the context of the injury along side when the target of return to play from the athlete’s perspective is also important. We review MRI images to help grade the injury according to the (BAMIC) criteria and for some hamstring injuries we may carry out a point of care ultrasound assessment. That can be helpful at times for decision making around the higher risk injuries. Generally, we like to have objective, physical and functional parameters to help guide the stages of rehabilitation. A process which we call the hamstring rehab lab with the help of our SSC and physiotherapy colleagues we will assess strength, biometric and biomechanical measures to give the individual objective targets.

At the Sports Surgery Clinic we use multi-joint strengthening strategies to achieve the aims of rehab. Lumbopelvic control basically means we need to control the pelvis effectively during movement and it does represent an important aspect to successful rehab and prevent hamstring injuries, an individual with an excessively anteriorly tilted pelvis or pelvic drop is already at a biomechanical disadvantage with increased tension placed on the hamstring muscles. Assessment and optimising running mechanics with each individual athlete are also important. Often, the hamstring is the victim of inefficient mechanics at the trunk, pelvis, hip and ankle. Then to find the reasons behind the recurring injury will lead to a more successful outcome. High speed running has always been the most common mechanism for injury and therefore forms a key stage at the end of rehabilitation. Delivering optimal rehab strategies represents the most effective element of a faster return to play by addressing these biomechanical movement pattern disfunctions it is also possible to enhance athletic performance and reduce the risk of future injury. The use of plate rich plasma has gained a lot of attention in tendon injuries. It is common practice among elite sport in other countries to have regular PRP injections after hamstring injuries. Evidence of effect is mixed with some studies suggesting a shorter return to play time when PRP was used. It does not form part of our standard management process at SSC for such injuries but we have an available guidance on a case by case basis. We are also lucky to work alongside orthopaedic surgeons some of whom have expertise in hamstring tendon repair. Surgical repair is limited for the very high-grade tendon injuries and thankfully such injuries are uncommon but it is great to be able to have a team to deal with them when they do occur. We have spoken about many of these prevention strategies and the management of hamstring injuries. Prevention of occurrence forms vital part of management of the actual injury itself. Just to highlight a few from the list, the FIFA 11+ warmup protocol has reduced hamstring and ACL injuries by about 60% in competitive soccer. The Nordic hamstring exercise protocol has helped reduce hamstring injuries by 51%. We know that clear lines of communication between medical and coaching teams have shown to reduce injury, so if you are working with a team consider your systems of communication for injury risk. I suppose, of upmost importance, prevention of the next injury starts with an appropriate management of the initial injury.

Just to run through a quick case discussion of an athlete that I recently managed. This was an intercounty GAA player and he was injured during a game. The injury occurred while running and rotating with a hand pass, initially the player thought it was a low-grade injury but he just did not feel quite right and was worried as he had been through recurrent hamstring injuries the previous season. His physio asked me for an opinion, so as we previously discussed it can be very difficult to clinically tell just by examining someone without imagine if there is tendon or muscle involvement. In this players case he didn’t feel a pop. However, he was more tender closer to the knee over the T-junction, there was a small amount of bruising noted also. His strength was good when I saw him at 2 weeks but he felt his hamstring was vulnerable while trying to increase his speed especially when trying to run on the turn. This apprehension was reduced with an Aisling H test in the clinic room when I saw him.

This is his MRI and I will just run through the slides. We can see on the right-hand side of the picture a white high signal which shows an injury at the tendon of the T-junction. With these injuries they have a very high and large rate of recurrence up to 60%. It can often present very subtly and not very obviously. The player himself wasn’t too surprised but often times we can be shocked at the high grade of injury with subtle clinical signs.

We help guide the player alongside his physio through the phases of rehab, given it was a tendon injury and a high-risk injury we delayed high speed running and high eccentric load of rehab to a little later in the rehab phases. We repeated an MRI at 4 weeks which gave the player and us confidence of good tendon healing there still remained a little amount of inflammation around the muscle tendon junction so all was not clear yet but in as good a situation as we could have hoped for. On ultrasound there was no dynamic gapping which also increased our confidence. With the help of our hamstring rehab lab here at Sports Surgery Clinic we assisted the player and his physio with objective markers he had regained concentric and eccentric strength of his hamstring muscles both left and right and his running mechanics had improved also with some coaching. He returned to a phase which was pitch-based training following then a discussion with the players coaching team you were aware that there were certain movements that had a higher chance of re-injury. He managed to return to an adapted role during the match in week 7. He then subsequently returned to full play and performance at week 8 and thankfully didn’t have any further injuries in his hamstring for the rest of the season. Overall, we are very lucky at the Sports Surgery Clinic to have access to all facets and management of such injuries. If you have a hamstring injury that you feel needs attention from us please let us know.

There is not a one size fits all approach for hamstrings and it does depend on the individual but generally there are a few different ones that have been shown to reduce the risk of hamstring injuries.

Some physiotherapists in the room might be familiar with the Aslings L protocol and it really involves 3 exercises to increase the hamstring length, that would be one thing.

Prehab can mean preventing injury but also including injury treatment it is all the one so strength through the hamstring.

The Nordic hamstring protocol is another programme to improve hamstring strength overtime and that has been shown to significantly reduce hamstring injuries overtime.

These are the two programmes I would generally direct people towards.

With acceleration and deceleration with regards to mechanism of injury you really want to recreate that in your rehab to make sure that the player or the athlete has enough robustness to have an increased threshold and really above that mechanism to cause an injury again if the injury was acceleration or deceleration then that will be a really important part of their rehab.

In terms of prevention and strategies of working with teams obviously in SSC strength & conditioning is very important as we all know but absolutely working on high speed running and working on acceleration and deceleration we know that over time if you have increased your exposure or you have maintained your ability to sprint and to highspeed run you do reduce the risk of hamstring injuries

There has been a lot of research done in the last number of years on supplements especially around tendon health. It is really the cherry on top type of stuff as if you miss out on the strength, you miss out on the highspeed running or you miss out on the ability to jump, sprint and rebound biometric type strength then I would say there is no point in taking supplements but if you have ticked all the other boxes and are in a good position then collagen and vitamin C has been shown in some instances to improve your ability and improve tendon health by 5-10%.

There is some evidence especially for let’s say the competitive athlete, many will be taking them anyway but I suppose the conscious thing with athletes is to ensure we batch test the supplements as well to make sure it is from a reputable source.

In relation to this, you want to look from the ground up. What I mean by that is firstly looking at the range of movement in the ankle often times people may have had a couple ankle sprains and they may have lost some of that ankle movement so keeping an eye on how far they can bring their knee over their big toe or ankle.

People that reduce dorsy flexion movement have a higher risk of hamstring injury. Then coming up to the knee with reduced knee extension i.e. the hamstring is tighter and that shortened hamstring muscle has an increased risk of injury as well so working on that hamstring length overtime through stretching and through the protocols like the asling and Nordic.

Then coming up to the hip, if you have reduced hip movement flexion or an extension then you have difficulty bringing you swing leg or follow leg through and that can increase tension on the hamstring and increase the risk of injury so I suppose in essence really improving the range of movement in the joints and improving the strength of the hamstring is key in biomechanics.

If you prevent the recurrence of injury then that is the best way from preventing that chronic scar from forming. Managing the initial injury is the best way to prevent the chronic scar.

Unfortunately, many athletes and players that will come to us after their 2nd, 3rd or 4th hamstring injury in the space of 12 months and it is a really difficult to manage its not like a day 1 injury it is an injury that has just occurred it is a tendon that generally has had to heal 3 or 4 times and has broken down 2 or 3 times so really managing the first injury is the best way to stop the chronic scar from forming.

RED-S is an energy deficiency in sports syndrome and it happens a lot when athletes under fuel and they don’t put enough fuel or calories into their body to exercise and a number of body systems then unfortunately lose out.

For females they will eventually end up losing out on some menstrual cycles and have less periods which is an obvious sign, some people will get stress fractures but there is definitely an increase in soft tissue injuries including hamstring injuries for anyone that is under fuelled.

It is hard to say without having an assessment. You do need to be seen and you should definitely have a scan if you have had a significant injury like that.

There are a couple of different surgical indications for hamstring injuries and thankfully they are rare but without a clinical assessment and a scan it is hard to say.

Date: 15th November 2023
Location: Online
This event is free of charge