Why Are My Hamstrings Such A Problem

Why are my Hammies Such a Problem?

My hamstrings connected to my ….

A guide to hamstring problems for the elite to everyday athlete and some information regarding the clinical reasoning process your sports med team can adopt for injury management, rehab and performance …

In the sports medicine clinics and on the sports park, we see a lot of lower limb injuries and pain.  From hamstring strains to ankle sprains and ACL’s through to Achilles pain, patellar pain and groin pain.  Most of the time the pain or injury impacts on one’s ability to perform their sport to the best of their ability.  Sometimes they cannot play at all.  Hamstrings injuries though are amongst the most common and most challenging injuries in sport and seemingly getting more common. This year a 25 man football squad will likely have 5-6 injuries and they will cost directly 19.7 days out. 

Many weekend warriors and athletes alike will divide their sporting career into 2 phases – before a hammy tear (BHT) and after a hammy tear (AHT).

Why are hammies such a problem?

Hamstrings are blamed for everything.  If I could choose to be a muscle group in the body would I choose to be the hamstring??? Certainly, an unforgiving role being one of the most functionally in-demand muscle units in the body for all activities. Speak to anyone in the rehab or physical performance world and the hamstrings come up as an ongoing issue and the term multi-factorial approach is often heard.  With good reason too. 

The hamstrings have a role in extending the hips, bending the knee, and rotating the shin and are affected by the position of the pelvis in all 3 planes of movement.  Their demand is based on the amount of bend at the hip; the amount of bend at the knee; the amount of rotation at the shin, the rotation of the trunk and the position of the foot. 

There are ill-defined relationships between the activation patterns of the 4 hamstring muscles and then how they are influenced by the other hip extensors and hip flexors (iliopsoas); as well as the trunk flexors and extensors, the quads, the calves as well as hip abductors, hip adductors and the hip rotators. 

Influence On Biceps Femoris Stretch
Adapted from Thelen et al 2006

Then we know recovery from hamstring injury is influenced by the size and location of the tear, previous injuries, age, sex, sport, load management, how the other side is working and anti-inflammatory use post injury and we see that they take a good deal of understanding when it comes to getting them good again.

The hard-working Hammy fun facts

  • Functionally the hamstrings are extremely active that when athletes sprinting at 75% of their max speed their BFLH was at 115% of their maximal voluntary isometric activity.  
  • At high speeds (~9 metres per second) the hamstrings are the second hardest working muscle group in the body (behind the hip flexors) generating work of up to 9 x bodyweight
  • In sprinting most of the hamstrings work is done just before the foot lands (terminal swing) and continues through to the stance phase.

Let’s meet the Hammies

The hamstring consists of 4 separate and individual muscles. 

  1. The Long Head of the Biceps Femoris (BFLH).  Runs from the inside upper part of your pelvic “sit bone” and runs to the outside of your shin bone.  Its known for its high speed and the resulting large amount of strain (stretch) when running.  The tendon from the top and the tendon connecting the bottom overlap in the middle and therefore the length of each fibre and the angle they run is crucial to their function to develop speed and power and resist stretch.  Tends to work more in extending the hip and rotating the shin bone outwards
  1. The Short head of the Biceps Femoris (BFSH).  Starts in the back of the thigh and meets up with BFLH.  Adds stability and stiffness to the BFLH.  Picks up the slack when the BFLH doesn’t function as well as it could. Works hard when the knee is bending and rotating the knee outwards.
Hamstring Muscles
  1. Semitendinosus (ST).  Starts attached to the BFLH sharing a tendon until it reaches the inside of your shine bone and wraps around towards the front of the knee.  Longest of the hamstring muscles with the longest fibres resulting in fastest speed of contraction.  Works best at outer range and contributes significantly in all hip and knee movements but primarily rotates the shin bone inwards.
  1. Semimembranosus (SM).  Starts on the outside of the pelvic “sit bone” and runs to the inside part of the knee joint. SM has the largest cross sectional surface area, shortest muscle fibre and is the strongest force producer of the hamstring group, especially when running.  SM also assists in resisting rotation of the shin bone outwards.

*note there is a hamstring component of the Adductor Magnus – a large half groin half hamstring muscle along the inside of the thigh.  AddMag (hams part) starts a little lower and more on the inside of the “sit bone” and runs along to the inner thigh bone near the knee.  It works extensively to pull the hip into extension when the hip is flexed.

How do I know if I’ve torn my hammy?

You are usually running.  Normally fast or taking off and bang – you feel it in the back of the thigh.  Generally, you cannot continue and the often-slow trundle to the sideline with all eyes-a-watching.   Expletive hammy indeed.  Other ways include changing direction and occasionally slide tackling and kicking.  There are cases of over-stretched related hamstring tears that occur to gymnasts and dancers.

Semimembranosus Tear
A tear to the Semimembranosus

Chances are you have done a hammy.  Sometimes they may not be so bad initially, but you will certainly not be able to continue at the same pace and intent after the tear. 

From your description we get a pretty good idea on what you have done before you have left the park but assessment within the first 2 days tells us a lot about confirming the diagnosis and giving an idea on prognosis.  Plus early treatment has a large positive effect on reducing time to return and risk of re-injury.

So if you’ve felt the twinge behind the thigh when running or taking off it is a pretty good bet that it is a BFLh tear, given they account for 60-85% of all first time hamstring tears and 94% of all sprinting type tears.  The SM accounts for around the next two-thirds and the ST the remaining third.   If the injury is an over stretch there is a higher likelihood that it was the SM, which accounts for 76% of these types of injuries.

Clinically we would look at the location, stretch – both active and passive and what happens when you contract the muscle against resistance.  The bruising and tenderness give us a fair idea as well.

If it isn’t the hammy what else could it be?

I was once told if it waddles like a duck, quacks like a duck and looks like a duck it’s a duck but what do we do when it looks like a goose? Important to be aware and make sure that if it doesn’t look like a hamstring tear we consider

  • Acute Proximal Hamstring tendon avulsion
  • Low back, hip or knee related hamstring pain (somatic referred pain)
  • Radiculopathy or sciatic related nerve pain
  • Ischial tuberosity avulsion Fracture or traction apophysitis 
  • Hamstring tendinopathy – proximal and distal
  • Myositis ossificans 
  • Bony issues including fractures and tumours
  • Compartment syndrome
  • Vascular-related issues

I have an acute on chronic grade 2b tear of the proximal musculotendinous junction of the biceps femoris long head

What do the gradings mean and is it important?

Hamstring injury classification has become more and more complicated but with good reason.   With such a high incidence of repeated in juries and ongoing issues the first thing we need to make sure is that the diagnosis is right.  However there seem to be more ways of classifying hamstring muscle tears than hamstring muscles these days which makes it confusing.

Basically we nominate the specific muscle if we can. This can assist with the specific type of rehab  and assisting with the body’s natural repair processes.  So we try to identify which of the 4 muscles it is.  Not a necessity though.  You can simply say medial or lateral hamstrings as well.  More often than not your physical examination should determine the rehab exercises specific to what you would like to achieve.

It is good to nominate if it is the proximal (closer to the hip), mid-belly or distal (close to the knee).

Now for the “grade”.  The typical grade one, two or three in relation to the “size” of the tear is not as common anymore as a sole classification but the principle still holds true for a 0 to 4 grading system.  The other key differentiator which has become of increasing importance is whether the tear is just in the muscle belly, the musculotendinous junction (where the tendon turns into muscle) or if it includes parts of the tendon that runs through the muscle belly.

Grade

Day 2 Imaging

Day 2 Clinical signs

0

MRI – ive

a: normal

b: may see a change in signal around the muscle in non-specific sites

Generalised muscle soreness

May have end of range tightness

No significant or measurable weakness

1

Signal over 0-10% of the width or cross section of the tear or up to 5cm in length. Less than 1cm of structural disruption

a: involves only the muscle belly

b: includes the musculotendinous junction without extension into the tendon

Specific muscle soreness

Minor strength deficit with pain on near-maximal contraction

Generally still full range but pain on stretch

Can often walk in and function okay

2

Signal 10-50% of the width or cross section of the tear or between 5cm to 15cm in length. Less than 5cm of structural disruption

a: involves only the muscle belly

b: involves the musculotendinous junction without extension into the tendon

c: involves the intra-tendinous region but the tendon remains intact and tense

Specific muscle soreness, likely haematoma or bruising present

Measurable strength deficit with pain and hesitation. Slow rate of contraction

Significant loss of range with pain

Noticeable limp and difficulty doing some day to day movements

3

Signal >50% of the width or cross section of the tear greater than 15cm in length. Greater than 5cm of structural disruption. The tendon may not be able to withstand tension but no retraction present and is still continuous

a: involves the muscle belly and fascia only

b: involves the musculotendinous junction without extension into the tendon

c: extends into the intra-tendinous region

Large but specific area of soreness. Lots of bruising and swelling.

Usually unable to generate a contraction due to pain and fear

Significant loss of range

Could be on crutches and struggling to walk

4

Complete disruption of the muscle-tendon unit

a/b: complete muscle tear with retraction

c: Complete tendon tear with retraction

Extensive bruising

Pain and movement levels may be variable

Little or no strength or ability to contract with significant force

Is Imaging needed?

Generally the answer is no.  MRI is useful for a Grade 0 classification which assists with pushing for a fast return to sport. MRI does not really change our prognosis in “grade” 1 and 2 tears. Physical exam tests and the presenting history taken should be enough in these cases to differentiate between the 4 muscles with some confidence.

However MRI and ultrasound do have some role in the more complicated hamstring issues.  This includes issues with the “free” tendon in isolation which may be difficult to pick up in a clinical test.  This includes primarily the tendon running to the SM muscle from above.  The common tendon between BFLH and ST can also be a source of symptoms.  These can be well imaged on MRI, ultrasound and more recently measured and diagnosed with UTC (ultrasound tissue characterisation). Likewise, near the knee the tendons there may have suffered an acute injury in the form of partial tear or reactive tendinopathy.  MRI, X-ray and ultrasound may also very useful for assisting in ruling in or out other diagnosis in the area if we have a goose pretending to be a duck.

Utc Scanner
UTC scanner being used to measure hamstring muscle-tendon quality. Courtesy of UTCimaging.com

If after a good rehab there are some issues or there are repeated injuries and ruled out other things, then MRI may assist in diagnosing the type c issues above.  Recent studies suggest up to 40% of hamstring tears involve the intramuscular tendon with 3% involving the free tendon.  The jury is still out on whether the intramuscular tendon or free tendon associated injuries delay return to sport or have a higher incidence of re-injury.

As a novel treatment idea one significant contribution to successful return to sport in BFLH includes measuring the length and angle of the muscle fibre.  The longer it is the better chance of reducing your re-injury risk.  And yes it can be changed with a the right exercise program and measured with MRI or ultrasound.

Mri Of Bflh Tear At 10 Days And 30 Days
MRI of BFLH tear at 10 days and 30 days. Courtesy of Heiderscheit et al 2010

Victim or Problem? (you may need a coffee for these ones)

This is the pandora’s box of questions but so important to understand why this hamstring has torn.  Some things to assess over the first few getting to know you sessions as the hammy is healing and shapes the criteria for return to sport.

Chronic hamstring dysfunction/weakness and inter hamstring imbalance –> acute muscle tear

  • This is looking at the 4 muscles as a unit and determining if one of them (may or may not be the injured one) had become dysfunctional and due to that one of the 4 muscles tore. For example the BFLH adapts to increase in strength and the ST cannot work as well at end range. Ultimately the BFLH takes up the slack and in an instant cannot handle the extra demand and tears
  • This can be due to biomechanics or skill based adaptations. Another example may be the SM may not control the rotation of the shin bone turning outwards due to other demands in stance phase and there is increased demand of BFLH in the kick back phase causing rotation of the shin outwards and as the leg comes through for heel strike the demand is too much for BFLH

Skill based biomechanics and adaptive strategies

  • When doing a skill there is a near sole focus on the result of the performance – as it should be – however it may increase the demand on the hamstring unit if it increases the primary demand on the hamstrings or one specific part of them. For example if the affected leg provides more drive in any power-based exercise the body may adapt to prepare to position It better. This may include early bending at the hip and rotation of the pelvis forward. To balance that out the thigh rotates in and shin rotates in to maintain your centre of mass over the heel strike. This may increase the demand on the SM and in one instance when asked to work fast it fails during a forward to backward change of direction transfer.

Muscle Dysfunction in the “kinetic chain”

This is where other muscles used within the skill become dysfunctional. It can include:

  • Abdominals not controlling pelvic tilt and increasing the stretch on the hamstrings
  • Quadriceps being over-dominant and the hamstrings not being able to resist the force to slow down the movement
  • Glute max not working to extend the hip and directly increasing the need for the hamstrings to do hip extension during stance phase
  • Calves not driving efficiently, especially the deep calf (soleus) which then could place extra demand on the hamstring at lower sprint speeds
  • Increased “tension” or tone in the opposite hip flexor which changes the mechanical forces on the hamstring (torque)

It is more than likely that these contributors need to be assessed, identified and managed if you wish to return to sport or activity and perform well and nor be re-injured.  This is the ultimate challenge for all therapists, coaches and athletes.

Give it to me straight – How long doc?

The golden question.   To be quite simple and this is proven with research.  How long do you think it will take? 

So a few things which give us a good idea. 

  • If you have a type 3 or 4 injury upgrade your netflix subscription
  • If you have nothing on MRI and we have excluded all other geese then higher likelihood you will return to sport within a week or 2
  • If the time to walk pain free is > 1 day or if day to day activities have pain after 3 days
  • If you were able to continue to play on for > 5/60 higher likelihood of a sooner return to sport
  • If you heard a Popping sound when it happened.  Increase that time
  • Ditto for large area of tenderness or presence of a haematoma
  • If your hamstring hurts when you bend your back forward –> incr time
  • The longer there is presence of pain with active knee extension test or passive straight leg raise the longer it will take (even if pain free there is increased risk of re-injury if movement is reduced relative to the other side) 
  • The further the tear is from the “sit bone” the better the prognosis
  • Reduced maximal isometric strength and pain with knee flexion at 15° of knee bend

Other contributors include the cause of the tear and all the biomechanical factors and other previous or co-existing injuries and dysfunction.  It is also crucial to abide by load management philosophy and allow enough time to recondition where possible.

Having said all that we are 95% confident that you will return within 8 to 47 days

BAppSc (Phty) Masters (Sports PHTY) APAM

High-Performance Sports & Exercise Physiotherapist, Director

Aaron Lewis is a Physiotherapist with a focus on Achilles tendon, ACL tears, hamstring, and Upper limb throwing and lifting pathology. He is also the founding director and senior consultant Physiotherapist at Performance 360.

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