Hamstring injuries are common among athletes and active individuals, and they refer to any type of damage to the muscles or tendons in the back of your thigh. The hamstrings are a group of three muscles that run from the pelvis to the knee and are responsible for hip extension and knee flexion, often referred to as a hamstring strain or pulled hamstring they are one of the most common injuries seen in football, rugby and athletics, indeed any sport or activity which will require sprinting.
The three hamstring muscles which make up the hamstring muscle group are
Biceps femoris sits on the outside of the thigh and is the hamstring injured most often during sprinting mechanisms of injury. Semitendinosus and Semimembranosus sit on the inside (medial) aspect of the thigh and are more commonly injured during stretch mechanisms of injury.
A hamstring injury would be strongly suspected when an individual feels a sharp pain or popping sensation at the back of the thigh during activity however they don’t always result in a sudden pain and can also come on as a more gradual tightness or cramp sensation (especially in the presence of muscle fatigue). This is why accurate assessment and diagnosis of the injury by a physiotherapist (physical therapist) or sports medicine doctor is so important.
How do hamstring injuries happen?
The vast majority of injuries happen during sporting activity when the muscles at the back of the thigh are being asked to worked hard. The hamstring muscles are speed muscles, they are most active during high speed activity such as sprinting or kicking but are also working during less explosive activities such as jogging.
In general hamstring injuries happen when an already fatigued muscle is pushed beyond its physiological capability or when they are suddenly asked to be explosive (such as sprinting maximally) or are stretched.
In simple terms they can be grouped as sprint or stretch injuries and this will impact slightly how they are managed later in the rehabilitation process. In the early stages however the medical advice and management is fairly simple and explained below.
I’ve injured my hamstring, what should I do now?
Until you can get formally assessed by a physical therapy specialist or sports doctor you can do some simple things in the first few hours to manage the hamstring injury.
Rest – This seems like simple advice but if you have just got a sharp pain at the back of the thigh then it’s a good idea to stop the activity that you are doing. Even if the pain eases and you feel you can continue it’s probably best to recognise that potential muscle strains have occurred and begin the management of it.
Apply Ice pack – Ice is a great way to reduce swelling and pain.
Use compression – Apply a compression bandage to the injured leg. The compression will also help to limit swelling and bleeding and in more severe injury this can make a big difference to your comfort. Any muscle tissue or muscle fibers which can be protected will help you further down the line.
Avoid putting weight on the injured leg – If the pain is severe and you are struggling to walk without pain, use crutches to protect the injured tissues. These simple things can really help things to begin to heal from day 1.
Take pain medicine – A doctor can guide on this but simple pain medication such a paracetamol will ease the pain in the injured muscle. Avoid taking Anti-inflams (NSAIDs) especially in the early phases. The first phase of healing is inflammation which means we don’t want to suppress this, instead we want the inflammatory phase to be kick started and encourage outstanding scar tissue formation.
How severe is my hamstring injury?
Most hamstring tears which only involve a partial muscle tear or mild hamstring strain recover well with appropriate treatment, rehabilitation and advice about returning to sport. On rare occasions with a more severe tear, complete muscle tear, hamstring tendon injury or rupture it can be advisable to have the muscle injury surgically repaired, but these injuries are very much in the minority. So how do we decide how severe the injury is and how to appropriately manage them?
When you visit a Physiotherapist or Sports Medicine Doctor such as those here at R4P Liverpool they will carry out a complete assessment of the injured muscle and grade it based on the severity.
This grading system combines clinical information (how you did it) with clinical assessment (palpation, muscle testing, length testing) and can also incorporate information from Ultrasound assessment (also available here at R4P) or MRI (which we can refer you for).
The clinical muscle injury grading system used is as follows
Grade 1 – Low grade hamstring muscle strain. Usually able to complete the activity or complain of a tightness only. Will present with full power though it may be painful when the muscle is asked to contract. The area of muscle tenderness is likely to be small and length testing will be normal or show only a mild loss of range of motion.
Grade 2 – A moderate grade hamstring injury. In these cases you are more likely to have had a sudden onset or more severe pain at the back of the thigh. It is likely that you had to stop the activity you were doing almost immediately. On assessment there will be pain and loss of power with muscle testing and more significant loss of range of motion with muscle length testing. The area of muscle length tenderness will be longer and more severe.
Grade 3 – A significant grade hamstring injury. Sudden onset of severe pain in the back of your thigh possibly with a popping sensation. Significant pain and loss of power with a large loss of range of motion. It is likely walking will be painful and difficult and you may not have been able to walk at all in the mediate aftermath of the injury needing a stretcher to leave the field or court of play.
Additional information to ensure accurate diagnosis – Imaging of hamstring muscle injuries
Which muscles are involved is clearly important, and at times this can be difficult to ascertain solely from a clinical examination. The hamstrings are all biarticular but they run extremely closely together and share common tendons. Certain parts of the hamstring can be trickier than others to manage and carry more risk for re-injury too. Have a read on T-junction injuries here.
Grade of muscle injury
Several criteria for evaluating and grading muscle injury have been presented in the literature, with significant variation in implementation across sports and among practitioners. However, the key information that informs diagnosis and possibly prognosis is recognised as the presence and extent of muscle fibre disruption, as well as the associated oedema pattern. Therefore, in an MRI report, the extent of muscle fibre disruption (sometimes referred to as macroscopic damage, tearing, architectural disruption or fibre damage), including cranio-caudal and cross-sectional area (CSA) of disruption, is noted. The percentage in relation to total muscle size should also be provided.
UEFA grading system
Measurements of fibre damage form the basis of the grading system proposed by UEFA in 2012. This classifies injury (graded 0-3) based on the CSA of muscle fibre disruption, regardless of oedema.
BAMIC – British Athletics Muscle Injury Classification
Muscle oedema length has been identified as an important finding on MRI, and furthermore has been shown to be associated with RTP times. The British Athletics Muscle Injury Classification proposed by Pollock and colleagues use oedema length (cm) and CSA (cm and % of total) to grade muscle injuries 0-4. Oedema should be measured and recorded as cranio-caudal dimension and also the CSA, both as absolute dimensions and also as a percentage of total muscle size.
Information to inform prognosis and rehabilitation planning after hamstring injury
Radiological research suggests that certain anatomical locations may be associated with longer recovery times, for example proximal hamstring injuries. Longer RTP times should also be expected for central distal soleus injuries compared to those situated on the lateral side of the muscle. However, it may be that the type of tissue, more so than the location, is of key importance.
2. Tissue type involved
The BAMIC grading system indicates the tissue structure and the specific location injured. Myofascial, musculotendinous and intra-tendinous are denoted as a, b and c respectively.
A myofascial injury is situated at the periphery of the muscle, involving the surrounding connective tissue layers (epimysium, perimysium, aponeurosis). A disruption of these structures may result in intermuscular fluid or haematoma, which should be noted.
The musculotendinous junction is thought of as the location of greatest force production within the muscle tendon unit, and therefore has a higher incidence of injury than other sites. This may be at the proximal or distal ends of the muscle belly, or indeed within the central part of muscles, which have a large intramuscular tendon component.
A tendon injury is noted if there is oedema within the tendon, or evidence of tendon fibre damage. This may be a cross-section tear, or a longitudinal split tear. Tendons have comparatively less vascularity than muscle tissue, likely resulting in a slower healing response. Intra-muscular tendon parts have relatively less sensory neural innervation when compared with muscle tissue or the free tendon.
3. Tendon involvement
Note should be made of involvement of the free tendon (above the level of the muscle tissue) or intramuscular tendon component, as well as any retraction or loss of tension. Care should be taken to correctly identify injuries involving the intramuscular and free tendon, and careful consideration of how this will influence Return to Performance (RTPerf) times and the rehabilitation process.
I’ve injured my hamstring, do I need an MRI scan?
While MRI grading of injury continues to be an important part of our diagnosis and prognosis process, it should only be confirmatory of an accurate clinical examination. An MRI report is useful when determining involvement of tendon tissue, because the healing properties of tendon tissue (which doesn’t result in early scar tissue formation) will impact on our decision to load early and slightly lengthen the initial prognosis.
I know my Grade of Hamstring Injury – now what?
The usual question when somebody injures their hamstring is when can I play sports again and with accurate diagnosis and prognosis it will be possible to determine this.
With a grade 1 hamstring injury you should be looking to get back to sport and previous activity in around 2 weeks, for a grade 2 hamstring injury it would be 3-4 weeks and for a grade 3 hamstring injury a minimum of 6 weeks.
It is important to note these are guidelines and every muscle injury and individual should be treated as an individual case based on physical exam as the injury recovers. The muscle needs to be given chance to rest and heal before gradually being reloaded with exercises. As the muscle gets stronger running can be started and progressed alongside this, extreme stretching should be avoided.
Each stage should be monitored by a physiotherapist and progressed based on how the muscle responds. In basic terms, let it settle, let it heal, get it strong and expose it to the demands of what you want to get back to gradually and you won’t go too far wrong.