Hamstring Strain

Original Editors - Bo Hellinnckx

Top Contributors - Admin, Boddengeen Ben, Bo Hellinckx, George Prudden, Mandeepa Kumawat, Vinit Kothekar, Shaimaa Eldib, Evan Thomas, Kim Jackson, Rachael Lowe, Uchechukwu Chukwuemeka, Aminat Abolade, Tomer Yona, Fasuba Ayobami, Iris Roelandt, Daphne Jackson, Wanda van Niekerk, Shoko Otsuka, WikiSysop, Simisola Ajeyalemi, 127.0.0.1, Livia Hoeben, Tony Lowe, Tania Appelmans, Claire Knott and Kai A. Sigel

Definition/Description

Hamstring strains are caused by a rapid extensive contraction or a violent stretch of the hamstring muscle group which causes a high mechanical stress. This results in varying degrees of rupture within the fibres of the musculotendinous unit.

Hamstring strains are common in sports with a dynamic character like sprinting, jumping, where quick eccentric contractions are regular. In soccer it is the most frequent injury.

The hamstrings consist of three muscles : The biceps femoris, the semitendinosus and the semimembranosus.

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Clinically Relevant Anatomy

The hamstrings are a group of muscles which are comprised of three separate muscles located at the back of the thigh. The M. Biceps Femoris, M. Semitendinosus and the M. Semimembranosus. These muscles start at the ischial tuberosity, extending down the back of the thigh and along either side of the knee. 

The M. Biceps Femoris exists out of two parts: the long head and the short head (Caput longum and Caput breve). These two parts are both attached to the head of the fibulae, but only the long head starts at the ischial tuberosity. The other part, the short head, starts at the lateral lip of the linea Aspera on the posterior aspect of the femur. The Caput Breve and Longum are innervated by 2 different nerves. The Caput Longum is innervated by the N. Tibialis, while the Caput Breve is innervated by the N. Fibularis, who are both originating from the spine segment L5-S2. The M. Semitendinosus starts at the ischial tuberosity but unlike the M. Biceps Femoris, it lays at the medial side of the thigh and is attached to the upper medial surface of the tibia, also called Pes Anserinus.

The M. Semimembranosus is the most medial of the three hamstring muscles. It also starts at the ischial tuberosity and is attached to the Condylus Medialis Tibiae. It’s also connected to the Lig. Popliteum Obliquum, and the fascia cruris .

This shows that all of the three hamstring muscles start at the same origin, but have different insertions .

Because the hamstrings cross 2 joints (the knee and the hip), their functions are varied.
The muscles function as movers and stabilizers of the hip and knee. The hamstrings are used to flex the knee, and extent the hip. The hamstrings help to get from a crouched position to an erect position. This refers to movements like getting up from a chair or in sprinting, where the front leg in starting position has to bear the effect or the start.

Because of the insertion of the muscles, the secondary function of the hamstrings is endo and exorotation of the knee. This makes the hamstrings extremely important muscles if it comes to walking and running.

Schematic review of structure and functional anatomy

Biceps Femoris:

Caput breve:

• Origin: labium laterale, lineae aspera, septum intermusculare laterale
• Insertion: caput fibula

Caput longum:

• Origin: tuber ishiadicum
• Insertion: caput fibula

Function:

• Hip extension
• Knee flexion
• Exorotation of leg

Semimtendinosus:

• Origin: Tuber ishidadicum
• Insertion: Pes Anserinus (facies Medialis Tibiae)

Function:

• Hip extension
• Knee flexion
• Endorotation of leg

Semimembranosus:

• Origin: tuber ishiadicum
• Insertion: condylus medialis tibiae, ligamentum popliteum obliquum, fascia curis

Function:

• Hip extension
• Knee flexion
• Endorotation of leg

Epidemiology /Etiology

The cause of a hamstring muscle strain is often obscure. In the late forward swing phase, the hamstrings are at their greatest length and at this moment, they generate maximum tension . In this phase, hamstrings contract eccentrically to decelerate flexion of the hip and extension of the lower leg . At this point, a peak is reached in the activity of the muscle spindles in the hamstrings. A strong contraction of the hamstring and relaxation of the quadriceps is needed. According to “Klafs and Arnheim”, a breakdown in the coordination between these opposite muscles can be a cause for the hamstring to tear.

Predisposing Factors/Risk Factors

There are various proposed risk factors which may play a role in hamstring injuries:

• Increased age
• Previous hamstring injury
• Limited hamstring flexibility
• Increased fatigue
• Poor core stability
• Strength imbalance

During activities like running and kicking, hamstring will lengthen with concurrent hip flexion and knee extension, this lengthening may reach the mechanical limits of the muscle or lead to accumulation of microscopic muscle damage. There is a possibility that hamstring injuries may arise secondary to the potential uncoordinated contraction of biceps femoris muscle resulting from dual nerve supply.

Another debate is on hamstring variation in muscle architecture. BFS possess longer fascicles (which allow for greater muscle extensibility and reduce the risk of over lengthening during eccentric contraction) and a much smaller CSA compared to BFL. Whereas BFL presents with shorter fascicles compared to BFS which undergo repetitive over lengthening and accumulated muscle damage.

Excessive anterior pelvic tilt will place the hamstring muscle group at longer lengths and some studies proposed that this may increase risk of strain injury.

Characteristics/Clinical Presentation

Hamstring strain results in a sudden sharp pain in the posterior thigh when it occurs during sport activities. Also a "popping" or tearing impression can be described. The patients may complain of tightness and improved range of motion like knee extension and hip flexion. Sometimes swelling and ecchymosis are possible but they may be delayed for several days after the injury occurs. Rarely symptoms are numbness, tingling and distal extremity weakness. These symptoms require a further investigation into sciatic nerve irritation. Large hematoma or scar tissue can be caused by complete tears and avulsion injuries.

Other possible symptoms: *Pain *Tenderness *Loss of motion *Decreased strength on isometric contraction *Decreased length of the hamstrings Hamstring strains are categorised in 3 groups, according to their severity.:

• Grade 1 (mild): just a few fibres of the muscle are damaged or have ruptured. This rarely influences the muscle's power and endurance. Pain and sensitivity usually happen the day after the injury (depends from person to person). Normal patient complains are stiffness on the back side of the leg. Patients can walk fine. There can be a small swelling, but the knee can still bend normally.
  
• Grade 2 (medium): approximately half of the fibres are torn. Symptoms are acute pain, swelling and a mild case of function loss. The walk of the patient will be influenced. Pain can be reproduced by applying precision on the hamstring muscle or bending the knee against resistance.  
• Grade 3 (severe): ranging from more than half of the fibres ruptured to complete rupture of the muscle. Both the muscle belly and the tendon can suffer from this injury. It causes massive swelling and pain. The function of the hamstring muscle can't be performed anymore and the muscle shows great weakness.

Differential Diagnosis

On examining the patient, the physiotherapist possibly has to differentiate between different injuries e.g. adductor strains, avulsion injury, lumbosacral referred pain syndrome, piriformis syndrome, sacroiliac dysfunction, sciatica, Hamstring tendinitis and ischial bursitis.  

Other sources of posterior thigh pain could also be confused with hamstring strains and should be considered during the examination process. Specific tests and imaging are used to asses and exclude those different pain source possibilities.

Sciatic nerve mobility limitations can contribute to posterior thigh pain and adverse neural tension could in some cases be the only source of pain without any particular muscular injury. In certain cases it is difficult to determinate whether it are the Hamstrings or other muscle groups like hip adductors (eg. M. Gracilis and M. Adductour magnus and longus.) that are injured due to their proximity. Sometimes imaging procedures may be required to determinate the exact location of the injury.

Other conditions with similar presentations as hamstring strains are strained popliteus muscle, tendonitis at either origin of the gastocnemius, sprained posterior cruciate ligament, apophysitis-pain in ischial tuberosity, Lumbar spine disorders and lesions of the upper tibio-fibular joint.

Diagnostic Procedures

Most of the acute injuries can easily be found by letting the patient tell how the injury occured. To be sure they must do a little investigation of the hamstrings as well.

When the therapist Isn't too sure, he can ask for medical imaging. This will exclude al other possibilities.

• Radiographs: a good thing about radiographs is that with that kind of imaging, its possible to differentiate the etiology of the pain. It can differentiate in muscular disease (e.g muscle strain) or a disease of the bone (e.g. Stress fracture).
• Ultrasound (US): this kind of imaging is used a lot because it is a cheap method. It is also a good method because it has the ability to image muscles dynamically. A negative point about Ultrasound is that it needs a skilled and experienced clinician.
• Magnetic Resonance Imaging (MRI): MRI gives a detailed view of the muscle injury. But sometimes it may not be clear according to the images. If that happens, the therapist must rely on the story that the patient told him (see characteristics/clinical presentation).

Outcome Measures

• FASH: The FASH questionnaire is a self-administered questionnaire which now can only be used in Greek, English and German languages. Because hamstring injuries represent the most common football injury, they tested the validity and reliability of the FASH-G (G = German version) questionnaire in German-speaking footballers suffering from acute hamstring injuries. The FASH-G is a valid and reliable instrument to assess and determine the severity of hamstring injuries in a population of athletes.
• LEFS: Lower Extremity Functional Scale  
• SFMA: The Selective Functional Movement Assessment (SFMA) is a clinical assessment system designed to identify musculoskeletal dysfunction by evaluation of fundamental movements for limitations or symptom provocation.
• PSFS: Patient Specific Functional Scale  
• VAS: Visual Analog Scale  
  
• NPRS: Numerical Pain Rating Scale  

Examination

Running gait: The physical examination begins with an examination of the running gait. Patients with a hamstring strain usually show a shortened walking gait. Swelling and ecchymosis aren’t always detectable at the initial stage of the injury because they often appear several days after the initial injury.

Observation: The physical examination also exists of visible examination. The posterior thigh is inspected for asymmetry, swelling, ecchymosis and deformity. When there is a palpable defect, it indicates a more severe injury, mostly with a full rupture of the muscle. Also the active and passive range of motion should be tested and compared with the other leg.

Clinical tests:

• Puranen-Orava test – Actively stretching the hamstring muscles in standing position with hip flexed at about 90*, the knee fully extended and foot on a solid surface. Positive – exacerbation of symptoms. (SN 0.76, SP 0.82, +LR 4.2, -LR 0.29)
• Bent-Knee stretch test (SN 0.84, SP 0.87, +LR 6.5, -LR 0.18)
• Modified Bent-knee stretch test (SN 0.89 SP 0.91, +LR 9.9, -LR 0.12)
• Taking off the shoe test/hamstring-drag test (SN 1.00, SP 1.00, +LR 280.0, -LR 0.00)
• Active ROM test (SN 0.55, SP 1.00, +LR 154.6, -LR 0.50)
• Passive ROM test (SN 0.57, SP 1.00, +LR 160.6, -LR 0.43)
• Resisted ROM test (SN 0.61, SP 1.00, +LR 170.6, -LR 0.40)

Tests Summery

Test	Sensitivity	Specificity	+LR	-LR
Puranen-Orava	0.76	0.82	4.2	0.29
Bent-Knee stretch	0.84	0.87	6.5	0.18
Modified Bent-knee stretch	0.89	0.91	9.9	0.12
Taking off the shoe	1.00	1.00	280	0.00
Active ROM	0.55	1.00	154.6	0.50
Passive ROM	0.57	1.00	160.6	0.43
Resisted ROM	0.61	1.00	170.6	0.40

Medical Management

Surgical intervention is an extremely rare procedure after a hamstring strain. Only in case of a complete rupture of the hamstrings, surgery is recommended. Almost all patients believed that they had improved with surgery. A study  shows that 91% was satisfied after surgery and rated their happiness with 75% or better. Hamstrings endurance tests and hamstring strength tests were better and highly scored after an surgical procedure. The muscle strength testing after surgery ranged from 45% until 88%. The hamstrings endurance testing ranged from 26% to 100% .The physical examination and follow-up reveals that all repairs stayed intact.

Physical Therapy Management

The primary objective of physical therapy and the rehabilitation program is to restore the patient’s functions to the highest possible degree and/or to return the athlete to sport at the former level of performance and this with minimal risk of reinjury.

Hamstring strain injuries remain a challenge for both athletes and clinicians, given their high incidence rate, slow healing, and persistent symptoms. Moreover, nearly one third of these injuries recur within the first year following a return to sport, with subsequent injuries often being more severe than the original. The use of a specific and adequate training programme to rehabilitate hamstring strains can be determinant for the healing and prevention of a recurrent hamstrings strain injury. Different kind of therapies are used to rehabilitate hamstring strains, but are they all as effective enough to prevent a recur within the first year following a return to sport? Different studies tried to show the impact of eccentric exercises, dry needling, deep stripping massage, etc. on hamstring strain rehabilitation.

The use of eccentric strengthening at long muscle lengths exercises as rehabilitation where used to examine the effects to prevent a recurrence hamstring injury following the revalidation. The results shown that the use of eccentric strengthening exercises at long muscle had a positif effect.

On the other hand, a study tried to compare eccentric strengthening exercises (STST) with progressive agility and trunk stabilization exercises (PATS). The rehabilitation of the STST group consisted of static stretching, isolated progressive hamstring resistance exercise, and icing. The PATS group consisted of progressive agility and trunk stabilization exercises and icing as treatment. The study found a significant better result in patients that were rehabilitated with progressive agility and trunk stabilization. Reinjury rate was significantly lower in the PATS group after one year returning to sport (1 of the 13 athletes instead of 7 on the 11 athletes in the STST group). A rehabilitation program consisting of progressive agility and trunk stabilization exercises is more effective than a program emphasizing isolated hamstring stretching and strengthening in promoting return to sports and preventing injury recurrence in athletes suffering an acute hamstring strain.

Deep stripping massage is another technique used as rehabilitation for hamstring strain injury. Most of the time it is combined with other rehabilitation technique. Deep stripping massage (DSMS) alone or with eccentric resistance where used to examine the impact on hamstring length and strength. These results suggest that DSMS increases hamstring length in less than 3 min but has no effect on strength. Furthermore, combining DSMS with eccentric resistance produces more hamstring flexibility gains than DSMS alone and does not affect strength.

Functional dry needling is a technique that has been reported to be beneficial in the management of pain and dysfunction after muscle strains and in combination with eccentric training program, but there is limited published literature on its effects on rehabilitation or recurrence of injury.

The impact of kinesiology tape has been demonstrated to be efficient on the improving of muscle flexibility, which can prevent or improve the risk of having injuries. Kinesiology tape can be used in combination of other rehabilitation programmes to improve the muscle flexibility.

There are lots of techniques and programmes that can be used for the revalidation of hamstring strains injuries but due to a lack of studies, the effectiveness of these techniques can not all been demonstrated. Therefore eccentric exercises are the most known and applied programme for the rehabilitation of hamstring strains injuries. The use of this kind of programme has shown good results. One common criticism of rehabilitation programs that emphasize eccentric strength training, is the lack of attention to musculature adjacent to the hamstrings. It has been suggested that neuromuscular control of the lumbopelvic region is needed to enable optimal function of the hamstrings during normal sporting activities.

Eccentric hamstrings training

Rehabilitation protocol

Phase I (week 0-3)

• Goals

Protect healing tissue

Minimize atrophy and strength loss

Prevent motion loss

• Protection

Avoid excessive active or passive lengthening of hamstring

Avoid antalgic gait pattern

• Rehab

Ice – 2-3 times daily

Stationary bike

Sub maximal isometric at 90, 60 and 30

Single leg balance

Balance board

Soft tissue mobs/IASTM

Pulsed ultrasound (Duty cycle 50%, 1 MHz, 1.2 W/cm2)

Progressive hip strengthening

Painfree isotonic knee flexion

Active sciatic nerve flossing

Conventional TENS

• Criteria for progession to next phase

Normal walking stride without pain

Pain-free isometric contracton against submaximal (50%-75%) resistance during prone knee flexion at 90.

Phase 2 (week 3-12)

• Goals

Regain pain-free hamstring strength, progressing through full ROM

Develop neuromuscular control of trunk and pelvis with progressive increase in movement and speed preparing for functional movements

• Protection

Avoid end-range lengthening of hamstring if painful

• Rehab

Ice – post exercise

Stationary bike

Treadmill at moderate to high intensity pain-free speed and stride

Isokinetic eccentrics in non-lengthened state

Single limb balance windmill touches without weight

Single leg stance with perturbations

Supine hamstring curls on theraball

STM/IASTM

Nordic hamstring Ex

Shuttle jumps

Prone leg drops

Lateral and retro bandwalks

Sciatic nerve tensioning

• Eccentric protocol

Once non-weight bearing exercises are tolerated start low-velocity eccentric activities such as stiff leg dead lifts, eccentric hamstring lowers/Nordic hamstring Ex, and split squats

• Criteria for progression

Full strength 5/5 without pain during prone knee flexion at 90

Pain-free forward and backward, jog, moderate intensity

Strength deficit less than 20% compared against uninjured limb

Pain free max eccentric in a non-lengthened state

Phase 3 (week 12+)

• Goals

Symptom free during all activities

Normal concentric and eccentric strength through full ROM and speed

Improve neuromuscular control of trunk and pelvis

Integrate postural control into sport-specific movements

• Protection

Train within symptoms free intensity

• Rehab

Ice – Post exercise – as needed

Treadmill moderate to high intensity as tolerated

Isokinetic eccentric training at end ROM (in hyperflexion)

STM/IASTM

Plyometric jump training

5-10 yard accelerations/decelarations

Single-limb balance windmill touches with weight on unstable surface

Sport-specific drills that incorporate postural control and progressive speed

• Eccentric protocol

Include higher velocity eccentric Ex that include plyometric and sports specific activities

Examples include squat jumps, split jumps, bounding and depth jumps

Single leg bounding, backward skips, lateral hops, lateral bounding and zigzag hops and bounding

Plyometric box jumps, eccentric backward steps, eccentric lunge drops, eccentric forward pulls, single and double leg deadlifts, and split stance deadlift (good morning Ex)

Return to sport criteria

Full strength without pain in the lengthened state testing position

Bilateral symmetry in knee flexion angle of peak torque

Full ROM without pain

Replication of sport specific movements at competition speed without symptoms.

Isokinetic strength testing should be performed under both concentric and eccentric action conditions. Less than a 5% bilateral deficit should exist in the ratio of eccentric hamstring strength (30d/s) to concentric quadriceps strength (240d/s).

Resources

Recent Related Research (from Pubmed)

https://www.ncbi.nlm.nih.gov/pubmed/27937671%7Ccharset=UTF-8%7Cshort%7Cmax=10

https://www.ncbi.nlm.nih.gov/pubmed/27632842%7Ccharset=UTF-8%7Cshort%7Cmax=10