Hamstring Injuries
Hamstring injuries are one of the most common strains to affect athletes and the most common type of strain to affect the lower extremity. Hamstring strains can also be one of the most disabling injuries to the lower extremity. These strains are most common amongst athletes that participate in sports that involve a lot of acceleration, deceleration, kicking, jumping, cutting, and pivoting. - sports such as soccer, rugby, football, and raquet sports.
Contents
How
do
hamstring injuries occur
Factors
that predispose an athlete to hamstring strains
Recurrence
of hamstring strains
Where do
hamstring strains occur
Physiology
of injuries to the hamstrings
What
does a hamstring injury look like
Classification
of injuries
Treatment of
hamstring problems
Is
Dynamic or Static Stretching Better for Hamstrings?
Will
Stretching Prevent Strains in Hamstrings?
How Does
Dynamic
Stretching Affect Previously Injured Athletes?
How do hamstring injuries occur
As with most muscle strains, the hamstrings are most commonly strained
during an eccentric contraction. Eccentric contractions involve the
lengthening of a contracting muscle. Hamstring strains are
usually caused by
a forceful hip flexion
while the hamstring is working to slow the extension of the knee as in
kicking or running.The
hamstrings contract
eccentrically during running to decelerate the forward movement of the
tibia. The hamstrings then change their role to
extend the
hip. It is at this point in running when the hamstrings go from
contracting eccentrically to concentrically that the hamstrings are
most vulnerable to injury.
What makes the hamstring particularly susceptible to injuries is the
fact that the role of the hamstrings can change quickly many times
during a task:
- hip extension
- deceleration of knee extension
- knee stabilization
- pelvic stabilization
All of these performed rapidly and repeatedly results in
intense
loading of the elongated hamstrings.
It is theorized that because the two heads of biceps femoris
are
innervated by two different nerves that there may be mistiming of
contractions leading to a reduction in force produced with rapid
eccentric contractions.
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Factors that predispose an athlete to hamstring injuries
It is thought that some of the following may predispose an individual
to a hamstring injury:
- Fatigue In animal studies fatigued muscles have been shown to absorb less energy early on in a stretch compared to muscles that are not fatigued. Viscoelastic properties of fatigued muscles are different such that fatigued muscles are less elastic.
- Lack of Flexibility Reductions in hamstring flexibility has been shown to be correlated to injury. The emphasis amongst trainers to warm up adequately is evidence of this awareness. Muscles that are regularly stretched are more able to increase in length prior to tearing.
- Prior Injury Evidence of a recent hamstring injury has been shown to predispose an individual to future hamstring and quadricep injuries. Several studies (sited below) have shown correlation between pre season tightness of the hamstrings and hamstring injury during games in soccer players, and sprinters.
- Weakness Hamstring injury is associated with weakness in the hamstrings and weakness in hamstrings relative to the quadriceps. A balance between the knee extensors and flexors results in a more stable joint with less risk of injury. It is commonly thought that the hamstrings should produce >60% of the force put out by the quadriceps.
- Poor lumbar posture Excessive lordosis of the lumbar spine puts hamstring and gluteal muscles at a mechanical disadvantage.
- Poor core stability Poor control over lumbar positioning forces the hamstrings to work inefficiently.
- Inadequate warm up A cold or inadequately warmed up muscle is stiffer and therefore more prone to tearing. As muscles increase in temperature they become less viscous and more elastic.
- Older Age
Recurrence of hamstring injuries
Hamstring injuries have almost double the rate of recurrence when
compared to other injuries in sports.(1,2,3,4) In football, studies
show 12% of
hamstring injuries will recur; whereas 7% is the recurrence rate of
other football injuries.
Animal research has shown that previous strains leaves the muscle more
prone to injury. Recurring hamstring strains have definitely been a
challenge in the clinic.
One reason for recurrence is the presence of scar tissue. Scar tissue
does not possess the elastic properties of normal contractile
and
connective tissues of a healthy muscle. The scar does not stretch as
easily and is therefore more susceptible to strain.
Another reason for recurrences is a failure to fully rehabilitate the
injury. Disuse for even a short period can lead to weakness in other
muscle groups and stiffness.
Although the most common period of reinjury is within a week of
returning to sport, the risk remains for several weeks after healing
has taken place. Players in my clinic are often anxious to return to
their sport and I'm often forced to discourage them.
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Where do hamstring injuries occur
The hamstrings make up the bulk of the muscle in the back of the thigh. They consist of the bicep femoris, semitendinosus, and semimembranosus. They function as extensors of the hip, flexors of the knee, and rotators of the tibia on the femur when the knee is flexed.
Origin
Insertion
Innervation
Semimembranosus
ischial tuberosity
medial tibial condyle
tibial nerve
Semitendinosus
ischial tuberosity
pes anserine insertion
tibial nerve
biceps femoris (long head)
ischial tuberosity
head of fibula
tibial nerve
biceps femoris (short head)
linea aspera near head of femur
head of fibula
common fibular nerve
The most common site of injury is at the musculotendinous junction of
the long head of the biceps femoris. The muscles of the body that cross
more than one joint are often those that are most susceptible to injury.
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Physiology of hamstring injuries
As muscle fibres tear the body initiates an inflammatory response. Tears are often accompanied by bleeding as evidenced by ecchymoses present. The scar that the body uses to heal this tear is initially very weak, accounting for the high rate of recurrence and the fact that healing takes place over such a long period of time. Muscle physiology link.
What does a hamstring injury look like
People that experience a hamstring injury will say that it felt like
someone kicked them in the thigh. There is often a sudden
weakness and pain in the back of the thigh. There is swelling, pain
with resisted flexion of the knee, occasionally a defect in the muscle,
usually ecchymoses, and limited range of motion with a straight leg
raise.
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Classification of hamstring injuries
Grading of a hamstring injury is based on the degree of damage done to
the muscle.
- Grade I Over stretching of the muscle results in tearing of a few muscle fibres an inflammatory response, but no loss of strength or function.
- Grade II Over stretching and tearing of the muscle results in loss of function and strength.
- Grade III Complete rupture of the muscle results in severe weakness. This is a rare occurrence and is most often found in water skiers.
Treatment of hamstring injuries
Physical therapy for hamstring injuries is based on the muscles healing response. Studies have shown that a program that includes trunk stabilization exercises reduces the rate of reinjury. (5,6) The goal of rehabilitation is to restore function in the shortest time possible while facilitating healing to minimize the chance of recurrence.
- Surgery may be indicated in the case of a complete avulsion of the proximal tendon or in the case of an avulsion fracture, but most strains can be treated with physiotherapy.
- The use of non steroidal anti inflammatory medications such as naproxen and ibuprophen has been placed under scrutiny lately as it has been found to slow healing and affect the tensile strength of healing tissues.
- The obvious first aid response is R.I.C.E. (rest, ice, compression, and elevation) It is also of benefit, when applying the ice to apply it with the knee in a position of extension as tolerated. This helps to reduce further bleeding, control inflammation, slow tissue damage, and control pain.
- Physiotherapy will often include the use of ultrasound to facilitate healing and improve the tensile strength of the healing musculotendinous unit.
- Early motion helps to minimize scar tissue formation, and promotes healing.
- Early strength work should begin gently and done under advice of a physical therapist.
- Most hamstring injuries require two weeks of rest prior to returning to practice and often take several weeks to allow for return to full function. This depends of course on the extent of tissue damage, pain tolerance, and other individual factors (ie smoker, diabetes, etc) For several months the risk of reinjury can remain high even in the absence of symptoms.
Is Dynamic or Static Stretching Better for Hamstrings
Your goals of hamstring stretching
will determine what type of
stretching is best for you. If you are looking to increase flexibility
of your hamstrings because you need an increased range of motion for
activities such as yoga, running hurdles, as a hockey goalie, or for
dancing, then that appears best achieved through a program of static
stretching when you are not practicing.
Bandy et al (7) in a study published in the Journal of
Orthopaedic ans
Sports Physical Therapy looked at the effects of static stretching,
dynamic stretching, and no stretching on hamstring flexibility.
58 people ranging in age from 21 to 41 performed the
following
stretching protocols over a course of six weeks:
- One group performed dynamic stretching five days a week for a total stretch time of 30 seconds per bout of stretching.
- The other group performed a 30 second static stretch once a day for five days.
- The control group didn't stretch.
Results followed:
- Both dynamic stretching and static stretching increased hamstring flexibility.
- A 30 second static stretch was more effective than a 30 seconds of dynamic stretching in improving hamstring flexibility.
- A 30 second static stretch over 6 weeks resulted in more than twice the gain in range of motion when compared to dynamic stretching.
Will Stretching Prevent Hamstring Injuries?
A study by Pope et al
published in Medicine
and Science
in Sports and Exercise examined male army
recruits to determine if static
stretches reduce the risk of injury.(8) It was found that
static stretches didn't result in a clinically meaningful
reduction in the
rate of injuries.
In this research the greatest predictor of injury
was poor
aerobic
fitness. It is thought that static stretching will not reduce injuries
for the following reasons:
- Some activities don't benefit from increased range of motion.
- Stretching won't effect muscle elasticity during eccentric activities which is when most injury occurs.
- Stretching may cause microtrauma in the muscle predisposing it to injury.
- An increased in stretching tolerance after static stretching can mask pain that would normally cause muscle guarding during an activity that would cause injury.
According to a study
done in
1999 (9) dynamic stretching prior to an explosive activity
will reduce
the likelihood of having an injury.
- This is probably because the dynamic stretching will permit muscles to tolerate the stresses of the particular sport with less strain.
- The specific dynamic stretches used will prepare the central nervous system for necessary activation of motor units and the necessary coordination.
- Rates of injury may be less because practicing the movement patterns will help eliminate the awkward and inefficient movements.
1.
Witvrouw
E, Daneels L, Asselman. Muscle flexibility as a risk factor
for developing muscle injuries in male professional soccer players:
a prospective study. Am J Sports Med Jan 2003:31;1: p 41-6
2. Jonhagen S, Nemeth G, Eriksson E. hamstring injuries in
sprinters:
the role of concentric and eccentric hamstring muscle strength and
flexibility. Am J Sports Med. March 1994:22:262-265
3. Orchard JW. Intrinsic and Extrinsic Risk Factors for
muscle strains
in Australian Football. Am J Spots Med, May 2001 :29;3 p300 Garrett W.
Muscle Strain Injuries. Am J Sports Med, Nov 1996 v 24:6;p32
4. Woods C, Hawkins RD, Maltby S, Hulse M, Thomas A, Hodson
A. The
football association medical research programme: An audit of injuries
in professional football – analysis of hamstring injuries. Br
J
Sports Med 2004;38:36-41.
5. Zuluaga M, Briggs C, Carlisle J, McDonald V, McMeeken J,
Nickson W, et
al. Sports Physiotherapy: Applied Science and Practice. 1st ed.
Melbourne: Churchill Livingstone, 1995.
6. Sherry MA, Best TM. A comparison of 2 rehabilitation
programs in the treatment of acute hamstring strains. J Orthop Sports
Phys Ther 2004;34:116;25.
7.
Bandy WD, Irion
JM, Briggler M. The effect of static stretch and
dynamic range of motion training on the flexibility of the hamstring
muscles. J Orthop Sports Phys Ther. 1998;27:295–300
8.
Pope, R. P., Herbert, R. D., Kirwan, J. D., & Graham, B. J.
(2000) A randomized trial of pre-exercise stretching for prevention of
lower-limb injury. Medicine
and Science
in Sports and Exercise, 32, 271–277
9.
Gesztesi, B. (1999).
Stretching during exercise. Strength and
Conditioning Journal, 21(6), 44.