Hamstring Injuries – Damn That Hurts!
Updated: Nov 19, 2020
Hamstring injuries are common problems that affect numerous people every year. Hamstring injuries are often associated with sports that require fast acceleration and deceleration such as running (intervals), football, soccer, hockey, tennis baseball and rugby. Hamstring injuries are often slow to heal and have a very high rate of re-occurrence.
Among medical researchers, there is a considerable lack of consensus about what precipitates a hamstring injury. Some of the more common theories include lack of strength, poor flexibility, muscle imbalances, and improper warm-up before an athletic event. However, most researchers agree that hamstring injuries are usually NOT the result of a direct trauma, and therefore are considered to be “Non-Contact Event”.
HAMSTRING ANATOMY - 101
The hamstrings are called bi-articular muscles because they cross both the hip and knee joints. This is an important consideration because a hamstring injury can affect your hips, low back, knees, as well as the motion patterns of the entire lower extremity. They are composed of three muscles in the back of your thigh, the semitendinosus, semimembranosus, and the biceps femoris.
When we also consider fascial connections (posterior line for example), we will see that a hamstring injury can affect a very large area.
The semitendinosus muscle originates in the lower pelvis (ischial tuberosity) and runs down the back of the leg to an area just below the inside of the knee (anterio-medial surface of the tibia, in an area called the pes anserinus). The semitendinosus shares its proximal attachment with the long head of the biceps femoris.
Three muscles insert into the pes anserinus: The gracilis, sartorius, and semitendinosus (GST –I knew the GST sales tax would come in handy for something, Canadian joke). The pes-anserinus is a common area to feel knee pain when the bursa that is under these muscles becomes inflamed. (4)
Fascial Expansion: The fascial expansion of the sartorius, gracilis, semitendinosus, semimembranosus, and gastrocnemius muscles act as complex fascial tensors that act as stabilizers of the medial side of the knee joint. (7)
The semimembranosus muscle also originates in the lower pelvis (ischial tuberosity) and runs down the back of the leg to an area below the knee on the posterior medial side (posterior medial tibia). The semimembranosus is often injured in dancers, this is stretch injury.
Inflammation of the semimembranosus is often confused with an injury of the medial meniscus.
Fascial Expansion: The semimembranosus has a small oblique myofascial expansion that fuses with the crural fascia, this expansion covers the medial head of the gastrocnemius. (7)
Clinical Tip: Removing a restriction from the semimembranosus can have a positive effect on meniscus function. The medial meniscus benefits from the fascial connection between the semimembranosus into the knee capsule, which act to create some retraction of the posterior horn of the meniscus. (7)
Numerous studies have shown that the biceps femoris is the most common site of hamstring injury (myotendinous junction), especially in sprinters. The biceps femoris has both a long and a short head. The long head originates in the lower pelvis (ischial tuberosity, the common tendon of semitendinosus, and the lower part of sacrotuberous ligament). The short head originates on the outside of the leg (posterolateral femur). Both heads insert just below the knee on the lateral side (head of fibula and lateral condyle of tibia). Note: Short head shown in this diagram.
Fascial Expansion: Through the fascial connections, force is easily transferred through the biceps femoris to the sacrotuberous ligament, then to the erector spinae and thoracolumbar fascia. The biceps femoris muscle also has several myofascial expansions that reach into the deep fascia of the leg (crural fascia). (7,8) It is easy to understand how low back pain can be also be referred from the hamstring with direct fascial attachments that run from the long head of the biceps femoris directly into the sacrotuberous ligament.
Note: The Adductor Magnus, is often thought as another hamstring. When injured it can present as medial hamstring pain.
THE FUNCTIONAL ACTIONS OF THE HAMSTRINGS
The hamstring muscles are multi-functional; they act as powerful hip extensors (second only to the gluteus maximus muscle), and are also knee flexors, medial and lateral rotators, and important stabilizers of the knee.
From a bio-mechanical perspective, depending on leg position, the hamstrings can function in several ways:
All of the hamstring muscles extend the thigh at the hip joint, flex the leg at the knee, and tilt the pelvis in a posterior direction.
The biceps femoris laterally rotates the leg outward.
Note: The short head of the biceps femoris is not involved in hip motion directly because it does not cross the hip joint. (1,2,3)
Some researchers have placed more emphasis on certain hamstring actions, while dismissing other actions as secondary or less important functions. For example, some researchers have shown that the hamstrings can act as knee flexors, but only in nonfunctional settings. Consequently, only the so-called primary tasks (such as extension of the hamstrings) are considered in standard training or rehabilitative routines. (1)
Personally, I view the hamstrings as a multi-functional, complex structure, full of neurological receptors that relay information to other muscles, and make them capable of performing numerous other tasks.
Lets take a few minutes to review these other functions as they do affect the treatment decisions that are made.
RUNNING - HAMSTRING FUNCTION
When running, your hamstrings function as shock absorbers, force generators, and stabilizers.
Shock absorption is achieved through eccentric contraction of the hamstring muscles, and is an efficient way of absorbing the kinetic energy of foot impact. This mechanism of shock absorption can be extremely effective if the hamstrings remain strong and, flexible, and are not compromised by adhesion or fibrosis from previous injuries.
The hamstrings also play a key role in force generation due to their synergistic action with the gluteal muscles during hip extension.
When running the hamstrings act as a stabilizer in several ways.
The hamstrings act as a dynamic stabilizer, by decelerating the forward movement of the shin bone (tibia) during knee extension. This is similar to the action of the anterior cruciate ligament (ACL), except that the ACL acts as a passive stabilizer.
After initial contact with the ground, the hamstrings lengthen, to stabilize the knee.
When we push off with the foot, the hamstrings contract (in conjunction with the quadriceps) to provide propulsion. (1,2)
After the initial tear of the hamstring muscle, there is usually some bleeding which may show up as a small to large bruise over the hamstrings.
The bleeding from a hamstring tear is followed by an inflammatory response with an increase in cells known as fibroblasts. Fibroblasts are involved in the synthesis of collagen (which provides the structural framework for all tissues), in wound healing and the formation of scar tissue. (1)
Scar tissue (fibrosis) can develop as the inflammatory response of a hamstring injury begins to resolve. Scar tissue is a weak, inflexible, easily re-injured tissue that can decrease range-of-motion and create abnormal motion patterns. It is this fibrotic tissue, and imbalances that results, that accounts for the high rate of re-occurrence of hamstring injuries. (Image http://www.sportsurgeryparis.com)
From a symptomatic (pain) perspective, most hamstring injuries seem to resolve with time. In reality, these injuries often do not completely heal, but instead become the catalyst for a series of other injuries that are caused by the residual alternation in tissue, and resulting bio-mechanical compensations that this tissue creates.
Grading a Hamstring Injury
It is important to evaluate the degree of hamstring injury so that appropriate treatments can be implemented. Hamstring strains are graded from 1 to 3, with 3 being the most severe. (1)
Hamstring - Grade 1 Strain
The injured person can still walk though with some degree of difficulty. There may be minor swelling, stiffness, and pain.
In a Grade 1 Strain there is only minor tearing of the hamstring muscle. A common analogy is comparing a muscle to a piece of tissue paper. In a Grade 1 injury there are only minor tears in the tissue.
There should be only minor pain on hamstring resistance with no significant loss of strength.
Hamstring - Grade 2 Strain
The injured person may have difficulty walking and could be in considerable pain. There may be swelling with some degree of bruising.
In a Grade 2 Strain there is moderate tearing of the muscle. To use the tissue analogy there would be a significant amount of tears in the tissue, compared to a Grade 1 Sprain.
The patient may not be able to straighten their knee, with considerable pain on hamstring resistance.
Hamstring - Grade 3 Strain
A Grade 3 Strain is a severe or complete tearing of the muscle. To use the tissue analogy, the tissue could now be torn into two pieces. This type of strain may require surgical intervention to reattach the muscle.
Any action that causes the hamstrings to contract will cause severe pain.
Walking will be extremely difficult; the injured person will require crutches, and there could be a complete loss of function.
IMAGING A HAMSTRING TEAR
X-Rays are only taken in a hamstring injury to rule out fractures and identify any possible pathological processes. An X-Ray will not provide information about the actual tear.
The best imaging modality for viewing a hamstring injury is magnetic resonance imaging (MRI). Both Computer Tomography (CT) and Ultrasound can also be useful, but are not as definitive as an MRI. The advantage of Ultrasound is its low cost.
Major sport teams often use MRI to determine if an athlete is going to recover from a hamstring injury. Research has shown that there is a direct correlation between the size and the number of tears seen on MRI imaging and the number of days that will be lost for athletes in competition. (Image of hamstring tear https://www.auntminnie.com/index.aspx?sec=log&itemID=55795)
Mobilization of the injured hamstring (as soon as possible) is essential for achieving a speedy recovery. Mobilization can include passive stretching and strengthening exercises that should be performed in a pain-free range-of-motion.
Initially, isometric strengthening exercises are recommended, followed by a gentle progression into isotonic exercises. Isometric exercises use static contraction of a muscle without any noticeable movement in the angle of the joint. In an isotonic exercise, tension remains unchanged but the muscle's length changes. An example would be weight lifting.
Upper body exercises should also be performed to maintain physical conditioning. Aerobic exercise should also be performed to encourage improved blood flow.
Aerobic exercise will also speed the healing process by increasing cellular energy (ATP production) and increasing circulatory function. Improving circulation will increase oxygen input to the muscles and increase the removal of waste byproducts. Swimming is an excellent exercise for a hamstring injury (stay within a pain-free-range of motion).
MANUAL THERAPY TO ADDRESS HAMSTRING INJURIES
Each case of hamstring injury must be assessed and treated as a unique dysfunction specific to that individual. Certain cases will only involve local structures while other cases involve a much larger kinetic chain. In MSR (Motion Specific Release) we use the terms Local Tensegrity and Global Tensegrity to denote issues limited to a localized area, or issues involving the larger kinetic chain. Tensegrity was first termed by Buckminster Fuller, and expanded for the human body Thomas Myers of Anatomy Trains.
Hamstring Injuries: Addressing Common Local and Global Tensegrity Issues
The following section provides examples of possible structures that are involved in both local and global tensegrities. Which structures are addressed and how they are addressed vary greatly based on the needs of each individual case. (Image www.bahdhayoga.com)
Structure: Quadriceps muscles
Anatomical Significance: Antagonist to hamstrings.
Hamstring Relationship: May affect hamstring function through reciprocal inhibition. Tight restricted quadriceps cause tension in the hamstrings.
Structure: Gluteus Maximus muscle
Anatomical Significance: Primary hip extensor.
Hamstring Relationship: Due to inhibition or delayed gluteus maximus activity, the hamstring muscles become dominant during hip extension, which can cause hamstring tension.
Structure: Gastrocnemius muscle
Anatomical Significance: Direct fascial connection into the gastrocnemius muscles.
Hamstring Relationship: Tension in the hamstrings is transferred to the gastrocnemius and from the gastrocnemius into the hamstrings. The biceps femoris muscle also has several myofascial expansions into the deep fascia of the leg (crural fascia). (7)
Structure: Iliopsoas muscle
Anatomical Significance: Gluteus maximus antagonists.
Hamstring Relationship: May decrease gluteus maximus function through reciprocal inhibition. This in turn increases the force placed on the hamstrings, which may increase tension or cause imbalances.
Anatomical Significance: Biceps femoris has direct fascial connections to the sacrotuberous ligament.
Hamstring Relationship: Force is transferred from the erector spinae and thoracolumbar to the sacrotuberous ligament and then into the biceps femor)
THE MOTION SPECIFIC RELEASE - (MSR) APPROACH
Motion Specific Release - MSR is a multidisciplinary, hands-on treatment system developed by Dr. Brian Abelson DC. Dr. Abelson has a developed a treatment protocols, specifically designed to address hamstring injuries. MSR is not technique but a treatment system that draws on multiple forms of manual therapy to achieve the best results for the patient.
Some of the most common forms of the treatments we integrate into our protocols are derived from: Pin and Stretch Modalities, Fascial Research, Joint mobilization, Acupuncture, Massage Therapy, and Sports Medicine. Below are example of MSR procedures that are often used in cases of hamstring injury.
The Hamstring Release - Motion Specific Release™ (MSR): In this video Dr. Abelson demonstrates one of ways that restrictions in the hamstrings can be released. (This video will be available to the public on September 16th/2020)
The Gluteus Maximus Release - Motion Specific Release (MSR): In this video Dr. Abelson demonstrates how to use Motion Specific Release (MSR) to release restrictions in the Gluteus Maximus muscle. Strong, flexible, engaged gluteal muscles are critical to optimum performance and injury prevention.
FUNCTIONAL HAMSTRING EXERCISES
It is very important that the hamstrings are trained in same manner that they function during real life activities. The hamstrings work in synergy with multiple muscles and do not act as a singular isolated muscle. For example, to mimic hamstring muscle function during running the hamstrings need to be training in both open and closed kinetic chain movements. Closed chain exercise will mimic the Stance Phase of running, while open chain exercises can mimic the Swing Phase of running (eccentric actions).
The following shows a typical exercise protocol that we may use to resolve hamstring injuries. Obviously we would customize this to address each patients specific needs and injury. The amount of load placed on the hamstrings must be appropriate for the individual.
The First Two to Three Weeks After Injury
Minimize atrophy and loss of strength.
Prevent motion loss.
Protect healing tissue.
Avoid abnormal gait pattern development.
Avoid excessive active or passive lengthening of hamstring.
Ice – 2-3 times daily.
Progressive hip strengthening.
Sciatic nerve flossing exercises.
Single leg balance exercises.
When to progress to the next phase
Normal gait patterns are regained without pain
The patient can perform pain-free isometric contraction (50%-75%) during prone knee flexion at 90 degrees. (9)
Weeks Three to Twelve After Injury
Develop neuromuscular control to start developing functional movement patterns.
Regain hamstring range of motion, and strength (pain free).
Avoid painful ROM, especially at end range.
Stationary bike (20 to 30 minutes).
Treadmill, pain-free speed and stride (moderate intensity).
Eccentrics hamstring loading exercises.
Sciatic nerve flossing and tensioning exercises.
Single leg stance on wobble board exercises.
Supine hamstring curls on Swiss ball exercises.
Walking band exercises.
Criteria for progression to next phase
Resumption of full strength.
Pain-free forward and backward gait (moderate intensity).
Strength at 80% of uninjured leg.
Week Twelve Plus After Injury
Improve neuromuscular control.
Normal concentric and eccentric strength through full AROM.
Pain and symptom-free during all activities.
All exercises must be within a pain-free range-of-motion.
Treadmill moderate to high intensity as tolerated.
Dead-lift exercises .
Squat jump, single leg jump, lateral hop exercises.
Box jump exercises.
Eccentric lunge drop exercises.
Forward and backward skipping exercises.
Return to sport criteria
Full strength without pain with normal AROM.
Bilateral symmetry in knee flexion under load.
Full AROM (no pain).
Duplication of sport specific movements without symptoms.
DR. BRIAN ABELSON DC.
Dr. Abelson believes in running an Evidence Based Practice (EBP). EBP's strive to adhere to the best research evidence available, while combining their clinical expertise with the specific values of each patient.
Dr. Abelson is the developer of Motion Specific Release (MSR) Treatment Systems. His clinical practice in is located in Calgary, Alberta (Kinetic Health). He has recently authored his 10th publication which will be available later this year.
Make an appointment with our incredible team at Kinetic Health in NW Calgary. Just scan the QR code with your phones camera and click the link, or call Kinetic Health at 403-241-3772 to make an appointment today!
Brian Abelson, Kamali Abelson, Release Your Pain: 2nd Edition Resolving Soft Tissue Injuries with Exercise and Active Release Techniques Rowan Tree Books Ltd.
Brian Abelson, Kamali Abelson, Resolving Plantar Fasciitis Rowan Tree Books Ltd.
Heiderscheit MT, Sherry M, Silder A, Elizabeth S. Chumanov, ES, Thelen DG. Hamstring Strain Injuries: Recommendations for Diagnosis, Rehabilitation, and Injury Prevention. International Journal of Sports Physical Therapy 2010;40: 67-81.
Mochizuki, T., Akita, K., Muneta, T., Sato, T., 2004. Pes anserinus: layered supportive structure on the medial side of the knee. Clin. Anat. 17 (1), 50–54.
Opar MD, Williams MD, Shield AJ. Hamstring strain injuries. Sports medicine; 2012: 1;42(3):209-26.
Sherry MA, Best TM. A comparison of 2 rehabilitation programs in the treatment of acute hamstring strains. J Orthop Sports Phys Ther. 2004;34(3):116-25.
Stecco, Carla; Stecco, Carla. Functional Atlas of the Human Fascial System. Elsevier Health Sciences.
Vleeming, A., Pool-Goudzwaard, A.L., Stoeckart, R., et al., 1995. The posterior layer of the thoracolumbar fascia: its function in load transfer from spine to legs. Spine 20 (7), 753–758.
Hamstring Strain https://www.physio-pedia.com/Hamstring_Strain
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