Hamstring Pain Injuries

Hamstring injuries are a common problem that affects a large number of athletes. These injuries can be slow to heal with a very high rate of recurrence or re-injury. Hamstring injuries are often associated with sports that require fast acceleration and deceleration such as running (intervals), football, soccer, handball, and rugby.

Among medical researchers, there is a considerable lack of consensus in regards to what precipitates a hamstring injury. Some of the more common theories are lack of strength, flexibility, muscle imbalances, and not warming up before an athletic event. However, it is agreed upon that hamstring injuries are usually not the result of direct trauma, referred to as a “Non-Contact Event”.

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Hamstring Anatomy

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, and the movement patterns of the entire lower extremity. If we consider fascial connections (posterior line), we will see that a hamstring injury can affect a very large area.

The hamstrings are composed of three muscles in the back of your thigh. They are called the:

Semitendinosus

This 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 (Anteroromedial surface of the tibia, in an area, called the Pes Anserinus).

Three muscles insert into the pes anserinus: The Gracilis, Sartorius, and semitendinosus (GST – Just remember sales tax). The pes anserinus is a common area to feel knee pain when the bursa that is under these muscles becomes inflamed.

Semimembranosus

This 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).

Inflammation of the semimembranosus is often confused with an injury of the medial meniscus. Removing a restriction from the semimembranosus can have a positive effect on meniscus function.

Biceps femoris

Numerous studies have shown that the biceps femoris is the most common site of hamstring injury (myotendinous junction). The biceps femoris has both a long and a short head. The long head originates in the lower pelvis (ischial tuberosity, common tendon of semitendinosus, and lower part of the sacrotuberous ligament). 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.

The short head originates on the outside and of the leg (posterolateral femur). Both heads insert just below the knee on the lateral side (head of the fibula and lateral condyle of the tibia).

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Hamstring Biomechanical Analysis

 

The hamstring muscles are multifunctional. They are powerful hip extensors, second only to the gluteus maximus muscle, as well as knee flexors, medial and lateral rotators, and important stabilizers of the knee.

From a biomechanical perspective the hamstrings function in several ways depending on leg position:

• 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 semimembranosus and semitendinosus rotate the leg inward (medially rotate).
• The biceps femoris rotates the leg outward (laterally rotates).
• Note: The short head of the biceps femoris is not involved in hip motion directly because it does not cross the hip joint.

Some researchers have placed more emphasis on certain hamstring actions 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 training or rehabilitative routines.

Hamstrings are a multifunctional complex performing numerous tasks, full of neurological receptors that relay information to other muscles.

Running Biomechanics

When running, your hamstrings function as shock absorbers, force generators, and stabilizers. Shock absorption is achieved through the eccentric contraction of the hamstring muscles, which is an efficient way of absorbing the kinetic energy of foot impact. This mechanism of shock absorption can be extremely effective if the hamstrings are strong, flexible, and not compromised by scar tissue from previous injuries.

The hamstrings are also a key component of force generation because of their synergistic action with the gluteal muscles in hip extension.

The hamstrings act as a stabilizer when running in several ways. On foot strike, the hamstrings act as a dynamic stabilizer. They decelerate 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 is a passive stabilizer.

After initial contact with the ground, the hamstrings lengthen. This also has the effect of stabilizing the knee. When we push off with the foot, the hamstrings contract (in conjunction with the quadriceps) to provide propulsion.

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Hamstring Tears

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 called fibroblasts. Fibroblasts are cells that are involved in the synthesis of collagen, which is the structural framework for all tissues. Fibroblasts are also involved in wound healing and the formation of scar tissue.

As the inflammatory process of a hamstring injury begins to resolve, scar tissue is often formed. Scar tissue is a weak, inflexible, easily re-injured tissue that can decrease range of motion and create abnormal motion patterns. It is scar tissue that most likely accounts for the high rate of recurrence of hamstring injuries.

From a symptomatic perspective, most hamstring injuries seem to resolve with time. In reality, these injuries often do not completely heal but are the catalyst for a series of injuries due to residual scar tissue and 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, 3 being the most severe.

Grade 1 Strain

The injured person can still walk through with some degree of difficulty. There may be minor swelling, stiffness, and pain. In a grade 1 strain, there is the only minor tearing of the hamstring muscle. A common analogy is comparing a muscle to a piece of tissue paper. In a grade one injury there are only minor tears in the tissue. There should be only minor pain on hamstring resistance with no significant loss of strength.

Grade 2 Strain

The injured person may have difficulty walking and could be in considerable pain. There may be swelling, and 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 one sprain.
The patient may not be able to straighten their knee. There also may be considerable pain in hamstring resistance.

Grade 3 Strain

A grade three 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. There could be a complete loss of function.

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Treatment of Hamstring Injuries

Trigger Points

Initial Acute Injury

Right after the injury in the acute stage, you should use RICE, the acronym for rest, ice, compression, and elevation. If you have access to laser therapy this will also reduce the inflammation and speed the healing process.

Medication

NSAID’s are often immediately prescribed for hamstring injuries. For short periods of time, these medications may be beneficial. Taking NSAIDs for longer than seven days is generally not advised, as they can slow the healing response and decrease the overall quality of tissue leading to further injury.

Steroid injections at one time were often used to treat hamstring injuries, but these injections are no longer advised by many practitioners. Corticosteroids have been linked to poor healing, infections, and even ruptures of the tissue.

There are several natural alternatives that can be used to decrease inflammation without inhibiting the healing process or causing further injury.

Start Treatment ASAP

Mobilization of the injured hamstring as soon as possible is essential in achieving a speedy recovery. This would include passive stretching and strengthening exercises that should be performed in a pain-free range of motion. This treatment would be done by your PT.

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. Aerobic exercise will 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

Manual therapy can reduce the formation of scar tissue and speed overall healing. The longer that the injured person waits for therapy to begin the longer the resolution time maybe.

The removal of any physical restrictions that form in the hamstrings, or other related areas, is essential for a full resolution. Some of these restrictions can be removed through the process of self-myofascial release (foam rollers, self-massage, and gentle stretching). If the restrictions are severe enough then a manual therapy practitioner (ART, Graston, Massage) will be needed to break the restrictions.

It is important to note that any time a restriction is removed from one muscle, the antagonistic and synergist muscles must also be assessed for restrictions. This is a key point that many manual therapists overlook. For a full resolution of a hamstring injury, myofascial adhesions must be removed from the entire kinetic chain not just at the site of pain. Many of these restrictions will only be found with a more in-depth biomechanical analysis and palpatory examination.

The following list of structures is common sites where restrictions are formed. These restrictions can form in a very short period of time. Common restriction sites are:

Hamstrings

• Biceps Femoris (Long head)
• Semimembranosus
• Semitendinosus

Antagonistic Muscles

• Quadriceps
• Iliopsoas

Synergist Muscles

• Gluteus Maximus
• Sartorius
• Gracilis
• Gastrocnemius

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Myofascial Considerations

The previous list of structures focused on restrictions primarily in muscles, and their tendons. Another key area we must consider in any hamstring injury is fascia. Fascia is everywhere, weaving through, and interconnecting every component of our body.

Muscle fibers originate from, and insert into, fascial fibers. These fascial fibers, in turn, insert into multiple regions of the bone, and even into adjacent muscles. These additional points of contact and control provide the muscle with the ability to generate force in multiple directions.

Only certain sections of the muscle contract when performing an action. Force is not generated from just the origin and insertion points, but also through the numerous fascial connections.

Muscles work together as functional units that coordinate their actions across multiple joints. Depending on the degree of motion required, and the amount of force that is needed, each muscle will contract only specific areas of the muscle, rather than the entire muscle. These very specific motions are largely coordinated by the neurological receptors embedded in the fascia, and not by the brain.

Fascia is full of two types of neurological receptors – mechanoreceptors and proprioceptors. A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion. A proprioceptor is a sensor that provides the brain with information about joint angle, muscle length, and tension.

Motion is coordinated by the feedback of the neurological receptors in the fascia when tension is transferred from one area to the next. (Previously these receptors were only thought to be located within just the muscles).

Fascial Lines and a Hamstring Injury

When we evaluate a hamstring injury, we must also take into consideration all the fascial connections to the structures that are involved in performing and coordinating motion. It is important to look at the big picture, and take into consideration that multiple muscles, working across multiple joints (all of which are interconnected by fascia) are all required to coordinate these motions.

In the case of a hamstring injury, the fascial connections we should consider are in the Superficial Back Line (see Anatomy Trains by Thomas Meyers). The following is a short synopsis of the posterior line.

Superficial Back Line

• Beginning at the bottom of the foot with the plantar fascia. This fascia passes over the heel bone (calcaneus) and inserts into the Achilles tendon.
• The Achilles tendon is formed by the calf muscles (gastrocnemius and Ssleus). There are direct fascial connections into the hamstrings.
• There are fascial connections directly into the sacrotuberous ligament, which runs into the sacral fascia.
  Connections from the sacral fascia run directly into the back muscles (erector spinae) from the low back (lumbar spine) up through the mid-back (thoracic spine) into the neck (splenius and semispinalis capitus).
• Fascial connections then continue up the neck to the fascia on the skull (nuchal line). This continues along the scalp fascia to the forehead just above the eyes.

You can try treating a hamstring injury with all the right techniques (ART, Graston, Massage, etc.) and find that you still have not resolved a chronic problem you need to consider and treat, the fascial interconnections.

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Exercise is Essential

It is very important that the hamstrings are trained in the 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 exercises will mimic the stance phase of running, and open chain exercises can mimic the swing phase of running (eccentric actions).

These are exercises where, in the case of the lower extremity, the foot is in constant contact with the ground. Examples would be: Lunges, squats, deadlifts, power cleans. These exercises focus on the co-contraction of multiple groups of muscles at the same time. They also involve multiple joints at the same time: those being the ankles, knees, and hips.

Open kinetic chain exercises – These are exercises where the leg/foot is free to move and is not in contact with a surface. These exercises are usually non-weight bearing.

Numerous researchers recommend that your hamstrings should be 60 to 80% as strong as your quadriceps.

Strengthening Your Hamstrings

Strengthening your hamstrings is an essential component in reaching full recovery from an injury. These are only a few of the strengthening exercises we recommend to our patients.

Romanian Dead Lift– This is a great closed kinetic chain exercise for training the hamstrings in eccentric contraction. Starting with low loads, for rehabilitation training, then building up to higher levels for athletic training.

• Stand straight with your lumbar spine in slight extension, with a barbell or dumbbells in your hands. Feet should be shoulder-width apart, legs are straight, but not hyperextended.
• Flex forward from the hips moving the barbell or dumbbells down the front of your legs. Do not bend your knees all motion needs to come from the hips.
• As you lean forward, the hamstrings will lengthen, placing them under considerable eccentric load.
• Continue to lower the weight until you can no longer hold your back in the extension position. This will probably be when the weight is in the middle of your shins.

Single Leg Dead Lift – This is a similar exercise to the Romanian deadlift but is performed one leg at a time holding a dumbbell with both hands.

The same procedure is used except that the back leg can be raised off of the ground for balance.

Stretching Your Hamstrings

Stretching after a hamstring injury is extremely important. Initially, stretching may have to be done passively within a pain-free range of motion. To get a better idea of why stretching is so important, consider this. During the first two days to six weeks after an injury, collagen is formed and laid down to repair the injured area. If an injured person is performing the correct stretching exercises, the majority of the collagen will be laid down in the same direction as the tissue being repaired. This makes the repaired tissue stronger and more capable of performing its function. If the individual is not stretching, the tissue will be laid down in more random patterns, leading to the development of weaker tissue that is easily re-injured (scar tissue).

Be careful not to be too aggressive with stretches after an injury. Do not stretch past the point of mild discomfort, doing so may delay healing and cause further injury.

Psoas Stretch

The psoas is a very important muscle to stretch if you have had a hamstring injury or wish to prevent one from occurring. There is an antagonistic relationship between the psoas muscle and your gluteal muscles. Essentially when the psoas become short and contracted it turns off your glute muscles. Your glutes and your hamstrings are your primary hip extensors. Therefore when your glutes get turned off, more of the load is placed on your hamstrings which then become susceptible to injury.

There are several ways that you can stretch out the psoas with either static or dynamic stretches.

Note that after the psoas muscle is stretched out, the gluteal muscles should be worked to regain activation of the muscle. This will help to take the stress off of the hamstring.

Balance and Proprioceptive Training

Whenever a sprain/strain injury occurs it is not just the ligament, tendon, or muscle fibers that are damaged. Often, the embedded neurological structures within these soft-tissue structures are also damaged. These neurological structures (Golgi tendon organs, muscle spindles, and joint receptors) are essential for postural control.

Both Golgi Tendon Organs and Muscle Spindle Cells are sensory neurons (proprioceptors). Sensory neurons monitor muscle and tendon motion (contraction and stretching) and relay this information back to your brain. This creates a feedback loop system that allows your body to discern its position and postural orientation. Joint receptors are located in joint capsules and respond to deep pressure and to other stimuli such as stress or change in position. They are also part of your body’s neurological feedback loop system.

What appears to be just a simple hamstring tear often involves some damage to several neurological structures. The good news is that the nervous system is very good at repairing itself given the right type of exercise.

That is why every patient that comes to us for a hamstring tear is also given exercises that involve balance training. Balance training helps to repair neurological damage, substantially decreasing the chance of re-injury.