Why are hamstring injuries so difficult to treat?

Ross A. Hauser, MD, Danielle R. Steilen-Matias, MMS, PA-C

In this article, we will examine the difficulties and frustrations athletes suffer from with acute and chronic hamstring recovery problems.

Article summary

  • “I thought stretching was the best thing for my hamstrings. . . it turned out to be the worst thing I could do.”
  • This is where the controversy of when to stretch and when not to stretch comes in.
  • You are not alone, overstretching is one of the things athletes will do when they have a hamstring injury.
  • The longer your hamstring problems go on, the more damaged the tendon gets. This is why you are “tight” all the time.
  • Tight hamstring muscle syndrome.
  • Grading the different types of hamstring injuries.
  • What are we seeing in this image?
  • Chronic ischiogluteal bursitis and hamstring tendinopathy.
  • Why are hamstring injuries so difficult to treat? Are doctors using ineffective treatments? Are you are stuck in Hamstring Syndrome problems because of treatments that do not work.
  • Back to the problems stretching causes. Stretching does not prevent hamstring injuries, stretching may cause them.
  • Is it time to retire flexibility as part of sports training?
  • More confusion about stretching. Researchers are unsure if flexibility causes or prevents injuries in sprinters during the end of races.
  • Does eccentric strengthening exercises help the acute hamstring injury?
  • Hamstring Muscle Syndrome, Buttock Pain, and High Hamstring Tendinopathy – Focus on strengthening the tendons may be the answer to muscle strains and hamstring problems.
  • Finding and treating tendon injuries may be the answer to your hamstring problems.
  • Platelet Rich Plasma Therapy and Prolotherapy treatments to repair damaged tendons and heal hamstring injuries.
  • “Platelet-rich plasma vs. steroid injections for hamstring injury-is there really a choice?”
  • A combination of hematoma aspiration and muscle strain PRP injection in partial hamstring muscle tears.
  • NFL players using PRP for hamstring injuries.
  • When PRP treatments did not help improve the hamstring.
  • PRP and dextrose Prolotherapy as a combination treatment.

Often people will be told by their doctors or read somewhere that a hamstring tear or strain was their own fault. They, the person with the tear, will be told that they did not stretch enough or warm up enough before an event. That may not be accurate in some cases. In some people, they have a degenerative situation going on from their low back to their knee. They have some type of muscular imbalance caused by low back, pelvic, hip, and/or knee instability. These are usually not conditions that can be fixed with stretching in fact stretching can make them worse.

To demonstrate this point here are some of the samples of the things we hear from people when they contact us about their hamstring problem.

” . . . and a torn hamstring”

When someone starts an email that goes something like this:

My medical history includes Ischiofemoral Impingement Syndrome, Deep Gluteal Syndrome, Femoroacetabular Impingement,  hip labrum tear, gluteus medius tendinopathy, and a torn hamstring.

This can be a clue that this person has something going on far more than a torn hamstring. Look at all the problems, it would be easy to believe that their chronic hamstring issues have something more to do with pelvic, hip, low back, knee instability that they are suffering from rather than simply poor stretching and weak conditioning of the hamstring problem.

“I am not healing”

Another person may tell their story of non-healing after prolonged periods of rest. Here the person will suggest that an MRI shows degenerative tendinosis (the tendon is no longer trying to heal itself. Tendinitis is pain with inflammation. The tendon is trying to heal. Tendinosis is pain without inflammation. The tendon has basically given up. The tendon is not accepting messages from the brain to start up the inflammatory process to see if it can heal. The tendon at this point sees no value in swelling up again. This patient will report that after long periods of rest, their hamstrings will feel a little better, but as soon as activity resumes, it hurts again. Something must be causing this tendon to stretch and become painful again. It can be hip, pelvic, or knee instability or usually a combination of them all.

“I thought stretching was the best thing for my hamstrings. . . it turned out to be the worst thing I could do.”

There is always confusion when it comes to the subject of not stretching a hamstring muscle. There are times to stretch there are times not to stretch. Many people watch instructional videos that talk about hamstring length and strength. Length comes from stretching.

Let’s get to the understanding of when to stretch and when not to stretch.

Let’s look at an August 2020 study (1) The feature of the study is Neurodynamic sliders helping a tight hamstring. Many of you with chronic hamstring problems have probably looked into Neurodynamic sliders, it is a stretching technique. Here are the learning points of the study:

“Hamstring injury prevention puts emphasis on optimizing the muscle’s strength-length relationship. To assure appropriate muscle length, flexibility training is imperative. As neurodynamics play an important role herein, the goal of this study was to explore the intervention effect of home-based neurodynamic slider program on hamstring flexibility.” The outcome of the study was Neurodynamic sliders seemed to work better than conventional stretching.

What is the point of this? In a normal muscle with uninjured tendons, stretching can be the way to “optimizing the muscle’s strength-length relationship.” BUT, what about stretching an overstretched hamstring? What if the hamstring is tight because of spasms because the muscle is constantly clenching trying to do a job it was not intended to do? What job is that? Take on the joint stability jobs of ligaments and tendons. A muscle isn’t supposed to do this job. When the muscle is forced into this job because supporting tendons and ligaments are themselves too stretched out. the muscle cramps and gets tight.

This is where the controversy of when to stretch and when not to stretch comes in.

For years when an athlete pulled up in a race or during a game and grabbed the back of their leg, the first thing the training staff or teammates would do is throw the athlete to the ground, grab an ankle and start stretching their leg. “They cramped up.” The research below will tell you that sometimes this may not be a good thing. Nor is the continued stretching of a leg to the point of pain.

If you are reading this article, it is likely that you have suffered from chronic hamstring problems and have been advised to stretch them out, or, you have been advised NOT to stretch them out.  It is also likely that it was hard for you not to stretch because you have been told your whole sports career to stretch.

For some of you, your stretching, you thought, was providing a benefit and you went a little more aggressive in your stretching. You wound up making things worse. The two example stories we gave above may demonstrate this. You have one person who has instability all over the place, they have one impingement or syndrome after another. All their joints are hypermobile, is stretching the answer for them? We have another person with tendinosis. Their tendon has given up trying to heal because its muscle is pulling too hard on it or the tendon is being stretched out by a boney attachment that is not being held in place by a ligament. Will stretching help this person?

You are not alone, overstretching is one of the things athletes will do when they have a hamstring injury.

You are not alone, overstretching is one of the things athletes will do when they have a hamstring injury. When these patients come into our clinic, we talk about treatments that may help muscles, stretching can help, HOWEVER, stretching may be disastrous for a tendon that is already overstretched. Amazingly enough, some patients, when told this will ask, “what is a tendon?” Immediately this tells us the patient may not have been given good care. A tendon attaches a muscle to a bone.

The longer your hamstring problems go on, the more damaged the tendon gets. This is why you are “tight” all the time

A tendon, we explain, is the elastic stretchy soft tissue that holds your muscle to the bone. When that tendon is stretched out, it loses its strength, your muscle compensates for lost strength by staying in spasm, “being tight all the time.” “Why does it do that?” the patient will ask? “Because,” we suggest, “the muscle is trying to protect the tendon so it can heal.”

The longer your hamstring problems go on, the more damaged the tendon gets. In other words, the tendon, which transmits the force from muscle to bone to propel and provide locomotion and strength, is not doing its job because it is hurt. Your muscle is in spasms because it is not only trying to do its own job as a muscle, it is trying to do the tendon’s job too. The muscle gets easily tired and fatigued. It rolls itself up in a knot to try to regain strength and spams to tell you that it needs rest. Below we will talk about treatments that tighten, repair, and restore strength to the damaged tendons of the semitendinosus, semimembranosus, and biceps femoris muscles of the hamstring.

Tight hamstring muscle syndrome

The difference between spasming hamstrings, tight hamstrings, and tight hamstring muscle syndrome is that tight hamstring muscle syndrome or simply hamstring syndrome is a complaint among some athletes. Athletes may experience gluteal sciatic pain (a pain in the bottom of the butt) from an inflammation of the sciatic nerve at the insertion site of hamstring muscles to the ischial tuberosity.

Tight hamstring muscle syndrome can also be a postural abnormality seen with spondylolisthesis in athletes, which is the dislocation of a vertebra and may be referred to as disc-related tight hamstring syndrome. Symptoms may include pinching of the nerve that extends to the hamstring muscle because of the dislocation of the vertebrae.

Grading the different types of hamstring injuries

Hamstring injuries are a hamstring strain/pull, a partial tear, or a complete tear. A diagnosis of chronic hamstring problems may include Tight hamstring muscle syndrome or simply Hamstring syndrome.

  • Grade 1 hamstring tears are considered the mildest injury.
  • Grade 2 hamstring tear and Grade 3 hamstring tear injuries may take months to heal if they respond at all to conservative treatments. In grade 3 tear the muscle can completely pull away from the bone at the tendon attachment.

What are we seeing in this image?

In this illustration the tendon insertion point, the entheses attachment is illustrated. The entheses are where the tendon attaches to the bone and is one of the leading culprits for chronic, non-healing hamstring injuries. The entheses also provide a point of resistance. If the entheses are damaged, you cannot get the needed resistance necessary to build or strengthen muscle during physical therapy. This is also where continued stretching will cause further damage.

In this illustration the tendon insertion point, the entheses attachment is illustrated. The entheses is where the the tendon attaches to the bone and is one of the leading culprits for chronic, non-healing hamstring injuries. The entheses also provides a point of resistance. If the entheses is damaged, you cannot get the needed resistance necessary to build or strengthen muscle during physical therapy. This is also where continued stretching will cause further damage.

For someone with a chronic hamstring problem, telling them that hamstring muscle syndrome or a “pulled hamstring”  can be difficult to treat would come as no surprise.

Chronic ischiogluteal bursitis and hamstring tendinopathy

In this video, Danielle Matias, PA-C discusses the diagnosis of chronic ischiogluteal bursitis and hamstring tendinopathy or tendinosis. In our clinic, we use Prolotherapy or PRP Prolotherapy when other conservative methods have not resolved the issue. Any type of chronic bursitis or tendinopathy may have an underlying joint instability as well that may need to be addressed. Correctly identifying the degenerating or injured structures is key to developing an effective treatment plan for this type of chronic pain.

We see patients diagnosed with the same problem under different names: Ischiogluteal Bursitis, Hamstring Tendinopathy, Bursitis of the Pelvis: The problem is an irritation of the bursa at the sits bones, your butt bones, the ischial tuberosity where your hamstrings attach. Within this area is the Ischiogluteal Bursa. When this bursa gets irritated it can be very very painful. Many times a patient can’t walk, they can’t sit. When I walk into an exam room, the patient is standing because it is too painful for them to sit.

In acute cases of bursitis, resulting typically from a fall, bursitis will calm itself down with rest, ice, and anti-inflammatories.  But in chronic bursitis, where anti-inflammatories, rest, possibly cortisone has not helped, then something is going on, an underlying problem that is irritating the bursa. In the case of the Ischiogluteal Bursa, it’s typically the hamstring tendon causing the problem. Once the hamstring tendon is weakened or damaged by acute or wear and tear injury, tendinopathy, or tendon degeneration which will cause the tendons to swell and thicken develops. This swelled up, the thick tendon will then put pressure on the bursa. The bursa reacts by becoming inflamed. So we have a primary injury: Hamstring tendinopathy causing secondary injury, inflamed bursa. You can not treat the bursa without addressing the cause of its inflammation. The hamstring tendon.

Why are hamstring injuries so difficult to treat? Are doctors using ineffective treatments? Are you are stuck in Hamstring Syndrome problems because of treatments that do not work.

In the Journal of Strength and Conditioning Research, (2) University and medical researchers in Taiwan wrote that medical treatment of hamstring muscle syndrome typically involves at least part of the RICE protocol, rest, ice, compression, and elevation. Although some of these treatment components do bring some initial pain relief from hamstring injuries. Research evidence shows that “ice application or topical cooling does not enhance and appears to delay the return to normal of muscle damage markers and subjective fatigue feeling after eccentric exercise.”

In other words, RICE hinders the healing of muscle tissue. Even the inventor of the RICE protocol is now saying both ice applications and rest delay muscle healing.

The dangers of ice therapy have been noted for decades, in a landmark 1992 study from Duke University published in the Journal of Athletic Training, (3) ice applications were shown to cause muscle damage, because of the dangers of freezing tissue. This danger could also extend to nerve damage.

Back to the problems stretching causes. Stretching does not prevent hamstring injuries, stretching may cause them

  • Dutch researchers at the University Medical Center in Utrecht released their findings in early 2017 (4) suggesting that in elite soccer players, although hamstring flexibility is thought to play a major role in preventing hamstring injuries, there is no significant relationship between hamstring flexibility and hamstring injuries.
    • Stretching does NOT prevent hamstring injuries.

Is it time to retire flexibility as part of sports training?

James L Nuzzo, Ph.D. of the University of New South Wales, Sydney wrote this May 2020 opinion in the medical journal Sports Medicine. (5)

“Flexibility refers to the intrinsic properties of body tissues that determine the maximal joint range of motion without causing injury. For many years, flexibility has been classified by the American College of Sports Medicine as a major component of physical fitness. The notion flexibility is important for fitness has also led to the idea static stretching should be prescribed to improve flexibility.

The current paper proposes flexibility be retired as a major component of physical fitness, and consequently, stretching be de-emphasized as a standard component of exercise prescriptions for most populations. First, I show flexibility has little predictive or concurrent validity with health and performance outcomes (e.g., mortality, falls, occupational performance) in apparently healthy individuals, particularly when viewed in light of the other major components of fitness (i.e., body composition, cardiovascular endurance, muscle endurance, muscle strength). Second, I explain that if flexibility requires improvement, this does not necessitate a prescription of stretching in most populations. Flexibility can be maintained or improved by exercise modalities that cause more robust health benefits than stretching (e.g., resistance training).”

More confusion about stretching. Researchers are unsure if flexibility causes or prevents injuries in sprinters during the end of races

Dr. Nuzzo was not the first to point out a realistic argument that flexibility, stretching, be “retired,” from essential sports training. No wonder patients are frustrated and confused by what stretching can and cannot do for their hamstring injuries. Here is a study that even the researchers admit is confusing.

Researchers at the Beijing Sport University wanted to help sprinters from pulling up with injuries in the last portion of their races. So they measured and tested the hamstring flexibility of runners competing as sprinters. They published their research in the Journal of Sport and Health Science. (6)

Here is a summary:

  • The researchers examined “the effect of hamstring flexibility on the peak hamstring muscle strains in sprinting, until now, remained unknown, which limited our understanding of risk factors of hamstring muscle strain injury (hamstring injury). . . . this study was aimed to examine the relationship between hamstring flexibility and peak hamstring muscle strains in sprinting.”

So hamstring flexibility is an unknown factor in hamstring injury. The researchers then wanted to see if hamstring flexibility prevented hamstring injury, at least in sprinters.

What did they find? The researchers are not sure. Here is what they said:

  • The relationships of hamstring flexibility and peak hamstring muscle strains found in this study are limited and only suggest that individuals with good hamstring flexibility may have lower peak hamstring muscle strains compared to those with poor flexibility, BUT does not necessarily mean that improving hamstring flexibility would result in a decrease in peak hamstring muscle strains in sprinting for a given individual.
  • ACTUALLY, the researchers COULD NOT DISPROVE their own previous research and that of others that suggested FLEXIBILITY IS A RISK FACTOR for hamstring injury in sprinting as previous studies showed.

WHAT? Are stretches and flexibility good or bad?

  • The results are inconclusive.
  • This leads to the idea that overstretched tendons may be THE factor that is being overlooked in all this muscle research.

Does eccentric strengthening exercises help the acute hamstring injury?

A July 2022 study in the British Journal of Sports Medicine (19) tested the idea of early versus delayed lengthening exercises (eccentric strengthening – such as the downward motion of a squat) for acute hamstring injury in male athletes.

  • 90 male participants (age: 18-36 years, average 26 years) with an MRI-confirmed acute hamstring injury were randomized into an early lengthening (at day 1 of rehabilitation) group or a delayed lengthening (after being able to run at 70% of maximal speed) group.
  • Both groups received an established rehabilitation program.
  • The primary outcome was time to return to sport (ie, time from injury to full unrestricted training and/or match play). The secondary outcome was reinjury rate within 12 months after return to sport.

Results: “Accelerating the introduction of lengthening exercises in the rehabilitation of hamstring injury in male athletes did not improve the time to return to sport nor the risk of reinjury.”

To systematically review the literature concerning evidence-based hamstring training and quantitatively assess the effectiveness of training programs in (1) reducing injury incidence and (2) managing injury risk factors.

An April 2022 study published in the American Journal of Sports Medicine (20) did find lengthening exercises to be beneficial helped reduced reinjury risk. The researchers here systematically reviewed 108 previously published studies “concerning evidence-based hamstring training and quantitatively assess the effectiveness of training programs in (1) reducing injury incidence and (2) managing injury risk factors. ” They concluded: “Several strategies exist to prevent hamstring injury and address known risk factors. Eccentric strengthening reduces injury incidence and improves hamstring strength, fascicle length, H/Q ratio (the measurement of torque and balance during activity of the hamstring muscles), and limb asymmetry, while stretching-based interventions can be implemented to improve flexibility. These results provide valuable insights to athletes, trainers, coaches, and therapists seeking to optimize hamstring training and prevent injury.”

Does hamstring injury preventative training put your knee at greater risk for injury?

Doctors at the University of Health and Sports in Berlin published these findings in the journal Medical Hypotheses. (7)

  • Both hamstring and ACL injuries are among the most typical injuries, particularly in a change of direction and high-speed running sports. They’re also difficult to treat.
  • In the past few years, sports medicine practitioners and exercise scientists have mainly been focusing on the development and implementation of preventive programs in order to reduce the number of lower limb injuries (Hamstring and ACL), mainly by improving knee alignment. (We call this creating knee stability. The problem of joint instability in the cause of hamstring injuries is discussed below).
  • A number of studies have been able to prove the success of training interventions which are mainly addressing sensorimotor (balance training, such as on a wobble board) abilities and plyometric (speed-strength training – rapid jumping up and down for example) activities in preventing hamstring and ACL injuries.
    • DESPITE THIS: The number of non-contact hamstring injuries has nevertheless been on the rise, particularly in sports like soccer and football.
  • The researchers introduce the hypothesis that some training interventions have a massive influence on the activation patterns in the targeted muscle group, and on the biceps femoris in particular. THEY CAUSE INCREASED INJURY RISK.
    • WHAT DOES THIS MEAN? It means that while your hamstring prevention program can help prevent strains, it may also cause them by creating an imbalance in the biceps femoris. As the biceps femoris attaches at the hip and the knee, when strength training focuses on the hip area it pulls at the knee area attachment. Equally, when the knee is is subjected to training, the biceps femoris pulls on its own hip attachments. What are the attachments in jeopardy? TENDONS.

Hamstring Muscle Syndrome, Buttock Pain, and High Hamstring Tendinopathy – Focus on strengthening the tendons may be the answer to muscle strains and hamstring problems

From a regenerative medicine perspective, the preferred long-term solution is to strengthen the ischial tuberosity, a point of attachment for the hamstring muscles with regenerative soft-tissue treatments such as Prolotherapy and Platelet Rich Plasma Therapy. These injection treatments stimulate repair of the buttock pain and posterior thigh pain. One way they do so is by strengthening the tendon attachments of the semitendinosus, semimembranosus, biceps femoris muscles of the hamstring.

Prolotherapy involves the injection of a small amount of dextrose, a simple sugar solution into multiple painful ligaments and tendon insertions (enthesis), pain trigger points, as well as into adjacent joint spaces to induce healing of the injured structures. Dozens of research studies have documented Prolotherapy’s effectiveness in treating chronic joint pain.

  • Danielle R. Steilen-Matias, MMS, PA-C, describes the pelvic anatomy and how these various structures in the pelvis can cause Ischial tuberosity pain.
  • The Ischial tuberosity, the bony prominences at the base of the pelvis, or commonly, the “sit bones” or the “seat bones,” are just that. The bones you sit on. This is a suspected pain origin when a patient complains of “pain in the butt.”
  • A patient will often complain of problems with tight hamstrings as well. They report that they do a lot of stretching, they “foam roll,” they have had cortisone shots, the pain returns.
  • There are varying reasons for pain in this area.
    • The patient’s pain is in fact related to the hamstring attachment at the ischial tuberosity.
    • (Image of Ischial tuberosity) If this hamstring tendon attachment is damaged, the patient will suffer pain when they put their whole body weight on it to sit.
    • Sometimes a patient will come in with chronic ischial tuberosity pain that doesn’t get better with anything they’ve tried because the pain is coming from elsewhere. It could be from the sacroiliac joints. When there is sacroiliac joint instability, this can tug on the hamstrings. This is why hamstring treatments may fail. The hamstrings are under constant stress from the sacroiliac joint. To fix the hamstring problems, the sacroiliac joint instability must be addressed. We have seen this more commonly in runners. This is why patients will tell us that they “pull their hamstring all the time, then I rest. Then I pull it again.” If hamstring treatments are not helping, an evaluation of the hip may reveal a labral tear or hip instability that is also pulling on the hamstring tendon attachment and injuring it.
  • Part of the workup when you come to Caring Medical with complaints of butt pain or a diagnosis of ischial tuberosity pain syndrome or impingement is an examination of all these areas, the hip, the sacroiliac joint, the low back, the groin area.
  • Treatment: Ischial tuberosity pain syndrome is a degenerative condition. We have to first stop the causes of the damage and then we can begin to repair the area and get these tissues to regenerate and be strong. We use Prolotherapy injections, this is an injection of simple dextrose or sugar. Sometimes we may use the platelets in your own blood, this is better known as Platelet Rich Plasma Therapy or PRP. It usually takes 4 to 6 treatments. These treatments are described in more detail below.

Finding and treating tendon injuries may be the answer to your hamstring problems

Is it your tendons? The answer is yes as attested to by the pain deep in the buttocks or upper back-side of the thigh reported by some patients and confirmed by physical examination as tendon injury near the origin of the hamstring muscle off of the ischial tuberosity.

That is the name of the bone which bears body weight in the seated position. It is an injury we see in mid to long-distance runners, yoga practitioners, and occasionally non-athletic individuals who have been injured by improper chiropractic adjustments or physical therapy.

  • Occasionally the damage to the tendon in chronic cases can be severe enough to cause irritation of the nearby sciatic nerve, thus producing back pain symptoms of referred pain down the entire back of the leg which is more typically associated with herniated lumbar discs.

The pain is worse when the patient is seated on a hard surface, and after running, especially at faster speeds. There can be pain at rest in severe cases.

  • The bent knee stretch test is applied for the diagnosis of this condition with the patient lying supine. The hip and knee are first maximally flexed towards the patient’s chest, and then the knee is extended gradually. Pain at the origin of the hamstring on that side which reproduces the patient’s pain is diagnostic.

Additionally, a diagnosis for injection treatments such as Prolotherapy relies on direct thumb pressure over the proximal (center) hamstring tendon in the buttocks, the so-called “jump sign” to reproduce the pain, localize the injury, and determine the best treatment. Direct firm pressure on affected areas causes the patient to “jump” because of the accentuation of the pain.

Finally, injection of a local anesthetic solution into the tendon-bone junction (enthesis) of the affected hamstring tendon can cinch the diagnosis by immediately eradicating all evidence of pain at rest or with motion or sitting.

In summary, there are several other conditions that can produce a similar symptom complex of high hamstring tendinopathy.

  • Herniated lumbar discs and sacroiliac ligament strain both refer to pain in the deep buttock area.
  • Spasm of the piriformis muscle is another common condition in athletes and, in older individuals, metastatic cancer to the bone and pelvic stress fracture must also be considered.

Fortunately, all of these conditions except for the latter two will respond to appropriately applied Prolotherapy, but making the differential diagnosis is critical in order to achieve the most rapid response. When necessary, X-rays, bone scan, or MRI imaging is ordered.

Prolotherapy injections can offer the fastest route to recovery from high hamstring tendinopathy. The only possible danger from Prolo for this disorder is the proximity of the hamstring tendons to the sciatic nerve, but proper experience and technique will always avert any problems in this regard. Should the nerve ever be touched by the slowly advancing Prolo needle (a precautionary measure on the Prolotherapist’s part), there will be a quick electrical sensation down the leg. As the needle is withdrawn or redirected, any discomfort will be mild and temporary.

Platelet Rich Plasma Therapy and Prolotherapy treatments to repair damaged tendons and heal hamstring injuries

Many people reading this article may have been told about Platelet Rich Plasma therapy. They may have heard very good things, they may have heard some not good things. The not-good things usually are confined to the “it will not work for you,” suggestion they are given.

We are going to challenge that statement with some independent research and the 298+ years of experience we have in offering patients treatments for their hamstring and sports-related injury problems.

  • Platelet Rich Plasma Therapy draws out your own blood into a vial. Your blood is then “spun,” in a centrifuge to isolate out the components that heal injuries. These would be the anti-inflammatory and growth factors found in the blood platelets. This “Platelet Rich,” solution is then reintroduced, via injection, into the areas causing pain and weakness.

All of the athletes in our case series with hamstring or patellar tendinopathy were fully able to return to sport.

An October 2019 study from Northwestern University and the University of Chicago published in the Journal of Orthopaedics (8) presented 15 cases in which PRP injection was used for either patellar or hamstring tendinopathy in varsity collegiate athletes. All of the athletes in our case series with hamstring or patellar tendinopathy were fully able to return to sport. Three of the athletes with patellar tendinopathy were referred for surgery, while none of the athletes with hamstring strain underwent a subsequent surgical procedure.

Hamstrings and the ischial tuberosity

Doctors from the University of Colorado School of Medicine and the Southern California Hip Institute published research in the Muscles, Tendons, Ligament Journal which cited the research surrounding the use of Platelet Rich Plasma Injections for hamstring tendinopathy. (9) Here is the summary:

  • Most chronic hamstring injuries result from tendinosis at the muscle origin site, the ischial tuberosity.
    • Tendinosis is ligament damage that no longer is inflamed. This is not a good thing. Inflammation means that the body is still trying to heal damage. When the inflammation stops, the body has given up.
  • Platelet-rich plasma has been shown to have positive effects on tendon healing.
  • Platelet-rich plasma is increasingly being used to treat various conditions within orthopaedics, including tendinopathies.
  • The majority of the currently available reports demonstrate improved healing and reduced pain when using PRP to treat various tendinopathies
  • The results of our study indicate that ultrasound-guided platelet-rich plasma injection at the ischial tuberosity for chronic recalcitrant hamstring tendinitis is an effective reliable treatment modality when traditional conservative treatment fails.

Time to return to sport was found to be significantly better in the PRP group

In a study from the British Journal of Sports Medicine, (10) doctors compared Platelet Rich Plasma Therapy, Platelet Poor Plasma Therapy (as an anti-inflammatory treatment), and no injection in professional athletes with MRI-positive hamstring injuries.

  • All patients underwent a standardized rehabilitation program. Time to return to sport was found to be significantly better in the PRP group (mean 21 days) compared with the PPP group (mean 27 days). No significant difference in re-injury rate was noted between the three groups at 2 months or 6 months following the intervention.

Chronic proximal hamstring tendinopathy and a single PRP injection

  • In another study led by the University of Colorado Hospital Department of Orthopedic Surgery, (11) doctors examined 18 patients with chronic proximal hamstring tendinopathy who received a single PRP injection by ultrasound guidance. Patients had chronic hamstring pain symptoms for an average of 32.6 months prior to their injection and all patients had attempted other non-surgical treatments such as cortisone injections and physical therapy prior to injection. Based on a visual analog scale (VAS) for pain, patients had an average improvement in pain of 63% at 6 months following PRP injection.

Cortisone vs PRP

  • Doctors from Northwestern University Feinberg School of Medicine recently suggested in the medical journal Orthopedics (12) that the typically difficult to treat hamstring patients may have already been given several traditional conservative treatments, including physiotherapy and nonsteroidal anti-inflammatory drugs, which are both considered inconsistent treatments. Corticosteroid injections are frequently recommended and have demonstrated limited success but can adversely affect local tissues and the detrimental long-term effect of cortisone has been well documented. In this study, however, doctors looked at 18 patients, 12 females and 6 males – average age 42.6 who had pain that lasted an average of 32 months.
  • The patients received one PRP treatment. Six months after the injection, 10/18 patients had 80% or greater improvement.

Overall, the average improvement was 63% with one patient – little to no improvement. The only documented side effect was post-injection discomfort that resolved within seventy-two hours.

This was ONE Injection – please see our article on choosing a PRP doctor, we discuss the idea of single injection PRP treatments.

These results could not be replicated long-term in cortisone groups. In a study from Stanford University, “Fifty percent of patients had symptomatic improvement lasting longer than 1 month after percutaneous corticosteroid injection, and 24% of patients had symptom relief for more than 6 months.” (13)  Compare that to the PRP treated patients at Northwestern who had 80% relief.

In other words, the typical conservative treatment of cortisone is not a guaranteed cure for this hamstring injury.

What these researchers found is what Prolotherapy doctors have long known: a better approach to a hamstring injury is to strengthen the fibro-osseous junction of the ischial tuberosity with Prolotherapy. The ischial tuberosity bears body weight in the seated position and is a point of attachment for the hamstring muscles. In the above research, Platelet Rich Plasma injection was used at the “muscle origin” of the fibro-osseous junction.

“Platelet-rich plasma vs. steroid injections for hamstring injury-is there really a choice?”

The above header is actually the title of an April 2019 paper in the journal Skeletal Radiology (14). It comes from a team of researchers at The University of Texas Health Science Center at Houston. The goal of this research? “To assess the effectiveness of pain relief in patients with grade 2 proximal hamstring injury, treated with platelet-rich plasma (PRP) or corticosteroid injection, by using the primary outcome of visual analog scale (VAS) at 1 week and 4 weeks of follow-up.” So what were the results?

  • Among 56 patients, 32 received PRP, and 24 received steroid injections with ages from 13 to 75 years old.
  • At one-week post-injection follow-up, 23 patients (71.9%) from the PRP group and 11 patients (45.8%) from the steroid group showed a positive response. The positive response rate in the PRP group was higher than the steroid group
  • At 4 weeks post-injection, 23 patients (71.9%) from the PRP group and 13 patients (54.2%) from the steroid group showed a positive response with no statistical significance.
  • “The PRP group had shown more favorable response compared to steroid group at 1-week post-injection, which suggests that PRP therapy can be considered as a conservative treatment choice for grade 2 proximal hamstring injuries with better short-term pain relief based on limited pilot data.”

A combination of hematoma aspiration and muscle strain PRP injection in partial hamstring muscle tears

Doctors at Thomas Jefferson University published a January 2022 paper in the journal Medicine and science in sports and exercise (21) in which they assessed the treatment effect using a combination of hematoma aspiration and muscle strain PRP injection in partial hamstring muscle tears (grade 2 strains) in athletes.

In this stuyd the doctors looked at athletes who had grade 2 hamstring strains and from 2013 to 2015, they were treated conservatively, and from 2016 to 2018, they were treated with a combination of ultrasound-guided hematoma aspiration and PRP muscle strain injection.

  • Fifty-five athletes (28 treated conservatively, 27 with hematoma aspiration/PRP injection) were included.
  • Average return-to-play time (average) was 32.4 days in the conservative group and 23.5 days in the aspiration/PRP group
  • Recurrence rate of the hamstring strain was 28.6% (8/28) in the conservative treatment group and less than 4% (1/27) in the aspiration/PRP group
  • Conclusion: “Athletes with grade 2 hamstring strains treated with a combination of hematoma aspiration and PRP injection had a significantly shorter return-to-play and a lower recurrence rate compared with athletes receiving conservative treatment.”

NFL players using PRP for hamstring injuries

Doctors at the University of Pittsburgh Medical Center and the professional American football team Pittsburg Steelers published these findings in the Orthopaedic Journal of Sports Medicine (15) in April 2020. The goal of this study, does PRP helps professional football players return off the injured list sooner if they are treated with PRP.

The learning points and conclusions of this paper are:

  • “Hamstring injuries are prevalent in professional athletes and can lead to significant time loss, with recurrent injury being common. “
  • “The efficacy of platelet-rich plasma (PRP) for augmentation of nonoperative treatment of partial musculotendinous hamstring injuries is not well established.”

In other words, do PRP injections help in promoting healing in the non-surgical treatment of hamstring injury? At the onset of this research, the doctors thought: “The addition of PRP injections to nonoperative treatment for acute partial musculotendinous hamstring injuries will lead to a shortened return to play in National Football League (NFL) players.” Players will get off the injured list sooner.

  • NFL players from a single team (The Pittsburg Steelers) who sustained acute grade 2 hamstring injuries, as diagnosed on magnetic resonance imaging (MRI) by a musculoskeletal radiologist from 2009 to 2018, were retrospectively reviewed.
  • Average days, practices, and games missed were recorded.
  • Players who did and did not receive PRP injections were compared. Those who received PRP did so within 24 to 48 hours after injury.


  • A total of 108 NFL players had MRI evidence of a hamstring injury, and of those, 69 athletes sustained grade 2 injuries.
  • Thirty players received augmented treatment with PRP injections and 39 players underwent nonoperative treatment alone.

Return to play:

  • Average time missed in those treated with PRP injections was:
    • 22.5 days, 18.2 practices, and 1.3 games.
  • In those who did not receive PRP injections, time missed was:
    • 25.7 days, 22.8 practices, and 2.9 games.

Conclusion: “Owing to the possible large financial impact of returning to play 1 game sooner, PRP injections for treatment of grade 2 hamstring injuries may be advantageous in professional athletes.”

Simply PRP made a difference.

When PRP treatments did not help improve the hamstring

In March 2019, doctors at the School of Medicine, University of Notre Dame Australia, Sydney did not get good results with PRP injection in patients with proximal hamstring tendinopathy.

Here is what happened and what was reported in the Journal of Science and Medicine in Sport. (16)

  • Twenty-nine patients with proximal hamstring tendinopathy received a single PRP injection under ultrasound guidance
  • Pain, function, and sporting activity were measured via a standard patient questionnaire. The questionnaire was taken before injection and at 8-weeks follow-up.

When the pre-injection and post-injection eight-week follow-up questionnaires were observed,  no statistically significant difference was found. When performing separate analyses for patients with mild, moderate, or marked proximal hamstring tendinopathy, no statistically significant difference was found in pre-and post-injection scores. Sixty-nine percent of patients reported no change in their ability to undertake sport or other physical activity at 8-weeks follow-up.

Here again, is a single injection PRP treatment not helping. Again as discussed above, we do not consider PRP treatments to be a one-and-done treatment. Even still, 31% of the patients in this study had a favorable outcome to the one injection.

PRP and dextrose Prolotherapy as a combination treatment

Although PRP is a type of Prolotherapy, we do not use PRP as a solution by itself. We offer PRP therapy with dextrose Prolotherapy treatments. The main reason is that dextrose Prolotherapy works on stabilizing injured structures by helping to repair damaged and elongated ligaments. The ligaments hold the bones to the bones whereas the tendons hold the muscle to the bone. When you stabilize bone-to-bone motion by way of the ligaments, you stabilize the bone-to-muscle motion and help prevent hamstring problems.

A multi-national team of researchers including those from Rutgers University, Virginia College of Osteopathic Medicine, and the University Regensburg Medical Centre in Germany tested the effects of Prolotherapy on tenocytes repair (tendon cells). Published in the journal Clinical Orthopaedics and Related Research(17) what the team was looking for was how did Prolotherapy injections change the immune system’s response to a difficult-to-heal tendon injury.

These are the highlights:

  • Prolotherapy injections changed the cellular metabolic activity to a healing, regenerative environment in the tendon cells.
  • Prolotherapy activated RNA expression. The healing phase of soft tissue injury starts spontaneously after the tendon injury. Healing occurs in three phases: inflammation, proliferation, and maturation. RNA expression is the communication changes in genes (remember the gene expression from above)  that coordinate the beginning and end of these three cycles of the healing and injury repair process.
  • Activated Protein secretion – the process of rebuilding. For a fascinating look at this subject please see our article on Extracellular matrix in osteoarthritis and joint healing.
  • Cell migration. The ability of healing cells to get to the site of an injury, and the denial of damaging inflammatory factors from reaching the same site.

In our own published research, we reported in the Clinical Medicine Insights Arthritis and Musculoskeletal Disorders, (18) we reported that the consensus is growing regarding the effectiveness of dextrose Prolotherapy as an alternative to surgery for patients with chronic tendinopathy who have persistent pain despite appropriate rehabilitative exercise.

Summary and contact us. Can we help you?

We hope you found this article informative and it helped answer many of the questions you may have surrounding your hamstring injuries.  If you would like to get more information specific to your challenges please email us: Get help and information from our Caring Medical staff


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This article was updated July 5, 2021



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