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Injury Types

Why are hamstring injuries so common in the NFL?



Written by: Lee R. Benaroch, BSc, MD student 

Edited by: Jesse A. Morse, MD, MBA, CAQSM 

Over the course of this NFL season, we will be beginning a new segment of bringing you articles detailing the physiological aspects of common injuries. We will be discussing how they occur, how they can be prevented, ways to treat them and medical imaging of the injured muscle, ligament or bone. We hope you enjoy! First up, the dreaded hamstring injury.

A study conducted in 2011 looked at 10 years’ worth of NFL injury data and found that the hamstring strain was the most common injury in the NFL, occurring on average 172 times per season*. More than half of these hamstring injuries end up taking place during training camp, preseason or the early weeks of the regular season. Why is that? 

Many theorize that the athletes increase their usage of their hamstrings from 50% in the offseason to 100% in training camp and the muscle is not able to tolerate that overload. This year in particular, COVID-19 has caused a shortened training camp further intensifying the issue.  

On top of that, why is it that during every NFL year, it feels like every team has a minimum of one impactful player go down with a hamstring injury? Already this year we’ve seen the likes of Tampa Bay’s Mike Evans, Detroit Lions’ Kenny Golladay, Philadelphia Eagles’ Miles Sanders, Atlanta Falcons’ Julio Jones and many more, struggle with a hamstring injury. Is it a previous injury history? Is it the strength and conditioning program? Or is it just luck? 

The Hamstrings 

The hamstrings are made up of three individual muscles located on the back of the thigh: the biceps femoris, semimembranosus and semitendinosus. All three muscles originate on the back of the hip and insert onto the back of the knee. The main function of the hamstrings is to primarily flex the knee joint and secondarily extend the hip joint. 

The Injury

A hamstring strain, like any other muscle strain, is graded based on its severity. Grade 1 is a mild strain but no tear. Grade 2 – a partial muscle tear and grade 3 – a complete muscle tear. It causes a sharp pain, weakness, swelling and bruising within the injured muscle.

Grade 1 strains are usually caused by overuse of the muscles which lead to friction at the insertion site, in turn leading to bursitis (i.e. bursae are small fluid-filled sacs that cushion the bones, tendons and muscles around joints – bursitis is an inflammation of these sacs). The problem with grade 1 strains is that injury to the tendon can develop, called tendinopathy. This can and often leads to repetitive pain and a potentially grade 2+ tear. 

Where most of the NFL players run into issues is during a traumatic non-contact eccentric contraction/stretch of the hamstring beyond its physiological capabilities. This can occur either during knee flexion or hip extension and cause a partial or complete tear of the hamstring. One of the most common sites for these tears is at the origin point of the biceps femoris at the hip. These grade 2+ tears are usually caused by one of the following issues: 

Poor Eccentric Strength – Eccentric strength is when a muscle lengthens under tension. One of the jobs of the hamstring is to stretch the knee and decelerate the lower leg of the player after sprinting. If the player’s hamstring lacks sufficient strength to do so, then the muscles can’t slow down the leg and an injury can follow. 

Muscle Imbalances – The quadriceps and hamstrings oppose the actions of one another. If a player has much stronger quads than they do hamstrings, then the lower leg will swing forward at a speed that the hamstring cannot handle, ultimately leading to extensive pressure on the hamstring and a possible tear. This is a common cause of hamstring injury in the NFL as many players tend to be quad dominant.


Prevention of these hamstring strains is essential for any NFL player and there are many techniques that can help with it. However, one of the most common techniques used in European soccer, and that has been found to reduce the overall injury risk of a hamstring strain to athletes, is the Nordic Hamstring Exercise (NHE). The NHE involves kneeling on a pad and lowering under control while the ankles are held in place by a partner, a loaded barbell, or any other immovable object. 

The athlete would then extend the hamstring muscles by leaning forward from the knee and not the hip. Van Dyk et al. (2019) found that when including NHE in injury prevention programs for athletes, the risk of hamstring injury was reduced by 50% when compared to usual training or other prevention programs. Therefore, NFL teams and strength coaches can do a great deal of good by making sure they include NHE in their strength and conditioning programs in order to help prevent a hamstring strain.


When it comes to treatment of a hamstring strain, the options are dependent on the severity of the injury. Ultimately there are two treatments available; the conservative or surgical method.  

If the strain is mild, a Grade 1, the doctor may suggest simple rest, ice and use of crutches for 3 to 5 days. This will be followed up with rehabilitation to re-establish strength and flexibility of the hamstring.  

If the injury is more severe, a grade 2, or the patient wants to be really aggressive (like an NFL athlete trying to return to the field quicker), then injections can be considered. An injection into the muscle or where the tendon inserts into the bone can further help with pain relief, healing, and recovery. Yong Soo Park et al., (2019) found that Platelet-Rich Plasma (PRP) injections (extracted from patient’s blood) provided a more favorable response when compared to steroid injections. They could be used as a conservative treatment choice for grade 2 proximal hamstring injuries with the added benefit of short-term pain relief.  

While the quality of cells and growth factors in PRP is very good, often times these can take a couple of injections to see significant improvement. Extracting cells and growth factors from either bone marrow or amniotic tissue (provided from a company that extracts it safely from the placenta of a woman delivering a baby via a C-section) have significant better success rates. In some studies, the number of cells and growth factors found in bone marrow is 3x that found in PRP. The numbers for amniotic tissue are even better than bone marrow.  

If the injury is more severe, the acute traumatic tear of the hamstring can be surgically treated. Surgery for a hamstring strain is quite rare. If the muscle completely tore off the bone and managed to take a piece of bone with it (Grade 3) then surgery is an option. Nonetheless, it is usually the last resort.  

Most NFL hamstring injuries tend to be treated with the conservative method, as the tear is usually either a Grade 1 or 2. However, where most players run into issues is the fact that even though the hamstring may feel healed, most players and teams do not give the hamstring enough time to properly heal.  

A 2007 study was done on professional sprinters with moderate strains that showed 20-55% of the original injury had not fully healed after 6 weeks. However, a 2011 study conducted by Cohen et al., found that players with a grade 1 hamstring strain missed only 1.1 week on average, those with a grade 2 strain missed 1.7 weeks on average, and those with a grade 3 strain missed 6.4 on average.

It is clear to see that both players and teams alike are willing to ignore the data and rush their players back following a hamstring injury. However, this is the precise reason why 16.2% of NFL players with hamstring injuries re-injure themselves.

Ultrasound Images (of Hamstring injuries) Written by Jesse A. Morse, MD 

Ultrasound is a fantastic way to evaluate the severity of hamstring injuries, even if an MRI doesn’t show much. Below are a bunch of fantastic images that were borrowed (source below) from one of the best Musculoskeletal Ultrasound Imaging books.  

The first image (Figure 6.75) is showing damage to one of the main hamstring tendons, but not a significant tear, this is called tendinosis.

Figure 6.76 is showing the most common area of injury in the hamstring, called the Conjoined Tendon, where two tendons come together. This demonstrates tendinosis, which is essentially early damage to the tissue, and not a large tear, which is what Figure 6.77 shows. Compare Figures 6.76 and 6.77, there is a clearer distinction between the amount of swelling (dark fluid) and the injured tissues look very different then the surrounding tissue. 

Figure 6.78 demonstrates a very large tear, likely a moderate ‘Grade 2.’ So, think of this image when you hear a player suffered a ‘Grade 2 hamstring injury.’ All of the black within the white arrows is blood that has filled the area after the injury. It’s not supposed to be there. As you can tell the tissues look completely different than the tissues above and below it.

Figures 6.79 & 6.80 demonstrate tears of multiple hamstring tendons. There is significant damage at the muscle and these injuries are going to take at least 6-10 weeks to properly heal, likely much longer.

Figure 6.81 demonstrates a chronic tendon injury, which has scar tissue within it. This scar tissue is not as strong or as flexible as regular muscle tissue, so it often tears much easier. Chronic ‘microtears,’ which I often describe to my patients like a rope that is trying to hold a boat to a dock for the past 20 years. The rope is the tendon, the boat is the bone. That rope is going to be beat up and while still holding the boat on, like the tendon attached to the bone, it is not as strong as it used to be. A large force on that tendon will cause it to tear, sometimes off of the bone. 

Hope this was helpful!  

All ultrasound images were taken from Jacobson’s Fundamentals of Musculoskeletal Ultrasound  

*Starting in 2012, the NFL started compiling and publishing sports injury data through the Play Smart Play Safe initiative and the concussion has now been recorded as the most common NFL injury coming in at 200-280 times per season.


Jacobson, Jon. Fundamentals of Musculoskeletal Ultrasound. Elsevier Science, 2018.,based%2 0on%20limited%20pilot%20data

Lee Benaroch was born and raised in Montreal, Canada and is currently a second-year medical student at McGill University. Prior to medical school, he obtained a double-major with honours in Medical Sciences and Biology at Western University. Lee has a keen interest in Orthopaedic sports medicine and hopes to one day pursue a career in it. Lee is a die hard fan of his hometown Montreal Canadiens as well as the Los Angeles Chargers. In his free time, he enjoys playing hockey, golf and reading.

Injury Types

High-Ankle Sprains



Written by: Lee R. Benaroch, BSc, MD student 

Edited by: Jesse A. Morse, MD, MBA, CAQSM 

Welcome back to our series on explaining common NFL injuries. This month we’re talking about the ever-so dreadful high ankle sprain. Already this year we’ve seen Carolina Panthers’ Christian McCaffery, New Orleans Saints’ Michael Thomas, San Francisco 49ers’ Raheem Mostert and others go down with high ankle sprains. However, as was so clearly demonstrated by the New York Giants phenomenal running back Saquon Barkley in 2019, the high ankle sprain is not an injury to take lightly. Why is it that this injury impairs players performance even after it’s healed and what can be done about it?

The Ankle

The ankle is made up of three bones and many ligaments. Those bones are the tibia and fibula, the two bones that make up the lower leg, and the talus. There are many ligaments on both the medial and lateral side of the ankle however, the ligament we are most concerned about is the syndesmotic ligaments that connect the tibia and fibula. The job of these ligaments are to stabilize the ankle as well as act as shock absorbers for the ankle joint.


How the Injury Occurs

A syndesmotic sprain of the ankle, also more commonly known as a high-ankle sprain or AITFL sprain is traditionally due to ankle dorsiflexion in combination with external rotation.

The high ankle sprain injury is most commonly acquired in the NFL by getting a direct blow on the lateral aspect of the ankle while there is excessive external rotation of the foot. The external rotation of the ankle causes the tibia and fibula to pull away from one another, putting pressure on the ligaments that connect them and the blow is enough to tear them. The image to the right is a great example that illustrates a player’s leg being externally rotated while also receiving a blow to the lateral side of the leg, a recipe for a high ankle sprain.

Another mechanism of injury is while the foot is hyperdorsiflexed (i.e. raising the foot upwards towards the shin).  This occurs when the athlete has his foot planted and falls or is pushed forward.

High-ankle sprains only make up 10% of all ankle sprains, although in certain sports (NFL) it feels like they make up a much higher percentage. This is the most common type of ankle sprain in collision sports.

This injury may also involve the posterior inferior tibiofibular ligament or syndesmotic membrane. If the force is severe enough this can lead to a proximal fibula fracture, commonly known as a Maisonneuve fracture (the fracture is near the knee).

The patient will have anterior ankle pain after the described mechanism above. On exam the patient will be tender over the AITFL ligament, and a squeeze of the mid-lower leg will generate significant pain. Additionally, external rotation of the leg will also cause significant pain.

The symptoms of the high-ankle sprain are pain and swelling around the injury. As well, the athlete may have difficulty putting pressure on the injured ankle when walking.

Just for note, the high-ankle sprain differs significantly from the common lateral ankle sprain. The lateral ankle sprain occurs when the foot is excessively plantarflexed (i.e. pointing the foot to the ground) and then invert your foot which causes injury to the lateral ligaments of the ankle (image below).

What does the syndesmotic ligament look like under ultrasound?


Determining Severity

High-ankle sprains are traditionally diagnosed with x-rays of the lower leg that should be weight-bearing. The technical guidelines demonstrate over 5 mm space on the AP view with little overlap between the two bones. While CT can be helpful, MRI is 100% sensitive, and 93% specific for high-ankle sprains.

Just like hamstring strains (if you haven’t read our hamstring injury article, we highly suggest doing that), any ligamentous sprain is graded based on its severity. A grade 1 high ankle sprain is clinically considered mild; there’s disruption of some syndesmotic fibers and the acute microscopic tearing is not visible on radiographic imaging. Grade 2 is a partial tear; there is considerable disruption of the syndesmotic fibers. Grade 3 is considered a complete tear of the syndesmotic ligament and commonly occurs alongside a fracture of the tibia or fibula.


Prevention of any ligamentous injury is much more difficult than a muscular injury for the simple reason that you cannot strengthen your ligaments through exercise. Exercises that increase the strength and muscle control around the ankle may help to resist the forces that cause the high-ankle sprain.


When treating a high-ankle sprain, the treatment method is ultimately determined based on the severity of the injury. The bulk majority of high ankle sprains are of the mild, grade one type, and therefore are treated conservatively. Grade 1 is the mildest, and usually responds to rest, ice and immobilization, and takes about 2 to 4 weeks to return. Once the acute inflammatory phase has subsided, the athlete will go through physiotherapy. Physical therapy is very important in order to get back to 100% pre-injury form. Initially they will focus on isometrics, then isotonics, and then proprioceptive and plyometrics before full return to play.

Most high ankle sprains take an average of 4 to 6 weeks to recover and players may use a functional ankle brace that can be used to limit diversion and external rotation to help further stabilize the joint and reduce the risk of re-injury.

In the case that imaging shows that there is significant damage to the ankle ligaments and that the tibia and fibula are separated, grades 2 and 3, this should warrant surgical evaluation. If there is significant space between the two lower leg bones on x-ray, or a fracture, surgery is often indicated. There are a couple different surgical techniques commonly used. The classic way is to use a screw to stabilize the two bones together, and the newer approach is to use surgical wire (‘rope’) instead of a screw.

If the injury needs to be reduced then a splint should be applied, and the patient should be non-weight bearing using either crutches or a wheeled scooter. The person is placed in a cast for 6 to 8 weeks, and then eventually walks with the cast before being able to shed it.

Rehabilitation for some more severe high-ankle sprains should first establish range of motion, then strength and finally proprioception. X-rays every two weeks should be taken to monitor the status of the healing. These can take several months to fully heal. After that, physiotherapy will be introduced at a gradual pace and on average an athlete can return after 10 to 12 weeks post-surgery.

Another way to treat high-ankle sprains is with injection, commonly using regenerative medicine products, including PRP, stem cells (extracted from bone marrow or fat), or an amniotic allograft tissue.

The best way to visualize the injury on ultrasound is in the long-axis, and the injury is approximately 2 cm underneath the surface of the skin. Common findings of an acute injury include ligament disruption, hematoma formation, and dynamic instability with stressing of the joint. Chronic injuries traditionally show more thickening of the ligaments with calcifications.

Regenerative medicine injections have been very successful in speeding up recovery times for athletes, however there are no well-designed studies to support this practice at this current time.

Discussion (as it pertains to the NFL) Written by: Jesse A. Morse, MD, CAQSM

High-ankle sprains, especially in running backs, wide receivers and tight ends have a tendency to be very challenging to return from. This injury really zaps the player’s power, and most players struggle when they return. Often they do not look like the same player until the following season.

This was evident with two high-profile running backs in 2019, as both Saquon Barkley and Alvin Kamara suffered the dreaded injury. Both never completely returned to form during the 2019 season and were able to return to 100% for 2020 after working diligently for months with physical therapists throughout the off-season (Google: Alvin Kamara, Dr. Sharif Tabbah).

These injuries are unfortunately very common, especially in the NFL. With so many people pushing, blocking and rolling on the ground near each other’s feet, many players have their ankles rolled up on, causing this injury. Other times players are tackled in an awkward fashion, which leads to this injury is well.

Unlike a traditional low ankle sprain, people suffering from a high-ankle sprain cannot just grin and bear it. The pain and discomfort are simply too much and the injury has been unfortunately very common again in 2020.

Speaking from experience, once I hear a player has suffered the high-ankle sprain, I anticipate they’ll struggle for the remainder of that season and immediately lower my expectations for them, regardless of the skill of the athlete. Thankfully, with appropriate and extensive rehabilitation, the athlete usually is able to return to 100% (pre-injury form).


Harrast, Mark A., and Jonathan T. Finnoff. Sports Medicine: Study Guide and Review for Boards. Demos Medical Publishing, 2017.

Hunt K, Phisitkul P, Pirolo J, Amendola A. High Ankle Sprains and Syndesmotic Injuries in Athletes. Journal of the American Academy of Orthopaedic Surgeons. 2015;23(11):661-673. doi:10.5435/jaaos-d-13-00135

Jacobson, Jon A. Musculoskeletal Ultrasound. Elsevier Saunders, 2007.

Malanga, Gerard A.., and Kenneth R.. Mautner. Atlas of Ultrasound-Guided Musculoskeletal Injections. McGraw-Hill Education Medical, 2014.

O’Connor, Francis G. ACSM’s Sports Medicine: a Comprehensive Review. Wolters Kluwer Health, 2015.

Sikka R, Fetzer G, Sugarman E et al. Correlating MRI Findings with Disability in Syndesmotic Sprains of NFL Players. Foot Ankle Int. 2012;33(5):371-378. doi:10.3113/fai.2012.0371a

Seidenberg, PH, Beutler, AI The sports medicine resource manual. Philadelphia, PA: Saunders/Elsevier. 2008.

Van Heest TJ, Lafferty PM Injuries to the Ankle Syndesmosis. J Bone Joint Surg Am. 2014 Apr 2;96(7):603-13.

Williams GN, Allen EJ. Rehabilitation of syndesmotic (high) ankle sprains. Sports Health. 2010;2(6):460–470. doi:10.1177/1941738110384573

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Injury Types

Are AC Joint sprains serious?-Dr. Morse



Photographer: Roy K. Miller/Icon Sportswire

Currently both Tampa Bay Buccaneers QB Jameis Winston and Detroit Lions WR Golden Tate are dealing with a common football injury, a sprained AC joint. What does this mean? A sprained AC joint, also known as the acromioclavicular joint, is commonly referred to as a ‘separated shoulder.’ This is an injury where there is a sprain of the supporting ligaments (acromioclavicular and coraco-clavicular ligaments) of the AC joint. Typically, this injury occurs when striking another player with the point of the shoulder, or in Winston‘s case, when a player lands directly on the point of their shoulder, often while being tackled/sacked.

The initial presentation of an AC joint sprain reveals exquisite tenderness over the AC joint, which is in between the tip of your shoulder and your neck, just above where the clavicle is (see picture). X-rays are typically ordered to evaluate for a clavicle fracture, which Green Bay Packers Aaron Rodgers just suffered, and to it as well is to assess the degree of AC separation. Pulling down on the arm of a player with a possible AC joint sprain is an easy way to evaluate the joint, as it will widen the AC joint, causing pain.

Management of this condition typically focuses on control of the inflammation and pain with ice, rest, and a sling, often for about three weeks. Integrating the use of protection with padding, early restoration of range of motion, and the preservation of the shoulder strength are all-important as well. If conservative options are still failing to control the pain, an ultrasound-guided AC joint steroid injection can be considered.

To keep it simple, there are basically three types of AC joint sprains, grades 1, 2, and 3. Mild AC joint sprains (Grade 1) involve just a mild sprain of the AC joint capsule and AC ligament, normal x-rays, with a return to play of about 1 to 2 weeks.

Moderate sprains (Grade 2) involve rupture of the AC capsule as well as the ligaments. X-rays will show upward displacement of the collarbone/clavicle, but the C-C ligaments are normal. These take about 3 to 4 weeks to fully heal. Grade one and two AC joint sprains often only result in the patient wearing a sling.

High-grade AC sprains (Grade 3) often do not require surgery, but there is complete AC joint dislocation, and complete rupture of both the AC and C-C ligaments. Grade 3 AC joint sprains typically heal in about 6 weeks. Some athletes, especially at the elite level, may decide to surgically stabilize their joint to help speed up their return to play. About 30 to 50% of patients who suffer an AC joint sprain will have residual pain at the AC joint. Surprisingly, patients who undergo surgery have a higher rate of AC joint arthritis than those who to choose a more conservative route.

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Injury Types

Jones fractures explained-Dr. Parekh



With an emergence of Jones fractures among elite athletes, our Dr. Selene Parekh breaks them down in order to give the audience a better understanding.

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