Hamstring Injury

What is Hamstring Injury?

The hamstring muscles are the three large muscles found at the back of each thigh. These are called the semimembranosus, which is the one closest to the inside of your leg, the biceps femoris (which has a long head and a short head), located on the outside of your leg, and the semitendinosus, which is in the middle of these two. These muscles are particularly likely to get injured, especially in athletes. The semimembranosus and the long head of the biceps femoris start from the back and outer side of a bone in the lower part of the hip called the ischial tuberosity, while the semitendinosus starts from a point towards the front of the same bone. The biceps femoris has a short head that comes from the back of the femur, which is the long bone in the thigh.

All three muscles attach at different points on the two bones of the lower leg – the fibula and the tibia. All hamstring muscles work across the hip and knee joint from where they start to where they attach. But, the short head of the biceps femoris only works on the knee joint. These muscles bend the knee and straighten the hip. Biceps femoris also helps to turn the hip outwards, while semimembranosus and semitendinosus help to turn the hip inwards.

Hamstring injuries frequently happen when athletes are running or sprinting. The way these muscles are built and how they function – working across two joints (knee and hip) with opposing effects on hamstring length – makes them more likely to get injured. Also, because they play a crucial role in slowing down your movements when you’re walking, running, or changing direction quickly, they are more susceptible to injury. The most strain is placed on the hamstrings when slowing down the extending knee and beginning to extend the hip. It’s during this quick change in muscle function that they are most likely to get injured. Moreover, the biceps femoris, in particular, is often injured because it has two different nerve supplies that stimulate it at different times and its two heads attach at different points.

Hamstring injuries can be classified into three grades:

* Grade 1: Slight pain or swelling, no noticeable tissue damage, no or very little loss of function.
* Grade 2: Clear partial tissue damage with moderate pain and swelling, leading to loss of function.
* Grade 3: Complete tear of the muscle or tendinous tissue with severe pain and swelling and loss of function.

What Causes Hamstring Injury?

Research has been conducted to understand the causes and risk factors of hamstring injuries—pulls or tears that can happen in the three muscles at the back of the thigh. The findings suggest that multiple factors contribute to hamstring injuries. The risk increases with a history of hamstring injuries, advancing age, and higher quadriceps muscle strength. Certain ethnic groups, including people of African and Aboriginal descent, are also more likely to experience hamstring injuries. And, if you’re involved in very competitive sport, your risk is higher. Other elements like hamstring flexibility, an athlete’s weight, hip flexibility, and the strength of the hamstring are being investigated for any links to injury risk.

In school-based research that disregarded the injury history, it was found that participants were more prone to hamstring injuries during high-speed running and extreme hamstring stretching during activities like dance and contact sports.

An analysis of professional soccer players performed by the Union of European Football Associations (UEFA) showed that having had a previous hamstring injury significantly increased the chances of a future one. Goalkeepers were less likely to get injured than other players, and players got injured less during away matches compared to home games. Additionally, the injury rate was higher during the regular season compared to the preseason.

A report in the British Medical Journal, based on a study of 100 pro soccer players, revealed that players were more likely to injure their hamstrings if their muscles functioned unevenly. Also, these injuries frequently occur in sports requiring quick starts and stops, such as American football, soccer, and Australian rules football. More severe injuries tended to happen during kicking, while most injuries occurred during running. Higher rates of hamstring injuries were also linked to more intense training sessions, higher levels of competition, and playing positions that required more running, like a wide receiver in American football.

Risk Factors and Frequency for Hamstring Injury

Research has found that injuries to the hamstring muscles typically occur in individuals between the ages of 16 and 25. These injuries are particularly common in sports that place high strain on the hamstrings, such as sprinting, soccer, football, and track and field sports. A 13-year study by UEFA found a year after year increase of 2.3% in hamstring injuries among top European soccer clubs.

Interestingly, the rate of injuries during actual matches was 9 times higher compared to those occurred during training. Another study conducted by FC Barcelona from July 2007 to June 2010 on their young athletes, with an average age of 13.56 years, found a lower rate of injury in this younger demographic compared to older athletes.

The typical time an athlete had to refrain from playing due to the injury was 21 days.
If the injury involved a pull from the ischium (part of the pelvis), the recovery period increased to an average of 43.4 days.

A ten-year study in the NFL found that over half of hamstring injuries occurred during the preseason, particularly among players in high-speed positions such as the defensive secondary and wide receivers. Interestingly, these injuries were more often caused by non-contact situations rather than physical contact.

Signs and Symptoms of Hamstring Injury

If an athlete experiences sudden pain in the back of their thigh while playing a sport, they may have a hamstring injury. This kind of injury can make it hard to put weight on the affected leg and may result in a strange way of walking due to the discomfort. The pain can be specific to the upper thigh area if the injury leads to a full tear from the base of the hip bone. This intense pain may even make it difficult for the patient to sit down. It’s common for upper thigh injuries to coincide with lower muscle strain, which could distract from the major injury. A few days following the injury, the person might notice a bruise on their buttock or the back of their thigh extending down the leg. Some people may also experience unusual sensations in the back of their thigh, which can be a sign of the sciatic nerve being compressed by a hematoma, scar tissue or a retracted muscle. Certain injuries near the knee may lead to difficulty in bending the knee.

A physical exam is key in the initial evaluation of a hamstring injury. However, due to the location of the hamstring muscles, the exam shouldn’t be the only determining factor for the nature of the injury. The usual findings include swelling and tenderness in the back of the thigh and possibly a palpable defect within the muscle if there is a full tear. It’s crucial to test the strength and range of motion of the affected hamstring and compare it to the uninjured side. These tests should ideally be performed with the patient lying face down and the hip positioned at zero degrees extension, then bending the knee with resistance applied at the heel and the knee at 15 degrees and 90 degrees of bending. If the patient experiences pain or weakness during this test, it’s considered a positive sign of a hamstring injury. It’s also recommended to check hip bending and knee extension, which can be limited due to pain in those with a hamstring injury.

Testing for Hamstring Injury

If your doctor suspects a hamstring injury, they will often use imaging tests to understand better the type, size and severity of the injury. The simplest of these is an x-ray, which can check for any broken bones, particularly an injury called an apophyseal fracture.

Two of the main tests doctors use to check for hamstring injuries are ultrasound and MRI (magnetic resonance imaging). Both of these tests provide images of the area, highlighting any signs of injury such as swelling (edema) and internal bleeding (hemorrhage). In an ultrasound, these signs are seen as changes in the texture of the image (echotexture), whereas in an MRI they appear as bright areas in the T2 weighted images.

An ultrasound can offer a real-time view of the injured hamstring muscles and is more effective if done shortly after the injury. On the other hand, an MRI is generally the preferred test for more serious injuries, such as those deep within the muscle, repeat injuries, or to distinguish new injuries from existing scar tissue. It can also give some indication of how long it will take to recover from the injury.

Though an MRI can give an idea of how long you may need to rest before returning to sports or physically demanding activities, it can’t predict the chances of the injury happening again. More research is needed in this area.

Treatment Options for Hamstring Injury

Currently, there’s no scientifically-based method for managing injuries. Doctors usually make decisions based on their own experiences, stories from others, and what they understand about how body tissue repairs itself. Injuries that are closer to the body tend to be more common and can range from mild to severe.

Mild to moderate injuries (known as Grades I and II strains) are typically handled without surgery. Doctors usually advise rest, use of ice packs, relative immobilization to limit movement, and control of pain and inflammation with drugs like NSAIDs and pain relievers. After this period, patients would gradually begin stretching and strengthening exercises. Doctors may give NSAIDs for 5 to 7 days at most and would not usually recommend glucocorticoids. Platelet-rich plasma (PRP) and other growth factors have not enough scientific backing to approve their use. In the first few days of injury, the focus is on managing bleeding, swelling, and pain.

After this, patients begin to move around progressively with the help of crutches until they can walk without pain. It’s important to consider postural control mechanisms and alignment of the pelvis when dealing with these kinds of injuries.

For severe injuries where the tendon detaches from the bone (known as grade III injury), the usual approach is to opt for non-surgical treatment if the tendon has retracted by less than 2 cm. However, research indicates that non-surgical treatment may lead to unsatisfactory results for injuries where the tendon has completely torn and retracted, such as the inability to return to an active lifestyle or sports, chronic knee bending weakness, mild hip extension weakness, sciatica, pain when sitting and deformation. Therefore, for severe injuries, surgery is often recommended. It’s generally better to perform the surgery as soon as possible to prevent the torn tendon from scarring to the sciatic nerve. The best time for surgery is considered to be 4 to 6 weeks after the injury happens.

There’s no proven benefit of other treatments like therapeutic ultrasound, therapeutic laser, electrical stimulation, massage, and extracorporeal shock wave (a non-invasive treatment) for these types of injury.

When it comes to diagnosing pain in the upper part of the thigh, the following conditions might be considered:

Lumbosacral facet syndrome (a back condition)
Chronic gluteal sciatic pain (also known as hamstring syndrome)
Lumbosacral radiculopathy (nerve condition)
Piriformis syndrome (a muscle condition)
Sacroiliac joint injury (an injury to the joint in the lower back)
Lumbosacral discogenic pain syndrome (pain originating from the spinal disc)
Sciatic nerve compression, which may be caused by an aneurysm in the inferior or superior gluteal artery

On the other hand, for diagnosing pain in the lower part of the thigh, these conditions might be considered:

Deep vein thrombosis (a blood clot)
Baker cyst rupture (a fluid-filled cyst behind the knee)
Knee meniscus injury (damage to the cartilage in the knee)
Proximal gastrocnemius injury (an injury to the calf muscle)
Popliteus injury (an injury to the muscle behind the knee)

What to expect with Hamstring Injury

Doctors use clinical evaluations and imaging processes, like MRIs, to predict how well and quickly a patient might recover from a hamstring injury. Patients with minor to moderate injuries (known as grade I and II), those who can walk without experiencing pain within a day after getting injured, or those with small muscle tears tend to recover more smoothly and in less time.

On the contrary, patients with severe injuries (also called grade III injuries), bone fractures as a result of the hamstring injury, muscle tears close to the hip, or injuries with large and deep bruising tend to face a rougher recovery and need a longer time to heal. Also, hamstring injuries caused by slow stretching movements usually take longer to heal compared to those caused by high-speed activities.

Possible Complications When Diagnosed with Hamstring Injury

People may experience long-lasting pain and injury in their hamstring if they return to physical activities too soon after an injury. Another risk is re-injury, which can occur if there are areas of hardening or inflammation in the hamstring following the initial injury. In some cases, people may develop what’s known as ‘Hamstring syndrome’. This is when scar tissue forms and starts to press on the sciatic nerve, causing discomfort and pain.

Known Issues:

Chronic hamstring pain and injury from returning to physical activity too soon
Re-injury due to areas of hardening or inflammation post-injury
Hamstring syndrome, where scar tissue impinges on the sciatic nerve

Recovery from Hamstring Injury

Rehabilitation (or ‘rehab’) after a hamstring injury is very important for an athlete to get back into their sport. It has been found that a rehab program which includes exercises to improve balance and stability as well as strengthening the trunk (the body excluding arms and legs) is more helpful than just focusing on the hamstring muscle alone. A study from Sweden revealed that certain types of exercises, which focus on increasing muscle length, were more successful in getting athletes back to their sport faster than traditional exercises.

Research also suggests that to recover faster, attention should be given to the lower part of the spine (lumbar spine), the joint that connects the spine to the pelvis (sacroiliac joint), how the pelvis is aligned, and how well one can control their posture. Exercises designed to lengthen the hamstring muscle were found to bring athletes back to their sport quicker, and with less chance of getting hurt again, compared to typical hamstring exercises. PRP, or Platelet-Rich Plasma therapy, involves injecting parts of the patient’s own blood to speed up healing, but it hasn’t been proven to reduce the time it takes to get back to play, or the risk of getting hurt again.

Before an athlete resumes their sport, it’s key to make sure they have regained normal muscle flexibility and stamina, because getting hurt again is common without these. The injured hamstring should have regained 90% of its original strength, and the strength ratio between the hamstring and the quadriceps (the muscle in front of the thigh) should be between 50% to 60%.

Sometimes, injuries to the upper part of the hamstring muscle called the ‘semitendinosus’ and its connecting tendon can result in a longer recovery time. Factors that lengthen recovery time include injuries caused by stretching, recreational sports, higher mobility deficit with the hip bent at a 90-degree angle, seeing a doctor less than a week after the injury, severe pain, and the inability to walk pain-free within a day of the injury. Rehab programs that put pressure on the hamstring muscle while stretching it out have been shown to hasten the return to sport. Additionally, four daily sessions of static hamstring stretching (keeping the muscle stretched out without moving) have given good results in reducing the time required to return to play.

Preventing Hamstring Injury

Hamstring injuries are among the most common injuries athletes face, particularly in high-level competitive sports. This type of injury often results in athletes needing to take extended breaks from their sport, as they need sufficient time to heal properly and undergo rehabilitation before they can play again. It’s particularly important to note that if the injury reoccurs multiple times, recovery may become more complicated.

Hamstring injuries are not exclusive to athletes but can also affect non-athletes like dancers. In both cases, if an individual feels a sudden, intense pain in the back of their thigh that stops them from continuing their sporting or physical activities, it could indicate a hamstring injury. This should only be ruled out if medical examinations and scans provide a definite alternative diagnosis.

When dealing with a hamstring injury, it’s essential that patients understand the recovery process. This includes being aware of how long they might have to rest from their sport. In severe cases, they should be informed that surgery may be necessary. Above all, patients should be made aware of how important it is to complete rehabilitation and physical therapy before returning to their regular activities, in order to heal effectively and prevent further injury.

Frequently asked questions

Hamstring injury refers to the damage or tear of the hamstring muscles, which are the three large muscles located at the back of each thigh. These injuries can be classified into three grades based on the severity of pain, swelling, tissue damage, and loss of function.

Hamstring injuries are common, particularly in sports that place high strain on the hamstrings such as sprinting, soccer, football, and track and field sports.

Signs and symptoms of a hamstring injury include: - Sudden pain in the back of the thigh while playing a sport. - Difficulty putting weight on the affected leg. - Strange way of walking due to discomfort. - Specific pain in the upper thigh area if there is a full tear from the base of the hip bone. - Difficulty sitting down due to intense pain. - Bruising on the buttock or the back of the thigh extending down the leg a few days after the injury. - Unusual sensations in the back of the thigh, which may indicate compression of the sciatic nerve by a hematoma, scar tissue, or a retracted muscle. - Difficulty bending the knee, especially if the injury is near the knee. - Swelling and tenderness in the back of the thigh. - Palpable defect within the muscle if there is a full tear. - Weakness and limited range of motion in the affected hamstring compared to the uninjured side. - Pain or weakness during specific tests, such as bending the knee with resistance applied at the heel and the knee at different degrees of bending. - Limited hip bending and knee extension due to pain.

Multiple factors contribute to hamstring injuries. These include a history of hamstring injuries, advancing age, higher quadriceps muscle strength, certain ethnic groups (such as people of African and Aboriginal descent), involvement in very competitive sports, hamstring flexibility, athlete's weight, hip flexibility, and the strength of the hamstring. Hamstring injuries are more prone to occur during high-speed running, extreme hamstring stretching, and activities like dance and contact sports.

The conditions that a doctor needs to rule out when diagnosing Hamstring Injury are: - Lumbosacral facet syndrome (a back condition) - Chronic gluteal sciatic pain (also known as hamstring syndrome) - Lumbosacral radiculopathy (nerve condition) - Piriformis syndrome (a muscle condition) - Sacroiliac joint injury (an injury to the joint in the lower back) - Lumbosacral discogenic pain syndrome (pain originating from the spinal disc) - Sciatic nerve compression, which may be caused by an aneurysm in the inferior or superior gluteal artery - Deep vein thrombosis (a blood clot) - Baker cyst rupture (a fluid-filled cyst behind the knee) - Knee meniscus injury (damage to the cartilage in the knee) - Proximal gastrocnemius injury (an injury to the calf muscle) - Popliteus injury (an injury to the muscle behind the knee)

The types of tests that a doctor would order to properly diagnose a hamstring injury include: 1. X-ray: This test is used to check for any broken bones, particularly an injury called an apophyseal fracture. 2. Ultrasound: This test provides a real-time view of the injured hamstring muscles and is more effective if done shortly after the injury. It can show signs of injury such as swelling (edema) and internal bleeding (hemorrhage) as changes in the texture of the image (echotexture). 3. MRI (Magnetic Resonance Imaging): This test is generally the preferred test for more serious injuries, such as those deep within the muscle, repeat injuries, or to distinguish new injuries from existing scar tissue. It can provide detailed images of the area and can also give some indication of how long it will take to recover from the injury.

Mild to moderate hamstring injuries (Grades I and II strains) are typically treated without surgery. Doctors advise rest, use of ice packs, relative immobilization, and pain and inflammation control with drugs like NSAIDs and pain relievers. After a period of rest, patients gradually begin stretching and strengthening exercises. Severe hamstring injuries (Grade III) where the tendon detaches from the bone may require surgery if the tendon has completely torn and retracted. Non-surgical treatment may lead to unsatisfactory results in these cases. Other treatments like therapeutic ultrasound, therapeutic laser, electrical stimulation, massage, and extracorporeal shock wave have no proven benefit for hamstring injuries.

The side effects when treating Hamstring Injury can include: - Chronic hamstring pain and injury from returning to physical activity too soon - Re-injury due to areas of hardening or inflammation post-injury - Hamstring syndrome, where scar tissue impinges on the sciatic nerve, causing discomfort and pain.

The prognosis for a hamstring injury depends on the severity of the injury. Here are some key points: - Grade 1 injuries have slight pain or swelling, no noticeable tissue damage, and no or very little loss of function. These injuries tend to have a smoother and quicker recovery. - Grade 2 injuries involve clear partial tissue damage with moderate pain and swelling, leading to a loss of function. The recovery period for these injuries may be longer. - Grade 3 injuries are complete tears of the muscle or tendinous tissue with severe pain and swelling and a loss of function. These injuries tend to have the longest and most challenging recovery.

Orthopedic doctor or sports medicine doctor.