Everything you need to know about your hamstring anatomy, movement, and injury from a Sports Medicine Physical Therapy Specialist.

Danh Ngo"Staying Active" Division, Hip, groin, pelvic pain, Knee Pain, Low Back Pain, Running

hamstring anatomy

We are starting a comprehensive guide to helping you to understand your body from a movement and Orthopedic science perspective. Your Hamstring Muscles are on the top 5 muscles of a misunderstood muscle group in your body.

We are starting a comprehensive guide to helping you to understand your body from a movement and Orthopedic science perspective. Your Hamstring Muscles are on the top 5 muscles of a misunderstood muscle group in your body.

We are starting this series with the good o’ “tight” hamstring that everyone tends to stretch to minimal results. The article will be in the order that is listed below.

  • Basic Anatomy 101: Muscle
  • Important anatomy important for hamstring muscle strain recovery
  • Movement Analysis
  • Pain Pattern
  • Orthopedic Muscle Injury Grading system
  • Holistic and Functional Perspective

Basic Anatomy 101: Muscle

Did you know that your Hamstring Muscle is a group of 4 muscles?

You have two muscles located on the inner back thigh called the Semimembranosus and Semitendinosus muscle. These two muscles connect to the ischial tuberosity of your pelvis. There is a ligament called the Sacrotuberous ligament that helps to connect the work energy of the Hamstring muscle to your pelvis, and vice-versa. Basically, the ligament is the bridge between what is happening at the pelvis, hip joint, femur bone, and knee joint. This is an important concept to remember for later.

You have two muscles located on the outer back thigh called the Bicep Femoris Short and Long Head muscle. The same-origin connection of the Bicep Femoris muscle goes for this group. They have a fascial connection to the Sacrotuberous ligament. This ligament plays a role in being a part of the sciatic notch and important to remember as we will elaborate more below on how muscles impact spinal health and the surround nerves, such as the infamous sciatic nerve.

As we go back to the two outer hamstring muscles, you will see that both Bicep Femoris muscles connect to the outer aspect of your tibia and fibula. As a muscle crosses over a joint, it plays a role in stabilizing and protecting that part of the joint. The Lateral or Fibular Collateral Ligament (LCL) runs intimately close by. If you have an issue with the LCL and sprain your lateral knee, the lateral hamstring muscles will be important in your Physical Therapy Sports Medicine rehabilitation.

Important anatomy to know for hamstring muscle strain recovery

There are two factors to consider when you are looking at optimal recovery and movement excellence: nerves and blood supply.

You cannot move well if your muscles are getting slow or delayed nerve input to your Hamstring muscles. This is where we will dive into key nerves that healthy hamstring muscles need so you can move well. We will go over how nerves that ARE IMPACTED when you have dysfunctional hamstring muscles.

The latter is important to understand as you may have symptoms that may think it is “normal” to live with. Everything is connected. If you nurture a healthy hamstring muscle group, you may be surprised at how other things begin to resolve. This is the difference between a Specialist Orthopedic Physical Therapist and a standard Physical Therapist.

In summary, muscles impact nerve health and nerves influence muscle health. Nerves stay healthy through the full range of mobility. The keyword is FULL. If you have tight hips, hamstrings, and knee joints, then your nerves can be healthier.

Okay, let us start with the basics.

Here is a list of your hamstring muscles and the nerve that allows them to move.

  • Semitendinosus muscle: Tibial nerve, L5-S2
  • Semimembranosus muscle: Tibial nerve, L5-S2
  • Biceps Femoris Long Head muscle: Tibial nerve, L5-S2
  • Biceps Femoris Short Head muscle: Common fibular nerve, L5-S2

As you notice 3 out of the 4 hamstring muscles are supplied by the Tibial nerve. The Tibial nerve is a collection of nerves that consist of spinal nerves that comes from the spinal segments between Lumbar vertebral segments of L5, S1, and S2.

Your Sciatic nerve includes your tibial nerve. If you have a history of sciatica, then your hamstrings are affected as a casual bystander. If you tight hamstrings that will not resolve, you may have an underlying sciatic nerve or spinal nerve L5-S2 dysfunction.

We have a common saying in that a nerve is only as healthy as the joint it surrounds. A source of spinal dysfunction is the inability to produce sufficient strength to stabilize your spinal segments. Instead of moving with a spine-sparing strategy, many tend to move with a spinal compression strategy.

Nerves are not fond of a quick timespan of compression overload.

Another important fact that impacts nerve health is your ability to move your spinal vertebrae within their healthy limits. If you lack this control, due to compensations or incomplete Physical Therapy from a history of spinal lower back pain, your spinal and sciatica nerve may be impacted.

Your body is not fond of having a joint move too much without control. The situation is similar to how noxious it is to be rocked around when on a small boat. You have no choice but to stay tensed and compressed.

This phenomenon of short and compression is your lower back and hamstring muscles being tight. You have to address the instability in order to get lasting relaxation of your hamstring muscles.

Blood supply.

When it comes to blood or vascular supply, you have to remember one artery. The important artery is called the Perforating arteries of the deep femoral artery.

Just think of the artery as the nutrient supply for your nerve to do its job. No food, no work.

One important concept in this recovery and blood supply connection is that your venous system work in tandem with your lymphatic system. Your lymphatic system and venous system collect inflammatory and toxic waste so tissues stay healthy. So you can stay healthy.

If you do not have good heart health and local good blood flow, then you cannot heal completely from a waste removal perspective.

As a quick summary, you need good spinal and pelvis control to have healthy nerves. Nerves need a full blood supply to function. Healthy nerves will allow happy hamstring movements.

Miscellaneous nerves to be aware of.

There is an important nerve called the pudendal nerve. In rare cases, you get sensory symptoms of numbness or diminished sensation to the region where you wipe yourself after using the bathroom. This is called saddle paresthesia.

The reason for this presentation is that the pudendal nerve runs below the sacrotuberous ligament. When there is tension from the Hamstring muscles, sacroiliac joint, or surrounding tissues that impact the sacrotuberous ligament, it can tick off the pudendal nerve. All nerves hate to be compressed.

The pudendal nerve comes from S2-4 and further spreads to the inferior rectus, perineal and dorsal branches.

As we are going down the rabbit hole of muscles’ impact on neighboring sensory nerves, you will learn about the Saphenous nerve and it’s a connection to the Pes Anserine muscle group, which includes the Semitendinosus muscle. The Saphenous nerve allows us to feel the inner knee and parts of the calves region. This is a common tissue that mimics inner knee pain, medial meniscus injury, and overlooked when dealing with an Anterior Cruciate Ligament (ACL) problem.

On the other side is the Common Fibular Nerve. The nerve runs behind the location of where the lateral hamstrings muscle insert.

Movement Analysis.

There is one concept to understand. If a muscle crosses over a joint, it has an impact on that joint. That muscle will help to move, stabilize, and/or support that joint.

We will repeat this idea, because it is that important. If your muscle spans over a joint, it impacts that joint in a positive or negative manner. There is actually nothing that is considered negative when it comes to the human body. This is the philosophy of a Primal and Holistic model of an Orthopedic Sports Medicine Specialist.

What tightness, discomfort, or recurrent symptoms you may feel as negative, is calculated and done to protect you from hurting yourself more. Allow us to elaborate.

All of your hamstring muscles, except your Biceps Femoris Short Head muscle, span from your sacrum and its sacroiliac joint to your posterior hip joint. The bottom portion of the Semimembranosus and Semitendinosus muscle spans to connect to the back and inner side of the tibia bone of your knee joint. Your Biceps Femoris muscles connect to the other side of the knee joint. As we talk about the outer or lateral side of your knee, the Biceps Femoris muscles blend towards your fibula bone too.

As we go step-by-step for our first muscle, you will see how the hamstring muscles, collectively help to extend the hip joint and flex the knee. Any muscle that is on the backside of your body tends to bring your limb away from the backside of your body. This is called extension.

If you can picture this movement pattern, your hamstrings play a role in supporting and bringing your legs behind your body as you walk. This is called a trailing stride pattern.


As the hamstring muscles are located on the backside (posterior) of your sacrum via the Sacrotuberous ligament, it has a crucial role in supporting and ensuring you have excellent control of your pelvis. Your pelvis is the foundation of all movement. Your sacroiliac joint is the fancy medical terminology and is the base of support of your spine.

If you imagine yourself paddleboarding. If you have good control of the paddleboard and your legs, you will not fall into the water. Your limbs connect to the board to allow you to get power and pull yourself forward with the paddle oars. This is how you walk with your legs.

There are many times that if the muscle has no foundation to work from, the muscle has a compensatory compression or “tight” muscle feeling. This is why we chose to write about the Hamstring muscle as our first muscle to dissect and elaborate for your understanding.

An inefficient spine and muscle system will cause your hamstring muscle to be stiff. This is one reason why you cannot get any good gains from continued and daily stretching of your hamstrings. Your body will tighten your hamstrings and its connection to the Sacrotuberous ligament to help you from harming your lumbopelvis region.

We did hint that your Semimembranosus and Semitendonsus muscles connect to your inner or medial tibia bone. This allows the two muscles to have a small force that helps to turn the knee joint inwards. To help you to visualize, but not 100% consistent, is that this muscle helps you to bring your heel towards your buttocks, with your toes pointing inwards.

If you or performing an athletic movement like cutting or pivoting, and your knee collapses inwards, your hamstrings help to control this motion.

You can guess that the Biceps Femoris muscles help to perform the same tasks in stabilizing and prevent too much collapse of your knee to the outside.

Your hamstring muscles help to collectively prevent your knee from spraining your Anterior Cruciate Ligament (ACL). Since your hamstring muscles are located on the posterior side of your knee, it helps to pull the tibia bone back with every contraction. You can think of that your tibia shift back when you bend your knee.

If you are unaware, your ACL becomes stressed when the tibia is excessively shifted forward or anteriorly.

Pain Pattern.

The idea of trigger points is useful in understanding what muscles are playing a role in your pain. When a muscle is in a state of dysfunction, there is a common occurrence of your muscle to develop predictable tension spots. The research is still inconclusive of the physiological reasons so we will not spend time writing about it.

You can see from the picture the “x” within the Hamstring muscles. There is no need to elaborate if your pain is located within your hamstring muscle region.

hamstring anatomy

The important thing to notice is how there are red shaded area that are located to your upper calves region. What this means is that if you are noticing upper calves pain or tension, you could have a silent hamstring muscle dysfunction. You can have no hamstring pain.

If you went ahead and pressed on any of the “X” spots in the picture, you know if the hamstring muscle is your problem if it brings on the familiar pain to your upper calves. This is importance if you have been chasing your pain with calves emphasis treatment.

This is good to know to be objective in treatment effectiveness. We re-press on the “X” region after any joint, neurology, or visceral manipulation to see if we made an impact on reducing a stress trigger to the hamstring muscles. An outside variable could influence a muscle to act up, or a muscle could be impacting a joint. The riddle is what is the chicken-or-the-egg dilemma. Trigger point can be good at answering this for you.

Orthopedic Muscle Injury Grading system.

An Orthopedist or Sports Medicine practitioner may have told you that you have a Grade 1, 2, or 3 muscle tear or injury to your hamstring muscles. Most of the time, this is a general grading system that does not factor in the specific hamstring muscles.

The grading system allows a clear and easy communication from a provider like us to another provider.

A grade 1 muscle strain takes days for the strain to heal. There is no disruption to the muscle or tendon unit. You do not feel weakness upon contraction of your hamstring muscles. There is soreness upon touching or palpation. You may notice some swelling at the location of injury.

Icing and rest is effective during this time. Modalities of muscle electrical stimulation like a Marc Pro device, kinesio-taping or Sports taping, generalized active movement (not stretching), and cryotherapy are effective treatment options. We incorporate red light and near infrared light therapy with the JOOVV device to speed up the recovery. We would like to add core strengthening and feet mobility work are appropriate options due to the connection to the pelvis and shin bone, respectively.

A grade 2 muscle muscle strain takes 2-3 weeks to recover. There tend to be mild to moderate disruption of the muscle and/or tendon fibers. You will weakness in bending your knee and engagement of your hamstring muscles. You can isolate which group of muscles by rotating your foot inwards or outwards upon bending your knee.


The treatment of choice for this is a gradual smart therapeutic exercise protocol that emphasize your hamstrings. Your start out with concentric or isometric based exercises. You need to always incorporate spinal and pelvis stabilization exercises at this time. In the later phase, eccentric type of exercises are important, as we explain later in this article.

A trained Sports Medicine Physical Therapist will have the understanding to address the soft tissue side effects of having a muscle strain. There are different technique but a trained expert will be able to address the soft tissue component in a few visits.

A grade 3 strain lasts for months as the disruption to the muscle or tendon is more severe. There is more pain and weakness involved. You can no pain if the disruption is a complete tear of your hamstring muscle. You will notice a bundle or big bump at your mid posterior thigh.

The evidence shows that you can rehabilitate this injury conservatively if your level of activity is mild. If you are in the position or desire more athletic activities, then surgery may be a valid option.

Holistic and Functional Perspective.

If you have been following us for some time now, you know that we believe there is no muscle that work in isolation. Your body works together and needs to be rehabilitated and trained together.

Your muscles are connected and join forces through the fascial system. In the work of Thomas Myers, the hamstring muscles are part of two system.

The Superficial back line and Spiral line. The hamstring muscles connect to the superficial muscles that you see when you look at someone’s back view. You can see the the hamstring muscles can be tensed and tight as a result of dysfunction to any muscle or fascial structures connected to your spine, head, scalp, calves, and arch of your feet.

If you are laying on your stomach and you are picking up your arms and legs up, like you are flying, your hamstring muscles play a role in solidifying this pattern. You can perform this movement more efficiently if your hamstrings are engaged. This is part of the superficial back line.

If you are swimming, running, or doing a pulling motion, the spiral line helps to connect your hamstrings to your opposite arm to extend. If you have a disruption to your right hamstrings, you may notice a weakness to your left shoulder pulling motion.

Your body moves in patterns.

As we are focusing on contraction type of movements, your muscles stretch and control movements. When you bend forward to touch your toes or perform a kicking motion, your hamstring muscles need to perform a powerful lengthening movement called eccentric. This is harder on your muscle fibers and the neurologic software to perform, but is crucial to address to have healthy muscles.

Eccentric type of training will result in micro-tears in the muscle fibers. When you have chronic muscle injury, the muscle fibers are healed in a manner that is disorganized. It is strategic to cause micro-inflammation in a smart manner to re-tear to RE-pair in an organized manner.

Our advice and experience has shown more effective rehabilitation when you address any tissue restriction, joint and/or muscles of the entire pattern.

Common joints that can impact performance of the hamstring muscles are included in the list below.

  • Subtalar joint (heel joint)
  • Calves muscle pliability and neuromuscular control
  • Sacroiliac joint dysfunction
  • Lumbar spine dysfunction (usually a combination of joint stiffness and muscle performance – reflexive, power, and endurance capacity)
  • Visual-ocular reflexes
  • Cervical and cranium joint and muscle dysfunction (usually a combination of joint stiffness and muscle performance – mainly reflexive and strength capacity).
  • Vestibular system dysfunction.
  • Middle thoracic muscle and joint dysfunction that does not allow proper reciprocate arm movement.
  • 1st toe extension restriction resulting in medial hamstring dysfunction.
  • Pelvic floor dysfunction as these muscles bridge the performance of your pelvis to your hips.

As you can see, that this is a comprehensive list that does not include the nervous system.

If you can recollect that your hamstring muscles run in the same path as your sciatic nerve. Your sciatic nerve splits to your tibial nerve, which impacts many of the muscles to your back leg and foot. If you have a nerve dysfunction, your nearby muscles commonly becomes adhere to that nerve.

Your sciatic nerve can be gently adhere to your hamstring muscles. Your hamstring tightness tend to have a sciatic nerve movement dysfunction. If you get the nerve to move well, the hamstring muscle will relax better. The exercise for this situation is call neuro-mobilization exercises.


We hope you picked up some anatomy and rehab knowledge nuggets that will help you to move and feel better.

If you have any hamstring muscle trouble, make sure you contact a Physical Therapy clinic that specialized in Sports Medicine.

Photo credit: Thanks https://traineracademy.org/ for use of the cover photo of the runner.  Please click on the link to learn more about Trainer Academy.