All posts by bearhanger

Student and professional athlete attending Griffith University on the Gold Coast campus studying a Bachelor of Exercise Science.

The Knee: Anatomy and Function Part 3 – Muscles

Here is a short and sweet list of all the muscles that produce movement of the knee joint. Of course their origin and insertion (WARNING: lots of fancy big words), specific function if necessary and easy-to-understand pictures of location are also included 🙂

The knee is able to produce three different kinds of movements, these movements being flexion, extension and rotation. Flexion is pulling you leg towards your buttocks, extension is pushing your leg forward, assisting during kicking, and helps lock and unlock the knee joint which  is important for knee stability. If you ever wanted strong, bad-ass knees these are the primary muscles that need to be strengthened and conditioned for whatever physical activity you plan to impose on them.

Muscles that produce extension (all located on the anterior side of the body)

*Quadriceps: Consists of the 4 following muscles:

-Rectus femoris – The prime mover and also a flexor of the hip. Origin: Anterior-inferior iliac spine of ilum. Insertion: Top of patella and patellar ligament.

-Vastus lateralis: Origin: Lateral lip/side of linea aspera. Insertion: Lateral half of upper patella + Patella ligament + Anterior tibial tuberosity

-Vastus medialis: Medial side of the linea aspera + internal condyloid ridge. Insertion: Medial half of upper patella and patellar ligament

-Vastus intermedius (underneath rectus femoris): Origin: Two thirds of the upper anterior surface of femur. Insertion: Upper patella and patellar ligament

Muscle that produce flexion

*The hamstring group consists of 3 different muscles. The semitendinosus and semimembranosus is on the medial side, while the biceps femoris is on the lateral side. They can also assist hip extension.

-Semitendinosus: Origin: Ischial tuberosity. Insertion: Anterior medial tibial surface. Also does internal rotation of knee.

-Semimembranosus: Same origin and insertion as semitendinosus, but lies deeper. Also does internal rotation of the knee.

-Biceps femori – Crosses over medially to laterally on posterior side. Long head origin: Ischial Tuberosity. Short head origin: lower half of linea aspera. Insertion of both: Head of fibula. Also does external rotation of the knee.

*Pes anserinus – The collective name of the muscles:
Sartorius, gracilis and semitendinosus (mate, both Pes and Hammy group? This guy has a lot of friends). The group also for some not fully clear to me has been called the “Goose Foot”, but I am guessing it has something to with the anatomical look when they all inserts at the same place.

-Gracilis – Origin: Pubis crest. Insertion: Antertior medial surface of tibia.

-Sartorius – Origin: Anterior-superior spine of ilium. Insertion. Anterior medial surface of tibia (note that as many as 4 flexor inserts here)

*Popliteus – lies on the back of the knee. Origin: Lateral condyle of femur. Insertion: On proximal third of posterior tibia. Also does internal rotation.

*Gastrocnemius, the “calf” muscle – Origin: Posterior Surface of the medial and lateral femoral condyles. Insertion: The calcaneus (this is at the ankle) through the Achilles tendon.

Flexors that are not commonly included:

*Plantaris – Origin: Lateral supracondylar ridge of femur. Insertion: Calcaneus, medial and deep to gastrocnemius.

*Tensor fascia latae – the muscle itself does not fully cross the knee but it crosses the iliotibial band does can minorly act upon the knee (IT band can become really tight so important to stretch. The muscle is more related to hip function but it is a key to maintain strong knees so I decided to throw it in here.

Quick overview of the muscles which act in rotation, which consist of no new muscles that we have not yet discussed (yey!)

Internal/medial rotation:
Popliteus, Semiteninosus and Semimembranosus

Exertnal/lateral rotation
Biceps femoris and Sartorius

That is it for knee anatomy! Next up for knees is getting into prevention of injuries and strengthening. Finally something that about knees that is going to be an easy read ey?

How Do We Breath? The Simple Science Behind Breathing

How do we breathe?

The process of breathing in and out 

Breathing in at rest is an active process (costs energy) – the diaphragm contracts (moving it downwards) and the external intercostal muscles help pull the ribs up and outwards. The cerebral cortex (this is some brain stuff for anti-nervous system people) facilitates this process. There is also accessory muscles (helpers) working, being the sternocleidomastoid (just think neck), scalenes group (neck) and pectoralis minor (chest) – these are way more active during heavy breathing.

Breathing out at rest is a almost entirely a passive process. This is due to muscles relaxing (for example the diaphragm, moving it upwards), elastic recoil of the lung alveoli (this is where gas exchange of oxygen, CO2 etc occurs between the lungs and the rest of the body) and stretched elastic tissues in the chest wall that pushes the air out.

Breathing in is basically like throwing a ball downtoward the ground, and it bouncing right back up again.You are controlling the throw, but you cannot control the fact that it wants to bounce up again (physics stuff).

During heavy breathing energy is used during both situations. During active expiration the internal intercostals (except interchondral part) will pull the ribs down and the abdominal muscles will help the diaphragm to be pushed superiorly (reducing the cavity volume and thereby force air out).

A little physics

During inspiration what we call the intrapulmonary pressure (pressure inside the lungs) is reduced by 1 compared t the standard atmospheric pressure at 760 mm Hg, this because of the increase in volume. During expiration the pressure is increased by 1 compared to the standard, because of the decrease of volume. This is explain by Boyle’s Law, which is C1*V1=C2*V2, but we will get more into all the physics stuff later and further explain the pressures inside the lung while doing that as well.

Fun Fact: It is also impossible to commit suicide through trying to stop breathing (please do not attempt this though) as when oxygen levels drops, the CNS will shut down and you will pass out, this is followed by it making you start breathing again automatically which is stimulated by the breathing centers – located in the brain stem.

– Bear

The Knee: Anatomy and Function Part 2 – Ligaments and Joint Capsule

Continuing where we left of in the last post! Hope the pictures are of some help for part 2, this is a tough one! WARNING: Big words ahead!

*Menisci – Fibrocartilaginous structures that has a crescent half moon shape. Their shape has also given them the alternative name of semilunar (halfmoon) cartilages. The functions of the menisci are mainly shock absorption (landing after a jump) and helps accomodate movement of the bones of the joint . You have both a medial and lateral meniscus that both attach at the central intercondylar region together with the ACL (on anterior side) and PCL (on posterior side).  The medial meniscus is attached medially to the tibial/medial collateral ligament and to the capsule of the joint of the knee,  while the lateral meniscus is attached to neither. This causes the lateral meniscus to become more mobile (and sadly more easy to tear).

*Transverse ligaments – Serves to connect the two menisci.

*Medial/tibial collateral ligament – proximal attachment of medial epicondyle of femur, distal attachment medially on tibia – more specifically a little bit above the tendonous insertion attachment points of the following muscles: Sartorius, gracilis and semitendinosus.

*Lateral/fibular collateral ligament – Proximal attachment point at lateral epicondyla of femur, distal attachment point on lateral head of fibula.

*Cruciate Ligaments – Fun fact: called cruciate because they cross over each other. The PCL crosses over the ACL from the medial wall of the intercondylar fossa (of the femur) to attach on the posterior side of the knee and the ACL crosses under the PCL from the lateral wall of the femurs intercondylar fossa to attach more on the anterior side of the knee (both attaches at the intercondylar region of the tibia)

*ACL – Prevents tibia from sliding forward.

*PCL – Prevents tibia from sliding backwards.

*Patella ligament – continuous of the femoris/quadriceps tendon which attaches at the proximal side of the patella, and becomes the tibial tuberosity at its distal side (point that sticks out of the upper anterior side of the tibia). Just behind and a little distal to the ligament we also have a small piece of fat called the infrapatellar fat pad which separates the ligament and the synovial membrane of the joint capsule.

Now that is mostly it for the ligaments and all that stuff, now onto the joint capsule which is a bit more tricky to explain. The joint surfaces (or articulate surfaces to just to make it a bit more fancy) is covered by hyaline cartilage.

*Joint capsule of the knee fibrous membrane medial and anterior support – Fibrous joint capsule of the knee. The fibrous membrane is reinforced by ligaments, namely the MCL (medially), medial meniscus (one of two reasons why it is not very mobile) and the patella ligament (anteriorly) where it blends with the quadriceps muscle fibers of the vastus medialis and vastus lateralis at the margins of the patella. This strengthens the capsule anteriorly.

*Joint capsule of the knee fibrous membrane lateral support – On the lateral side of the knee the fibrous membrane is not reinforced by its respective collateral ligament as it is separated from the joint capsule by the fibular bursa which is located underneath the LCL. However, the capsule is supported laterally by the iliotibial tract which is located more medially towards the patellar ligament and runs downward alongside it.

*Joint capsule of the knee fibrous membrane posterior support – Posteriorly the fibrous capsule is supported by the oblique popliteal ligament, which is an extension from the semimembranosus tendon which attaches onto the tibia.

*Joint capsule synovial membrane – The synovial membrane lines the fibrous membrane which attaches to the margins of the articulate surfaces and the outer aspects of the menisci (the membrane does not enclose the cruciate membrane as they are not actually contained within the articular cavity.

*Synovial membrane bursas – The synovial membrane folds in various places to form bursa (gaps). These are the following: Suprapatella bursa (above patellar ligament behind patellar/quadriceps femoral tendon), Subpopliteal recess (lies between lateral meniscus and popliteus tendon), infrapatellar fat pad (see patellar ligament), deep and superficial infrapatella bursa (inside and outside of the patellar tendon respectivelly) prepatella bursa (subcutaneous at patella, which just means under the skin).

Next up is muscles, saved the best for last! Part 3 here we come!

The Knee: Anatomy and Function Part 1 – Knee Joint Fundamentals

Knees are one the more troublesome joints of the body especially for athletes or elderly whose knee has been subject to a lot of wear and tear. Having personally torn an ACL (anterior cruciate ligament) and meniscus, the knee is probably my least favorite joint and I catch myself saying ****ing knees a bit too much… However this has also motivated me to learn a lot more about how the knees work, and the reason why this is the first of many musculoskeletal system anatomy articles.

The knee is classified as a hinge joint which are formed between two or more bones and is limited to movement along one axis (flexion or extension). Fun fact: The knee is the largest and most complex synovial joint of the body (hinge is a common synovial joint class). However because of the complexity of the knee joint it may also be referred to as a “modified” hinge, bicondylar as well as biaxial joint. It might a good idea to check with your lecturer if you are at university.

The joint articulates between the femur and the tibia as well as the femur and patella. Flexion of the knee pulls the tibia posteriorly and extension pushes it anteriorly. Now this is where the complexity of the knee comes in, as during flexion the knee may rotate both laterally and medially, and during extension (standing position) the femur will rotate the knee medially to lock the knee into position (you can see this very well if you hyperextend your knee, but no over-hyperextension experiments please as that is painful). To unlock the knee the femur will rotate it laterally.

Now that the basics of the knee joint itself has been covered let us take a closer look at the landmarks of the knee and their functions:

*Femoral condyles at the articulate surfaces (posterior side of knee)- One medial, one lateral. The femoral condyles have an intercondylar fossa that separates them, which is home to the proximal attachment points of the anterior and posterior cruciate ligaments (ACL and PCL)

*Epicondyles – upper portion of the femoral condyles. These are home to the proximal attachment of the lateral and medial collateral (NOTE: NOT CRUCIATE) ligaments (LCL and MCL). The MCL (medial) is of course on the medial condyle 🙂 These bad boy ligaments are also known as fibular and tibial according which side they are on. The lateral collateral is for example on the same side as the fibula as the fibula is the most lateral of the fibula and tibia (yay, easypiecy).

*Tibial Plateu – Superior proximal surface of the tibia. Has a couple tibial condyles (medial and lateral) at the articulate surfaces. These condyles also has an intercondylar region between them which is where the cartilage of the menisci as well as the ACL and PCL.

*Intercondylar eminence – The point thing that sticks out of the superior surface of the tibia. The point thing also has two other pointy things, which are the lateral and medial intercondylar tubercle.

Continued in Part 2…

Nutrition for special populations: Children and Adolescence

What you see on TV or on the internet talking about what we are supposed to eat, how much of each blablablablablabla, is not always right, as it is mostly directed towards your average bloke down the street (if you live in a regular street of course. If you live in a mansion or luxury villa without neighbors, feel free to switch spots with me). For example the nutrient needs of an adult average bloke is different than that of a child and teenager/adolescent that is still growing, which is the topic of this post.

Defining children and adolescent

It is safe to say that the little troublemakers (children aged 0-12ish ) do not usually know a lot about what  they consume, but are experts on whether they like it or not. This means that it is also safe to say that parental influence is probably the key factor of what a kid eats, for example packing them full of lollies to make them shut the **** up. This influence of course diminishes with age but remains a key factor, as it is the parent that can choose what to stock the fridge with, as well as most of the time choose what a meal will contain.

Once adolescence (13-18/20ish) is reached the  individual starts developing a closer relationship to the food consumed (food literacy), and the connection between diet, exercise and body image starts to form. Hormones fluctuate, stuff just gets crazy.

The importance of developing food literacy

During the growing years as biological maturity is pursued, there is a higher chance of suffering bone fractures. Growth spurts weaken the bones as the bone density will not often have time to catch up. Nutrition can play a key role preventing this. Imagine a newborn kid, the skeleton only holds about 30g of calcium, and by the age of 20, it will hold about 1500 grams. Peak bone mass and density is not achieved until the end of puberty, this is why calcium is extremely important, especially during puberty as calcium plays a superduper major role in bone growth.

Managing energy imbalance issues in young folks is complex. Constant negative energy balance can result in the following: short stature, puberty and menstrual irregularities, and poor bone health. Did you know that the mechanically inefficient movement of children causes them to expend more energy doing it? So yes kids spend a higher percentage of their energy just walking than adults do. This is one of the reasons negative energy imbalance in some children occurs – as some may logically think children will need less food as they are not fully grown yet, but that is of course not true, as ATP is also used in the growth process.

Nutrient Requirements

Now there is not a lot of evidence on the timing recommendations of the different nutrients for young folks so this post will be limited to the RDIs, and a short paragraph for young elite athletes will be included at the end.

Protein (first, cause you know, protein)
The grams per bodyweight (note bodyweight of the kid, not the parent) of protein required for a youngster is actually higher than the average bloke.  Now these requirements are usually reached by just eating healthy, but here is a table for you anyways with RDIs (athletes would of course have a higher need).

Age 1-3 4-8 9-13 14-18
All 1.08g/kg 0.91g/kg
Boys 0.94g/kg 0.99g/kg
Girls 0.87g/kg 0.77g/kg

Your average young folk (yes I said young folk mate) will not be competing in events that will deplete muscle glycogen, and this is little evidence that adolescent requirements should differ from adults. It is simply recommended to be adjusted to daily energy demands. Only things that are to worry about is pretty much dental caries, so stay away from the acidic candy kids!

One interesting thing about fats is that young athletes tend to utilize fats as the major fuel source during exercise, but there are still no RDIs about how much they should consume. However it is likely that that enough is consumed through a normal diet and typically it would not differ that of an adult.


Did you know children and adolescence have less effective thermoregulation and lower exercise tolerance? This is because developed sweat glands are not instantly given to you at birth, but you might have noticed them when they started firing during puberty. Two other reasons are the increased energy expenditure from motor movements as previously mentioned, and because higher surface area-to-body mass ratio they will tend to get hotter faster on warm days and lose heat faster on cold ones. So yes water is extremely important, always have water present and keep sipping (not excessive amount of course) across the day. Recent studies have actually shown that given matched fitness levels and hydration status, the capacity to deal with thermal loads and exercise tolerance in the heat are similar in children and adults (Instead of sweating for cooling, peripheral blood redistribution are relied upon to maintain thermal equilibrium). And in the case of the athlete, it is common knowledge that just a slight decrease in hydration will cause significant performance drops.

The key is to drink water before, during and immediately after. The guidelines (assuming that the exercise lasts about 30-70minutes) are: 150-200ml for children, 300-400ml for adolescent 45minutes before exercise. 75-100ml for children and 150-200ml for adolescent during. A liberal good amount as soon as possible after exercise for both.

Vitamins and Minerals

Now this is the most important part of the diet of young folks. There are high requirements for a good amount of specifically calcium, iron and zinc in these individuals diets. Here is why: Calcium – bone growth. Iron – mostly a problem in females (menses, loss of iron in blood), but training may also increase the loss of the mineral. Zinc – a deficiency of zinc may lead to  a delay of sexual maturity and slower bone growth.

Ergogenic aids (for athletes)
The thing about the use of sports supplements in young athletes is that it is mostly not tested and therefore simply not recommended. The athlete however may be vulnerable to the use of supplements because of: Performance pressure, pursuit of physical ideals or body image and impulsive behaviors caused by commercials and the availability of it (caffeinated energy drinks is a big one)

In the case of young elite athletes

Elite performance during a young age will not always coexist with optimal health, something that is more normal in some sports than others, as the athlete sometimes would wish to achieve a low bodyweight and compliment that with lean body mass. The want to achieve this often comes along with inadequate energy intake and building poor eating practices and habits. This often causes a delay in the maturation process. A good example of this is gymnasts and sports requiring a high level muscular endurance, which may end up having growth spurts after they have finished their career (however it unsure if their “if-not” height is reached) . An opposite example might a basketball player, as explosive short bursts and the constant striving for height may in fact support bone growth, but of course it also sets them at a higher risk for bone fractures.

– Bear