The Anatomy of the Knee

The knee joint, what I refer to as the modern day joint of evolution.  Why?  I'll share with you later, but for now I'd like to introduce you to the complexity of the knee.  By now it's probably not uncommon to you that joints are a detailed manufactured natural construction.  Therefore the complexity of the knee joint won't surprise you if you've read my previous two blogs.

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The knee is consists of three bones, the femur (thigh bone), the tibia (shin bone) and the fibula (located on the lateral aspect of the tibia).  The femur is the proximal bone and connects onto the superior pole of the patella forming the patellofemoral joint.  Then there is the distal bone, in this case the tibia, which latches onto the inferior pole of the patella to form the tibiofemoral joint.

These joints are supported by a diverse list of ligaments.  At the top of the knee we have a lateral and medial groove in which the patella ligament inserts.  What does medial and lateral mean?  Well medial is the inside of the knee, defined as close to the mid-line and lateral is the outside of the knee simply put as away from the mid-line.  So of each bone of the knee we have a ligament.  These are medically known as the lateral and medial femoral condyles attaching the femur and patella whilst contributing to the support of the structure.

We also have the lateral and medial tibial condyles.  These again aid support and connect the tibia bone to the patella.  The knee bone allows movements such as extension, flexion, and slight medial and lateral rotation.  The knee by basic design theoretically should only allow for extension and flexion however the aid of ligaments enables additional movements such as medial and lateral rotation.  

There is also a medial and lateral collateral ligament.  What's the difference?  Well these ligaments connect the femur and tibia bones.  The medial collateral ligament is long and strap like because this is the impact side and therefore the medial aspect of the knee needs to be longer and stronger essentially to aid protection of collisions of the lateral aspect of the knee.  The lateral collateral ligament is short and cord like and provides a smaller amount of support in comparison.

We can refer to ligaments on the medial aspect of the knee as intracapsular ligaments and ligaments on the lateral surface of the knee as extracapsular ligaments.  In addition, we have two more intracapsular ligaments, these are located internally.  The patella bone is a sesamoid bone and provides the knee with protection and increases the efficiency of quadriceps movement, enabling more of a pull action.  I'd like you to hold this thought.  Imagine the removal of the patella bone from the knee joint.  What you would encounter is a web of ligaments, tendons, and menisci all overlapping one another .  Lost you?  Let me break it down for you...

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Within the internal aspects of our knee structure we have a anterior cruciate ligament and posterior cruciate ligament.  Otherwise put as ACL and PCL.  Our ACL ligament travels along the anterior surface of our tibia diagonally in an upwards direction and connects onto the posterior inferior surface of our femur.  This ligament stops the leg shunting forwards avoiding hyperflexion of the knee.  In comparison to our PCL ligament which runs along the posterior superior surface of our tibia in a diagonal upwards direction and latches on to the anterior inferior surface of our femur.  This ligament also aids support preventing the leg shunting backwards avoiding as you can probably guess, hyperextension of the knee.

There are two key tendons of the knee joint, the easiest tendon of the two to palpate is the infra patellar tendon, medically referred to as the tibial tuberosity.  The other tendon is palpated on the supra surface of the patella attaching the quadriceps muscles to the patella.

Finally we have fibrocartilage also referred to as meniscus which enables many functions of the knee.  These functions can be abbreviated as SLAPS: 

S - Stability (support to the knee)
L - Lubrication (enabling movement)
A - Aids rotation (Additional movements such as medial & lateral rotation)
P - Protection (Hyaline cartilage)
S - Shock absorber (aids running, jumping, lifting etc...)

 

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The menisci can be located medially and laterally on the internal aspects of the knee.  It is a type of cartilage that allows for load distribution and reduces friction during movement.  This allows for a greater mechanical effect and spread the load of the bodies weight.

I referred to the knee joint as a modern day evolving joint.  This is because when we are born, we are born without this joint and without bones in our knees.  These bones only develop through areas of friction and in effect alter the size of the patella.  In effect my knee cap is of a different structural integrity to yours.  The knee is a sesamoid bone which means it's a bone that develops in the tendons of the knee.  To be more specific, through the course of child development as we learn to walk for the first time, we produce enormous amounts of tension on our tendons around are evolving knee cap.  Thus when we fall over we land on our hands and knees producing more tension among these tendons.  When we are encouraged to walk by our parents and loved ones, our patella bone is in the process of evolving within the environment, consisting of many of the above factors that aid the speed of the process.