Weak at the knees

This article has the purpose of describing the simple anatomy of those muscles and components that are most commonly the cause of knee joint pain in the gym population.

 

There are two major bones involved, one being the femur the other being the tibia. Yes, the lower leg has two bones (tibia and fibula) but only the tibia is of relevance to this dissertation. Then there is the patella or kneecap, which is an unusual bone in that it is classified as a sesamoid bone (root of the word being sesame seed indicating the likeness to this seed). A sesamoid bone is a bone with a tendon. The purpose of the patella is to increase the leverage pull of the quadriceps upon their insertion into the tibia. Interestingly where the quadriceps tendon is above the patella it is known as the quadriceps tendon, but below the patella it is known as the patella ligament. Let us begin describing the muscles involved in the quadriceps.

 

Okay, so the smarter of you know that the word quad means to have four parts. So therefore quadriceps means this muscle has four parts. The quadriceps is also the biggest muscle in the human body, just ask Tom Plantz.

 

So let us now name the four parts of the Quadriceps: Rectus femoris, Vastus lateralis, Vastus intermedialis, Vastus medialis.

 

Now, know these more intimately.

 

Rectus femoris: This is the only part of the quadriceps that crosses above the hip joint. It arises from the ilium in two parts. It joins commonly with the vastus components into the tibial tuberosity by way of, at this point, the patella tendon.

 

Vastus Lateralis: Originates at the upper area of the femur and joins in towards the knee with the quadriceps tendon.

 

Vastas Intermedialis: Arises about the upper 2/3 of the femur and joins down with the quadriceps tendon. But guess what Holmes you won't see it because it is covered by the other quadriceps muscles.

 

Vastus Medialis: Yes, the "teardrop muscle" on your inner knee area. This arises from the medial lip of the linea aspera on your femur and also from the tendon of adductor magnus. It inserts into the aponeurosis of vastus intermedialis, the tendon of rectus femoris and, most important to us in this article, the lowest fibres lie nearly horizontal inserting directly into the medial border of the patella.

 

Now all these muscles have a nerve supply from the femoral nerve which originated at the lumbar levels of L3 and L4.

 

The basic action of the quadriceps is that of knee extension.The attachment of rectus femoris to the pelvic girdle (via the ilium) has an effect of stabilizing the hip joint while also flexing the hip.

 

 

As the wording suggests, the patellofemoral joint is the articulation, or joint, between the femur and patella. The best way for you to understand their relationship is to investigate the patella surfaces. The undersurface of the patella is divided by a vertical ridge, creating a large lateral surface and a smaller medial condyle. For the purposes of knee pain you need to know that the lateral surface glides around but contacts with the lateral condyle or surface of the femur, in all ranges of knee flexion. Now this is fine when both the femur and patella surfaces are covered with shiny smooth cartilage, but do this often enough with a slight disturbance to the perfect relationship and you can begin to irritate and even wear away the cartilage. Welcome to knee pain whenever you bend, flex or squat on that knee.

 

So it is the stability of the patella in particular that dominates the advent of knee pain in most athletes.

 

 

The patella, because it lives in the patella tendon/ligament, is very mobile. Especially in the side-to-side motion. Just put your own leg out in front of you, relax, grab your patella between your fingers and wobble it from side to side. See what I mean.

 

The patella tendon/ligament is vertical, but the pull of the quadriceps is oblique. So when the quads pull on the patella it moves laterally. There are three factors that restrict lateral patella dislocation by the quadriceps pull. One is the bony lateral prominence of the femoral condyle, another is the tension in a band known as the medial patella retinaculum, but the main one is the lowest fibres of the vastus medialis which insert onto the medial border of the patella medially when the quads contract. This is the most important concept to understand. When a knee joint swells these fibres may waste significantly and knee pain will result.

 

For weight trainers you can see that if your rectus femoris, vastus lateralis and vastus intermedialis grow out of proportion to your vastus medialis then this will disrupt the relationship, and knee pain may result from the patella beginning to rub irritatingly upon the lateral femoral condyle.

 

So how do you fix this? Well, one way is to make sure that you balance your leg training with exercises that emphasize vastus medialis, these are for example, leg press or hack squats with your toes pointed out. Another exercise commonly used in rehabilitation of people with knee pain is leg extensions with five degrees of movement. That is fully extend your knees then let go five degrees only and contract to full extension again. This is a very small movement but emphasizes this area perfectly.

 

There are many diagnostic methods a good sport physiotherapist will use, such as the McConnell critical tests, which can determine other specific interventions you might need. It may save you years of pain and have you back at full training quicker then you may have dreamed. So prevention is the key, but once pain begins see a physiotherapist with extensive sports experience for a definitive diagnosis and treatment plan to get you on track faster. It sure beats the hell out of surgery many years later, that may be necessary if left untreated.