Patellofemoral knee pain syndrome one of the most common sources of knee pain.
5 takeaways on patellofemoral knee pain
- Patellofemoral syndrome is the most common knee pain that we see in the clinic and can be a source of pain for a wide range of age groups; from adolescents right up to the oldest of children – those in their 70’s and beyond.
- The patella or kneecap helps reduce the effort required by the knee to lift weight.
- The back of the patella tis covered with a thick layer of cartilage and has lots of nerve fibres associated with it.
- Patellofemoral pain is usually due to lack of strength and control of the muscles around the knee.
- Patellofemoral pain is successfully treated with exercise, activity modification and strapping.
What is patellofemoral knee pain syndrome ?
Quite simply this is pain behind the kneecap . It is seen more commonly in females than males and is probably one of the most common knee issues that is seen in adolescents and children. It does present in older populations as well especially with development of osteoarthritis in later life.
The cause of Patellofemoral knee pain, ( PFK from now on ), can be broadly categorised into the following groups:
- Instability related patellofemoral knee pain.
- Compressive type patellofemoral knee pain.
- Patellofemoral pain related to trauma.
- Patellofemoral pain following surgery.
What is the Patella and what does it do ?
The patella or kneecap as its more commonly known is sesamoid bone which means it is formed and contained within the tendon attaching the quads to the tibia (lower leg bone).
The under surface of the patella is a V shape and has some of the thickest cartilage in the body and this allows smooth movement on the femur which has a U-shaped cartilage covered groove when we bend and straighten the knee.
When your knee is straight there is no contact between the patella and the femur and that is why you can move it from left to right quite easily with your fingers, especially when the thigh muscles are relaxed.
As you bend the knee the patella starts to slide into the femoral groove at about 20 degrees and stays in the groove until 70-80 degrees flexion. The maximum contact between the patella and the femur occurs in the 20 – 80 degree range which is exactly the range the knee is in when we go up and down stairs or squatting to a chair.
however it also has a large nerve supply which means it has the potential to be a source of pain if it gets injured or overloaded.
The kneecap/ patella reduces the forces that are put through the joint when we squat to sit, go up and down stairs, walk or run as well as decreasing the amount of effort we need to straighten the knee by about 33-50%.
So it helps us be much more efficient in the movement of our leg and reduces the amount of energy we need to squat, go from sitting to standing and going up or down stairs.
Here is how it works to make the knee more efficient.
Anatomy of the Patella
It’s a sesamoid bone which means it is formed and contained within the tendon attaching the quads to the tibia (lower leg bone).
The under surface of the patella is a V shape and has some of the thickest cartilage in the body and this allows smooth movement on the femur which has a U-shaped cartilage covered groove when we bend and straighten the knee.
It also helps the knee tolerate the forces that are put through the joint when we squat to sit, go up and down stairs, walk or run.
This animation below gives you a good idea of the structure and function of the patella.
When your knee is straight there is no contact between the patella and the femur and that is why you can move it from left to right quite easily with your fingers, especially when the thigh muscles are relaxed.
As you bend the knee the patella starts to slide into the femoral groove at about 20 degrees and stays in the groove until 70-80 degrees flexion.
So the maximum contact between the patella and the femur occurs in the 20 – 80 degree range which is exactly the range the knee is in when we go up and down stairs or squatting to a chair.
Patellofemoral knee pain can be divided into 4 categories;
-
Instability related patellofemoral knee pain:
This type of knee pain is most common in younger age groups and has a higher incidence in females. It can be caused by the following:
-
Muscle weakness and control and patellofemoral joint
It is usually caused by weakness of the muscles surrounding the knee and hip that then leads to altered movements when we walk, run, climb or descend stairs and squat.
As well as getting the muscles stronger it is important to retrain the movements that cause you the most pain such as squatting or stepping down. It may also be important to look at improving running style or walking technique if these are problem activities.These symptoms may also be associated with movement issues at the foot.
-
Bony stabilising factors and patellofemoral joint
It can also be related to skeletal maturity with the patella running in a shallow trochlea which provides minimal help with stability.
-
Compressive type patellofemoral knee pain:
Especially common in age groups over 40 and is more related to the outer edge of the patella being squashed against the cartilage of the long thigh bone , (femur). This is usually associated with tightness of the muscles around the knee as well as some hip related weakness and can respond to hands on physiotherapy.
-
Post surgery patellofemoral pain:
Not a common problem but if someone has had knee surgery and has not been able to straighten the knee fully this can cause irritation of the knee cap due to sustained compressive forces placed upon it. Similar in its treatment to the compressive type knee pain.
-
Traumatic patellofemoral pain:
Thankfully we don’t see a lot of this but any direct blow to the knee cap with the knee in a flexed position can create irritation to the cartilage on the back of the knee cap.
What is the best treatment for anterior or patellofemoral pain ?
In our next blog we go in depth about about the different causes of patellofemoral pain and our top tips to get rid of this condition and what treatment may suit you.
.If you have any problems with your knee feel free to book in to see one of our team to get you back on track.
Cheers
Dave
