Understanding Patellofemoral Pain

Patellofemoral pain (PFP) refers to a condition in which pain is felt in the anterior (front) aspect of the knee and is a common complaint of horse riders. Sufferers usually describe a pain in the front of their knee that can be hard to localise and that often comes on with activities that involve flexion (bending) of the knee, such as squatting, walking up stairs, sitting for prolonged periods or riding. It is more common in females than males, and is particularly common in adolescent females. An x-ray or scan will often come up clear, is there is usually no structural damage causing the pain. This condition is typically caused by biomechanical factors, causing a less than optimum functioning of the knee, leading to irritation to the undersurface of the patella (kneecap).

The cause of this condition is often debated and there is no definitive answer. Certainly it can differ between individuals and a thorough assessment of the entire person, not just the knee, is warranted. 

 A - normal alignment B - unlevel pelvis, increased hip internal rotation and adduction, with inwardly rotating femur  

A - normal alignment
B - unlevel pelvis, increased hip internal rotation and adduction, with inwardly rotating femur
 

  • Recent research suggests that in individuals with PFP there is evidence of an increase in hip internal rotation and/or adduction, creating internal rotation of the femur (Witvrouw et al 2013). This internal rotation of the femur can cause rubbing and irritation to the under surface of the patella. Weakness in the muscles that externally rotate and abduct (move away from the body) the hip, in particular the gluteus medius, is common. This is often in conjunction with tightness of the adductors (inner thigh muscles) and medial hamstrings. This posture is most obvious when the patient performs a functional task, such as squatting or running.
  • Imbalances in the quadriceps muscle group, particularly a weakness in the inside muscle (VMO), leading to a maltracking issue of the patella. This used to be the most commonly believed cause of the condition, however there have been recent questions as to whether this is true in sufferers of PFP (Pattyn et al 2013). Further research is needed to investigate this further. In my clinical experience I do often see that patients with PFP have an obvious wasting of the VMO. Whether it is a cause or a symptom of the condition can be hard to tell! 
  • Inwards rotation of the tibia (shin bone), typically caused by over-pronation of the foot. However as mentioned above this posture is also seen in those with increased hip internal rotation and adduction. Over-pronation describes a foot that collapses inwards (think of someone who is 'flat-footed'). I have had patients with PFP whose pain has improved with the use of an orthotic, but I rarely find that it is the only cause and that looking above the knee at the hip and pelvis is also very important.

So how does this relate to riding and why is it common in riders?

Think about when you first started riding, or if you come back to riding after a significant break. Where did you hurt the most? In most people it will be the inner thigh muscles, the adductors. We use these muscles probably more in riding than in most other activities. This is why we are so sore when we first start riding, we haven’t worked these muscles as much before! So as riders we already tend to have increased activity in these muscles, often more so than in our hip abductor muscles. The hip abductors are very important in stabilising the pelvis, and a weakness in them gives rise to a drop in the pelvis when we weight-bear on one leg, leading to that inwardly rotated hip and femur position.

Think also about the more beginner and less stable rider. They tend to grip with their thighs for balance, rather than having a nice open hip position with legs that just drape the horse. When we grip with the thighs we really work our hip adductors and internal rotators. 

In jumping when we come up into 2-point position, we lose upper thigh contact with the saddle and instead have more calf contact with the horse to give our aids. Ideally we should have the heels down and toes slightly out, which comes from slightly externally rotating at the hip. This is the ideal posture, however novice riders or those who have a weakness in the pelvis and core, tend to grip with the knees when jumping, adducting and internally rotating at the hips. The typical posture of these riders is to have a lower leg that shots back and comes off the horse, heels raised and their body collapsing over the horses neck. It is in riders with these weaknesses that we more often see PFP.

 

  © Olgaru79 | Dreamstime.com

© Olgaru79 | Dreamstime.com

Rider demonstrating poor lower leg posture by gripping exclusively with the lower thigh and knee and using his adductor and medial hamstring muscles to keep him on the horse. His lower leg has come too far back and his heels have lifted considerably. Overall this posture just looks like hard work and he is setting himself up for knee pain!

It's also worth looking at your saddle and ensuring that it is the right fit for you. We are often more concerned about having a saddle that fits our horse, but we need to make sure that the saddle also fits us, particularly in relation to the knee rolls.

If you have symptoms of PFP, I recommend that you see a health professional experienced in diagnosing the condition. As mentioned above, there can be various causes of the condition and it's important to identify the causative factors so that they can be appropriately addressed.

References

Pattyn E, Verdonk P, Steyaert A, et al Muscle functional MRI to evaluate quadriceps dysfunction in patellofemoral pain. Med Sci Sports Exerc 2013; 45: 1023–9.

Witvrouw E, Callaghan M, Stefanik M, et al Patellofemoral pain: consensus statement from the 3rd International Patellofemoral Pain Research Retreat held in Vancouver, September 2013. Br J Sports Med 2014; 48: 411-414.