Key Points
- Sedentary females with one-sided PFPS showed muscle weakness of the hip extensors, lateral rotators, abductors, and flexors.
- Those with PFPS in both knees had weakness in all six hip muscle groups.
- Hip strength may need to be addressed to improve pain and function in this population.
Pain in the front of the knee. It could be PFPS!
Having pain in the front of the knee is common, and is usually harmless. Many conditions may cause pain in the front of the knee and one such condition is called Patellofemoral Pain Syndrome (PFPS). It is commonly felt in the front of the knee, or aggravated by activities such as climbing up or down the stairs, kneeling, or squatting. It often presents as a gradual onset of poorly defined pain and may persist for years, if not treated well.
This pain can happen due to many reasons, but let’s first understand the relevant structures of the knee that can contribute to PFPS.
Our knee joint functions as a hinge. The knee is inclusive of 3 key bone structures, the Femur (thigh bone), Patella (kneecap), and Tibia (shin bone), enclosed within a capsule. When we straighten and bend our knees, the patella glides smoothly over the Femur within the knee capsule to allow movement without pain.
The muscle structures in our legs and hips play a part in the proper hinging of our knee joints as well. Simply put, there are muscle groups on the front, back, and sides of our thigh that act out a delicate balance in the stability of our knees.
The knee joint
Now, if the muscles in our legs are imbalanced, it will change the angle at which our kneecap glides over our thigh bone, resulting in the unequal distribution of pressure when we bend or straighten our knees. This awry weight distribution contributes to the pain you may be feeling when you walk, climb the stairs, or squat.
How does the hip affect the pain in my knee?
A common misconception with PFPS is that your knee pain is due to a problem with your knee joint. But in fact, the strength of your hips may be the cause of your knee pain instead.
With poor hip control, the resulting position of your knee might look like its buckling inwards. Knee buckling can be attributed to excessive hip adductor (inner thigh) strength and internal rotation of the femur or thigh bone, which consequently results in the glide of our kneecaps at awkward angles. This is a possible factor in the cause of knee pain in PFPS.
Why do sedentary people experience pain in the front of the knee?
PFPS is a common source of anterior knee pain, especially among females, whether athletic or sedentary. It represents nearly 20-40% of the knee pain found in individuals. This study aims to compare the hip strength between sedentary females with and without PFPS to study the observation made that hip weakness may be a factor in causing PFPS. Sedentary females with PFPS on one or both knees were recruited for this study together with a control group of sedentary females without PFPS to do a comparison.
The hypothesis is that females with PFPS on one side of the knee will present specific weaknesses of that injured limb compared to their uninjured limb and the group without PFPS. Meanwhile, females with PFPS on both knees would present overall hip weakness when compared to the group without PFPS.
What does the science tell us about pain in the front of the knee?
| Control group (no PFPS) | Unilateral PFPS (one knee) | Bilateral PFPS (both knees) |
| Participants had similar hip strength on both sides | Hip abductors (outer thigh) on affected side were weaker compared to unaffected side | No significant difference in strength on both sides for all 6 hip muscles |
| Strength deficit (15-20%) on affected side for muscle groups: hip abductor, lateral rotators, hip flexors, and hip extensors, compared to control group | All 6 muscle groups were weaker compared to control group | |
| Participants reported pain doing daily activities that required single-leg squats and stair climbing |
This study demonstrates that with participants who had PFPS in one knee, the strength of their hip muscles in the affected leg were much weaker compared to their unaffected side. Similarly with participants who had PFPS on both knees, their hip strength was found to be weaker when compared to participants without PFPS.
How does this knowledge inform our lifestyle? What happens now?
Now that you’re informed of the possible cause of the pain in your knee, what can you do about it?
It doesn’t have to be complicated, nor do you need to commit yourself to a new lifestyle. It can be as simple as setting aside 10 minutes a day to clock in some squats or step ups, or getting in more steps a day. Exercises focused on strengthening the hips and knees have been proven to help manage pain better than knee exercises alone. It is also beneficial in improving pain and function of the knee in the long term.
What type of exercises are helpful for pain in the front of the knee? Where do I start?
With so many exercises out there, it can be confusing to know which exercises you should focus on to improve your knee function. Muscle strengthening and functional exercises are a good place to start! However, always remember that the exercises you engage in should not cause you more pain. A slight discomfort is fine. Also, it is important to gradually load your knee joint. Doing too much, too soon might not be a good idea as well!
How can exercises help the pain in the knee?
Think of it this way, the muscle on the inner side of your thighs is stronger than that of the outer side, causing your knee to collapse inwards. So we want to strengthen these muscles on the outer side to balance it and prevent your knees from collapsing when you do functional activities such as climbing the stairs.
These exercises work on hip strengthening to improve pain and function in the knee, as weak hip musculature can be a contributing factor to PFPS.
Unsure of what to do? Contact us to speak to our Physiotherapist who will be able to ascertain the source of pain and have it addressed early!
Ref:
Magalhães, E., Fukuda, T., Sacramento, S., Forgas, A., Cohen, M., & Abdalla, R. (2010). A Comparison of Hip Strength Between Sedentary Females With and Without Patellofemoral Pain Syndrome. Journal Of Orthopaedic & Sports Physical Therapy, 40(10), 641-647. https://doi.org/10.2519/jospt.2010.3120
DISCLAIMER: These advise and exercises should not replace the need for a consultation with a Physiotherapist especially if your condition doesn’t improve. Therapeutic exercise should be carefully selected to suit your condition.
