What is Patellofemoral Pain Syndrome (PFPS)?
Patellofemoral pain syndrome is commonly known as “runners knee” due to its high prevalence in the running population. It is most common in adolescent females, but can be seen with any age or gender.
Runners knee involves anterior knee pain with certain activities, the most common of those are; squatting, running, and walking up and down stairs. The pain usually comes on over time, getting worse if the aggravating activities are continued – although occasionally it can be caused by an acute, traumatic incident. The pain is usually described as sharp during the activity, which may then develop into an ache.
What causes PFPS?
Patellofemoral pain syndrome is caused by malalignment of the patella (knee cap). The patella naturally sits in a depression of the femur, called the trochlear groove, and moves down the groove as the knee bends. In patients with PFPS, the patella does not run in the groove smoothly, but instead can be pulled to the side, rotated, or tilted, depending on the imbalances of forces at the knee joint or in the kinetic chain.
The shift in the patella causes anterior knee pain. These are several reasons for the pain, as the patella is pulled laterally, it rubs against the side of the trochlear groove, and although cartilage does not have any pain receptors, it can irritate the subchondral bone that lays underneath the articular surface. Another source of pain may be the ligaments and other tissues surrounding the knee cap being stressed as the patella is repetitively being pulled out of its natural position.
When the forces from the lateral structures are more than the forces from the medial structures, the patella is pulled laterally
PFPS can be caused by a number of different things, but overall, the forces of the knee are altered which changes the knee mechanics. Some of the causes can be due to the body’s natural variance – such as a shallow trochlear groove, or a small bony spur – in these cases, surgical intervention may be required. Other force discrepancies may be able to be altered, these include lateral muscle and iliotibial band tightness, hip weakness, and over-pronation at the feet. Think of it as a tug-of-war between the lateral and medial structures, in normal circumstances, the medial side will give an initial tug to get it in line and then the forces on each side are balanced. In PFPS, the lateral structures win and succeed in pulling the knee cap out of alignment.
Short term management
If you find yourself with anterior knee pain of an unknown origin, the first thing to do is to rest from the aggravating activities and allow the pain to settle down. It is important to find the source of the problem in order to fix it as rest is not a permanent solution; it can become a recurring injury if the underlying cause is not explored. During this rest time, some short term solutions can be; ice, taping, and bracing. Though not permanent solutions, these strategies can provide some pain relief.
Make sure to go to a qualified practitioner such as those at Absolute to get properly assessed. Once you know the source of the problem, there are several strategies to fix it. It could be as simple as getting some orthotics fitted, and should involve specific strengthening exercises.
Exercises for Patellofemoral Pain Syndrome
When thinking about which exercises we can do to help decrease the chance of getting PFPS, or to help to manage the symptoms, we need to think of making the forces acting on the patella equal.
Vastus Medialis Oblique (VMO) Strengthening
The VMO is a part of the vastus medialis muscle near the knee cap where the muscle fibres run obliquely – the vastus medialis is part of the quadriceps muscle group. The role of the VMO is to control the tracking of the patella so that it stays aligned. It may be a long-term weakness, but mis-firing of the VMO can also come following a traumatic knee injury, where the muscle tends to ‘switch off’ and can lead to patella maltracking and future knee pain.
One of the best exercises to initially get this muscle firing again is a straight leg raise. Lying flat on your back with your legs out straight, turn your toes out slightly to focus on the vastus medialis, tense your quad and in a controlled movement lift your heel off the ground until your leg is at about 45 degrees.
To progress the quadriceps strength, we can start to do the step down exercise. Step downs are great for developing hip and knee control, as well as strengthening the quad muscle. Make sure your hips stay aligned throughout this exercise. If you feel or see your hip dropping, don’t go down quite so far.
Hip Strengthening
The gluteus medius muscle is a pelvic stabiliser, and a hip abductor and external rotator. Weakness of this muscle can cause internal rotation of the femur, and a tilt of the knee cap as a consequence. This can develop into PFPS due to the tilted knee cap rubbing against the trochlear groove.
A great exercise to help to strengthen the hips is a banded crab walk. For this exercise, place a looped theraband around the ankles and walk sideways in a partial squat position, making sure to keep your knees straight and stay strong at the hips. This is a great exercise to incorporate into your warm-up, or to do between sets.
If you find yourself troubled with anterior knee pain during exercise or in everyday life, you may be suffering from patellofemoral pain syndrome. The most important thing to do is get it properly assessed and diagnosed. Once that is done, we can figure out the individualised management plan for you! Come on down to Absolute Health & Performance in Melbourne CBD for all of your injury needs.
Written by Physiotherapist Kristin Cameron
References
- Peterson W., Ellermann A., Gosele-Koppenburg A., Best R., Rembitzki I.V., Bruggemann G.P., & Liebau C. (2014). Patellofemoral pain syndrome. Knee Surg Sports Traumatol Arthrosc. 22: 2264.
- Collado H. & Fredericson M. (2010). Patellofemoral Pain Syndrome. Clinics in Sports Medicine. 29; 379-398.
- Thomee R., Augustsson J., Karlsson J. (1999). Patellofemoral Pain Syndrome – A review of current issues. Sports Medicine. 4; 245-252.
