Patellofemoral Pain Syndrome (PFPS) is one of the most common and most challenging injuries a runner might face. What makes it challenging is it's complexity and sensitivity. It can be hard to pin down the exact cause and easy to aggravate. A difficult combination but hey, RunningPhysio likes a challenge!
PFPS is pain from the tissues within or surrounding the joint between the knee cap (patella) and the femur. The patella rests in a groove on the femur where it acts like a pulley to transmit the force of the quadriceps muscle onto the tibia via the patella tendon.
Picture from Gray's Anatomy (1918)
There is some debate as to what causes the pain in PFPS. One brave researcher, Scott Dye, who has done some excellent work in this field, experimented by having an arthroscopy probe moved around inside his knee while he was awake! He describes it in this paper. What he found was that while they were probing the underside of his patella he had no pain, but when they used it to probe his synovium, he had “excruciating” pain. The synovium is the membrane that surrounds a joint and in his case it was very sensitive to pressure. The underside of the patella is reportedly poorly innervated and so may not be a significant cause of pain. That said “chondromalacia” involves changes in the cartilage on the underside of the patella and usually causes pain, so nothing is set in stone! There are also a range of other tissues around the patella including the lateral retinaculum, plica, bursa and infra- patella fat pad that are all capable of producing pain and make this a complex area.
My thoughts on this are, that despite its complexity and multiple potential causes of pain the approach is as follows;
- Settle symptoms and inflammation by reducing load on the patella and surrounding tissues
- Identify the cause of problem
- Rehab to deal with the cause
- Gradually “reload” the area and return to normal running
It's a pattern we've seen in nearly every article on RunnngPhysio offload, rehab, reload.
First though, we need to understand the symptoms of PFPS and what activities have a high PF (Patellofemoral) load.
Symptoms of PFPS
Pain is typically felt under or around the patella, not down the outside of the leg into ITB or lower down in the joint line of the knee. It is usually aggravated by activities with high PF load – squatting, lunging, kneeling, going down stairs, running, especially downhill. It is also often aggravated by prolonged periods of flexion, especially sitting long periods. This is sometimes called movie goers knee or movie goers sign. Usually there is no true locking or giving way of the knee and minimal swelling. The knee may feel stiff but usually has full range of movement. There may also be clicking or grinding (physios call this crepitus).
Reducing symptoms of PFPS
The aim here is to reduce load by modifying or reducing aggravating movements. For some, if their pain is severe, this may mean stopping running and avoiding kneeling, squatting etc for at least a few days until things settle. For many it will mean PACING these activities – doing them in small manageable amounts. This applies particularly with running – if you do continue to run try and stick to what is pain free rather than continually aggravating it by running in pain. Remember this is a temporary measure to reduce symptoms and you will aim to return to normal as soon as symptoms allow. You can try modifying speed, distance, frequency of running, stride length, footwear etc etc or use tape (detailed below) to offload the knee, often there are ways in which you can continue running but ideally you need to find a way to do this pain free. If you can't you probably need to rest, settle symptoms and rehab before hitting the road again.
Work and lifestyle also play a big part, it's not just running. If for work you kneel all day (as carpenters, plumbers, tilers etc may well do) then you need to consider using gel knee pads and take regular breaks. If you're kneeling playing with small children could you sit on a pillow instead? If you're up and down stairs all day, is there a lift or could you plan to make fewer trips for a while? I know it's a nuisance but unless load is reduced a little it can be hard to change symptoms.
Anti-inflammatories or pain relief might also help. Ice is also a good option to reduce pain and swelling. If it's been niggling a while it's also worth giving heat a try, especially if ice hasn't worked.
The thing I find most effective is McConnell taping. I use it for a lot of knees, including my own and find it reduces symptoms in the majority of cases;
Research has suggested this type of taping reduces PF load. It can work not only to reduce symptoms but also to be used when running to decrease load and therefore reduce or prevent pain.
You'll see there is some overlap with ITBS in this post. PFPS and ITBS are similar, in both cases an area of the knee is being overloaded and you need to find strategies to reduce load. Some treatments work very well for both, like the tape detailed above and gently mobilising the knee cap (although this should be avoided if you have any history of patella instability);
Identifying the cause of PFPS
Now the tricky bit…you've reduced load and settled your symptoms, many people just get back out running again. Sometimes this is fine, often though, unless the cause is addressed, the symptoms return.
- Training error – ah, that old chestnut! We all know it, too much, too soon, too little rest. PFPS can be caused by an increase in distance, speed or intensity of training. Hill work is a common cause as descending hills has a high patellofemoral load. The solution is a graded return to running, avoiding hill or speed workouts intially before gradually reintroducing them.
- Muscle weakness – there are 2 main groups to consider quads and glutes (mainly Gluteus Medius but also Gluteus Maximus). Details on glutes rehab are here and quads rehab will be detailed in part 2 of this blog. An important consideration here is how to strengthen without increase in PF load. You can use pain as a general guide – just strengthening in a pain free zone – but there is a more scientific way and I'll explain that in the next part of this blog.
- Poor movement control and timing of muscle contraction – poor single leg balance and control of single knee dip are common in PFPS. Often people will adduct the hip (moving towards the other leg) or rotate at the knee placing greater load on the patellofemoral joint. Details on assessing and rehab of control of movement are here. Another issue with PFPS is timing of muscle contraction. A number of EMG studies have shown changes in the speed at which muscles contract in people with PFPS. They have shown Gluteus Medius contracting later in PFPS and the muscles on the inside of the knee (known as VMO) contracting later than the outside (VML). These changes in timings are in milliseconds but the theory is that the knee is lacking adequate support during this time and with thousands on movements a day this adds up. I'm not aware of many studies showing the effect of treatment on timing of contraction, but it would make sense that working on control of movement could improve this. One treatment that has shown changes to timing of contraction is taping. It has been suggested it improves the timing of VMO contraction as well as reducing pain.
- Reduced flexibility – the movement of the knee cap is effected by tissues that attach to it (quads, ITB) and around the knee area (hamstring and calf muscles). Tightness in the ITB is thought to pull the patella slightly laterally (towards the outside of the knee) leading to increase load on the joint. The quadriceps attach to the patella directly and so any tightness in this muscle will effect the way the patella moves and potentially increase the load upon it. Hamstring and calf tightness can increase patella load indirectly by the way they affect knee movement. I like this seated hamstring stretch (although the lady is either tiny or sat on the biggest chair ever!) and this “ultimate calf stretch“. Quads and ITB can be stretched using my old favourite, the “sofa stretch” (below). Gradually work into this stretch and make sure you knee on a pillow or something soft as the stretch itself can increase load on the patella.
The foam roller can also be very useful to reduce muscle tightness around the knee. Rolling the quads, ITB, hamstring and the calf can all help.
- Biomechanics – this is, as you might imagine, a complex area in PFPS. Broadly you can think of it as changes either in the knee itself or below in the leg and ankle or above in the thigh and hip. Or a mixture! The shape and position of the patella and how it sits relative to the femur and tibia can affect load on the joint. Sometimes this is referred to as the “Q-angle“. Some of these factors can't really be changed, some can. Overpronation of the foot can be related to PFPS, especially if associated with hip adduction. This is easier to change than Q-angle. Patella position can be altered by taping but only temporarily. To some degree you have to work within your biomechanics. Assessment from a physiotherapist or podiatrist may help you identify biomechanical factors and address them where possible. There is a huge variety in how people are shaped. Many have biomechanical changes with no pain, if your tissues can tolerate the extra load that this places on them, it may not be an issue. Orthotics have shown mixed results in treatment of PFPS – Neptune et al. 2000 compared use of orthotics with strengthening of the medial quads on a 3D model. They concluded that medial quads strengthening yielded more consistent results than orthotics in reducing PF load during running. It should be noted though that this was a 3D model examining treatment effects not real people actually running! Collins et al. 2009 compared orthotics with physiotherapy and found “no significant differences” although when orthotics were added to physiotherapy it didn't achieve better results than physiotherapy alone.
- Running form – how we run is closely linked to muscle strength, movement control and biomechanics. Improving these areas may help running form but it can also help to have your running gait analysed to look for changes that may be related to your pain. Foot strike, stride length, overpronation, supination and hip adduction all have the potential to affect PF load. Variables in these are all also totally normal. It can be hard to determine, what, if anything to change and how to do it. Excellent work from @runblogger has looked into foot strike and running form in more detail, one conclusion he made is that increasing step rate and reducing stride length may reduce load on the knee. I would echo this thought. Reducing stride length can be a relatively easy way to reduce load on the knee during running. You may find by doing this you are able to run with less pain, or even pain free. Personally I've found this very useful in reducing knee pain if I get it when running.
More in part 2!
Including details of the principles of managing PFPS + quads and glutes rehab
And remember our usual advice with injury…..if in doubt get it checked out! Always seeks medical advice if you are struggling to manage an injury.