Which muscle group is more important in patellofemoral pain (PFP) – the quadriceps (quads) or the gluteals (glutes)? This article aims to uncover the latest research behind the age-old debate with actionable steps that you, as a clinician, can immediately take to improve your patient’s outcomes.
What is PFP and why should we care?
PFP is defined as peri- or retro-patellar pain, exacerbated by activities that increase compressive loads on the patellofemoral joint (PFJ), such as running, navigating stairs and squatting (1). PFP is prevalent in 22.7% of the population and is significantly more common in women. It is also associated with the onset of knee osteoarthritis (2). Due to this, improving PFP is important not just to assist in its short-term management, but to provide better long-term outcomes as well.
Anatomy of the Patellofemoral Joint
As the name suggests, the patellofemoral joint (PFJ) is the joint between the patella and the femur. The stress placed on the PFJ is determined by its joint reaction force (based on knee joint angle and muscular tension) divided by its contact area. The greater the contact area between the surfaces of the femur and patella, the less stress is placed on the tissues (3).
This explains how joint forces vary depending on the degree of knee flexion and whether the movement is closed or open chain. To put this into context, open chain exercises between 30-90 degrees of knee flexion minimize PFJ stress (3). This is where activity modification plays an important role in the rehabilitation of PFP.
Risk factors for PFP
It is well documented that several non-modifiable risk factors can lead to PFP. As with all pain, we cannot ignore potential psychosocial contributions. In addition to this, there are several biomechanical factors referenced throughout the literature that play a part in the presence or absence of PFP (3) .
Causes of increased PFJ stress include:
- Decreased patellofemoral contact area as a result of patella morphology and shallow trochlear grooves (5)
- Patellar maltracking (only present in 50% of PFP cases) (3)
- Increased hip adduction and internal rotation moments (6)
While the effect of anatomical structures is important to acknowledge, the real benefit of rehabilitation is the impact that we, as clinicians, can have on the modifiable risk factors. A large component of this involves strengthening the supporting musculature to minimise the stress placed on the PFJ (4).
The direct attachment of the quads to the patella via the quadriceps tendon demonstrates how the quads can impact PFJ forces. As a result of this, numerous studies have been done which test whether quad strengthening programs are beneficial to outcome measures in both the short and long-term. In isolation, the overwhelming majority of research suggests that quad strengthening exercises improve PFP, not just in pain levels but functional activities as well (4,7,8,9).
Initially, most research for PFP centred around quad strengthening. However more recently, the addition of glute strengthening has become popularized, and for good reason. A growing body of research cites alterations in proximal mechanics, appearing in women with PFP. This is often demonstrated by excessive hip adduction and/or internal rotation (9). The glutes directly oppose these forces through their abduction and external rotation moments, and have therefore been associated with improving pain and function in those with PFP (4,10).
People with PFP have been shown to exhibit a combination of:
- Decreased hip abductor and external rotation strength (not just concentrically, but eccentrically and isometrically as well) (11,12)
- Gluteus maximus weakness when compared to healthy counterparts (13)
What About Strengthening Other Muscles?
While the quads and glutes are the key muscles with direct impacts on PFJ forces, they aren’t the only muscles that demonstrate improvements in PFP outcomes.
- Lower leg / foot muscles – Greater tibial internal rotation has also been observed in people with PFP, indicating a need for further research on the influence of distal muscles such as the posterior tibialis and intrinsic foot musculature (9).
- Anteromedial or posterolateral muscles – One study showed no difference between anteromedial (hip flexor and adductor) or posterolateral (hip extensor and abductor) muscle strengthening to improve pain and function in women with PFP (14). The exercises used in this study can be found in the video below.
- Hip flexors – A 4-week intervention found that in addition to hip abductors and external rotators, hip flexor strengthening was also related to successful PFP rehabilitation. This was identified by a >15% improvement in pain and activity, and was found to be superior to isolated quad strengthening (15).
Can you Improve PFP Without Strength Training?
Strength training is a great “bang for your buck” exercise modality with additional benefits in stability and proprioception. However, positive outcomes have been shown without strength training in the following studies:
- Cueing valgus – While the consensus is that quad and glute strengthening does not change valgus forces (19), an intervention that focused on instructing athletes to avoid valgus proved that this could decrease pain, improve strength and increase functional performance (12).
- Training stability – Abnormal neuromuscular control, particularly of the hips and core, is evident in most cases of PFP (4). This includes an increased medial-lateral displacement in the centre of pressure, expressing a lack of stability at the knee (11). Two other studies revealed that lateral core endurance (10), and trunk / hip control and strength exercises, provided better outcomes than quad strengthening exercises alone (16).
- Performing stretching – Another intervention concluded that stretching, with or without stability based exercises, displayed greater outcomes for PFP patients when compared to no intervention (8).
What About Prevention of PFP?
As a result of there being primarily retrospective studies on PFP, we are often left wondering whether any of the above mentioned deficiencies are causes or symptoms (4). Unfortunately, we don’t yet have these answers. Until we know more, it can’t hurt to strengthen the glutes and the quads, with the potential upside of reducing the chances of PFP.
Quads or Glutes for PFP Rehabilitation?
A 2018 systematic review confirmed that adding hip strengthening exercises to knee strengthening programs provide positive results for those with PFP (17). However, hip strengthening alone has been proven to reduce pain and improve function in people with PFP (4,8), and so has quadriceps strengthening alone (8).
This indicates that perhaps the best option is to not pick between the two, and instead perform both quad AND glute strengthening!
Which Exercises are Best?
There isn’t enough research detailing which exact exercises are best. However, based on the research, a combination of the following may be beneficial in the treatment of PFP.
- Hip abduction and external rotation exercises (primarily for gluteus medius) (18)
- Eccentric and isometric contractions (for gluteus medius) (4)
- Knee extension exercises (8)
- Knee extension and hip flexion exercises (15)
- Hip extension exercises (for gluteus maximus) (4)
- Open chain exercises between 30-90 degrees of knee flexion (3)
- Cue to avoid valgus (12)
- Strengthening other hip and knee movements and subsequent musculature (14)
- Lower limb stability exercises (16)
- Core strengthening (10)
- Lower limb stretching (16)
If you want to learn more about when and how to train the glutes and quads for PFP rehab, be sure to check out Claire Patella’s Masterclass where she dives deep on this topic. She delves into open vs closed chain knee exercises, when to use glute med vs glute max strengthening, and squat progressions and regressions for someone with PFP.
Keep in mind the main goal should be to ensure you are utilizing exercise therapy and education in an attempt to help your patients with PFP perform the physical activities they enjoy.