Patellofemoral pain (PFP) describes pain around, behind or under the knee. Essentially a vague term to describe non-specific knee pain that doesn’t fit into other categories. Often presenting with vague symptoms and mechanisms of injury, it can be difficult to manage. There is plenty of debate in the literature regarding whether the key issue remains with the alignment of the patella (the train) or the intercondylar groove (the tracks). I will summarise current evidence to show that for a typically vague presentation such as this, it is necessary to consider both the train and the tracks and many other influences. In this blog, I will quickly cover factors influencing the pain response:
- Global influencing factors
- Structures involved
- Causes of weakness
- Altered pain response
Of course, there will be a big focus on what you can do to help manage PFP:
- Goals of rehabilitation
- Passive interventions
- Priorities of rehabilitation
- Timing of VMO activation?
- Relevant statistics
Global influencing factors
The following factors can all contribute independently or combined to create increased stress on the patellofemoral joint:
- Loss of trunk and pelvic control
- Hip muscle function deficits
- Increased hip adduction and internal rotation
- Quadriceps weakness and delayed VMO activation
- Increased foot mobility
It is entirely possible that multiple structures may be effected simultaneously. Most likely however, one pathology would have developed first, leading to altered biomechanics and avoidance patterns increasing pressure on other structures over time. The most likely pain drivers are:
- Articular cartilage
- Fat pad
- PFJ Stress (Farrokhi, 2011)
- Increase in lateral patellofemoral joint stress from patella maltracking
Causes of weakness
PFP is typically provoked during everyday activities, leading people to adopt avoidance behaviours on a regular basis in an attempt to offload the knee and reduce pain and discomfort. These fear avoidance behaviours can result in:
- Altered biomechanics
- Reduced knee flexion during
Altered pain response
Some studies have shown increased sensitisation in and around the injured area. This results in a heightened pain response due to a reduced pain threshold.
Goals of rehabilitation
- Reduce pain (short, medium, long term)
- Improve function (medium, long term)
To optimise biomechanics by improving mobility, stability, flexibility and movement control.
- Taping (can provide short term pain relief)
- Bracing when taping is inappropriate (eg. skin irritation)
- Foot orthoses (based on assessment findings such as excessive dynamic pronation)
Priorities of active rehabilitation
Combined hip and knee exercises best represent functional activities and have been shown to achieve greater results that isolated quadriceps exercises alone. Proximal rehabilitation programs (focusing on gluts and core control) have been shown to demonstrate greater improvements in the short and medium term. Combining proximal and quadriceps exercises also results in greater benefits based on performance and subjective measures. This suggests that more exercise can lead to better results! The following progressions are encouraged:
- Closed kinetic chain to represent functional activities
- Hip control is a key driver, therefore combine quadriceps strengthening with hip stability
- Open kinetic chain can be used if necessary to target specific strength deficits and movements
- 3-4 exercises for home based programs
- 5-6+ exercises for gym or supervised programs
- Pattern re-training, running re-training (especially if these activities have been provocative in the past)
- Stretching of calves and hamstrings can be included
- Core and distal (calf) strengthening exercises should be included
- Load management
- Activity modification
- Patient expectations (goal based)
- Encourage active participation in their rehabilitation
Timing of VMO activation
Timing of VMO activation can be delayed in people with PFP. However, timing can be impaired in non-symptomatic people too! Essentially, a delayed activation is normal, but a large delay can result in dysfunction. Also, atrophy of VMO has been found in persons with PFP, however it is unclear whether this is due to PFP or causes PFP. MRI studies have shown similar atrophy of other quadriceps muscles, therefore global strengthening is encouraged.
Ultimately, we as therapists serve to guide rehabilitation through providing appropriate and specific exercises and education to help facilitate recovery and return to life.
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