Patellofemoral pain (PFP) is a common condition of the knee that is characterized by the pain behind and around the patella. It is present in 7 – 28% of population and is slightly more common in women. As different researchers define the condition differently in their research, so do the clinicians. This results in difference in the assessment, diagnosis and management of the problem. PFP is not a common diagnosis among clinicians, especially in Nepal.
Due to lack of international consensus on various aspects of PFP, experts from all over the world met last year in Manchester UK to come to a consensus on PFP. The result is published in British Journal of Sports Medicine (BJSM) last week in this paper. In this post, I will summarize the key points from this consensus statement.
When is knee pain = patellofemoral pain?
“When the knee pain is behind or around the patella” AND “when pain aggravates by activities that load the patella during weight bearing knee flexion such as squatting, stair ambulation, jogging, running, hopping or jumping”.
Additional criteria (but not essential) are: presence of crepitus, tenderness on the facets of patella, mild effusion, pain on sitting, pain while getting up from sitting and extending the knee when sitting.
Does PFP have any synonym?
Yes – patellofemoral pain syndrome, chondromalacia patella, runner’s knee and anterior knee pain/ syndrome.
How can we diagnose PFP?
By clinical examination. The best test is the squatting test which should elicit anterior knee pain (present on 80% people with PFP). Tenderness around the patella is present in 71 – 75% people with PFP.
Test which has less diagnostic value but routinely performed are the Patellar grinding test e.g., Clark’s test, range of motion assessment and presence of effusion.
What are the Risk factors for PFP and patellofemoral osteoarthritis (PFOA)?
PFP can progress to PFOA. The factors that are strongly associated with PFP are:
1. Abnormal morphology of femoral surfaces of patellofemoral joint and frontal plane knee alignment.
2. Weakness of quadriceps.
3. Hip abductor muscle weakness.
4. Hip extensor and external rotator weakness may contribute to PFP, but requires further (longitudinal) research to verify.
5. Abnormal knee biomechanics is observed during gait in people with PFP. More research is required in this area.
6. Anterior cruciate ligament reconstruction increases the risk of PFP.
Does infrapatellar fat pad have any role in PFP?
Yes, may be. Infrapatellar fat is highly innervated structure which is extra synovial but intra-capsular. Individuals with PFP or PFOA have larger/ enlarged fat pad compared to those who do not have PFP.
What should we assess in people with PFP?
Patient reported outcome measures are the subjective reports by the patients, thus these measurements minimize the observer bias and does not require a clinician to be expert. Also, the answer would be same even if different clinicians assess the patients. Recommended measurements are:
1. Core measurements: Pain, Function, Global assessment
2. Optional measurements: Quality of life and physical activity
You will need to wait until the next blog post to know what are these recommended core measurements, or find another article by the same authors in BJSM.
So, how can you treat this condition?
First, it is important to differentiate between tibiofemoral OA. Treatments that may work are:
1. Combined treatment including exercise therapy, education and taping
2. Patellofemoral bracing
PFP is diagnosed by pain behind or around the patella and that increases by knee bending activities in weight bearing. Best test to diagnose this condition is the squatting test, followed by tenderness around the patella. Abnormal femoral articular component morphology, anterior cruciate ligament reconstruction surgeries, Quadriceps weakness and hip abductor muscle weakness may cause PFP. It is imperative to measure pain, function and global assessment in PFP. This problem may be treated by exercise, taping, education and patellofemoral bracing.
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