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Patellofemoral pain syndrome (PFPS)

Patellofemoral pain syndrome (PFPS) is also known as runner’s knee or jumper’s knee. This medical condition causes pain under or around the kneecap (patella). PFPS can occur in one or both knees. It affects both children and adults.

 

CASE STUDY REFLECTION BLOG POST.

The purpose of this blog was to assist one of our graduates to fully reflect on a client that they had seen throughout a week. This blog also forms part of information and training that we distribute to students, Graduates and clients so they can read up on real life cases.

Section 1: About your client and how you diagnosed the condition (think about how they presented, what subjective and objective information did you gather to help you diagnose?)

A 39-year-old female recreational runner presented to our clinic with diffuse L) medial knee pain after a recent return to running. She described it as an aching pain that was occasionally sharp, deep within the knee joint. This was aggravated by running, occasionally by walking, and felt as though it would swell up after long runs. Upon assessment, she instantly felt pain when performing a single leg squat, and displayed a moderate Trendelenburg sign with poor knee control. She had a tender medial joint line upon palpation, and significantly decreased quadriceps strength on the L) side. All other usual special tests for the knee came back negative (McMurray’s, Lachman’s, Thomas, etc). After applying McConnell tape to medially redirect her patella, her single leg squat pain was significantly reduced.

Given the lack of any other positive signs that would indicate a medial meniscus injury (excluding joint line tenderness), the painful single leg squat (the closest thing we have to a validated special test for patellofemoral pain, and the reduction in pain with the application of McConnell tape, I clinically reasoned that this patient was most likely suffering from Patellofemoral Pain Syndrome (PFPS).

Section 2: Your diagnosis and about the condition (what is your possible diagnosis?)

Possible diagnosis:
PFPS

Pathophysiology background:
The exact pathophysiology of PFPS is poorly understood, with a range of possible causes and structures involved. There is a significant crossover between patients suffering with PFPS and patellofemoral osteoarthritis,1 with some evidence suggesting that PFPS is a precursor to patellofemoral osteoarthritis.2 PFPS is associated altered contact area between the patella and femur, resulting in increased joint stress, chondral changes, and cartilage injury. Several biomechanical and physiological associations have been made between PFPS, including; abnormal patellofemoral joint and trochlear morphology, muscle weakness (particularly quadriceps and hip abductors), and biomechanical abnormalities during gait including reduced knee extension moments. This condition is common in running athletes, and has been colloquially termed ‘runner’s knee’.

Section 3: Differential Diagnosis (what is another condition to consider and why?)

Differential diagnosis:
Medial meniscus injury
Medial knee OA

Pathophysiology background:
Meniscal injuries can occur as a result of rotational or shearing forces across the tibiofemoral joint which exceed the capacity of the menisci to withstand those forces. This commonly occurs as a result of trauma or rotational/shearing loading on a flexed knee in a closed-kinetic chain movement. In these injuries, the medial meniscus is more prone to injury due to its decreased mobility stemming from its attachment to the MCL. Meniscal injuries can also occur in the presence of much lower forces as a result of degenerative changes to tibiofemoral joint or meniscal structures.3 These injuries typically occur in younger, sporting populations (acute) and older populations (degenerative), and given the lack of a traumatic incident resulting in an acute meniscal injury, it is unlikely that this patient was suffering from either kind of injury.

Medial knee OA is shown to frequently co-exist with PFPS, and should also be considered as a possible diagnosis. Knee OA is considered a disease of the whole knee joint, and is associated with inflammatory processes resulting in chondral and subchondral bone changes within the tibiofemoral joint. These chondral changes are thought to change tibiofemoral joint mechanics, resulting in increased nociception and the presence of pain with movement.4 Clinically, this is seen in older individuals (typically >55 years), those with previous knee injury, and is more common in females. Because the criteria for a clinical diagnosis of medial knee OA is vague (knee pain, morning stiffness, etc), we cannot discount the possibility of medial knee OA being an additional diagnosis for this patient. Importantly, load management and lower limb strengthening forms the cornerstone of treating either of these conditions, so distinction between OA of differing knee compartments is only necessary to tailor treatment adjuncts such as taping or other methods of joint unloading.

Section 4: Treatment (what did you do and why?)

My treatment strategy broadly had four components; load management, gait retraining, strengthening, and adjuncts.

Load management: designed to reduce the ongoing irritation to the patellofemoral joint caused by this patient’s running. This included eliminating high patellofemoral joint load activities such as high tempo work, hills, and long-distance runs, and substituting them for shorter, more moderate tempo work. Similarly, we modified the running surface to something softer (grass), and implemented walking breaks where necessary. The gauge for whether the knee was loaded appropriately was post-run pain, with a VAS score of <4/10 that settled within 4 hours of running considered appropriate. We also discussed ways to modify the load if we continued to inappropriately load the knee despite these changes. These principles of load management were adapted for other work in tendinopathy, but removing abusive loading is considered an important first step to recovery by many running physios.

Gait retraining: designed to minimise PFJ loading and reduce pain, as demonstrated by this RCT.5 This included increasing this patient’s cadence by 10% (to around 170 BPM – designed to correct overstriding and reduce breaking forces at the knee). Additionally, we saw an excessive knee adduction moment with a contralateral hip drop which is associated with increased PFPS risk.1 This was addressed through strengthening the hip abductors…

Strengthening: hip and knee strengthening is shown to be effective at reducing PFPS symptoms, likely by modifying biomechanical errors (such as the aforementioned hip drop or knee tracking issues).6 This included exercises to strengthen the hip abductors’ lateral control over the pelvis in weightbearing (lateral step down), running specific exercises to strengthen the hip and knee extensors (Bulgarian split squat), and some calf strengthening (calf raises) to improve distal lower limb stability (thereby affecting knee loading).

Adjuncts: Patellar taping (McConnell technique) has low quality evidence supporting its use in reducing PFPS symptoms,6 but was instantly relieving for the patient, so self-taping techniques taught and used as needed by the patient. Soft tissue massage was employed where necessary to reduce pain, influence muscle tone, and potentially influence patellar tracking (single leg squat pain was improved immediately after massage).
Section 4: Plan (where to go from here? How many sessions might they need? What’s the goal?)

Future sessions will involve progression of this patient’s strength exercises in order to ensure she is able to maintain the improvements she’s made to her gait and mechanics as she progresses into longer and faster runs, under an increased level of fatigue. As we initially removed tempo runs, hills, etc, a graded return to these activities as they become no longer provocative will be employed, ensuring she is able to meet and exceed her baseline running volume. We will continue to monitor her running technique, and modify exercises and drills appropriately to ensure she is running in a way that is least likely to lead to injury. As she returns to full running, pain-free, we will then shorten and modify her exercise program to a ’maintenance’ program, designed to maintain the strength and biomechanical improvement she’s made, without spending a significant amount of time or energy on doing so. We will also educate her about reducing her risk of re-injury, ways to monitor her running load, and any other self-management strategies she may need to manage her pain long after discharge.

This will likely require 3-4 more sessions, spread out over two week intervals (6-8 weeks total), as strength changes typically take at least 6 weeks before we see any major changes, and she will require time for her gait retraining to become natural for her.

References:
1. Crossley KM, Stefanik JJ, Selfe J, et al 2016 Patellofemoral pain consensus statement from the 4th International Patellofemoral Pain Research Retreat, Manchester. Part 1: Terminology, definitions, clinical examination, natural history, patellofemoral osteoarthritis and patient-reported outcome measures British Journal of Sports Medicine 2016;50:839-843.

2. Eijkenboom, J., Waarsing, J. H., Oei, E., Bierma-Zeinstra, S., & van Middelkoop, M. (2018). Is patellofemoral pain a precursor to osteoarthritis?: Patellofemoral osteoarthritis and patellofemoral pain patients share aberrant patellar shape compared with healthy controls. Bone & joint research, 7(9), 541–547. https://doi.org/10.1302/2046-3758.79.BJR-2018-0112.R1
3. Raj MA, Bubnis MA. Knee Meniscal Tears. [Updated 2021 Jul 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK431067/
4. Mora JC, Przkora R, Cruz-Almeida Y. Knee osteoarthritis: pathophysiology and current treatment modalities. J Pain Res. 2018;11:2189-2196. Published 2018 Oct 5. doi:10.2147/JPR.S154002
5. Esculier JF, Bouyer LJ, Dubois B, Fremont P, Moore L, McFadyen B, Roy JS. Is combining gait retraining or an exercise programme with education better than education alone in treating runners with patellofemoral pain?A randomised clinical trial. Br J Sports Med. 2018 May;52(10):659-666. doi: 10.1136/bjsports-2016-096988. Epub 2017 May 5. PMID: 28476901.
6. Crossley KM, van Middelkoop M, Callaghan MJ, et al 2016 Patellofemoral pain consensus statement from the 4th International Patellofemoral Pain Research Retreat, Manchester. Part 2: recommended physical interventions (exercise, taping, bracing, foot orthoses and combined interventions). British Journal of Sports Medicine 2016;50:844-852.

 

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