As many as 1 in 4 runners will develop patellofemoral pain syndrome (PFPS) during their running career. Despite the high prevalence, there is conflicting evidence as to the etiology of this condition. This article will serve to dispel the myths of its etiology as well as provide helpful tools to consider when treating this condition.
The patella (knee cap) is an important structure for dissipating ground reaction forces associated with walking and running. The patella serves to displace the quadriceps tendon away from the knee's axis of motion, and improves the mechanical efficiency of the knee by as much as 50%.
Early research, based on a non weight-bearing (open kinetic chain) model suggested that the most likely cause of PFPS was a lateral shifting of the patella. A weak vastus medialis obliques muscle or a high Q-angle could cause this. As a result, past treatments involved correcting faulty movements locally at the patellofemoral joint. This involved patellar taping, soft tissue techniques, and strengthening of the VMO. These treatment protocols have had mixed results.
A number of more recent studies have evaluated the patellofemoral joint in a much more appropriate weight-bearing model. MRI studies of weight bearing knee flexion have shown that the cause of lateral displacement of the patella is rather a medial shifting and rotation of the lateral aspect of the distal femur into the patella.
Instead of the patella shifting into the lateral femoral condyle, the unstable femur internally rotates into the stable patella. Rather than looking at the knee in isolation, the approach to care of the PFPS patient should focus on prevention of internal femoral rotation. Runners with weak hip abductors have greater ranges of internal femoral rotation during stance phase and the degree of internal rotation increases when the runner is fatigued.
While hip strengthening has become the most important clinical goal of treating PFPS, patients also present with delayed recruitment of the vastus medialis obliquus muscle. Patients should incorporate VMO isolation exercises by palpating the distal portion of the muscle and isometriclally contracting their quadriceps.
A controversial intervention for PFPS is the use of orthotics. Orthotics can be effective in reducing internal tibial rotation and therefore femoral internal rotation in patients presenting with excessive foot pronation. Although there is a growing body of research showing a limited connection between arch height and PFPS, the challenge for clinicians is determining whether an orthotic is appropriate for their PFPS patient. Crossley et al. (2010) performed a clinical prediction study and observed that if PFPS patients report less discomfort when single leg squatting with an orthotic then they are more likely to positively respond to an orthotic intervention. These patients also report an increased ability to complete pain free step-ups from a 20cm high platform.
A number of other strategies should be incorporated into the evaluation and treatment of PFPS, including evaluation of ankle mobility, leg length discrepancy, body weight, and footwear choice. Running amplifies ground-reactive forces 5-fold and therefore overweight individuals should be encouraged to reduce body mass index. Individuals with PFPS should also consider shorter stride lengths and consider switching to a mid foot or forefoot strike pattern which lessens the transfer of ground reaction forces through the knee by up to 50%.
A rehabilitation guideline from Tyler et al. (2006) is included below to provide some strategies for manual therapy and rehabilitation of the PFPS patient. This is by no means an exhaustive list but rather a guideline that can be followed for treatment.
Phase 1 • Off weight-bearing hip flexion, adduction, extension, and abduction performed while maintaining a stable pelvis. • Stretches for hip flexors, hamstrings, quadriceps, and iliotibial band. • Manual therapy to restore flexibility to the medial/lateral retinaculum • Home exercises including single-leg balance, rocker board, 4-inch step-ups (varying height of step, reps, speed)
Phase 2 Begins when patient can minisquat to 45 degrees and perform pain-free step-ups with good form. • Continue off weight-bearing exercises and stretches. Increase resistance with exercises. • Lower extremity reaches (e.g. star excursion exercises). Focus on weakest movements. • Step-downs: vary height of step, reps, and speed. • Increase difficulty of balance exercises.
Phase 3 Begins when patient can perform 4-inch step-downs with no pain and good eccentric control. • Continue home stretching. • Begin plyometric drills while maintaining proper form. • Begin lunges and incorporate return-to-sport drills such as crossover running and single leg hop drills
Return to activity clinical milestones:
A) Vertical jump test B) Pain-free vertical hop test C) Pain-free sport-specific test
PFPS can no longer be thought of as a local problem at the knee but rather as a regional dysfunction of the proximal hip joint and/or distal dysfunction of the ankle and foot joints. Proper evaluation of these related regions will help guide the patients treatment plan.
Dr. Trevor Vander Doelen, BSc (Hon), ART®, DC
Cavanagh P, Lafortune M. Ground reaction forces in distance running. Journal of Biomechanics. 1980; 13:397-406.
Crossley KM, Barton CJ, Menz HB. Clinical Predictors of foot orthoses efficacy in patellofemoral pain syndrome. Medicine and Science in Sports and Exercise. 2010; 42(suppl 5): Abstract 2611: S485.
Devereaux M, Lachman S. Patellofemoral Arthralgia in athletes attending a sports injury clinic. British Journal of Sports Medicine. 1984; 18: 18-21.
Fulkerson J. Disorders of the Patellofemoral joint. 3rd edition. Baltimore (MD): Williams&Wilkins; 1997.
Lin YF, Jan MH, Lin DH, Cheng CK. Different effects of femoral and tibial rotation on the different measurements of patella tilting: An axial computed tomography study. Journal of Orthopedic and Surgical Research. 2008; 3:5.
Powers C, Ward S, Fredericson M, et al. Patellofemoral kinematics during weight-bearing and non-weight-bearing knee extension in persons with lateral subluxation of the patella: a preliminary study. Journal of Orthopedics and Sports Physical Therapy. 2003; 33: 677-685.
Souza R, Draper C, Frederickson M, et al. Femur rotation and patellofemoral joint kinematics: a weight-bering magnetic resonance imaging analysis. Journal of Orthopedic and Sports Physical Therapy. 2010; 40: 277-285.
Tyler T, Nicholas S, Mullaney M, McHugh M. The role of hip muscle function and the treatment of patellofemoral pain syndrome. American Journal of Sports Medicine. 2006; 34:630.