Carlos Prada MD MHSc1 and Sebastián Irarrázaval MD2 1 Division of Orthopaedic Surgery, Department of Surgery, McMaster University, Hamilton, ON, Canada 2 Department of Orthopaedic Surgery, Pontificia Universidad Católica de Chile, Santiago, Chile The term patellofemoral pain is the preferred term, and is a synonym for other terms including: PFP syndrome, chondromalacia patellae, anterior knee pain and/or syndrome, and runner’s knee.1 Diagnostic imaging tools represent an important cost for the healthcare system and/or patients. Given the high prevalence and clear clinical presentation of this condition, it is reasonable to analyze if imaging is necessary in the diagnosis and treatment process of these patients. In addition, potential association between this disorder and patellofemoral osteoarthritis has been reported. Runner’s knee, also known as patellofemoral pain (PFP) is a common syndrome. Usually, when patients decide to pursue medical attention, they expect to be referred for diagnostic imaging tests. Nevertheless, these tests represent an economic burden to patients and/or the healthcare system, without necessarily changing treatment or prognosis. In addition, some studies had shown an association between PFP and patellofemoral osteoarthritis, which have increased the awareness of this condition.2 This search produced the following level I studies: one systematic review and meta‐analysis3 and three randomized controlled trials (RCTs). Whenever possible, these level I studies will be used to answer the question. Lower level of evidence studies will be used to address the role of other imaging modalities that lack high‐quality evidence. Magnetic resonance imaging (MRI) Drew et al. found that an increased MRI bisect offset at 0° flexion angle under load was associated with PFP, and that there was a large standardized mean difference (SMD = 0.99; 95% confidence interval [CI]: 0.49–1.49) as determined from moderate level evidence.3 MRI bisect offset has been shown as the most significant feature related to patellofemoral joint (PFJ) space narrowing in adults between 70 and 79 years with knee pain.4 There is also a moderate SMD for the association between PFP, patellar tilt (0.63; 95% CI: 0.37–0.90) and patellofemoral contact area (−0.53; 95% CI: −1.01 to −0.06). Computed tomography (CT) CT‐derived congruence angles at 15° flexion angle, with and without load, have shown a large SMD from moderate evidence level (1.40; 95% CI: 0.04–2.76) and (1.24; 95% CI: 0.37–2.12), respectively. There is limited evidence to support a difference between PFP patients and the normal population regarding tibial tubercle rotation angle at 0° without load5,6 and trochlear depth at 15° without load.7 In addition, there is controversial evidence for patellar tilt at 15° under load.8,9 Ultrasound (US) Different studies comparing US findings between patients with PFP and healthy individuals have been conducted. Limited evidence supports a difference between PFP patients and healthy controls in terms of: vastus medialis oblique (VMO) fiber angle, VMO insertion, and volume;10 VMO contraction ratio and capacity reduction;11 and an increase in VMO electrical mechanical delay and vastus lateralis delay.12 In addition, evidence suggests that the atrophy is not specific for VMO, but for the quadriceps as a whole muscular group.13 X‐rays There is controversial evidence regarding a difference in congruence angle, support sulcus angle, and Insall–Salvati index at 30° without load, between patients with PFP and healthy individuals. Limited evidence support a difference in congruence angle at 45° with load,14,15 but not at 35°.16 Similarly, limited evidence supports sulcus angle difference at 45° without load,14,15 but no evidence shows a difference at 35°16 or 30°.17 Two studies have revealed that, after quadriceps strengthening exercises, there was a significant increase in PFJ contact area which might reduce mechanical stress, improving PFJ function. These studies also exhibited that the patellofemoral bisect offset and patellar tilt changed with bracing.18,19 The patient’s imaging did not show any specific abnormalities, which is the case in the majority of cases of PFP. Eventually, some dynamic imaging exam measurements can be performed to identify certain features associated with PFP, but this will probably not change the patient’s initial management (overall quality: moderate). Patients with PFP are frequently sent to physiotherapy. NMES has been extensively used during physiotherapy sessions despite the lack of consensus in its benefit. This search produced the following level I studies: one systematic review20 and eight RCTs. Whenever possible, these level I studies were used to answer the question.
142 Patellofemoral Pain Syndrome (Runner’s Knee)
Clinical scenario
Top four questions
Question 1: In patients with a diagnosis of runner’s knee, are there specific imaging findings that are different compared with patients without runner’s knee?
Rationale
Clinical comment
Available literature and quality of the evidence
Findings
Diagnostic modalities findings in runner’s knee patients compared to the normal population
Changes observed during intervention through imaging modalities
Resolution of clinical scenario
Question 2: In patients with a diagnosis of runner’s knee, does neuromuscular electrical stimulation (NMES) associated with conservative treatment result in better patient‐reported outcome measures (PROMs), compared with conservative treatment without NMES?
Rationale
Clinical comment
Available literature and quality of the evidence
Findings
NMES
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