David M. Bazett-Jones

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

Patellofemoral pain (PFP) typically presents as diffuse anterior knee pain, usually with activities such as squatting, running, stair ascent and descent. It is common in active individuals across the lifespan,1–4 and is a frequent cause for presentation at physiotherapy, general practice, orthopaedic and sports medicine clinics in particular.5 ,6 Its impact is profound, often reducing the ability of those with PFP to perform sporting, physical activity and work-related activities pain-free. Increasing evidence suggests that it is a recalcitrant condition, persisting for many years.7–9 In an attempt to share recent innovations, build on the first three successful biennial retreats and define the ‘state of the art’ for this common, impactful condition; the 4th International Patellofemoral Pain Research Retreat was convened. The 4th International Patellofemoral Research Retreat was held in Manchester, UK, over 3 days (September 2–4th, 2015). After undergoing peer-review for scientific merit and relevance to the retreat, 67 abstracts were accepted for the retreat (50 podium presentations, and 17 short presentations). The podium and short presentations were grouped into five categories; (1) PFP, (2) factors that influence PFP (3) the trunk and lower extremity (4) interventions and (5) systematic analyses. Three keynote speakers were chosen for their scientific contribution in the area of PFP. Professor Andrew Amis spoke on the biomechanics of the patellofemoral joint. Professor David Felson spoke on patellofemoral arthritis,10 and Dr Michael Ratleffs keynote theme was PFP in the adolescent patient.11 As part of the retreat, we held structured, whole-group discussions in order to develop consensus relating to the work presented at the meeting as well as evidence gathered from the literature. ### Consensus development process In our past three International Patellofemoral Research Retreats, we developed a consensus statement addressing different presentation categories.12–14 In Manchester in 2015, we revised the format. For the exercise and …

Normalizing Hip Muscle Strength: Establishing Body-Size-Independent Measurements

OBJECTIVE To investigate the effectiveness of computing body-size-independent hip strength measures using muscle-specific allometric scaling and ratio standard normalization methods. DESIGN Cross-sectional study. SETTING University laboratory. PARTICIPANTS A convenience sample of healthy participants (N=113; 42 men, 71 women). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Anthropometric measurements of the leg and thigh were obtained, and maximal hip strength was tested (medial and lateral rotation, abduction, adduction, flexion, extension). Strength was measured isometrically as force (kg) and then converted to torque (Nm). RESULTS The allometric scaling analysis resulted in exponents for normalizing body mass (BM) in each muscle group assessed. In addition, a 6-muscle average exponent was also computed (bavg) for force (men, .554; women, .335) and torque (men, .792; women, .482). The nonsignificant results of the linear regression analysis revealed that normalizing hip strength to BM(bavg) (hip strength/BM(bavg)) effectively removed the influence of BM on force and torque. However, sex should be factored into analyses of allometric scaling because men have higher b-values than women for both force and torque. The linear regression analyses also demonstrated that force normalized to BM (P=.162-.895) and torque normalized to BM × Height (P=.146-.889) were body-size-independent measures. Force normalized to BM⁰·⁶⁷ (P=.001-.191) and body mass index (BMI) (P=<.001-.066), and torque normalized to BM (P=.004-.415) and BMI (P<.001) were significantly related to BM and therefore were not body-size independent. CONCLUSIONS Normalizing force and torque to BM(bavg) is the most effective method of removing body-size dependence and allowing comparisons of persons with differing body sizes.

Effect of Patellofemoral Pain on Strength and Mechanics after an Exhaustive Run

PURPOSE To investigate the effects of an exhaustive run on trunk and lower extremity strength and mechanics in patients with and without patellofemoral pain (PFP), we hypothesized that strength would decrease and mechanics would change after the exhaustive run. METHODS Nineteen subjects with PFP and 19 controls participated (10 men and 9 women per group). Lower extremity and trunk mechanics during running, body mass-normalized strength, and pain assessments before and after an exhaustive run were quantified. A repeated-measures ANOVA was used to assess group differences and exhaustion-related changes (P < 0.05), with t-test post hoc analyses performed when significant interactions were identified (P < 0.0125). RESULTS Pain significantly increased with the exhaustive run in the PFP group (P = 0.021). Hip strength was reduced after the exhaustive run, more so in those with PFP (abduction: before = 0.384 ± 0.08, after = 0.314 ± 0.08, P < 0.001; external rotation: before = 0.113 ± 0.02, after = 0.090 ± 0.02, P < 0.001). Persons with PFP also demonstrated increased knee flexion (before = 41.6° ± 5.5°, after = 46.9° ± 7.5°, P < 0.001), hip flexion (before = 30.4° ± 6.8°, after = 42.5° ± 9.7°, P < 0.001), and anterior pelvic tilt (before = 7.2° ± 5.1°, after = 13.3° ± 6.7°, P = 0.001) after the exhaustive run compared to controls. Trunk flexion increased in both PFP (before = 13.09° ± 6.2°, after = 16.31° ± 5.3°, P < 0.001) and control (before = 1393° ± 4.7°, after = 15.99° ± 5.9°, P < 0.001) groups. Hip extension (before = -2.09 ± 0.49 N · m · kg(-1), after = -2.49 ± 0.54 N · m · kg(-1), P = 0.002) moments increased only in subjects with PFP. CONCLUSIONS Exhaustive running results in reduced hip strength in subjects with PFP; however, this did not result in changes to hip internal rotation or adduction kinematics. Kinematic and kinetic changes after the exhaustive run are more indicative of compensatory changes to reduce pain. Increasing trunk flexion during running might provide pain relief during running; however, reducing anterior pelvic tilt may also warrant attention during treatment.

The Relationship Among Foot Posture, Core and Lower Extremity Muscle Function, and Postural Stability

CONTEXT Identification of impaired balance as a risk factor for lower extremity injury regardless of injury history has led to subsequent investigation of variables that may adversely affect balance in healthy individuals. OBJECTIVES To investigate the relationship among core and lower extremity muscle function, foot posture, and balance. DESIGN Descriptive laboratory study. SETTING Musculoskeletal injury biomechanics laboratory. PATIENTS OR OTHER PARTICIPANTS A total of 108 individuals (40 men, 68 women; age = 22.8 ± 4.7 years, height = 168.5 ± 10.4 cm, mass = 69.9 ± 13.3 kg) participated in the study. MAIN OUTCOME MEASURE(S) Core endurance was assessed during 1 time-to-failure trial, and isometric hip and ankle strength were assessed using a handheld dynamometer and isokinetic dynamometer, respectively. Foot structure was quantified using the digital photographic measurement method. Single-limb-stance time to boundary was assessed using a force plate during an eyes-closed condition. Hierarchical multiple regression analyses were performed to predict balance using lower extremity strength, foot posture, and core endurance. RESULTS Foot posture (β = -0.22, P = .03) and ankle-inversion strength (β = -0.29, P = .006) predicted mediolateral balance. Increasing arch posture and ankle-inversion strength were associated with decreased mediolateral single-limb-stance balance. CONCLUSIONS Increasing arch height was associated with decreased mediolateral control of single-limb stance. The relationship between time to boundary and injury risk, however, has not been explored. Therefore, the relationship between increasing arch height and injury due to postural instability cannot be determined from this study. If authors of future prospective studies identify a relationship between decreased time to boundary and increased injury risk, foot structure may be an important variable to assess during preparticipation physical examinations. The relationship between increasing ankle-inversion strength and decreased balance may require additional study to further elucidate the relationship between ankle strength and balance.

Acute Responses of Strength and Running Mechanics to Increasing and Decreasing Pain in Patients With Patellofemoral Pain

CONTEXT   Patellofemoral pain (PFP) is typically exacerbated by repetitive activities that load the patellofemoral joint, such as running. Understanding the mediating effects of changes in pain in individuals with PFP might inform injury progression, rehabilitation, or both. OBJECTIVE   To investigate the effects of changing pain on muscular strength and running biomechanics in those with PFP. DESIGN   Crossover study. SETTING   University research laboratory. PATIENTS OR OTHER PARTICIPANTS   Seventeen participants (10 men, 7 women) with PFP. INTERVENTION(S)   Each participant completed knee pain-reducing and pain-inducing protocols in random order. The pain-reducing protocol consisted of 15 minutes of transcutaneous electric nerve stimulation (TENS) around the patella. The pain-inducing protocol was sets of 20 repeated single-legged squats (RSLS). Participants completed RSLS sets until either their pain was within at least 1 cm of their pain during an exhaustive run or they reached 10 sets. MAIN OUTCOME MEASURE(S)   Pain, isometric hip and trunk strength, and running mechanics were assessed before and after the protocols. Dependent variables were pain, normalized strength (abduction, extension, external rotation, lateral trunk flexion), and peak lower extremity kinematics and kinetics in all planes. Pain scores were analyzed using a Friedman test. Strength and mechanical variables were analyzed using repeated-measures analyses of variance. The α level was set at P < .05. RESULTS   Pain was decreased after the TENS (pretest: 3.10 ± 1.95, posttest: 1.89 ± 2.33) and increased after the RSLS (baseline: 3.10 ± 1.95, posttest: 4.38 ± 2.40) protocols (each P < .05). The RSLS protocol resulted in a decrease in hip-extension strength (baseline: 0.355 ± 0.08 kg/kg, posttest: 0.309 ± 0.09 kg/kg; P < .001). Peak plantar-flexion angle was decreased after RSLS (baseline: -13.97° ± 6.41°, posttest: -12.84° ± 6.45°; P = .003). Peak hip-extension (pretest: -2.31 ± 0.46) and hip-abduction (pretest: -2.02 ± 0.35) moments decreased after both the TENS (extension: -2.15 ± 0.48 Nm/kg, P = .015; abduction: -1.91 ± 0.33 Nm/kg, P = .015) and RSLS (extension: -2.18 ± 0.52 Nm/kg, P = .003; abduction: -1.87 ± 0.36 Nm/kg, P = .039) protocols. CONCLUSIONS   This study presents a novel and effective method of increasing pain in persons with PFP. Functionally increased pain after RSLS coincides with reduced hip-extensor muscle strength and decreased plantar-flexion angle during running. The TENS treatment decreased pain during running in those with PFP but failed to influence strength. Hip moments were reduced by both protocols, which may demonstrate that acute increases or decreases in pain cause runners to change their mechanics.