ASSOCIATION OF ISOMETRIC STRENGTH OF HIP AND KNEE MUSCLES WITH INJURY RISK IN HIGH SCHOOL CROSS COUNTRY RUNNERS

Background

High school cross country runners have a high incidence of overuse injuries, particularly to the knee and shin. As lower extremity strength is modifiable, identification of strength attributes that contribute to anterior knee pain (AKP) and shin injuries may influence prevention and management of these injuries.

Purpose

To determine if a relationship existed between isometric hip abductor, knee extensor and flexor strength and the incidence of AKP and shin injury in high school cross country runners.

Materials/Methods

Sixty‐eight high school cross country runners (47 girls, 21 boys) participated in the study. Isometric strength tests of hip abductors, knee extensors and flexors were performed with a handheld dynamometer. Runners were prospectively followed during the 2014 interscholastic cross country season for occurrences of AKP and shin injury. Bivariate logistic regression was used to examine risk relationships between strength values and occurrence of AKP and shin injury.

Results

During the season, three (4.4%) runners experienced AKP and 13 (19.1%) runners incurred a shin injury. Runners in the tertiles indicating weakest hip abductor (chi‐square = 6.140; p=0.046), knee extensor (chi‐square = 6.562; p=0.038), and knee flexor (chi‐square = 6.140; p=0.046) muscle strength had a significantly higher incidence of AKP. Hip and knee muscle strength was not significantly associated with shin injury.

Conclusions

High school cross country runners with weaker hip abductor, knee extensor and flexor muscle strength had a higher incidence of AKP. Increasing hip and knee muscle strength may reduce the likelihood of AKP in high school cross country runners.

Level of Evidence

2b     

DEMOGRAPHIC AND EPIDEMIOLOGICAL TRENDS IN PATELLOFEMORAL PAIN

Background

Understanding the demographics of patellofemoral pain is important to determine the best practices in diagnosis and treatment of this difficult pathology. The occurrence of patellofemoral pain has been reported from isolated sports medicine clinics and from within the military, but its incidence has never been examined in the general population within the United States.

Purpose

The purpose of this study was to examine the reported occurrence of patellofemoral pain for those individuals seeking medical care and to compare that to all other pathologies that result in anterior knee pain, such as tendinopathies, patella subluxation, osteoarthritis, or meniscal and bursal conditions. Occurrence rates were examined across sex, age and region within a large healthcare provider database that contains over 30 million individuals.

Methods

Data were queried with the PearlDiver Patient Record Database, a national database containing orthopedic patient records. Two common International Classification of Disease, Ninth Revision (ICD‐9) codes for patellofemoral pain (717.7 – Patella Chondromalacia and 719.46 – Pain in joint, lower leg) were utilized and were searched from the years 2007‐2011. The top twenty additional ICD‐9 codes that were concurrently coded with 717.7 and 719.46 were removed from the data. Chi‐squared and Mantel‐Haenszel tests were utilized to identify statistically significant differences in the diagnosis of patellofemoral pain between sex, age, and year.

Results

During this five‐year period, there were 2,188,753 individuals diagnosed with patellofemoral pain. The diagnosis was more common in females compared to males with 1,211,665 and 977,088 cases respectfully (p<0.001). Statistically significant differences between ages was found, with 50‐59 year olds having the most cases with 578,854, p<0.001. And, during the five‐year examination period, there was a steady increase between 2007‐2011, p<0.01.

Conclusion

Patellofemoral pain was diagnosed between 1.5% and 7.3% of all patients seeking medical care within the United States. Females experienced patellofemoral pain more often than males and there was a steady increase of cases in the United States during the 2007‐2011 examination period. The diagnosis of patellofemoral pain increased with age and the 50‐59 year old age group had the most cases.

Level of Evidence

2b     

QUANTIFYING FRONTAL PLANE KNEE MOTION DURING SINGLE LIMB SQUATS: RELIABILITY AND VALIDITY OF 2‐DIMENSIONAL MEASURES

Background:

Clinical assessment of lower limb kinematics during dynamic tasks may identify individuals who demonstrate abnormal movement patterns that may lead to etiology of exacerbation of knee conditions such as patellofemoral joint (PFJt) pain.

Purpose:

The purpose of this study was to determine the reliability, validity and associated measurement error of a clinically appropriate two‐dimensional (2‐D) procedure of quantifying frontal plane knee alignment during single limb squats.

Methods:

Nine female and nine male recreationally active subjects with no history of PFJt pain had frontal plane limb alignment assessed using three‐dimensional (3‐D) motion analysis and digital video cameras (2‐D analysis) while performing single limb squats. The association between 2‐D and 3‐D measures was quantified using Pearson''s product correlation coefficients. Intraclass correlation coefficients (ICCs) were determined for within‐ and between‐session reliability of 2‐D data and standard error of measurement (SEM) was used to establish measurement error.

Results:

Frontal plane limb alignment assessed with 2‐D analysis demonstrated good correlation compared with 3‐D methods (r = 0.64 to 0.78, p < 0.001). Within‐session (0.86) and between‐session ICCs (0.74) demonstrated good reliability for 2‐D measures and SEM scores ranged from 2° to 4°.

Conclusion:

2‐D measures have good consistency and may provide a valid measure of lower limb alignment when compared to existing 3‐D methods.

Clinical Relevance:

Assessment of lower limb kinematics using 2‐D methods may be an accurate and clinically useful alternative to 3‐D motion analysis when identifying individuals who demonstrate abnormal movement patterns associated with PFJt pain.

Level of Evidence:

2b     

THE RELIABILITY AND DIAGNOSTIC ACCURACY OF ASSESSING THE TRANSLATION ENDPOINT DURING THE LACHMAN TEST

Background

Interpretation of Lachman testing when evaluating the status of the anterior cruciate ligament (ACL) typically includes a numerical expression classifying the amount of translation (Grade I, II, III) in addition to a categorical modifier (Grade A [firm] or B [absent]) to describe the quality of the passive anterior tibial translation''s endpoint. Most clinicians rely heavily on this tactile sensation and place value in this judgment in order to render their diagnostic decision; however, the reliability and accuracy of this endpoint assessment has not been well established in the literature.

Purpose

The purpose of this study was to determine the intertester reliability of endpoint classification during the passive anterior tibial translation of a standard Lachman test and evaluate the classification''s ability to accurately predict the presence or absence of an ACL tear.

Study design

Prospective, blinded, diagnostic reliability and accuracy study.

Methods

Forty‐five consecutive patients with a complaint of knee pain were independently evaluated for the endpoint classification during a Lachman test by two physical therapists before any other diagnostic assessment. The 21 men and 24 women ranged in age from 20 to 64 years (mean +/‐ SD age, 40.7 +/‐ 14) and in acuity of knee injury from 30 to 365 days (mean +/‐ SD, 238 +/‐157).

Results

17 of the 45 patients had a torn ACL. The agreement between examiners on A versus B endpoint classification was 91% with a kappa coefficient of 0.72. In contrast, classification agreement based on the translational amount had an agreement of 65% with a weighted kappa coefficient of 0.52. The sensitivity of the endpoint grade alone was 0.81 with perfect specificity resulting in a positive likelihood ratio of 6.2 and a negative likelihood ratio of 0.19. The overall accuracy of the Lachman test using the endpoint assessment grade alone was 93% with a number needed to diagnose of 1.2.

Conclusions

Nominal endpoint classification (A or B) from a Lachman test is a reliable and accurate reflection of the status of the ACL. The true dichotomous nature of the test''s interpretation (positive vs. negative) is well‐served by the quality of the endpoint during passive anterior tibial translation.

Level of Evidence

2