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James J Irrgang

Publications and source records attributed to James J Irrgang.

At least 19 recordsLinked to original sources
PubMed2007

Assessment of normal ACL double bundle anatomy in standard viewing planes by magnetic resonance imaging.

Anatomical studies show that the native ACL consists of two distinct functional bundles, termed the anteromedial (AM) and posterolateral (PL) bundles. The utility of using routine magnetic resonance imaging (MRI) to distinguish the individual bundles of the ACL has not been evaluated. The purpose of this study was to evaluate the intra- and inter-observer agreement for assessment of the AM and PL bundles using MRI in the axial, coronal, and sagittal viewing planes. We identified a series of patients seen in the senior author's clinic during a 16-month period. Images were independently evaluated in blinded fashion at two separate time points by a musculoskeletal radiologist and two orthopaedic residents. The AM bundle was detected in most planes of view with high frequency and reliability, while detection of the PL bundle was less frequent and had a lower associated reliability. Our results indicate that it is difficult to reliably detect both the AM and PL bundles using a low-field strength magnet with standard planes of view. It has been demonstrated that the ACL may be imaged effectively in planes that are based on the natural course of the ligament, and it is likely that this will also facilitate visualization of the individual AM and PL bundles. The use of additional oblique planes of view offers a potential approach for improved evaluation of the ACL, even with low field strength magnets. Future work in this area may assist in the pre-operative assessment of isolated AM or PL bundle injuries, facilitating a more anatomic approach to ACL reconstruction.

Adult↗
PubMed2006

Responsiveness of the International Knee Documentation Committee Subjective Knee Form.

BACKGROUND AND PURPOSE: The International Knee Documentation Committee Subjective Knee Form was developed to measure change in symptoms, function, and sports activity in patients treated for a variety of knee conditions. Although previous research has demonstrated reliability and validity of the form, its responsiveness has not been evaluated. The purpose of this study was to determine responsiveness of the International Knee Documentation Committee Subjective Knee Form. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 1. METHODS: Patients who participated in the original validation study for the International Knee Documentation Committee Subjective Knee Form completed the form and a 7-level global rating of change scale that ranged from greatly worse to greatly better after a mean of 1.6 years (range, 0.5-2.3 years). Analyses included calculation of the standardized response mean and mean change in International Knee Documentation Committee Subjective Knee Form score compared to the patient's perception of change on the global rating of change scale. In addition, a receiver operating characteristic curve was plotted to determine the change in score that best distinguished patients who improved from those who did not. RESULTS: The overall standardized response mean was 0.94, which is considered large. With the exception of those who were slightly worse or unchanged, the mean change in the International Knee Documentation Committee Subjective Knee Form score compared to the patients' perceived global ratings of change was as expected (greatly worse, -15.1; somewhat worse, -8.4; slightly worse, 20.6; no change, 10.7; slightly better, 5.9; somewhat better, 18.1; greatly better, 38.7). The receiver operating characteristic curve analysis revealed that a change score of 11.5 points had the highest sensitivity, and a change score of 20.5 points had the highest specificity to distinguish between those who were or were not improved. CONCLUSION: The International Knee Documentation Committee Subjective Knee Form is a responsive measure of symptoms, function, and sports activity for patients with a variety of knee conditions.

Adolescent↗
PubMed2006

Reliability of measures of impairments associated with patellofemoral pain syndrome.

BACKGROUND: The reliability and measurement error of several impairment measures used during the clinical examination of patients with patellofemoral pain syndrome (PFPS) has not been established. The purpose was to determine the inter-tester reliability and measurement error of measures of impairments associated with PFPS in patients with PFPS. METHODS: A single group repeated measures design was used. Two pairs of physical therapists participated in data collection. Examiners were blinded to each others' measurements. RESULTS: Thirty patients (age 29 +/- 8; 17 female) with PFPS participated in this study. Inter-tester reliability coefficients were substantial for measures of hamstrings, quadriceps, plantarflexors, and ITB/TFL complex length, hip abductors strength, and foot pronation (ICCs from .85 to .97); moderate for measures of Q-angle, tibial torsion, hip external rotation strength, lateral retinacular tightness, and quality of movement during a step down task (ICCs from .67 to .79); and poor for femoral anteversion (ICC of .45). Standard error of measurement (SEM) for measures of muscle length ranged from 1.6 degrees to 4.3 degrees. SEM for Q-angle, tibial torsion, and femoral anteversion were 2.4 degrees, 2.9 degrees, and 4.5 degrees respectively. SEM for foot pronation was 1 mm. SEM for measures of muscle strength was 1.8 Kg for abduction and 2.4 Kg for external rotation. CONCLUSION: Several of the impairments associated with PFPS had sufficient reliability and low measurement error. Further investigation is needed to test if these impairment measurements are related to physical function and whether or not they are useful for decision-making.

Adolescent↗
PubMed2006

Does irradiation affect the clinical outcome of patellar tendon allograft ACL reconstruction?

The clinical implications of using irradiation to sterilize allograft bone-patellar tendon-bone (BPTB) remains unknown. The purpose of this study was to compare the clinical outcome of anterior cruciate ligament (ACL) reconstruction with irradiated allograft versus autograft BPTB. We hypothesized that patients undergoing ACL reconstruction with irradiated BPTB allograft would have no significant differences in patient-reported and objective parameters compared to those undergoing autograft BPTB reconstruction. Patients who underwent ACL reconstruction with either irradiated allograft or autograft BPTB from 1996 to 2002 were eligible for this study. One hundred and two patients (39 allograft, 63 autograft) met the study criteria and were available for follow-up. The BPTB allografts were obtained from a single tissue bank and were sterilized with 2.5 Mrad of irradiation prior to distribution. Participants completed the International Knee Documentation Committee (IKDC) subjective knee form and returned for physical and radiographic examinations, instrumented measurement of laxity, and functional testing. Patients were evaluated at an average follow-up of 4.2 years (range 1.8-8.4). Those undergoing allograft reconstruction were older (44+/-8.4 vs. 25.3+/-9.3 years, p<0.001) and had a longer median time from injury to surgery (17.1 weeks vs. 9.7 weeks, p=0.04). There was no difference in IKDC Subjective Knee Scores between groups (86.7 allograft vs. 88.0 autograft, p=0.65). The average maximum manual KT-1000 side-to-side difference was 1.3 and 2.2 mm for allograft and autograft, respectively (p=0.04); however, after adjusting for age, this difference was no longer significant. 90.6% of the allograft and 82.8% of the autograft had normal/nearly normal overall IKDC physical examination rating (p=0.37). 66.7% of the allograft and 77.8% of the autograft returned to the same or more strenuous level of sports (p=0.25). Patients undergoing ACL reconstruction with irradiated allograft BPTB had similar clinical outcomes compared to those reconstructed with autograft BPTB. These data suggest that irradiation can be used to sterilize BPTB allograft without adversely affecting clinical outcome.

Activities of Daily Living↗
PubMed2006

Clinical outcomes following isolated lateral meniscal allograft transplantation.

PURPOSE: The purpose of our study was to determine the clinical outcomes following isolated lateral meniscal allograft transplantation. METHODS: Thirty-two patients were retrospectively reviewed following isolated lateral meniscal allograft transplantation. Twenty-five were available for subjective follow-up, and 17 were available for a complete physical examination and postoperative radiographs. The average duration of follow-up was 3.3 years (range, 2 to 6 years), and the average age of the subjects was 30 years (range, 19 to 45 years). In all, 17 patients had bony fixation and 8 had suture fixation of the anterior and posterior horns of the meniscal allograft. RESULTS: Ninety-six percent of patients believed that their overall function and activity level were improved following surgery. Short Form-36 (SF-36) physical and mental component summary scores for these subjects were higher than age- and sex-matched scores from the US population. Joint space narrowing of the transplanted lateral compartments was not significantly different when compared with the joint space narrowing of the lateral compartment of the contralateral knee. In addition, preoperative and postoperative radiographic joint space measurements of the involved lateral compartment were significantly associated with subjective assessment, symptoms, sports activity score, Lysholm score, and final International Knee Documentation Committee (IKDC) rating at latest follow-up. Finally, patients fixed with the bony technique had significantly better range of motion, according to IKDC criteria at latest follow-up, compared with the suture fixation group. CONCLUSIONS: Our results suggest that isolated meniscal allograft transplantation can be a beneficial procedure in properly selected symptomatic patients with a lateral meniscus-deficient knee. The data also suggest that earlier meniscal transplantation, before the onset of significant joint space narrowing, may result in improved outcomes. Finally, bony fixation may have a significant advantage over suture fixation, particularly with regard to knee range of motion. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Adult↗
PubMed2006

Reduction of verbal pain scores after anterior cruciate ligament reconstruction with 2-day continuous femoral nerve block: a randomized clinical trial.

BACKGROUND: Single-injection femoral nerve block analgesia and spinal anesthesia have been associated with fewer postoperative nursing interventions and successful same-day discharge after anterior cruciate ligament reconstruction. In the current study, the authors prospectively determined the effect of continuous femoral nerve block on a numeric rating scale (NRS) of pain intensity with movement for 7 postoperative days. METHODS: Patients undergoing this surgery with no history of previous invasive surgery on the same knee were recruited for this study. After standardized spinal anesthesia, intravenous sedation, and perioperative multimodal analgesia, patients received a femoral nerve catheter with (1) saline bolus (30 ml) plus saline infusion (270 ml at 5 ml/h, placebo group); (2) levobupivacaine (0.25%) bolus with saline infusion (group I), or (3) levobupivacaine (0.25%) bolus and infusion (group II). Patients were surveyed preoperatively and on postoperative days 1-4 and 7 to determine NRS scores (scale 0-10). RESULTS: Data from 233 participants were analyzed. On days 1-2, 50% of placebo patients had NRS scores of 5 or above, whereas among group II patients, only 25% had scores of 5 or above (P < 0.001). In regression models for NRS scores during days 1-4, group II was the only factor predicting lower pain scores (odds ratios, 0.3-0.5; P = 0.001-0.03). Overall, patients with preoperative NRS scores greater than 2 were likely to report higher NRS scores during days 1-7 (odds ratios, 3.3-5.2; P < 0.001). CONCLUSIONS: Femoral nerve block catheters reliably keep NRS scores below the moderate-to-severe pain threshold for the first 4 days after anterior cruciate ligament reconstruction.

Adolescent↗
PubMed2006

The intertester reliability of the Scapular Assistance Test.

STUDY DESIGN: Test-retest reliability study. OBJECTIVE: To determine interrater reliability of the modified scapular assistance test (SAT). The modified SAT is designed to assess the contribution of scapular motion to shoulder pain. BACKGROUND: Abnormal scapular motion has been implicated in different shoulder disorders. However, there is a lack of clinical evaluation tools to assess the scapular component of shoulder dysfunction. METHODS AND MEASURES: Forty-six subjects who were referred to physical therapy for treatment of various shoulder pathologies were recruited for this study. The modified SAT was performed on each participant by 2 different examiners. Percent agreement and kappa coefficient were utilized to determine interrater reliability of the modified SAT. RESULTS: The kappa coefficient and percent agreement were .53 and 77%, respectively, when the test was performed in the scapular plane, and .62 and 91%, respectively, when the test was performed in the sagittal plane. CONCLUSIONS: The modified SAT possesses acceptable interrater reliability for clinical use.

Adult↗
PubMed2005

The International Knee Documentation Committee Subjective Knee Evaluation Form: normative data.

BACKGROUND: The International Knee Documentation Committee Subjective Knee Evaluation Form may be used to measure symptoms, function, and sports activity for people with a variety of knee disorders, including ligamentous and meniscal injuries, osteoarthritis, and patellofemoral dysfunction. To date, normative data have not been established for this valid, reliable, and responsive outcomes instrument. PURPOSE: To provide clinicians and researchers with normative data to facilitate the interpretation of results on the International Knee Documentation Committee Subjective Knee Evaluation Form. STUDY DESIGN: Cross-sectional survey. METHODS: The Subjective Knee Evaluation Form was mailed to 600 people in each of 8 age/gender categories (18-24 years, 25-34 years, 35-50 years, and 51-65 years for both male subjects and female subjects). Participants were drawn from a panel of 550 000 households (1 300 000 subjects) representative of noninstitutionalized persons in the United States and were matched to data from the United States Census Bureau on geographical region, market size, income, and household size. RESULTS: Complete data were available for 5246 knees. Twenty-eight percent of respondents reported an injury, weakness, or other problem with one or both knees. Normative data were determined for respondents as a whole and for the subset of respondents with no history of knee problems. Mean scores were determined for men aged 18 to 24 years (89 +/- 18), 25 to 34 years (89 +/- 16), 35 to 50 years (85 +/- 19), and 51 to 55 years (77 +/- 23); mean scores were also determined for women aged 18 to 24 years (86 +/- 19), 25 to 34 years (86 +/- 19), 35 to 50 years (80 +/- 23), and 51 to 65 years (71 +/- 26). Scores were higher for the subset of respondents with no history of current or prior knee problems. CONCLUSION: Scores on the International Knee Documentation Committee Subjective Knee Evaluation Form vary by age, gender, and history of knee problems. The normative data collected in this article will allow clinicians to interpret how patients with knee injuries are functioning relative to their age- and gender-matched peers and will enable researchers to determine the clinical outcomes of treatment.

Adolescent↗
PubMed2005

Development of a clinical prediction rule for the diagnosis of carpal tunnel syndrome.

OBJECTIVES: To develop a clinical prediction rule (CPR) and to assess the reliability and diagnostic accuracy of individual clinical examination items for the diagnosis of carpal tunnel syndrome (CTS). DESIGN: Prospective diagnostic test study with blind comparison to a reference criterion of a compatible clinical presentation and abnormal electrophysiologic findings. SETTING: Multicenter medical center and community hospital with patient referrals from ambulatory primary care and specialty practice settings. PARTICIPANTS: Eight-two consecutively referred patients (50% men; mean age, 45+/-12 y) with suspected cervical radiculopathy or CTS referred for electrophysiologic examination. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Sensitivity, specificity, and likelihood ratios. RESULTS: The CPR identified in this study consisted of 1 question (shaking hands for symptom relief), wrist-ratio index greater than .67, Symptom Severity Scale score greater than 1.9, reduced median sensory field of digit 1, and age greater than 45 years. The likelihood ratio for the CPR was 18.3 when all 5 tests were positive. Interrater reliability was acceptable for all but 2 clinical examination items. CONCLUSIONS: The CPR identified was more useful for the diagnosis of CTS than any single test item and resulted in posttest probability changes of up to 56%. Further investigation is required both to validate the test-item cluster and to improve point-estimate precision.

Adult↗
PubMed2005

Clinical outcomes after isolated arthroscopic single-bundle posterior cruciate ligament reconstruction.

PURPOSE: The purpose of this study was to evaluate the clinical outcomes after arthroscopic single-bundle posterior cruciate ligament (PCL) reconstruction in patients with isolated grade III PCL injuries. TYPE OF STUDY: Retrospective review. METHODS: Twenty-one patients who underwent an isolated arthroscopic single-bundle PCL reconstruction for the treatment of a grade III PCL injury between 1989 and 1998 were included in the study. There were 15 male and 6 female patients with an average age of 38 years (range, 20 to 62 years). The length of follow-up was 5.9 years (range, 2.6 to 11 years), and the average time from injury to surgery was 4.5 years (median, 1.3 years; range, 2 weeks to 25 years). All patients completed a subjective evaluation and 14 patients returned for a physical examination and radiographs. One patient underwent an acute reconstruction (<3 weeks), 4 had a subacute (<3 months), and 16 underwent a chronic (>3 months) reconstruction. The anterolateral bundle of the PCL was reconstructed using an Achilles tendon allograft passed through femoral and tibial bone tunnels. RESULTS: The overall average Activities of Daily Living Scale (ADLS), Sports Activities Scale (SAS), and SF-36 scores were 79.3, 71.6, and 98 points, respectively. There was a significant difference identified when the ADLS (91.3 v 75.6) and the SAS (90.4 v 65.8) scores of the subacute/acute group were compared with those of the chronic reconstruction group. Using the International Knee Documentation Committee (IKDC) subjective assessment, 57% of the patients had normal/near normal knee function, and 62% had a normal/near normal activity level. The average extension and flexion losses were 1 degrees and 5 degrees , respectively. Instrumented laxity examination revealed that 62% had less than a 3-mm and 31% had a 3- to 5-mm side-to-side difference in corrected posterior displacement. Radiographs at follow-up showed that 75% had normal/near normal findings according to IKDC guidelines. CONCLUSIONS: The clinical outcomes after arthroscopic single-bundle PCL reconstruction in this study produced a satisfactory return of function and improvement in symptoms. All patients in this study had improved laxity of at least 1 grade. When compared with chronic reconstructions, acute reconstructions had statistically significant better ADLS and SAS scores. LEVEL OF EVIDENCE: IV, case series.

Achilles Tendon↗
PubMed2005

Evidence of validity for the Foot and Ankle Ability Measure (FAAM).

BACKGROUND: There is no universally accepted instrument that can be used to evaluate changes in self-reported physical function for individuals with leg, ankle, and foot musculoskeletal disorders. The objective of this study was to develop an instrument to meet this need: the Foot and Ankle Ability Measure (FAAM). Additionally, this study was designed to provide validity evidence for interpretation of FAAM scores. METHODS: Final item reduction was completed using item response theory with 1027 subjects. Validity evidence was provided by 164 subjects that were expected to change and 79 subjects that were expected to remain stable. These subjects were given the FAAM and SF-36 to complete on two occasions 4 weeks apart. RESULTS: The final version of the FAAM consists of the 21-item activities of daily living (ADL) and 8-item Sports subscales, which together produced information across the spectrum ability. Validity evidence was provided for test content, internal structure, score stability, and responsiveness. Test retest reliability was 0.89 and 0.87 for the ADL and Sports subscales, respectively. The minimal detectable change based on a 95% confidence interval was +/-5.7 and +/--12.3 points for the ADL and Sports subscales, respectively. Two-way repeated measures ANOVA and ROC analysis found both the ADL and Sports subscales were responsive to changes in status (p < 0.05). The minimal clinically important differences were 8 and 9 points for the ADL and Sports subscales, respectively. Guyatt responsive index and ROC analysis found the ADL subscale was more responsive than general measures of physical function while the Sports subscale was not. The ADL and Sport subscales demonstrated strong relationships with the SF-36 physical function subscale (r = 0.84, 0.78) and physical component summary score (r = 0.78, 0.80) and weak relationships with the SF-36 mental function subscale (r = 0.18, 0.11) and mental component summary score (r = 0.05, -0.02). CONCLUSIONS: The FAAM is a reliable, responsive, and valid measure of physical function for individuals with a broad range of musculoskeletal disorders of the lower leg, foot, and ankle.

Activities of Daily Living↗
PubMed2005

Differences in quadriceps femoris muscle torque when using a clinical electrical stimulator versus a portable electrical stimulator.

BACKGROUND AND PURPOSE: There have been conflicting views and evidence reported in the literature concerning differences in muscle torque-generating capacities between clinical ("plug-in") console devices whose power source is provided by an electrical outlet (60 Hz, alternating current-driven) and portable electrical muscle stimulators (smaller, battery-operated stimulators). The purpose of this study was to compare the torque-generating capacity of the quadriceps femoris muscle during neuromuscular electrical stimulation (NMES) between a clinical neuromuscular electrical stimulator (VersaStim 380) and a portable neuromuscular electrical stimulator (Empi 300PV). SUBJECTS: Forty volunteer subjects with no known knee, neurological, or cardiovascular pathology (22 male, 18 female) participated in the study. METHODS: All subjects were tested with the clinical and portable stimulators on 2 separate days. Peak isometric torque of the quadriceps femoris muscle was measured using a Biodex dynamometer. Peak isometric quadriceps femoris muscle torque achieved during NMES and the average quadriceps femoris muscle torque integral produced over 10 NMES contractions were measured for each stimulator. Subjects also rated the amount of pain they experienced during the 10 NMES contractions using a numeric pain scale. Paired t tests were used to compare mean differences in measured variables between stimulator conditions. RESULTS: There were no differences in the peak torque or numeric pain ratings during the electrically stimulated contractions between stimulator conditions. The Empi 300PV produced a greater average torque integral compared with the VersaStim 380 during 10 electrically stimulated contractions (Empi 300PV=988.6-/+330.4 N.m-s, Versastim 380=822.7-/+292.6 N.m-s). DISCUSSION AND CONCLUSION: The portable Empi 300PV stimulator produced comparable levels of average peak torque at comparable levels of discomfort to those produced by the VersaStim 380 clinical stimulator. The Empi 300PV maintained greater amounts of torque production during a 10-contraction training session compared with the VersaStim 380. Based on these data, we believe that the Empi 300PV has the potential to produce adequate levels of torque production for NMES quadriceps femoris muscle performance training. Further study is needed to determine the effectiveness of using the Empi 300PV for quadriceps femoris muscle performance training.

Adult↗
PubMed2004

A clinical prediction rule to identify patients with low back pain most likely to benefit from spinal manipulation: a validation study.

BACKGROUND: Conflicting evidence exists about the effectiveness of spinal manipulation. OBJECTIVE: To validate a manipulation clinical prediction rule. DESIGN: Multicenter randomized, controlled trial. SETTING: Physical therapy clinics. PATIENTS: 131 consecutive patients with low back pain, 18 to 60 years of age, who were referred to physical therapy. INTERVENTION: Patients were randomly assigned to receive manipulation plus exercise or exercise alone by a physical therapist for 4 weeks. MEASUREMENTS: Patients were examined according to the clinical prediction rule criteria (symptom duration, symptom location, fear-avoidance beliefs, lumbar mobility, and hip rotation range of motion). Disability and pain at 1 and 4 weeks and 6 months were assessed. RESULTS: Outcome from spinal manipulation depends on a patient's status on the prediction rule. Treatment effects are greatest for the subgroup of patients who were positive on the rule (at least 4 of 5 criteria met); health care utilization among this subgroup was decreased at 6 months. Compared with patients who were negative on the rule and received exercise, the odds of a successful outcome among patients who were positive on the rule and received manipulation were 60.8 (95% CI, 5.2 to 704.7). The odds were 2.4 (CI, 0.83 to 6.9) among patients who were negative on the rule and received manipulation and 1.0 (CI, 0.28 to 3.6) among patients who were positive on the rule and received exercise. A patient who was positive on the rule and received manipulation has a 92% chance of a successful outcome, with an associated number needed to treat for benefit at 4 weeks of 1.9 (CI, 1.4 to 3.5). LIMITATIONS: The response rate for the 6-month follow-up resulted in inadequate power to detect statistically significant differences for some comparisons. CONCLUSIONS: The spinal manipulation clinical prediction rule can be used to improve decision making for patients with low back pain.

Adolescent↗
PubMed2004

Reports of joint instability in knee osteoarthritis: its prevalence and relationship to physical function.

OBJECTIVE: To report the prevalence and relationship of self-reported knee instability to physical function in a sample of subjects with knee osteoarthritis (OA), and to discuss the implications of these observations for rehabilitation. METHODS: Subjects were 105 individuals (80 females) with knee OA who rated their knee instability severity on a 6-point numeric scale in response to the query "To what degree does giving way, buckling, or shifting of the knee affect your level of daily activity?" A principal component analysis was used to combine The Western Ontario and McMaster Universities pain, stiffness, and physical function subscale scores, and the Timed Get Up and Go Test score into a principal component score for physical function (PCPF). Other variables that could affect the PCPF such as age, sex, years with knee OA, radiographic severity of knee OA, knee pain, knee motion, and quadriceps strength were also recorded. The prevalence of self-reported knee instability was determined by calculating the proportion of subjects who reported each severity level of knee instability. Hierarchical regression analysis was performed to determine if the level of self-reported knee instability could predict the PCPF, even after accounting for the effects of the other variables. RESULTS: Sixty-three percent of the subjects reported knee instability during activities of daily living, and 44% reported that instability affects their ability to function. The severity of self-reported knee instability was associated with the PCPF (eta2=0.40, P <0.001), and after controlling for all other independent variables, significantly increased the prediction of the PCPF (r2=0.56, r2 change=0.05; P <0.001). CONCLUSION: The results indicate that a substantial proportion of individuals with knee OA report episodes of knee instability during activities of daily living, and instability affects physical function beyond that which can be explained by contributions from other impairments such as knee pain, range of motion, and quadriceps strength. Knee instability is a problem that should be specifically addressed in rehabilitation programs and may require interventions beyond those that address pain, joint motion, and muscular strength, to maximize the effectiveness of rehabilitation for individuals with knee OA.

Activities of Daily Living↗
PubMed2004

Quadriceps activation failure as a moderator of the relationship between quadriceps strength and physical function in individuals with knee osteoarthritis.

OBJECTIVE: To determine if quadriceps activation failure (QAF) moderates the relationship between quadriceps strength and physical function in individuals with knee osteoarthritis (OA). METHODS: Quadriceps strength and QAF were measured in 105 subjects (80 females) with radiographically confirmed knee OA using a burst-superimposition maximum voluntary isometric quadriceps torque test procedure. Subjects performed the Get Up and Go test as a physical performance measure of function and completed the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) as a self-report measure of function. A principal component analysis was performed to combine the Get Up and Go score and the WOMAC subscores into a single function score. Hierarchical regression analysis was performed to examine the ability of 3 models to predict physical function (strength = function; strength + QAF = function; strength + QAF + [strength x QAF] = function). Partial F tests were used to compare differences in R(2) values between each model. RESULTS: Each model independently predicted the principal component score for function. Adding the strength x QAF interaction term with strength to the model resulted in the highest prediction of function. The strength x QAF interaction indicated that subjects with lower levels of quadriceps strength and higher levels of QAF had lower levels of function than those with comparable levels of weakness but low levels of QAF. CONCLUSION: The magnitude of QAF serves to moderate the relationship between quadriceps strength and physical function. Physical function may be more severely affected by weakness of the quadriceps muscles in individuals with knee OA who have higher degrees of QAF than those who may have quadriceps weakness, but do not have QAF.

Exercise Test↗