Impulse-forces during walking are not increased in patients with knee osteoarthritis

Background Impulsive forces in the knee joint have been suspected to be a co-factor in the development and progression of knee osteoarthritis. We thus evaluated the impulsive sagittal ground reaction forces (iGRF), shock waves and lower extremity joint kinematics at heel strike during walking in knee osteoarthritis (OA) patients and compared them to those in healthy subjects.

Subjects and methods We studied 9 OA patients and 10 healthy subjects using three-dimensional gait analyses concentrated on the heel strike. Impulse GRF (iGRF) was measured together with peak accelerations (PA) at the tibial tuberosity and sacrum. Sagittal lower extremity joint angles at heel strike were extracted from the gait analyses. As OA is painful and pain might alter movement strategies, the patient group was also evaluated following pain relief by intraarticular lidocaine injections.

Results The two groups showed similar iGRF, similar tibial and sacral PA, and similar joint angles at heel strike. Following pain relief, the OA patients struck the ground with more extended hip and knee joints and lower tibial PA compared to the painful condition. Although such changes occurred after pain relief, all parameters were within their normal ranges.

Interpretation OA patients and healthy subjects show similar impulse-forces and joint kinematics at heel strike. Following pain relief in the patient group, changes in tibial PA and in hip and knee joint angles were observed but these were still within the normal range. Our findings make us question the hypothesis that impulse-forces generated at heel strike during walking contribute to progression of OA.     

Impulse-forces during walking are not increased in patients with knee osteoarthritis

Background?Impulsive forces in the knee joint have been suspected to be a co-factor in the development and progression of knee osteoarthritis. We thus evaluated the impulsive sagittal ground reaction forces (iGRF), shock waves and lower extremity joint kinematics at heel strike during walking in knee osteoarthritis (OA) patients and compared them to those in healthy subjects.

Subjects and methods?We studied 9 OA patients and 10 healthy subjects using three-dimensional gait analyses concentrated on the heel strike. Impulse GRF (iGRF) was measured together with peak accelerations (PA) at the tibial tuberosity and sacrum. Sagittal lower extremity joint angles at heel strike were extracted from the gait analyses. As OA is painful and pain might alter movement strategies, the patient group was also evaluated following pain relief by intraarticular lidocaine injections.

Results?The two groups showed similar iGRF, similar tibial and sacral PA, and similar joint angles at heel strike. Following pain relief, the OA patients struck the ground with more extended hip and knee joints and lower tibial PA compared to the painful condition. Although such changes occurred after pain relief, all parameters were within their normal ranges.

Interpretation?OA patients and healthy subjects show similar impulse-forces and joint kinematics at heel strike. Following pain relief in the patient group, changes in tibial PA and in hip and knee joint angles were observed but these were still within the normal range. Our findings make us question the hypothesis that impulse-forces generated at heel strike during walking contribute to progression of OA.     

Conversion of fused hip to total hip arthroplasty with presurgical and postsurgical gait studies

This case study presents a subject with a fused hip converted to total hip arthroplasty. Kinematic gait analysis was conducted on 3 occasions, presurgery, 4 months postsurgery, and 2.5 years postsurgery. Presurgery data showed decreased cadence and shorter step length; sound limb possessed increased hip, knee range of motion (ROM), and increased knee flexion during stance; the affected limb had minimal hip motion and normal knee ROM with abnormal pattern. At 4 months postsurgery, the sound limb showed decreased step length, whereas the affected limb showed increased knee extension during stance and increased hip ROM. Data obtained at 2.5 years postsurgery indicated decreased cadence and speed and increased ROM in both limbs. The total hip arthroplasty had provided relief of chronic back and affected hip pain and improved mobility. Gait-specific training is recommended.     

Changes in pain, stiffness and physical function in patients with osteoarthritis waiting for hip or knee joint replacement surgery

OBJECTIVE: Little has been reported on changes in health status in patients with osteoarthritis (OA) while waiting for hip or knee replacement surgery. In this study we assessed (1) changes in self-reported pain, stiffness and physical function in patients with OA of the hip or knee, from the decision to undergo surgery to 14 days prior to surgery, and (2) the determinants of these changes. METHODS: Among 353 baseline respondents, 170 waited >30 days for surgery, completed the Western Ontario and McMaster Universities Arthritis Index (WOMAC) before surgery and were included in the analysis of changes; 120 with OA of the hip and 50 of the knee. We analyzed changes in WOMAC scores using the paired t test and determinants of the changes using multiple linear regression. RESULTS: Patients with OA of the hip did not change on any WOMAC scale before surgery. Knee patients deteriorated with time on the WOMAC stiffness and total scales, but not on the pain or physical function subscales. In both patient categories, higher baseline WOMAC scores were associated with smaller changes on all subscales and the total score, and female sex was associated with deterioration on the pain subscale. CONCLUSIONS: Patients with OA of the hip reported no change in pain, stiffness or physical function while waiting for joint replacement surgery, whereas patients with OA of the knee deteriorated on the stiffness and total scales of the WOMAC. This suggests a difference in patient selection, referral pattern or disease development between the patient categories.     

Adipokines correlate with pain in lower limb osteoarthritis: different associations in hip and knee

Purpose

Our aim was to investigate whether serum and synovial-fluid (SF) concentrations of interleukin-6 (IL-6), leptin, adiponectin, resistin or visfatin are associated with joint pain in hip and knee in end-stage osteoarthritis (OA).

Methods

A cross-sectional study assessing patients with hip and knee OA undergoing total joint arthroplasty between January and December 2010 was conducted at a large university hospital. Serum and SF cytokine and adipokine concentrations were determined in samples obtained on the day of surgery. The main outcome was pain severity measured pre-operatively using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and visual analogue scale (VAS) pain scores.

Results

A total of 206 patients were involved (112 with hip and 94 with knee OA). Median age was 72 years [interquartile range (IQR) 66–79], 59 % were women. All adipokine levels were significantly higher in the SF of hip joints than in that of knee joints, except for leptin, which tended to be higher in the knee. In both hip and knee OA, median serum concentrations of leptin, adiponectin, resistin and visfatin exceeded those in SF, whereas for IL-6, median concentrations were much higher in SF than in serum. In hip OA, worse pain was significantly associated with high SF concentrations of IL-6, visfatin and leptin; in knee OA, it was associated with high SF leptin and low SF adiponectin concentrations and a low adiponectin–leptin ratio.

Conclusion

Our findings support a connection between intra-articular concentrations of several adipokines and severity of preoperative OA pain. However, the specific adipokines differed by joints: in hip OA, pain was associated with IL-6 and visfatin and in knee OA with adiponectin; leptin played a role in both hip and knee OA.     

Reduced muscle radiological density, cross-sectional area, and strength of major hip and knee muscles in 22 patients with hip osteoarthritis

BACKGROUND: Patients with hip osteoarthritis (OA) typically suffer joint pain, and often experience muscular weakness. We hypothesized that substantial atrophy would manifest in multiple muscle groups along the affected limb, resulting in severe muscle dysfunction. PATIENTS AND METHODS: We assessed 22 elderly patients with unilateral OA for maximal voluntary isometric strength of hip and knee muscles using a dynamometer that was developed for the purpose. Cross-sectional area (CSA) and radiological density (RD; in Hounsfield units: HU) of hip and knee muscles were assessed using CT. We determined SF-36, HHS, and EQ-5D. RESULTS: Hip extension, flexion, adduction, abduction, and knee extension strength were reduced (11- 29%; p < 0.01) in the OA limb relative to the healthy limb. Muscle CSA of hip extensors, flexors, adductors, knee extensors and flexors, but not hip abductors, was reduced (11-19%; p < 0.01) in the OA limb, where RD of all muscle groups except hip flexors was reduced (5-15 HU; p < 0.01). The clinical scores confirmed impairment. INTERPRETATION: Major muscles functioning around the hip and knee showed substantial loss of strength and mass, which contributes to the reduced ambulatory capacity of OA patients. Reduced muscle CSA could not fully explain the loss in strength. Infiltration with fat or other non-contractile components, as indicated by a reduced RD, in OA limb muscles was substantial.     

Knee and hip radiographic osteoarthritis predict total hip bone loss in older adults: A prospective study

The relationship between osteoarthritis (OA) and osteoporosis remains controversial. This study was designed to determine the association between hip and knee radiographic OA and change in total hip bone mineral density (BMD) over 2.6 years. A total of 867 population‐based randomly selected subjects (mean age 62 years, range 51 to 80 years, and 49% female) were included. Hip and knee joint space narrowing (JSN, 0 to 3) and osteophytes (0 to 3) in both lower limbs was assessed using Altman's atlas. Total hip BMD was measured by dual‐energy X‐ray absorptiometry (DXA). We found that radiographic OA (score of JSN or osteophytes > 0) was common in this sample (hip 45%, knee 68%). In multivariable analyses, percentage change in total hip BMD per year was predicted by right and left hip axial JSN (β = –0.25% and –0.29% per grade, respectively, both p < .05), right hip superior femoral osteophytes (grades 2 and 3 versus 0: β = –1.60, p < .05), combined right and left knee tibiofemoral JSN (β = –0.06 per grade from grades 0 to 12, p < .05), and osteophytes (β = –0.06 per grade from grades 0 to 14, p < .05) independent of each other and joint pain. In conclusion, older subjects with radiographic hip and knee OA have higher total hip bone loss over 2.6 years regardless of symptoms, suggesting that consideration should be given to the monitoring of bone mass in these subjects. © 2010 American Society for Bone and Mineral Research.     

A comparison of outcomes in osteoarthritis patients undergoing total hip and knee replacement surgery

OBJECTIVE: The aims of this study were to assess changes in physical function and quality of life with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the instrument of the Medical Outcomes Study SF-36 Health Survey (MOS SF-36), respectively, in patients undergoing hip anf knee joint replacement surgery and to compare the responsiveness of these two outcome measures 1 year after surgery. DESIGN: One hundred and ninety-four patients with osteoarthritis (OA knee 108, OA hip 86) admitted to four hospitals in Sydney were followed over a period of 1 year at 3 monthly intervals. RESULTS: WOMAC measures improved significantly after 1 year for OA hip and OA knee: there was reduction in pain of 71% and 53%, reduction of stiffness of 55% and 43% and improvement in physical function of 68% and 43%, respectively. MOS SF-36 measures in those having hip surgery improved significantly for pain (222%), physical function (247%), physical role functioning (402%), general health (110%), vitality (143%0, social functioning (169%) and mental health (114%). For those in the knee surgery group, significant improvement was seen for pain (175%), physical function (197%), physical role functioning (275%), vitality (125%) and social functioning (119%). The WOMAC was a more responsive measure than the MOS SF-36. CONCLUSION: WOMAC and MOS SF-36 detect significant and clinically meaningful changes in outcome after hip and knee replacement. WOMAC requires a smaller sample size and is more responsive in the short term. For a follow-up longer than 6 months MOS SF-36 provides additional information. The improvement in outcomes following hip joint surgery were significantly greater than those following knee surgery.     

A 5-year randomized controlled, double-blind study of glycosaminoglycan polysulphuric acid complex (Rumalon) as a structure modifying therapy in osteoarthritis of the hip and knee

OBJECTIVE: To determine the structure (disease) modifying effect of a glycosaminoglycan polypeptide association complex (GP-C; Rumalon) in patients with knee and hip osteoarthritis (OA). METHODS: Double-blind, randomized, placebo-controlled five-year study. Primary assessment criterion was change in radiographic joint space width between baseline and follow-up at 5 years. Secondary outcome criteria included Lequesne algofunctional index (LAI), pain on passive motion and consumption of non-steroidal antiinflammatory drugs (NSAIDs). The patients received 10 courses of injections of placebo or GP-C 2 ml intramuscularly in 5 years (two courses each year). Each course included 15 injections administered twice weekly. RESULTS: There were 277 patients with knee OA and 117 patients with hip OA. Control and GP-C treated groups were comparable as to sex, age, duration of disease, body weight, X-ray stage and value of LAI at the baseline. Knee joint space at 5 years decreased 0.37+/-0.08 (mean+/-standard deviation) mm for GP-C and 0.42+/-0.08 mm for placebo groups (P=0.68). Hip joint space at 5 years decreased 0.21+/-0.08 mm for GP-C and 0.22+/-0.08 mm for placebo groups (P=0.53). In a subset of patients with hip OA, Kellgren-Lawrence> or =2 and JSW> or =1 mm, there was a trend in favor of GPC for lower joint space narrowing in 5 years (P=0.11). In addition, there were no statistical differences between the treatment groups in LAI, pain on passive motion and consumption of NSAIDs. Side-effects after GP-C (14.5%) were rare, mild and not more frequent than in the placebo group (15%). CONCLUSION: We were not able to demonstrate a structure modifying effect of GP-C in OA of the hip or knee. Radiographic progression of OA in both knee and hip OA was lower than expected in both study groups.     

Osteoarthritis of the knee and hip and activity: a systematic international review and synthesis (OASIS)

The goal of this study was to determine which activities in four domains, daily life, exercises, sports and occupational activities, should be recommended, in favor or against, for the patient suffering from knee or hip OA. METHODS: Scientific literature was searched in Medline, Embase and Cochrane databases for articles in French or English, reporting original data. The articles were evaluated with standardized epidemiological criteria. Seventy-two articles were retained. Recommendations were graded according to the level of scientific evidence (A high, B moderate, C clinical consensus) and were formulated for primary care. CONCLUSIONS AND RECOMMENDATIONS: For activity of daily life (ADL), the OASIS group states with a moderate level of scientific evidence, that ADL are a risk factor for knee OA and that risk increases with intensity and duration of activity. The group concludes that healthy subjects as well as OA patients in general can pursue a high level of physical activity, provided the activity is not painful and does not predispose to trauma (grade B). Radiographic or clinical OA is not a contraindication to promoting activity in patients who have a sedentary lifestyle (grade C). For exercises and other structured activities pursued with a goal of health improvement, the group states with a high level of scientific evidence that they have a favourable effect on pain and function in the sedentary knee OA patient. The OASIS group recommends the practice of exercises and other structured activities for the sedentary patient with knee OA (grade A). Static exercises are not favored over dynamic exercises, availability, preference and tolerance being the criteria for the choice of an exercise (grade A). As results deteriorate when exercises are stopped, they should be performed at a frequency of between one and three times per week (grade B). Professional assistance can be useful in improving initial compliance and perseverance (grade B). There is no scientific argument to support halting exercise in case of an OA flare-up (grade C). For sports and recreational activity, the group states with a high degree of scientific evidence, that these activities are a risk factor for knee and hip OA and that the risk correlates with intensity and duration of exposure. The group also states, with a high degree of scientific evidence, that the risk of OA associated with sport is lesser than that associated with a history of trauma and overweight. No firm conclusion could be drawn about the possible protective role of sports such as cycling, swimming or golf. The OASIS group recommends that athletes should be informed that joint trauma is a greater risk factor than the practice of sport (Grade A). The high level athlete should be informed that the risk of OA is associated with the duration and intensity of exposure (Grade B). The OA patient can continue to engage regularly in recreational sports as long as the activity does not cause pain (Grade C). The OA patient who practices a sport at risk for joint trauma should be encouraged to change sport (Grade C). For occupational activity, the OASIS group states with a high level of scientific evidence that there is a relationship between occupational activity and OA of the knee and hip. The precise nature of biomechanical stresses leading to OA remains unclear but factors such as high loads on the joint, unnatural body position, heavy lifting, climbing and jumping may contribute to knee and hip OA. The group recommends that taking an occupational history should always be part of managing the OA patient (Grade B). In the knee or hip OA patient, work-related activity that produces or maintains pain should be avoided (Grade B). Physicians should be alerted by the early knee and hip signs and symptoms in workers exposed to stresses that are known or supposed to favour knee or hip OA (Grade C).     

The KHOALA cohort of knee and hip osteoarthritis in France

ObjectivesThis study aimed to describe the prevalence of symptomatic knee and hip osteoarthritis (OA) and its course over time, as well as identify prognostic factors of OA course and determinants of costs and access to care in France in a patient cohort.MethodsSubjects aged 40 to 75 years, with uni- or bilateral symptomatic hip and/or knee OA (ACR criteria), Kellgren and Lawrence (KL) stage 2 or greater, were recruited from a French national prevalence survey for the multicenter KHOALA cohort study. Data collected at baseline included sociodemographic and clinical data; WOMAC, IKS and Harris scores for pain and function; MAQ score for physical activity; functional comorbidity index; GHQ28 score for psychological status; and SF-36 (generic) and OAKHQOL (specific) scores for quality of life. Blood and urine samples were collected.ResultsEight hundred and seventy-eight subjects were included, 222 with OA of the hip (mean age 61.2 ± 8.8 years), 607 knee (mean age 62.0 ± 8.5 years) and 49 both hip and knee (mean age 64.9 ± 7.9 years). Mean body mass index was 26.9 ± 4.5 for hip OA and 30.3 ± 6.3 for knee OA. Hip and knee OA patients had 1.99 and 2.06 comorbidities, on average, respectively. Disease severity on X-rays for KL stages 2, 3 and 4 for hip OA was 69.8, 26.1 and 4.1%, respectively, and for knee OA, 44.5, 30.3, and 25.2%. As compared with population norms, age- and sex-standardized SF-36 scores were greatly decreased for both knee and hip OA in all dimensions, particularly physical and emotional dimensions.PerspectivesPatients will be followed up annually, alternately by mail and clinical visit. This cohort of representative patients with knee and hip OA will be an opportunity for future collaborative research.     

Gentamicin concentrations in diagnostic aspirates from 25 patients with hip and knee arthroplasties

BACKGROUND: There is little information on long-term release of antibiotics from impregnated bone cement. PATIENTS AND METHODS: We assayed joint fluids obtained for diagnostic purposes from 25 patients for the presence of gentamicin. All patients had presented with failing or painful joints up to 20 years following primary hip or knee arthroplasty, using gentamicin-impregnated cement. RESULTS: Gentamicin was detected in the joint fluids from 9 of 15 patients with knee prostheses and 4 of 10 patients with hip prostheses. The concentrations ranged from 0.06 mg/L to 0.85 mg/L with no significant differences in concentration between the patients with hip or knee prostheses, or the type of prosthesis. We found no relationship between the gentamicin concentration and the time after primary arthroplasty. INTERPRETATION: Although most concentrations were below the levels required to inhibit susceptible pathogens, we conclude that gentamicin release around failing implants may lead to false negative cultures in some patients and provide selective pressure for the emergence of resistance where infection is present in others.     

Development of a clinical prediction rule for diagnosing hip osteoarthritis in individuals with unilateral hip pain

STUDY DESIGN: Prospective cohort/predictive validity study. OBJECTIVE: To determine the diagnostic accuracy of common clinical examination items and to construct a preliminary clinical prediction rule for diagnosing hip osteoarthritis (OA) in individuals with unilateral hip pain. BACKGROUND: The current gold standard for the diagnosis of hip OA is a standing anteroposterior (AP) radiograph of the pelvis. Other than for Altman's criteria, little research has been done to determine the accuracy of clinical examination findings for diagnosing hip OA. METHODS AND MEASURES: Seventy-two subjects completed the study. Each subject received a standardized history, physical examination, and standing AP radiograph of the pelvis. Subjects with a Kellgren and Lawrence score of 2 or higher based on the radiographs were considered to have definitive hip OA. Likelihood ratios (LRs) were computed to determine which clinical examination findings were most diagnostic of hip OA. Potential predictor variables were entered into a logistic regression model to determine the most accurate set of clinical examination items for diagnosing hip OA. RESULTS: Twenty-one (29%) of the 72 subjects had radiographic evidence of hip OA. A clinical prediction rule consisting of 5 examination variables was identified. If at least 4 of 5 variables were present, the positive LR was equal to 24.3 (95% confidence interval: 4.4-142.1), increasing the probability of hip OA to 91%. CONCLUSION: The preliminary clinical prediction rule provides the ability to a priori identify patients with hip pain who are likely to have hip OA. A validation study should be done before the rule can be implemented in routine clinical practice. LEVEL OF EVIDENCE: Diagnosis, level 2b.J Orthop Sports Phys Ther. 2008;38(9):542-550, published online 14 July 2008. doi:10.2519/jospt.2008.2753KEYWORDS: arthritis, diagnosis, OA, predictive validity.     

Medial and lateral osteoarthritis of the knee is related to variations of hip and pelvic anatomy

OBJECTIVE: We evaluated if increased risk of combined hip and lateral knee osteoarthritis (OA) could be attributed to anatomical reasons in the hip region resulting in increased abductor moment over the knee. METHODS: We measured pelvic width, femoral offset, femoral neck length and angle in 29 women with lateral knee OA (13 unilateral, 16 bilateral) and 27 women with bilateral medial OA. Twenty-one of these patients with normal hips (lateral/medial OA of the knee=12/9) and 35 with associated hip OA (lateral/medial OA of the knee=17/18) were evaluated separately. Radiographic examinations in 14 women planned for hip prosthesis because of failures after hip fracture acted as controls. RESULTS: Patients with lateral OA of the knee had wider pelvis than controls (13.7 mm increased distance between the medial borders of the acetabulum, P=0.001). Patients with medial OA had 11.4mm longer distance from the centre of the femoral head to the centre of the proximal part of the femoral shaft (P=0.005), corresponding to a higher offset. The pelvic and hip anatomy also differed between patients with medial and lateral OA of the knee. In the groups without hip OA, presence of lateral knee OA was associated with a wider pelvis (P=0.009), shorter femoral neck (P=0.02) and Head-Shaft distance (P=0.04). In the groups with OA of the hip associated lateral OA of the knee also implied increased Neck Shaft angle (coxa valga, P=0.008), but there was no difference in pelvic width (P=0.15). We found a shorter lever arm over the hip in lateral knee OA compared to medial knee OA (P=0.02), but not when compared to controls. CONCLUSION: Our findings suggest that occurrence of medial or lateral OA has a biomechanical background originating from pelvis and hip anatomy.     

Disability and quality of life of patients with knee or hip osteoarthritis in the primary care setting and factors associated with general practitioners' indication for prosthetic replacement within 1 year

OBJECTIVE: To assess disability and health-related quality of life (HRQoL) of patients with knee or hip OA in primary care and to determine factors associated with GPs' opinion that their patients will need prosthetic replacement within 1 year after the consultation. METHODS: Design: A cross-sectional national survey. Setting: Primary care in France. Participants: 1471 GPs and 4183 patients with hip or knee OA. Measures: Pain on an 11-point numeric scale (0-10), disability on the Western Ontario and MacMaster Universities Osteoarthritis Index (WOMAC) (1-100) and Lequesne index (0-24), and quality of life on the Medical Outcomes Study 36-item Short Form (MOS SF-36; 0-100). RESULTS: We analyzed records of 4121 patients (2540 knee, 1581 hip OA). Patients with knee or hip OA exhibited high and similar levels of pain (5.2+/-2.1 and 5.3+/-2.3) and disability (Lequesne score: 12.0+/-4.2 and 11.8+/-4.3; WOMAC score: 45.7+/-19.3 and 45.2+/-17.3) The decrease in HRQoL was similar for patients with either location of the disease. GPs more often considered that their patients with hip OA would need prosthetic replacement within 1 year (28.1%) than those with knee OA (15.8%). Most factors associated with GPs' opinion were identified for both locations of disease and were related to disability and pain levels. CONCLUSIONS: In the primary care setting, patients with knee or hip OA have similar, high disability levels and substantially low HRQoL. Patients' disability seems to play a central role in GPs' opinion of the need for their patients with either type of OA to undergo prosthetic replacement within 1 year.     

Knee injury in patients experiencing a high-energy traumatic ipsilateral hip dislocation

BACKGROUND: Traumatic hip dislocation results from the dissipation of a large amount of energy about the hip joint. Clinically, these forces often are first transmitted through the knee en route to the hip. It is therefore logical to look for coexistent ipsilateral knee injury in patients with a traumatic hip dislocation. METHODS: Over a one-year period, we prospectively evaluated the ipsilateral knee of all patients who had a traumatic hip dislocation on the basis of a standardized history, physical examination, and magnetic resonance imaging. RESULTS: Twenty-one (75%) of the twenty-eight knees were painful. Twenty-five (89%) of the twenty-eight knees had visible evidence of soft-tissue injury on inspection. Magnetic resonance imaging revealed evidence of some abnormality in twenty-five (93%) of twenty-seven knees, with effusion (37%), bone bruise (33%), and meniscal tear (30%) being the most common findings. CONCLUSIONS: The present study provides evidence of a high rate of associated ipsilateral knee injuries in patients with a traumatic hip dislocation. Bone bruises may provide a plausible explanation for persistent knee pain following a traumatic hip dislocation. The liberal use of magnetic resonance imaging is recommended for the evaluation of these patients in order to detect injuries that may not be discoverable on the basis of a history and physical examination alone.     

Analysis of hip strength in females seeking physical therapy treatment for unilateral patellofemoral pain syndrome

STUDY DESIGN: Cross-sectional. OBJECTIVES: To investigate whether females seeking physical therapy treatment for unilateral patellofemoral pain syndrome (PFPS) exhibit deficiencies in hip strength compared to a control group. BACKGROUND: Decreased hip strength may be associated with poor control of lower extremity motion during weight-bearing activities, leading to abnormal patellofemoral motions and pain. Previous studies exploring the presence of hip strength impairments in subjects with PFPS have reported conflicting results. METHODS AND MEASURES: Twenty females, aged 12 to 35 years, participated in the study. Ten subjects with unilateral PFPS were compared to 10 control subjects with no known knee pathologies. Hip abduction, extension, and external rotation strength were tested using a handheld dynamometer. A limb symmetry index (LSI) was used to quantify physical performance for all tests. RESULTS: The symptomatic limbs of subjects with PFPS exhibited impairments in hip strength for all variables tested. LSI values in subjects with PFPS (range, 71%-79%) were significantly lower than those in control subjects (range, 93%-101%) (P< or =.007). A secondary analysis of data normalized to body mass demonstrated that the symptomatic limbs of subjects with PFPS had 52% less hip extension strength (P<.001), 27% less hip abduction strength (P = .007), and 30% less hip external rotation strength (P= .004) when compared to the weaker limbs of control subjects. CONCLUSION: Females aged 12 to 35 presenting with unilateral PFPS demonstrate significant impairments in hip strength compared to control subjects when LSI values or body mass normalized values are used to quantify physical performance of the symptomatic limb.     

Hip strength and hip and knee kinematics during stair descent in females with and without patellofemoral pain syndrome

STUDY DESIGN: Cross-sectional. OBJECTIVE: To determine if females presenting with patellofemoral pain syndrome (PFPS) from no discernable cause other than overuse demonstrate hip weakness and increased hip internal rotation, hip adduction, and knee valgus during stair descent. BACKGROUND: Historically, PFPS has been viewed exclusively as a knee problem. Recent findings have indicated an association between hip weakness and PFPS. Researchers have hypothesized that patients who demonstrate hip weakness would exhibit increased hip internal rotation, hip adduction, and knee valgus during functional activities. To date, researchers have not simultaneously examined hip and knee strength and kinematics in subjects with PFPS to make this determination. METHODS AND MEASURES: Eighteen females diagnosed with PFPS and 18 matched controls participated. Strength measures were taken for the hip external rotators and hip abductors. Hip and knee kinematics were collected as subjects completed a standardized stair-stepping task. Independent t tests were used to determine between-group differences in strength and kinematics during stair descent. RESULTS: Subjects with PFPS generated 24% less hip external rotator (P = .002) and 26% less hip abductor (P =. 006) torque. No between-group differences (P > .05) were found for average hip and knee transverse and frontal plane angles during stair descent. CONCLUSION: Subjects with PFPS had significant hip weakness but did not demonstrate altered hip and knee kinematics as previously theorized. Additional investigations are needed to better understand the association between hip weakness and PFPS etiology.