Effect of platelet-rich plasma on the degenerative rotator cuff tendinopathy according to the compositions.

BACKGROUND: There are controversies about platelet-rich plasma (PRP) as an established treatment option for rotator cuff (RC) tendinopathy. The purpose of the study was to find the relation of cellular component with clinical efficacy in RC tendinopathy and to find the composition of PRP in treating RC tendinopathy. METHODS: A total 30 patients were recruited and divided into PRP and control groups. In the PRP group, 2 ml of PRP solution was injected to the hypoechoic lesion of degenerative supraspinatus via 22-gauge syringe with peppering technique. Patients in the control group were taught rotator cuff strengthening exercises. American Shoulder and Elbow Surgeons (ASES), Constant-Murley score, and numeric rating scale (NRS) were measured before, 6 weeks after, 12 weeks after, and 24 weeks after the procedure. PRP compositions were analyzed using the 1 ml of PRP solution. RESULTS: Linear regression analysis showed no significant difference of ASES and Constant-Murley scores between the groups at 6 weeks (P = 0.582 and 0.258) and at 12 weeks (P = 0.969 and 0.795) but showed a significant difference at 24 weeks (P = 0.050 and 0.048). Independent t test showed significant group difference of NRS at 6 weeks (P = 0.031) but not at 12 and 24 weeks (P = 0.147 and 0.935). 5.19 pg/ml in IL-1ß and 61.79 µg/ml in TGF-ß1 were acquired as cutoff values to predict meaningful improvement. The PRP subgroup above IL-1ß or TGF-ß1 cutoff value showed significant differences in all clinical outcomes compared with the exercise group while the PRP subgroup below the cutoff value showed no significant differences in linear regression analysis. CONCLUSIONS: Our study can help to find the optimal PRP condition and to enhance the effect of PRP on RC tendinopathy. TRIAL REGISTRATION: All the patients were registered in our Institutional Ethics Committee (approval number 2014-05-009).

Influence of repetitive mechanical loading on MMP2 activity in tendon fibroblasts.

Matrix metalloproteinase2 has been implicated in tendon pathology caused by repetitive movements. However, its activity in the early stages of the tendon's response to overuse, and its presence in the circulation as a possible indicator of tendon degradation, remain unknown. Human tendon cells were repetitively stretched for 5 days, and the rabbit Achilles tendon complex underwent repetitive motion 3× per week for 2 weeks. Quantitative polymer chain reaction analysis was performed to detect matrix metalloproteinase2/14 and tissue inhibitor of matrix metalloproteinase2 messenger ribonucleic acid of cells and rabbit tissue, and matrix metalloproteinase2 protein levels were determined with an enzyme linked immunoassay. Matrix metalloproteinase2 activity was examined using zymography of the conditioned media, tendon and serum. Immunohistochemistry was used to localize matrix metalloproteinase2 in tendon tissue, and the density of fibrillar collagen in tendons was examined using second harmonic generation microscopy. Tendon cells stretched with high strain or high frequency demonstrated increased matrix metalloproteinase2 messenger ribonucleic acid and protein levels. Matrix metalloproteinase2 activity was increased in the rabbit Achilles tendon tissue at weeks 1 and 2; however, serum activity was only increased at week 1. After 2 weeks of exercise, the collagen density was lower in specific regions of the exercised rabbit Achilles tendon complex. Matrix metalloproteinase2 expression in exercised rabbit Achilles tendons was detected surrounding tendon fibroblasts. Repetitive mechanical stimulation of tendon cells results in a small increase in matrix metalloproteinase2 levels, but it appears unlikely that serum matrix metalloproteinase2 will be a useful indicator of tendon overuse injury. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1991-2000, 2016.

Is higher serum cholesterol associated with altered tendon structure or tendon pain? A systematic review.

BACKGROUND: Tendon pain occurs in individuals with extreme cholesterol levels (familial hypercholesterolaemia). It is unclear whether the association with tendon pain is strong with less extreme elevations of cholesterol. OBJECTIVE: To determine whether lipid levels are associated with abnormal tendon structure or the presence of tendon pain. METHODS: We conducted a systematic review and meta-analysis. Relevant articles were found through an electronic search of 6 medical databases-MEDLINE, Cochrane, AMED, EMBASE, Web of Science and Scopus. We included all case-control or cross-sectional studies with data describing (1) lipid levels or use of lipid-lowering drugs and (2) tendon structure or tendon pain. RESULTS: 17 studies (2612 participants) were eligible for inclusion in the review. People with altered tendon structure or tendon pain had significantly higher total cholesterol, low-density lipoprotein cholesterol and triglycerides, as well as lower high-density lipoprotein cholesterol; with mean difference values of 0.66, 1.00, 0.33, and -0.19 mmol/L, respectively. CONCLUSIONS: The results of this review indicate that a relationship exists between an individual's lipid profile and tendon health. However, further longitudinal studies are required to determine whether a cause and effect relationship exists between tendon structure and lipid levels. This could lead to advancement in the understanding of the pathoaetiology and thus treatment of tendinopathy.

Cholesterol level in non-insertional Achilles tendonopathy.

Familial hypercholesterolaemia is an autosomal dominant disease, with a prevalence of 1 in 500, where lipid deposits occur in the skin, tendons (particularly Achilles tendon) and arteries. It has a high risk of early coronary artery disease and mortality but is treatable with cholesterol lowering strategies if patients are diagnosed early. Studies in patients attending lipid clinics have shown that half the patients may have suffered from Achilles tendon symptoms 20 years earlier and it has been proposed that all patients presenting with Achilles tendon pain should have a serum cholesterol test. All consecutive patients seen in an adult foot and ankle clinic with non-insertional Achilles tendonopathy between April 2012 and March 2014 had their serum cholesterol measured. Only one patient in 83 (p=0.19) was diagnosed with heterozygous familial hypercholesterolaemia but 3 relatives of the proband patient were also diagnosed by cascade testing. Measurement of cholesterol in all patients presenting with achillodynia does not seem to be justified but the literature suggests that it should probably be considered in patients with bilateral extensive disease or those who give a history of intermittent episodes of severe pain lasting a few days.

Serum levels of oxylipins in achilles tendinopathy: an exploratory study.

BACKGROUND: Linoleic acid-derived oxidation products are found in experimental pain models. However, little is known about the levels of such oxylipins in human pain. In consequence, in the present study, we have undertaken a lipidomic profiling of oxylipins in blood serum from patients with Achilles tendinopathy and controls. METHODOLOGY/PRINCIPAL FINDINGS: A total of 34 oxylipins were analysed in the serum samples. At a significance level of P<0.00147 (<0.05/34), two linoleic acid-derived oxylipins, 13-hydroxy-10E,12Z-octadecadienoic (13-HODE) and 12(13)-dihydroxy-9Z-octadecenoic acid (12,13-DiHOME) were present at significantly higher levels in the Achilles tendinopathy samples. This difference remained significant when the dataset was controlled for age, gender and body-mass index. In contrast, 0/21 of the arachidonic acid- and 0/4 of the dihomo-γ-linolenic acid, eicosapentaenoic acid or docosahenaenoic acid-derived oxylipins were higher in the patient samples at this level of significance. The area under the Receiver-Operator Characteristic (ROC) curve for 12,13-DiHOME was 0.91 (P<0.0001). Levels of four N-acylethanolamines were also analysed and found not to be significantly different between the controls and the patients at the level of P<0.0125 (<0.05/4). CONCLUSIONS/SIGNIFICANCE: It is concluded from this exploratory study that abnormal levels of linoleic acid-derived oxylipins are seen in blood serum from patients with Achilles tendinopathy. Given the ability of two of these, 9- and 13-HODE to activate transient receptor potential vanilloid 1, it is possible that these changes may contribute to the symptoms seen in Achilles tendinopathy.

Platelet-rich plasma modulates the secretion of inflammatory/angiogenic proteins by inflamed tenocytes.

BACKGROUND: Platelet-rich plasma therapies for tendinopathy appear to provide moderate pain reduction. However, the biological mechanisms behind the observed clinical effects remain poorly characterized. QUESTIONS/PURPOSES: The purpose of this study was to explore whether platelet-rich plasma modifies the inflammatory/angiogenic status of already inflamed tenocytes by examining (1) gene expression; (2) modulation of chemokine and interleukin secretion; and (3) differences between healthy and tendinopathic tenocytes. METHODS: Cells from both healthy and tendinopathic tendons were exposed to interleukin (IL)-1ß and after treated with platelet-rich plasma. Modifications in the expression of selected genes were assessed by real-time reverse transcription-polymerase chain reaction and changes in secretion of angiogenic/inflammatory molecules by enzyme-linked immunosorbent assay. Platelet-rich plasma-induced changes in tendinopathic cells were compared with normal after normalizing platelet-rich plasma data against IL-1ß status in each specific sample. RESULTS: In IL-1ß-exposed cells, platelet-rich plasma downregulates expression of IL-6/CXCL-6 (mean, 0.015; 95% confidence interval [CI], 0.005-0.025; p = 0.026), IL-6R (mean, 0.61; 95% CI, 0.27-0.95; p = 0.029), and IL-8/CXCL-8 (mean, 0.02; 95% CI, 0.007-0.023; p = 0.026). Secretion of IL-6/CXCL6, 0.35 (95% CI, 0.3-0.4; p = 0.002), IL-8/CXCL8, 0.55 (95% CI, 0.5-0.7; p = 0.01), and monocyte chemoattractant protein-1/CCL2, 0.40 (95% CI, 0.2-0.6; p = 0.001) was reduced by platelet-rich plasma, whereas vascular endothelial growth factor increased by twofold, (95% CI, 1.7-2.3; p < 0.001). RANTES/CCL5 increased by10-fold (95% CI, 4-17) and hepatocyte growth factor by 21-fold (95% CI, 0.2-42) in tendinopathic and by 2.3-fold (95% CI, 2-3) and threefold (95% CI, 1-5) in normal cells (p = 0.005 for both). CONCLUSIONS: Platelet-rich plasma induces an immunomodulatory and proangiogenic phenotype consistent with healing mechanisms with few differences between tendinopathic and normal cells. CLINICAL RELEVANCE: Platelet-rich plasma injections in pathological and nearby tissue might help to recover tendon homeostasis.

Adipokines as predictors of recovery from upper extremity soft tissue disorders.

OBJECTIVES: To study the associations of adipokines with recovery from upper extremity soft tissue disorders (UESTDs) and to explore whether overweight or obesity modify these associations. METHODS: In this follow-up study, patients seeking medical advice due to incipient upper extremity symptoms with symptom duration <1 month were included (n = 163). The outcome of the study was full or substantial recovery from UESTDs, assessed at 2, 8 and 12 weeks of follow-up. We studied the associations of four adipokines (leptin, adiponectin, resistin and visfatin) with recovery using the generalized estimating equation. RESULTS: Of the study population, 27.5% reported full or substantial recovery at the 8-week follow-up and 32% at 12 weeks. Higher levels of resistin [odds ratio (OR) = 1.58, 95% CI 1.18, 2.11 for 1 s.d. increase] and visfatin (OR = 1.29, 95% CI 0.94, 1.78 for 1 s.d. increase) at baseline predicted a higher recovery rate at the 8-week follow-up. Moreover, higher levels of leptin predicted a lower rate of recovery (OR = 0.73, 95% CI 0.51, 1.02 for 1 s.d. increase). Adipokines did not predict recovery at 12 weeks. In subgroup analyses, high levels of resistin and visfatin at baseline predicted a higher recovery rate during follow-up in non-overweight patients. CONCLUSION: The adipokines resistin and visfatin predicted recovery from UESTDs and the associations may be related to stimulation of anti-inflammatory response mechanisms. A higher level of leptin may prevent recovery from UESTDs.

Platelet rich placebo? Evidence for platelet rich plasma in the treatment of tendinopathy and augmentation of tendon repair.

Platelet rich plasma (PRP), an autologous sample of blood with a platelet concentration above baseline values, is hypothesized to augment soft tissue healing. Its use in sports medicine has risen dramatically, with common applications including the treatment of refractory tendinopathy and augmenting tendon repair. Many commercial preparation systems are available, but the optimal preparation remains unknown. Increasing numbers of clinical studies evaluating PRP have been reported and have provided both positive and negative evidence for its effectiveness. Well-designed, controlled studies are still lacking, but PRP may have a benefit for patients with tendinopathy that is refractory to other non-surgical treatments. Its use in tendon repair is currently not supported. Randomized, controlled studies with documentation of platelet, white blood cell, and growth factor concentration in the PRP preparation are necessary for future comparative research. Use of PRP should be approached judiciously until further evidence is available.

Platelet rich plasma in tendinopathies: how to explain the failure.

Tendinopathies are very common in athletes and in people practicing sport activities. The experimental evidence that growth factors (GFs), present in platelets, enhance the recruitment, proliferation and differentiation of cells involved in tissue regeneration, has prompted the use of platelet rich plasma (PRP) preparations in the treatment of these diseases. However, at present, a sound demonstration of the clinical efficacy of PRP is still lacking. Several theoretical and practical reasons can explain the failure of the treatment: a) animal experiments have been carried out on normal tendons submitted to surgical lesions, and it is questionable whether these models may best mimic human pathology; b) the pathway of chronic tendinopathies is very complex, involving, besides GFs, many other pathogenetic factors, which operate at different stages of the disease; c) several methods have been used to produce PRP, which can result in a large variation in GF content, and in kinetics of release. Therefore, further research is desirable. As a preliminary step, it is necessary to standardize PRP preparation, and to establish the modalities of its activation and administration. Secondly, prospective, randomized, double-blind studies are needed, selecting subjects with homogenous forms of tendinopathies: load-bearing and non-load-bearing tendons, midportion and insertional tendinopathies, with or without neovascularization. Finally, new strategies in PRP use should be exploited: among them, the association of PRP with autologous stem cells or the administration of selective GFs (fibroblast growth factor, vascular endothelial growth factor, or anti-angiogenic factors), which could be better options in specific situations.

Physical activity level in Achilles tendinosis is associated with blood levels of pain-related factors: a pilot study.

Physical activity affects the pain symptoms for Achilles tendinosis patients. Brain-derived neurotrophic factor (BDNF), tumor necrosis factor-alpha (TNF-α) and their receptors have been detected in human Achilles tendon. This pilot study aimed to compare serum BDNF and soluble tumor necrosis factor receptor I (sTNFRI) levels in Achilles tendinosis patients and healthy controls and to examine the influence of physical activity, and BMI and gender, on these levels. Physical activity was measured with a validated questionnaire, total physical activity being the parameter analyzed. Physical activity was strongly correlated with BDNF among tendinosis women [Spearman's rho (ρ)=0.90, P<0.01] but not among control women (ρ=-0.08, P=0.83), or among tendinosis and control men. Physical activity was significantly correlated with sTNFRI in the entire tendinosis group and among tendinosis men (ρ=0.65, P=0.01), but not in the entire control group or among control men (ρ=0.04, P=0.91). Thus, the physical activity pattern is related to the TNF and BDNF systems for tendinosis patients but not controls, the relationship being gender dependent. This is new information concerning the relationship between physical activity and Achilles tendinosis, which may be related to pain for the patients. This aspect should be further evaluated using larger patient materials.

Ultrasonography for detecting enthesitis in juvenile idiopathic arthritis.

OBJECTIVE: Enthesitis is a major feature of juvenile idiopathic arthritis (JIA) but is difficult to diagnose clinically. Our objective was to compare the accuracy of ultrasonography with power Doppler (US-PD) versus clinical examination for diagnosing enthesitis in patients with JIA and healthy controls. METHODS: Twenty-six consecutive patients with JIA and 41 healthy volunteers underwent standardized clinical and US-PD examinations of 5 entheseal sites (proximal and distal quadricepital tendon insertions, Achilles tendon, and plantar fascia). US-PD reproducibility was evaluated. US-PD enthesitis was defined as a PD signal at the enthesis insertion. Bursitis, erosions, and cartilage vascularization were recorded. RESULTS: In the JIA group, 27 (12.5%) of the entheseal sites exhibited clinical enthesitis (distal patellar ligament in 45% of cases) and 20 (9.4%) exhibited US-PD enthesitis (distal patellar tendon in 30%), including 10 clinically normal sites (50%). US-PD enthesitis was found in several patients with oligoarthritis or polyarthritis. Clinical enthesitis (P < 0.0001) and HLA-B27-positive (P = 0.05) status were significantly associated with US-PD enthesitis. Erosion and bursitis, but not tendon thickening, were associated with US-PD enthesitis. US-PD enthesitis was not found at any of the 410 entheseal sites in controls; grade 1 cartilage vascularization was noted at 6% of the control sites. CONCLUSION: Enthesitis is a rare phenomenon in JIA. Clinically silent enthesitis is detected by US-PD and can be found in JIA categories other than enthesitis-related arthritis. Tendon thickening and cartilage vascularization can be detected in healthy controls. These findings may have implications for patient classification of the use of US-PD.

Treatment of tendon and muscle using platelet-rich plasma.

Tendon and muscle injuries are common in elite and weekend athletes. Treatment of these injuries in both groups is rapidly evolving. Sports medicine patients are demanding better and less invasive solutions for all types of musculoskeletal disorders. In this context, platelet-rich plasma (PRP) has emerged as a potential solution. PRP is a fraction of whole blood containing concentrated growth factors and proteins. These cytokines direct tissue healing through autocrine and paracrine effects. The number of basic science, animal, and human investigations of PRP for tendon and muscle injuries worldwide has risen sharply in recent years. These studies are helping clinicians better understand the mechanisms of PRP and are guiding novel treatment protocols. In this paper, the value of PRP as a treatment for acute or chronic tendon and muscle disorders is explored.

Influence of overall and abdominal adiposity on C-reactive protein levels in elderly women.

OBJECTIVE: To investigate how overall and abdominal adiposity, measured by waist circumference (WC), body mass index (BMI), and sum of skinfolds (sigmaSK), affect plasma C-reactive protein levels (CRP) in elderly women. METHODS: Study sample consisted of 387 women older than 60 years (mean age 68.9; standard deviation 5.9 years). BMI, WC, sigmaSK, and CRP levels were all measured. One-way ANOVA was performed to detect differences in study variables among the CRP levels investigated. Logistic regression analysis was used to determine the influence of body fat measurements on CRP levels. The significance level was set at p < 0.05. RESULTS: The analysis of variance showed that mean WC was lower in women with normal CRP levels, as compared to those with high CRP levels. Logistic regression analysis examined the influence of BMI, WC, and sigmaSK quartiles on CRP levels, yielding the following results: only WC was predictive of elevated CRP levels, its highest quartile (cut-off point of 94.0 cm) showing levels nearly two times higher than its lowest quartile (odds ratio = 2.23; 95% confidence interval = 1.92-4.18; p = 0.012). CONCLUSION: The results of this study indicate that abdominal adiposity is a strong predictor of elevated CRP levels.

Influência da adiposidade global e da adiposidade abdominal nos níveis de proteína C-reativa em mulheres idosas / Influence of overall and abdominal adiposity on C-reactive protein levels in elderly women

OBJETIVO: Examinar como a adiposidade global e a adiposidade abdominal, expressas pela circunferência da cintura (CC), pelo índice de massa corporal (IMC) e pelo somatório de dobras cutâneas (sigmaDC), influenciam os níveis de proteína C-reativa (PCR) em mulheres idosas. MÉTODOS: A amostra foi composta por 387 mulheres idosas, com idade superior a 60 anos (média, 68,9; desvio padrão, 5,9 anos). Foram avaliados o IMC, a CC, o sigmaDC, e os níveis de PCR. Foi utilizada a análise estatística ANOVA one-way para verificar as diferenças nas variáveis entre as categorias investigadas. Para avaliar a influência das medidas de adiposidade nos níveis de PCR foi utilizada a regressão logística. O nível de significância adotado foi de p < 0,05. RESULTADOS: A análise de variância demonstrou que o valor médio da CC foi menor na categoria normal de PCR, quando comparada aos níveis elevados de PCR. A regressão logística analisou a influência dos quartis do IMC, da CC e do sigmaDC nos níveis de PCR, em que apenas a CC foi preditora de níveis elevados de PCR, tendo o quartil extremo superior (ponto de corte de 94,0 cm) apresentado níveis quase duas vezes maiores que o quartil extremo inferior (risco estimado = 2,23; intervalo de confiança de 95 por cento = 1,92-4,18; p = 0,012). CONCLUSÃO: Os resultados do presente estudo apontam que a adiposidade abdominal é um forte preditor de níveis elevados de PCR.

OBJECTIVE: To investigate how overall and abdominal adiposity, measured by waist circumference (WC), body mass index (BMI), and sum of skinfolds (sigmaSK), affect plasma C-reactive protein levels (CRP) in elderly women. METHODS: Study sample consisted of 387 women older than 60 years (mean age 68.9; standard deviation 5.9 years). BMI, WC, sigmaSK, and CRP levels were all measured. One-way ANOVA was performed to detect differences in study variables among the CRP levels investigated. Logistic regression analysis was used to determine the influence of body fat measurements on CRP levels. The significance level was set at p < 0.05. RESULTS: The analysis of variance showed that mean WC was lower in women with normal CRP levels, as compared to those with high CRP levels. Logistic regression analysis examined the influence of BMI, WC, and sigmaSK quartiles on CRP levels, yielding the following results: only WC was predictive of elevated CRP levels, its highest quartile (cut-off point of 94.0 cm) showing levels nearly two times higher than its lowest quartile (odds ratio = 2.23; 95 percent confidence interval = 1.92-4.18; p = 0.012). CONCLUSION: The results of this study indicate that abdominal adiposity is a strong predictor of elevated CRP levels.

Soft tissue rheumatic lesions and HIV infection in Zambians.

OBJECTIVE: To explore the relationship between human immunodeficiency virus (HIV) infection and soft tissue rheumatic lesions in HIV-positive black Zambians. METHODS: We performed a prospective study of all patients over 18 years of age attending a rheumatic clinic in a teaching hospital. All patients underwent routine blood tests, and radiographs were performed when indicated. HIV status was determined by ELISA, and clinical staging was determined by World Health Organization criteria. Patients with isolated sacroiliac pain, enthesitis, or a soft tissue lesion were selected for analysis. For HIV-positive patients, only those in clinical stage 1 (asymptomatic or persistent generalized lymphadenopathy) were selected. RESULTS: Our study cohort comprised 120 patients (41 men, 79 women, age 23-70 yrs). Diagnosis and number (% HIV positive) were distributed as follows: sacroiliitis, 14 (100%); heel pain, 14 (100%); costochondritis, 3 (100%); polyenthesitis (> or = 4 sites), 20 (100%); carpal tunnel syndrome, 8 (63%); rotator cuff syndrome, 18 (30%); tendinitis, 8 (25%); sciatica/cervical spondylosis, 12 (16%); sacroiliac strain, 7 (0%); and de Quervain's tenosynovitis, 16 (0%). HIV seroprevalence was 54% overall, 74% in those under 45 years of age, and 17% in those over 45 years of age. Population prevalence of HIV in Lusaka is about 30% in the 30-40-year age range. Mean erythrocyte sedimentation rate (ESR) in 65 patients positive for HIV was 80 mm/h and in 55 patients negative for HIV, 18 mm/h. Within each subgroup the mean ESR was significantly higher in HIV-positive patients. CONCLUSION: A young age and a raised ESR are both good indications of HIV infection in Zambian patients with soft tissue lesions. Enthesitis is a distinct HIV-related phenomenon, either an early form or a forme fruste of HIV-related spondyloarthropathy.

Similarly increased serum IgA1 and IgA2 subclass antibody levels against Klebsiella pneumoniae bacteria in ankylosing spondylitis patients with/without extra-articular features.

IgA1 and IgA2 subclass serum antibodies against whole Klebsiella pneumoniae bacteria were studied earlier in the sera of 98 patients with ankylosing spondylitis (AS) and in 100 healthy blood donors by enzyme immunoassay. In this study, the patients were divided into groups according to the clinical picture, i.e., the presence or absence of iritis and enthesitis. The previous findings of increased IgA1 and IgA2 subclass antibody levels against K. pneumoniae in AS patients when compared to the healthy controls were not specifically associated with any single AS patient group in the present study, but instead were similarly seen in all patient groups with/without extra-articular features. This is in line with the previous studies suggesting a role for K. pneumoniae in the pathogenesis of AS.

ABO blood groups and musculoskeletal injuries.

The distribution of the ABO blood groups was studied in 917 patients with specific musculoskeletal diagnoses. The ABO blood group distribution of patients with rupture of the Achilles tendon (P = 0.030) and of patients with chronic Achilles peritendinitis (P = 0.10) differed from the controls. The ABO blood group distribution was not associated with other musculoskeletal injuries studied. The blood group A/O ratio was 1.42 in the control population. In the group with rupture of the Achilles tendon this ratio was 1.0, and in the group with Achilles peritendinitis it was 0.70. The association between injuries of the Achilles tendon and the ABO blood group distribution was in accordance with an earlier report. There may be a genetic linkage between the ABO blood groups and the molecular structure of the tissue of Achilles tendons.