Journal of Clinical Sciences

: 2019  |  Volume : 16  |  Issue : 3  |  Page : 93--97

Normative value of the patellar tendon size: A sonographic study of a cohort of healthy adults in a suburb of Lagos, Southwest Nigeria

Cletus Uche Eze1, Chinenye Emmanuella Nwaizugbo2, Adekunle A Adeyomoye3, Ernest Ruto Upeh4,  
1 Department of Radiography, Faculty of Clinical Sciences, College of Medicine of the University of Lagos, Idi-Araba, Lagos, Nigeria
2 Scancare Diagnostic Center, Ojodu-Berger, Ikeja, Nigeria
3 Department of Radiodiagnosis, Lagos University Teaching Hospital, Idi-Araba, Lagos, Nigeria
4 Ultrasound Unit, Ave Maria Hospital, Victoria Island, Lagos, Nigeria

Correspondence Address:
Dr. Cletus Uche Eze
Department of Radiography, Faculty of Clinical Sciences, College of Medicine of the University of Lagos, Yaba Campus, Lagos


Aim: This study aimed to determine patellar tendon (PT) size using sonographic technique. Materials and Methods: PT thickness (PTT), width, and cross-sectional area (CSA) were measured in 277 healthy adults. Mean was computed for patella tendon thickness, its width and CSA for the population. Thereafter, PT was correlated with, height, weight, and body mass index (BMI). Results: In the sample, 31.0% were male and 69.0% were female. Mean PTT, width, and CSA for the population were 4.7 ± 0.4 mm, 22.4 ± 3.8 mm, and 8.3 ± 1.7 mm2, respectively. Mean PTT was 4.8 ± 0.9 mm for men and 4.7 ± 0.2 mm for women; PT was significantly wider and thicker in men than women (P < 0.05). Difference in left and right PT sizes was not statistically significant (P > 0.05). Correlation between PT size and BMI was statistically significant. Conclusion: In healthy controls, a sonographically measured PTT >6 mm could be diagnostic of patellar tendinopathy as it appears to be 4 standard deviations greater than the mean. When using sonographic method to define population-specific normal value of PT size, individuals' gender and weight should be taken into cognizance.

How to cite this article:
Eze CU, Nwaizugbo CE, Adeyomoye AA, Upeh ER. Normative value of the patellar tendon size: A sonographic study of a cohort of healthy adults in a suburb of Lagos, Southwest Nigeria.J Clin Sci 2019;16:93-97

How to cite this URL:
Eze CU, Nwaizugbo CE, Adeyomoye AA, Upeh ER. Normative value of the patellar tendon size: A sonographic study of a cohort of healthy adults in a suburb of Lagos, Southwest Nigeria. J Clin Sci [serial online] 2019 [cited 2019 Oct 20 ];16:93-97
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Full Text


As an essential component of the extensor mechanism of the knee joint, the patellar tendon (PT) is one of the most commonly injured tendons in the lower extremity in persons who engage in sports or activities that require jumping or running.[1],[2] In humans, the PT is associated with acute and overuse injuries including rupture as a result of substantial force during locomotion.[3] It has been estimated that the PT can reach tensile force ranging from 1400 N to 2500 N and 3100 N to 5330 N during walking and running, respectively.[3],[4] The PT bears load twice or thrice the size of the human body's weight during walking and ≥10 times the body weight during sporting activities.[5],[6],[7]

The prevalence of PT pathologies and ruptures is in direct relationship with the increasing number of recreational amateurs and professional athletes competing in sporting activities globally.[6] In fact, age, body weight, and habitual physical activity moderate tendon size in health and sickness among adults.[8] While imaging modalities such as magnetic resonance imaging (MRI) and multiple detector computed tomography are preferred in the evaluation of the PT, ultrasound equally plays an important role. MRI is perhaps the gold standard in knee imaging, yet ultrasound can be used to perform immediate correlation of anatomical structures and/or pathology in one knee with the contralateral one.[9] Sonography has the added advantages of being noninvasive, widely available, and less expensive than MRI. It is well tolerated by patients and allows for static evaluation with a detailed representation of the intrinsic anatomic structure of the tendons and dynamic evaluation, which is an important element for accurate diagnosis.[10],[11] Sonographic measurement of PT thickness (PTT) is, in fact, reliable in establishing or ruling out patellar tendinopathies or tendon ruptures; hence, it is appropriate for treatment planning and evaluation of prognosis.[12]

Lagos state in Southwest Nigeria has an estimated population of >20 million people, and many people in this state attempt to “keep fit” and stay healthy by engaging in different sporting activities. In fact, sports and the sports industry are big employers of youths in Nigeria, with Lagos state having many stadia and other sports centers. The huge number of people who engage in sporting activities in Lagos (amateurs and professionals) do need special attention because people who constantly engage in physical exercise for fitness and sports are more susceptible to PT injury.[13] As it is known that age, body weight, gender, ethnicity, and habitual physical activity moderate PT size in health and sickness among adults,[8],[14] knowledge of normal values of PT size is important in the evaluation of patients with sports injury of the knee and/or PT. This makes it imperative for different population groups to have a set of normal values that can be used as reference values in the evaluation of PT size in such groups. While many people of different age groups engage in routine physical fitness and sporting activities, there is a paucity of data on normal values for PT size suitable for use in different populations in Lagos state, in particular, and in Nigeria, in general. Sonography is common in Lagos state and is reliable in establishing or ruling out patellar tendinopathies or ruptures; hence, it is appropriate for treatment planning and evaluation of prognosis.[12] The present study was, therefore, carried out to derive normal values of PT in a population of healthy adults in Lagos metropolis.

 Materials and Methods

This prospective cross-sectional study was conducted in the ultrasound center of a hospital located in Ikeja local government area of Lagos state between June and September 2018. A minimum sample of 277 participants was computed from an infinite population of eligible participants using the formula recommended by Murungi.[14] Participants were recruited on first to-come-first-to-be recruited basis. The research proposal was reviewed and approved by the hospital's health research ethics committee before the study commenced. Each participant gave an informed oral consent before being recruited. Only participants who were ≥18 years old at the time of the study were recruited. Similar to a previous study, eligible participants who had a history of knee pain, pathology, and/or knee surgery and those involved in intense physical activity for at least 6 months before the study were not recruited.[15],[16]

Anthropometric details such as sex, age, height, and weight of each participant were recorded. The participants were weighed using a HealthScale Mechanical weighing scale which was adjusted daily to ensure that the indicator line was always zero. Each participant was asked to remove heavy clothing such as jackets/coats and shoes with their pockets emptied before being weighed. A straight and sturdy height rule (SECA height rule; CE 0123) was used for height measurement. Before height measurement, each participant was asked to remove his/her shoes and hair accessories and instructed to stand in the Frankfurt position during height measurement. To ensure accurate height measurement, the sliding part of the height rule was lowered so that the hair is pressed flat. Body mass index (BMI) of each participant was computed using the following formula: BMI = weight (kg)/height (m 2).

A single sonographer measured PT size using Mindray diagnostic ultrasound system (DC-30; Shenzhen Mindray Bio-Medical Electronics Co., Ltd, Shenzhen, China) with a 10 MHz linear probe. A standardized scanning protocol described by Anil et al.[16] was adopted during sonographic examination. Prior to ultrasound examination, the participant was made to lie supine on the examination couch, with knees slightly flexed by placing a pillow below the popliteal space.[17] The PT was examined in longitudinal and transverse planes to allow PTT to be measured just beneath the patella.[18],[19] Using the trackball and freeze facility of the ultrasound scanner, PTT was measured as the maximum anteroposterior diameter of the PT in the longitudinal plane and its width as the maximum superoinferior distance of the PT in the transverse plane.[18] The PT is an elliptical structure; hence, its cross-sectional area (CSA) was computed using the following formula: CSA = π (thickness) × width/4.[17] The right and left PT were measured one after the other for each participant. The measurement of PTT was done as recommended [Figure 1].[19]{Figure 1}

Statistical analysis

The mean (± standard deviation [SD]) for PTT, width, and CSA was computed. The relationship between PT size and participants' age, height, weight, and BMI was determined using Karl Pearson's correlation coefficient. Unpaired t-test was used to compare the right and left mean PTT and to compare the mean PT size for men and women. Paired t-test was used to compare mean PTT obtained in the present study with published data. Results were tested for statistical significance at P ≤ 0.05.


A total of 554 PTs were measured in a sample of 277 participants comprising 87 (31.0%) men and 190 (69.0%) women. The mean PTT, width, and CSA in the population were 4.57 ± 0.35 mm, 22.04 ± 1.25 mm, and 9.73 ± 0.27 mm 2, respectively. The left PT was not significantly thicker and wider than the right one [P > 0.05; [Table 1]; difference in PT size between different age groups was not statistically significant [Table 2]. Mean PTT was 5.8 ± 0.9 and 4.7 ± 0.20 mm for men and women, respectively; PT was significantly wider and thicker in men than women [P = 0.0031; [Table 3]. PT size correlated positively with anthropometric variables [Table 4], [Table 5], [Table 6].{Table 1}{Table 2}{Table 3}{Table 4}{Table 5}{Table 6}


In the study carried out to determine PT size using sonographic method, the mean PTT (4.57 ± 0.35 mm) in the population was smaller than 6.00 mm, which is the generally accepted upper limit for normal PTT. Although Panni et al.[19] had previously reported 5.8 mm as mean PTT (normal range = 5–7 mm with 7.0 mm as the upper limit of normal), the difference in mean PTT observed in the present study was not statistically significant when compared to 4.2 ± 0.35, 4.6 ± 0.09, 4.2 ± 0.12, 4.8 ± 0.35, and 4.2 ± 0.12 mm that had been reported in different cohorts.[19],[20],[21],[22],[23],[24] Whereas Panni et al. reported 7.00 mm as the upper limit of normal PTT and suggested that any sonographically measured PTT ≥7.00 is 4 SDs above the actual mean, we have to reemphasize the fact that several researchers [19],[21],[22],[23],[24] have reported 6 mm as the upper limit of normal PTT and that any measurement which is ≤4.0 or ≥6.0 mm is 2 SDs above the actual mean. With all this, it is safe to submit that any sonographically measured PTT ≥4 or ≤6 mm could be described as normal, whereas any measurement >6 mm could be regarded as a marker for PT abnormality.

When PTT (mean PTT) obtained in the present study was compared to the pooled mean (4.15 ± 0.34 mm) that was computed using various means reported by previous researchers in different populations, no statistically significant difference was observed. This suggests that ethnicity appears not to play a significant role in PT size. It is rather interesting to note that the mean PTT in the present study as well as the pooled mean is [20],[25],[26],[27],[28] While Visnes and Bahr [27] reported a significantly thicker PT in males aged 16–20 years than female volleyball players within the same age group, Cassel et al.[21] opined that the PT is generally thicker in male athletes and suggested a sex-specific adaptation of PTs due to loading. According to Visnes and Bahr,[27] hormonal levels or genetic prerequisites could be the cause of the difference in PT size between men and women. Visnes and Bahr equally opined that cyclical surges in estrogen levels could cause inhibition of the acute exercise-related collagen fibers in women. Because professional sportsmen and women were not included in the present study, it is likely that hormonal differences rather than genetic configuration affected PT size in the population studied (most women do undergo cyclical surge in estrogen levels during ovulation, anyway). The fact that the PT was slightly wider and thicker in men than in women in the present study suggests that gender ought to be taken into cognizance when defining what should constitute the upper and lower limits of normal PT size for a given population.

The PT size did increase marginally with age in the population studied as depicted by the rather weak positive correlation (r = 0.38; P > 0.05) found between PTT and age of the participants. This result is similar to what has been previously reported.[21],[24],[29],[30] The rather weak correlation observed between age and PTT reaffirms the earlier assertion (and indeed, it supports the opinion of Ricardo et al.[30]) to the effect that except for pediatric and elderly patients, definition of normal values of PT size for different age groups among adults is clinically not expedient. The assertion that the development of nomogram of PT size for different age groups appears to be of little clinical value equally supports the opinion previously expressed by Taş et al.[31] The weak positive correlation between height and PTT, a rather strong positive and significant correlation between PTT and BMI, as well as statistically significant difference in mean PTT, width, and CSA observed across the various weight groups suggest that increase in PT size should be expected with weight gain. This implies that sportsmen and women are likely to have thicker and possibly wider PT than their age group members who are not sports people. This assertion supports the opinion of some researchers who had earlier suggested that the weight of the individual should be considered when defining the upper limit of normal PT size.[21],[22],[24],[31]

The generalizability of results obtained in the present study will be limited by the sample studied which can be considered too small compared to the population of Nigerians living in Lagos state. The fact that MRI was not used in the population could be another limitation of the present study.


Among healthy adults who are not sportsmen and women, a sonographically measured PTT >6 mm could be diagnostic of patellar tendinopathy because it is about 4 SDs higher than the recommended mean PTT. When defining population-specific normal values of PT size using the sonographic technique, participants' gender and weight should be taken into cognizance while the right and left PT should be evaluated separately only when it is clinically necessary to compare both.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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