December 2014 221 OBJECTIVES: To examine Achilles and patellar tendon mor- phology in dancers with and without tendon pain. METHODS: Fifty-three dancers with and without Achilles and/or patellar tendon pain participated. Eleven age-matched non-dancers served as controls. Longitudinal ultrasound images of the middle and distal Achilles and proximal and distal patellar tendons were acquired. To assess macromorphology, the thickness of the middle and distal Achilles and proximal and distal patellar tendons were measured. Micromorphology was analyzed by selecting 2 × 2-mm 2 regions of interest in the ten- dons; spectral analysis using the fast Fourier transform was run for several kernels (2 × 2-mm 2 subimages) within each image, and the peak spatial frequency (PSF) was extracted. A one-way ANOVA compared asymptomatic, symptomatic, and control tendon thickness and PSF. RESULTS: Macromor- phology: There was no significant difference between asympto- matic and symptomatic dancers in middle or distal Achilles tendon thickness and distal patellar tendon thickness. Proxi- mal patellar tendons in control subjects were thinner than those in asymptomatic (p=0.036) and symptomatic (p=0.003) dancers. Micromorphology: There was no significant difference in PSF between asymptomatic and symptomatic dancers and controls in the Achilles or patellar tendon. CONCLUSION: Increased proximal patellar tendon thickness without changes in tendon micromorphology suggests that tendon adaptations are more likely activity-related and less likely influenced by degeneration. Med Probl Perform Art 2014; 29(4):221–228. A thletes who participate in sports involving running, sprinting, and frequent jumping incur repetitive, high rates of loading to tendons of the lower extremity. It is thought that those high loading rates, when combined with suboptimal technique, may produce aberrant strain to lower extremity tendons, contributing to microtrauma that may trigger tendinopathies. The prevalence of Achilles and patellar tendinopathies in dancers is reported at 9% and 8%, respectively. 15,28 Tendinopathies can be cat- egorized as a “tendinitis,” if signs of inflammation are pres- ent, or as a “tendinosis,” a degenerative condition lacking clinical or histological signs of inflammation. 21 Another category of painful tendons may include those which do not exhibit inflammation or degeneration, but which may be accompanied by chemical substances associated with pain and increased tendon loading, such as the neuropep- tide substance P. 3 It is important to distinguish tendinoses from other pathologies of tendons and surrounding tissues. By doing this, health practitioners can provide a specific and there- fore more effective plan of care for each athlete’s condi- tion. Observation of histopathologic features such as col- lagen fiber structure and organization, collagen strain intensity, tendon cell shape, quantity and distribution, and the presence of macrophages and intracellular fatty deposits in a tendon sample is one reliable method for identifying tendinoses. 2 However, from a nonsurgical standpoint, it is not feasible to take tissue biopsies to deter- mine the nature of the dancer’s tendinopathy. Hence, the clinical presentation, such as swelling, warmth, respon- siveness to anti-inflammatory medication and recurrence of symptoms, collectively provides for a provisional diag- nosis as an -itis or an -osis. Alternatively, release of sub- stance P may also accompany pain without the overt hall- marks of inflammation or degeneration, making further diagnosis reliant on the patient’s response to intervention. To supplement athletes’ reports of symptoms, results of clinical ultrasound imaging can be included in the diagnos- tic process. The benefits of using ultrasound are that it is noninvasive, as reliable as magnetic resonance imaging (MRI) in diagnostic capacity 1,24 but more cost effective, and it lends itself to the quantitative analysis of tendon morphology. Tendon thickness, a macromorphologic characteristic of the tendon, can be measured on ultra- sound images and may be reflective of adaptations or mal- adaptations. Considering the tendon’s micromorphology, spatial frequency parameters can be mathematically extracted to quantify the regularity of striation patterns made by collagen bundles comprising tendons. Decreased regularity of collagen bundle fibers has been shown to cor- relate positively with decreased collagen organization, as well as with athletes’ reports of recurrent episodes of pain in the Achilles tendon. 4 Hypoechocity, defined as regional Dr. Kulig is Professor, University of Southern California, Division of Biokinesiology and Physical Therapy, Los Angeles, CA; Dr. Oki is Physical Therapist, Rehabilitation Hospital of the Pacific, Honolulu, HI; Mr. Chang is PhD Candidate, Jacquelin Perry Musculoskeletal Biomechanics Research Laboratory, Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA; and Dr. Bashford is Biomedical Engineer and Associate Professor, Department of Biological Systems Engineering, University of Nebraska- Lincoln, Lincoln, NE. Address correspondence to: Dr. Kornelia Kulig, Musculoskeletal Biome- chanics Research Laboratory, Division of Biokinesiology and Physical Therapy, University of Southern California, 1540 East Alcazar Street, CHP-155, Los Angeles, CA 90089, USA. Tel 323-442-2911, fax 323- 442-1515. kulig@usc.edu. © 2014 Science & Medicine. www.sciandmed.com/mppa. Achilles and Patellar Tendon Morphology in Dancers with and without Tendon Pain Kornelia Kulig, PT, PhD, Kari C. Oki, PT, DPT, Yu-Jen Chang, PT, MS, and Gregory R. Bashford, PhD, PE