The Achilles Tendon Length Measure and the Achilles Tendon Resting Angle show acceptable construct validity using the Copenhagen Achilles Length Measure as gold standard

Brorsson, 2018, Calf muscle performance deficits remain 7 years after an Achilles tendon rupture, Am J Sports Med, 46, 470, 10.1177/0363546517737055 Olsson, 2011, Major functional deficits persist 2 years after acute Achilles tendon rupture, Knee Surg Sports Traumatol Arthrosc, 19, 1385, 10.1007/s00167-011-1511-3 Silbernagel, 2012, Deficits in heel-rise height and achilles tendon elongation occur in patients recovering from an Achilles tendon rupture, Am J Sports Med, 40, 1564, 10.1177/0363546512447926 Heikkinen, 2017, Tendon length, calf muscle atrophy, and strength deficit after acute Achilles tendon rupture, J Bone Joint Surg Am, 99, 1509, 10.2106/JBJS.16.01491 Kangas, 2007, Achilles tendon elongation after rupture repair: a randomized comparison of 2 postoperative regimens, Am J Sports Med, 35, 59, 10.1177/0363546506293255 Eliasson, 2018, The ruptured Achilles tendon elongates for 6 months after surgical repair regardless of early or late weightbearing in combination with ankle mobilization: a randomized clinical trial, Am J Sports Med, 46, 2492, 10.1177/0363546518781826 Schepull, 2012, Early E-modulus of healing Achilles tendons correlates with late function: similar results with or without surgery, Scand J Med Sci Sport, 22, 18, 10.1111/j.1600-0838.2010.01154.x Mortensen, 1999, Early motion of the ankle after operative treatment of a rupture of the Achilles tendon. A prospective, randomized clinical and radiographic study, J Bone Joint Surg Am, 81, 983, 10.2106/00004623-199907000-00011 Carmont, 2015, The Achilles tendon resting angle as an indirect measure of Achilles tendon length following rupture, repair, and rehabilitation, Asia-Pacific J Sport Med Arthrosc Rehabil Technol, 2, 49 Speedtsberg, 2019, Gait function and postural control 4.5 years after nonoperative dynamic treatment of acute Achilles tendon ruptures, Orthop J Sport Med, 7, 10.1177/2325967119854324 Matles, 1975, Rupture of the tendo achilles: another diagnostic sign, Bull Hosp Joint Dis, 36, 48 Carmont, 2013, Reliability of Achilles tendon resting angle and calf circumference measurement techniques, Foot Ankle Surg, 19, 245, 10.1016/j.fas.2013.06.007 Hansen, 2017, Development and reliability of the Achilles tendon length measure and comparison with the Achilles tendon resting angle on patients with an Achilles tendon rupture, Foot Ankle Surg, 4, 275, 10.1016/j.fas.2016.08.002 Barfod, 2015, Validation of a novel ultrasound measurement of Achilles tendon length, Knee Surg Sports Traumatol Arthrosc, 11, 3398, 10.1007/s00167-014-3175-2 Silbernagel, 2016, Extended field of view ultrasound imaging to evaluate Achilles tendon length and thickness: a reliability and validity study, Muscles Ligaments Tendons J, 1, 104 Brouwer, 2018, Ultrasound measurements of Achilles tendon length using skin markings are more reliable than extended-field-of-view imaging, Knee Surg Sports Traumatol Arthrosc, 7, 2088, 10.1007/s00167-017-4815-0 Hansen, 2020, Reliability of the Copenhagen Achilles length measure (CALM) on patients with an Achilles tendon rupture, Knee Surg Sports Traumatol Arthrosc, 1, 281, 10.1007/s00167-019-05672-3 Vandenbroucke, 2007, Strengthening the reporting of observational studies in epidemiology (STROBE): explanation and elaboration, PLoS Med, 4, 1628, 10.1371/journal.pmed.0040297 Barfod, 2019, Efficacy of early controlled motion of the ankle compared with immobilisation in non-operative treatment of patients with an acute Achilles tendon rupture: An assessor-blinded, randomised controlled trial, Br J Sports Med, 10.1136/bjsports-2019-scandinavianabs.12 R Core Team, 2019 Costa, 2006, The effect of achilles tendon lengthening on ankle dorsiflexion: a cadaver study, Foot Ankle Int, 6, 414, 10.1177/107110070602700605 Zellers, 2018, Achilles tendon resting angle relates to tendon length and function, Foot Ankle Int, 3, 343, 10.1177/1071100717742372 Indino, 2019, Biologics in the treatment of Achilles tendon pathologies, Foot Ankle Clin, 24, 471, 10.1016/j.fcl.2019.04.009 Svensson, 2019, Persistent functional loss following ruptured Achilles tendon is associated with reduced gastrocnemius muscle fascicle length, elongated gastrocnemius and soleus tendon, and reduced muscle cross‐sectional area, Transl Sport Med, 2, 316, 10.1002/tsm2.103 Ganestam, 2016, Increasing incidence of acute Achilles tendon rupture and a noticeable decline in surgical treatment from 1994 to 2013. A nationwide registry study of 33,160 patients, Knee Surg Sports Traumatol Arthrosc, 12, 3730, 10.1007/s00167-015-3544-5 Gravare Silbernagel, 2015, Sex differences in outcome after an acute Achilles tendon rupture, Orthop J Sport Med, 6