Introduction Patellar tendinopathy is a common musculoskeletal dysfunction in athletes and it is considered an important cause for physical disability. Previous studies have demonstrated that athletes with patellar tendinopathy present diminished torque generation capacity for knee extension in comparison to asymptomatic athletes.2 Therefore, quadriceps muscle strengthening exercises have been recommended for the rehabilitation of athletes presenting this dysfunction. It is important to consider, however, that the hip and ankle joints are also involved in the dissipation of the ground reaction force during closed kinetic chain activities such as jump-landings. Thus, weakness of the muscles surrounding these joint might result in excessive overload of the knee extensor mechanism. However, to date, no study evaluated the torque generation capacity of the hip and ankle joints of subjects presenting patellar tendinopathy. Therefore, the purpose of this study was to compare the hip, knee and ankle isometric torque between athletes with patellar tendinopathy and asymptomatic controls.
Methods Young male and female athletes, 18 to 30 years of age, were recruited from local volleyball, basketball and handball teams. They were submitted to an ultrasonographic (US) evaluation of both patellar tendons by an experienced radiologist. Subjects presenting history or current symptoms in the patellar tendon during tendon-loading tasks (i.e., jumping, squatting) for at least 3 months and presenting patellar tendon abnormalities (PTA)1 were included in the patellar tendinopathy group (PTG; n = 6, 5M and 1F). Asymptomatic subjects with no PTA were included in the control group (CG; n = 6, 4M and 2F). The subjects were submitted to a torque evaluation during isometric hip extension, knee extension and ankle plantar flexion. Straps were used to stabilise the subjects and the handheld dynamometer (Lafayette Instruments, Lafayette, IN, USA). The hip extensor torque was evaluated with the subject lying in prone with the knee in 90º of flexion.3 The knee extensor torque was measured with the subject in supine lying with 30° of knee flexion.4 The ankle plantar flexor torque was evaluated with the subject in prone lying with his foot positioned outside the examining table in a neutral position.3 For each test, 1 practice and 3 experimental trials were performed for 5 seconds, with 15 seconds of rest between contractions. The average normalised peak-force values produced during the 3 trials was normalised to the subject’s body mass and height. Independent t-tests were used for statistical analysis with a significance level of 5%.
Results Results demonstrated that the PTG presented smaller torque for hip extension when compared to the control group. No group differences were observed for knee extension and ankle plantar flexion torques (Table 1).
Discussion Previous research has shown that athletes with patellar tendinopathy have smaller knee extensor torque in comparison to asymptomatic controls.2 However, the strength of the hip and ankle joints had not yet been investigated in this population. Our preliminary results showed that athletes with patellar tendinopathy have diminished hip extensor torque in comparison to healthy athletes. This diminished hip strength may be a consequence of a ‘quadriceps dominant’ jump-landing strategy, involving less hip flexion. This strategy increases the demand for ground reaction force dissipation at the knee joint and diminishes the demand at the hip joint.5 Hip strengthening exercises should be encouraged in the rehabilitation of subjects with patellar tendinopathy.
References 1 Cook, et al . Scand J Med Sci Sport. 2001;11:321–7
2 Crossley, et al. J Orthop Res. 2007;25:1164–75
3 Fukuchi, et al. Clin Biomech. 2014;29:304–10
4 Willson, Davis J. Sport Rehab. 2009;18:76–90
5 Zhang, et al. Med Sci Sports Exerc. 2000;32:812–9