Muscle-tendon related pain in 100 patients with hip dysplasia: prevalence and associations with self-reported hip disability and muscle strength

Introduction Intra-articular injury has been described as primary cause of pain in hip dysplasia. At this point, it is unknown whether external muscle-tendon related pain coexists with intra-articular pathology. The primary aim was to identify muscle-tendon related pain in 100 patients with hip dysplasia. The secondary aim was to test if muscle-tendon related pain is linearly associated to self-reported hip disability and muscle strength in patients with hip dysplasia. Materials and methods One hundred patients (17 men) with a mean age of 29+9 years were included. Clinical entity approach was carried out to identify muscle-tendon related pain. Muscle strength was assessed with a handheld dynamometer and self-reported hip disability was recorded with the Copenhagen Hip and Groin Outcome Score (HAGOS). Results Iliopsoas- and abductor-related pain were frequently identified with prevalences of 56% (CI 46; 66) and 42% (CI 32; 52), respectively. Adductor-, hamstrings- and rectus abdominis-related pain were less common. There was a significant inverse linear association between muscle-tendon related pain and self-reported hip disability ranging from -3.35 to -7.51 points in the adjusted analysis (p<0.05). Likewise an inverse linear association between muscle-tendon related pain and muscle strength was found ranging from -0.11 Nm/kg to -0.12 Nm/kg in the adjusted analysis (p<0.05). Conclusion Muscle-tendon related pain seems to exist in about half of patients with hip dysplasia with a high prevalence of muscle-tendon related pain in the iliopsoas and the hip abductors and affects patients’ self-reported hip disability and muscle strength negatively.