Objective Generalized joint hypermobility predisposes some individuals to a wide variety of musculoskeletal complaints, especially in the shoulder joint. Proprioception, which includes joint position sense and sense of movement, has an important role in the functional stability of shoulder joint. Given the critical role of proprioception in the functional stability of shoulder, the primary aim of this study was to compare shoulder joint position sense and sense of movement (kinesthesia) between individuals with and without general joint hyper mobility. The secondary aim of this study was to compare proprioception between dominant and non-dominant sides in each group.
Materials & Methods In this causal-comparative study, 20 females with generalized joint laxity (Mean[SD] age=22.05[2.30] y) and 20 females without generalized joint laxity (Mean[SD] age=22.65[2.53] y) participated in the study. Testing was performed in the supine position. Prior to beginning each proprioception tests, the participants were given to practice trials to become familiar with the testing procedure. Proprioception tests were performed during passive repositioning and kinesthesia using an isokinetic dynamometer. The shoulder external rotation range was measured with a standard goniometer, and 90% of its range was considered as a target angle in passive reposition test. The kinesthetic sense of the shoulder was evaluated by measuring the threshold for passive external rotation. The speed of threshold to detection of passive motion test was at 0.5 deg/s and passive reproduction of joint position was at 2 deg/s. Both dominant and non-dominant sides of all the subjects were evaluated. Test sequences for measuring the threshold to detection of passive motion and passive reproduction of joint position, as well as dominant and non-dominant shoulder were random. The blindfold and headphones were used to remove visual and auditory feedback. The mean of three repetitions of passive reproduction of target angle and threshold to detection of passive motion were calculated. Independent t-test was used to compare joint position sense and kinesthesia between females with and without generalized joint laxity, and paired t test was used to statistically analyze differences between dominant and non-dominant sides in each group.
Results  No significant difference was observed in joint position test acuity and of detection of motion in each of dominant and non-dominant sides between females with and without generalized joint laxity (dominant side: P=0.47, non-dominant: P=0.70). Females with generalized joint laxity exhibited significantly larger errors in passive joint reproduction tests in both dominant and non-dominant sides (P=0.001) compared with those without generalized joint laxity. 
Conclusion The results revealed that the angle repositioning sense in the extreme range of shoulder joints in females with generalized joint laxity is reduced compared to those without generalized joint laxity. Lower joint position test acuity in females with generalized joint laxity may relate to the disturbance or loss of sensory messages from joint receptors to the central nervous system. Reduced proprioception feedback may lead to biomechanically unsound limb positions being adopted. Such a mechanism may allow acceleration of degenerative joint conditions and may account for the increased prevalence of musculoskeletal complaints seen in subjects with generalized joint laxity.