Referred pain can be defined as pain experienced at a site distant to the tissue damage. The report of shoulder pain during a myocardial infarction is a common example of referred visceral pain. While the physical therapist is less likely to see patients whose pain is due primarily to visceral pathology, there is a need for the physical therapist to be able to identify patients whose pain is partially or solely due to a nonmusculoskeletal source. Patients with undiagnosed systemic disease may be referred to a physical therapist for treatment of musculoskeletal complaints unrelated to the coexisting systemic disease. Moreover, patients with systemic disease may also be referred to a physical therapist for treatment because the disease, due to referred pain, is masquerading as a musculoskeletal problem. To properly identify local and referred pain, an understanding of the pain pathways for local and referred pain is essential. The convergence-projection theory of referred pain suggests that visceral and somatic afferents converge on the same or associated neurons or interneurons at the spinal cord. Consequently, excitatory input to the cord from a visceral site may be misconstrued as originating from a somatic site or vice versa. It has been proposed that this theory also applies to the diaphragm, an example of a somatic organ. Routinely, patients undergoing laparoscopy report shoulder or neck symptoms following the procedure. It is hypothesized that diaphragmatic irritation occurs during laparoscopy due to the introduction of gas during the procedure that causes the diaphragm to be displaced. Because the phrenic nerve supplying the diaphragm and the shoulder share common innervation from C3-C5, the diaphragmatic irritation is perceived as originating in the shoulder region. Postsurgically, the subdiaphragmatic gas dissipates over several days, relieving the stress on the diaphragm and, therefore, easing the shoulder pain. A variation of the convergence-projection theory of pain is that of convergence-facilitation, or summation. This hypothesis is based on the fact that convergent afferent input from several sources amplifies the effect each input would have separately. Subsequently, an individual with excitatory input to the cord from the shoulder may be pain-free; if there is convergent excitatory input from visceral sources, such as the diaphragm, the patient is more likely to experience pain. The reduction of input from either source may be sufficient to allow the patient to return to a less painful or even pain-free state. The physical therapist should recognize musculoskeletal and nonmusculoskeletal sources of pain. Screening for medical disease and vigilantly monitoring for unexpected patient responses to physical therapy intervention will help ensure the prompt identification of medical conditions that are not truly musculoskeletal in nature. This report highlights a case that, in retrospect, was an instance of systemic disease contributing to left shoulder pain.

J Orthop Sports Phys Ther. 2001;31(12):696-701.

Key Words: referred pain, visceral pathology, convergence-projection theory of pain

Study Design: Mixed, repeated measures design. Objectives: To determine if previous experience with loads of similar weight influences the anticipatory lifting force and postural adjustments during the squat lift. To examine a multijoint, functional task for coordination between stability and movement. To determine if lifting unexpected loads results in trunk loading patterns associated with greater risk injury. Background: Workers are increasingly exposed to variability in materials handling thereby increasing the risk of injury. Understanding the control processes underlying lifting will support clinical decision making for preparing injured workers to return to realistic working conditions. Subjects: (19 men, 4 women; mean age, 25.4 ± 3.5 y) lifted a series of boxes weighing 5%, 20%, and 35% of their maximal lifting capacity. The loads were delivered via a gravity conveyor. The identical-appearing loads were ordered so that the subjects lifted several loads of similar weight, immediately followed by a lighter or heavier than expected load based on the previous lift. Results: Generally, the vertical lifting force, force rate, horizontal momentum, and angular momentum increased with an increase in expected load. Higher peak lumbar extensor moments occurred with lighter than expected loads (expected 20% and lifted 5% load = 238.2 ± 91.2 N-m; expected 35% and lifted 5% load = 278.2 ± 101.8 N-m) compared to expected loads of similar weight (expected and lifted 5% load = 205.0 ± 73.2 N-m). Heavier than expected loads led to eccentric trunk movements when there were large mismatches between the expected and actual loads. Conclusions: The vertical lifting forces and whole body momentum were predictively scaled according to the expected load. The loading phase relationships indicated coordination between the lifting force, force rate, horizontal momentum, and angular momentum. Trunk loading during the lifts with unexpected loads showed patterns associated with increased injury risk.

J Orthop Sports Phys Ther 2OOl;3l(12):7O8-729.

Key Words: equilibrium, low back injury, posture control

Study Design: Comparative study of differences in functional control during ankle supination in the standing position in matched stable and unstable ankles (ex post facto design). Objectives: To document acceleration and deceleration during ankle supination in the standing position and to determine differences in control of supination perturbation between stable and unstable ankles. Background: Repetitive ankle sprain can be explained by mechanical instability only in a minority of cases. Exercise therapy for ankle instability is based on clinical experience. Joint stability has not yet been measured in dynamic situations that are similar to the situations leading to a traumatic sprain. The process of motor control during accelerating ankle supination has not been adequately addressed in the literature. Methods and Measures: Patients with complaints of ankle instability (16 unstable ankles) and nonimpaired controls (18 stable ankles) were examined (N = 17 subjects, 10 women and 7 men). The average age was 23.7 ± 5.0 years (range, 20-41 y). Control of supination speed was studied during 50° of ankle supination in the standing position using accelerometry (total supination time and deceleration times) and electromyography (latency time). Timing of motor response was estimated by measuring electromechanical delay. Results: The presence of an early, sudden, and presumably passive slowdown of ankle supination in the standing position was observed. Peroneal muscle motor response was detected before the end of the supination. Unstable ankles showed significantly shorter total supination time (109.3 ms versus 124.1 ms) and significantly longer latency time (58.9 ms versus 47.7 ms). Conclusions: Functional control in unstable ankles is less efficient in decelerating the ankle during the supination test procedures used in our study. Our conclusions are based on significantly faster total supination and significantly slower electromyogram response in unstable ankles. The results support the hypothesis that both decelerating the total supination movement during balance disturbance and enhancing the speed of evertor activation through exercise can be specific therapy goals.

J Orthop Sports Phys Ther.2OOl;3l(12):741-752.

Key Words: accelerometry ankle instability, dynamic supination, electromechanical delay, electromyography, proprioception, supination speed

This index includes all authors and co-authors of manuscripts published in the Journal during 2001.

J Orthop Sports Phys Ther. 2001;31(12):771-783.