Pain is a cardinal symptom in musculoskeletal diseases involving the knee joint, and aberrant movement patterns and motor control strategies are often present in these patients. However, the underlying neuromuscular mechanisms linking pain to movement and motor control are unclear. To investigate the functional significance of muscle pain on knee joint control during walking, three-dimensional gait analyses were performed before, during, and after experimentally induced muscle pain by means of intramuscular injections of hypertonic saline (5.8%) into vastus medialis (VM) muscle of 20 healthy subjects. Isotonic saline (0.9%) was used as control. Surface electromyography (EMG) recordings of VM, vastus lateralis (VL), biceps femoris, and semitendinosus muscles were synchronized with the gait analyses. During experimental muscle pain, the loading response phase peak knee extensor moments were attenuated, and EMG activity in the VM and VL muscles was reduced. Compressive forces, adduction moments, knee joint kinematics, and hamstring EMG activity were unaffected by pain. Interestingly, the observed changes persisted when the pain had vanished. The results demonstrate that muscle pain modulated the function of the quadriceps muscle, resulting in impaired knee joint control and joint instability during walking. The changes are similar to those observed in patients with knee pain. The loss of joint control during and after pain may leave the knee joint prone to injury and potentially participate in the chronicity of musculoskeletal problems, and it may have clinically important implications for rehabilitation and training of patients with knee pain of musculoskeletal origin.

OBJECTIVE: To analyze whether fibromyalgia (FM) and FM-like symptoms are related to an increased incidence of cancer.

METHODS: We identified 1361 patients referred on suspicion of FM in the period 1984-99 from hospital records. Following the American College of Rheumatology (ACR) criteria, patients were divided into subgroups with and without confirmed FM. The cohort was followed to the end of 1999 and linked to the files of the Danish Cancer Register. Site-specific standardized incidence ratios (SIR) were calculated.

RESULTS: We found no association between FM and cancer in 1132 female patients with confirmed FM at our institution (SIR 1.2, 95% CI 0.8-1.8). In 106 women referred for muscle pain and/or tenderness who did not meet the criteria for FM, an increased overall SIR was observed (SIR 2.5, 95% CI 1.2-4.6), with increased risk for breast cancer (SIR 4.8, 95% CI 1.6-11.3) and lymphatic and hematological cancers (SIR 10.6, 95% CI 1.2-38.2). There were 4 lung cancers in 84 men with confirmed FM (SIR 12.6, 95% CI 3.4-32.4).

CONCLUSION: Neither confirmed FM nor those without confirmed FM predicted cancer. An increased risk of breast cancer was found among those who did not meet the ACR criteria for FM. These patients should be investigated if they develop any new or warning symptoms of malignancy, and treating physicians should be vigilant with screening procedures such as mammography.

UNLABELLED: We investigated whether the age of the bones endogenously exerts control over the bone resorption ability of the osteoclasts, and found that osteoclasts preferentially develop and resorb bone on aged bone. These findings indicate that the bone matrix itself plays a role in targeted remodeling of aged bones.

INTRODUCTION: Osteoclasts resorb aging bone in order to repair damage and maintain the quality of bone. The mechanism behind the targeting of aged bone for remodeling is not clear. We investigated whether bones endogenously possess the ability to control osteoclastic resorption.

METHODS: To biochemically distinguish aged and young bones; we measured the ratio between the age-isomerized betaCTX fragment and the non-isomerized alphaCTX fragment. By measurement of TRACP activity, CTX release, number of TRACP positive cells and pit area/pit number, we evaluated osteoclastogenesis as well as osteoclast resorption on aged and young bones.

RESULTS: We found that the alphaCTX/betaCTX ratio is 3:1 in young compared to aged bones, and we found that both alpha and betaCTX are released by osteoclasts during resorption. Osteoclastogenesis was augmented on aged compared to young bones, and the difference was enhanced under low serum conditions. We found that mature osteoclasts resorb more on aged than on young bone, despite unchanged adhesion and morphology.

CONCLUSIONS: These data indicate that the age of the bone plays an important role in controlling osteoclast-mediated resorption, with significantly higher levels of osteoclast differentiation and resorption on aged bones when compared to young bones.