Discover the most talked about and latest scientific content & concepts.

Concept: Synovial joint


Cracking sounds emitted from human synovial joints have been attributed historically to the sudden collapse of a cavitation bubble formed as articular surfaces are separated. Unfortunately, bubble collapse as the source of joint cracking is inconsistent with many physical phenomena that define the joint cracking phenomenon. Here we present direct evidence from real-time magnetic resonance imaging that the mechanism of joint cracking is related to cavity formation rather than bubble collapse. In this study, ten metacarpophalangeal joints were studied by inserting the finger of interest into a flexible tube tightened around a length of cable used to provide long-axis traction. Before and after traction, static 3D T1-weighted magnetic resonance images were acquired. During traction, rapid cine magnetic resonance images were obtained from the joint midline at a rate of 3.2 frames per second until the cracking event occurred. As traction forces increased, real-time cine magnetic resonance imaging demonstrated rapid cavity inception at the time of joint separation and sound production after which the resulting cavity remained visible. Our results offer direct experimental evidence that joint cracking is associated with cavity inception rather than collapse of a pre-existing bubble. These observations are consistent with tribonucleation, a known process where opposing surfaces resist separation until a critical point where they then separate rapidly creating sustained gas cavities. Observed previously in vitro, this is the first in-vivo macroscopic demonstration of tribonucleation and as such, provides a new theoretical framework to investigate health outcomes associated with joint cracking.

Concepts: Magnetic resonance imaging, Observation, Joint, Synovial joint, Joints, Phenomenon, Cavitation, Cracking joints


There are several well-described causes of a painful mass following total hip arthroplasty including polyethylene and metal wear debris, infection, expanding hematoma, dislocation, and synovial cysts. In addition to causing pain, these lesions, when large enough, may cause neurologic and vascular compromise. Rapid growth of the mass may clinically and radiographically resemble a sarcoma. Here, we report a case of a large painful hip mass which developed after total hip arthroplasty. The well-circumscribed mass was overlying and extending into the hip joint containing thousands of highly organized fibrin-containing “rice bodies”. To our knowledge, this is the first report of a large, highly organized (rice-body-containing) cyst complicating total hip arthroplasty.

Concepts: Causality, Hip replacement, Hip, Pelvis, Orthopedic surgery, Joint replacement, Synovial joint, Polyethylene


Synovial joints are the lubricated connections between the bones of our body that are commonly affected in arthritis. It is assumed that synovial joints first evolved as vertebrates came to land, with ray-finned fishes lacking lubricated joints. Here, we examine the expression and function of a critical lubricating protein of mammalian synovial joints, Prg4/Lubricin, in diverse ray-finned fishes. We find that Prg4 homologs are specifically enriched at the jaw and pectoral fin joints of zebrafish, stickleback, and gar, with genetic deletion of the zebrafish prg4b gene resulting in the same age-related degeneration of joints as seen in lubricin-deficient mice and humans. Our data support lubricated synovial joints evolving much earlier than currently accepted, at least in the common ancestor of all bony vertebrates. Establishment of the first arthritis model in the highly regenerative zebrafish will offer unique opportunities to understand the aetiology and possible treatment of synovial joint disease.

Concepts: DNA, Gene, Genetics, Evolution, Fish, Joint, Synovial joint, Actinopterygii


The flexibility and posture of the neck in sauropod dinosaurs has long been contentious. Improved constraints on sauropod neck function will have major implications for what we know of their foraging strategies, ecology and overall biology. Several hypotheses have been proposed, based primarily on osteological data, suggesting different degrees of neck flexibility. This study attempts to assess the effects of reconstructed soft tissues on sauropod neck flexibility through systematic removal of muscle groups and measures of flexibility of the neck in a living analogue, the ostrich (Struthio camelus). The possible effect of cartilage on flexibility is also examined, as this was previously overlooked in osteological estimates of sauropod neck function. These comparisons show that soft tissues are likely to have limited the flexibility of the neck beyond the limits suggested by osteology alone. In addition, the inferred presence of cartilage, and varying the inter-vertebral spacing within the synovial capsule, also affect neck flexibility. One hypothesis proposed that flexibility is constrained by requiring a minimum overlap between successive zygapophyses equivalent to 50% of zygapophyseal articular surface length (ONP50). This assumption is tested by comparing the maximum flexibility of the articulated cervical column in ONP50 and the flexibility of the complete neck with all tissues intact. It is found that this model does not adequately convey the pattern of flexibility in the ostrich neck, suggesting that the ONP50 model may not be useful in determining neck function if considered in isolation from myological and other soft tissue data.

Concepts: Bone, Soft tissue sarcoma, Tissues, Soft tissue, Synovial joint, Ostrich, Struthio, Somali Ostrich


Quality improvement initiatives combined with pulsed xenon ultraviolet room disinfection were implemented to reduce surgical site infections (SSIs) in patients undergoing total joint procedures. After 12 months, knee SSIs were reduced from 4 to 0 (P = .03) and hip SSIs were reduced from 3 to 0 (P = .15) for a combined prevention of 7 SSIs (P = .01) and a savings of $290,990.

Concepts: Infectious disease, Infection, Hydrogen, Hydrogen peroxide, Joint, Antiseptic, Synovial joint, Joints


The aim of this study was to evaluate the clinical and radiological results of 37 consecutive patients (Ø age 37.9; 4♀, 33♂) following arthroscopically assisted and image intensifier-controlled AC joint reconstruction using the double TightRope™ technique for acute AC joint separations grade V according to Rockwood.

Concepts: Synovial joint, Joints, Acromioclavicular joint, Acromioclavicular ligament


Acute acromioclavicular joint dislocations indicated for surgery can be treated with several stabilization techniques. This in vitro study evaluated the acromioclavicular joint stability after 3 types of validated repair techniques compared with the native situation.

Concepts: Synovial joint, Joints, Joint dislocation, Acromioclavicular joint, Acromioclavicular ligament


To evaluate whether increased laxity of the knee during daily physical activities such as stair climbing is associated with progression of knee joint osteoarthritis (OA).

Concepts: Medicine, Cartilage, Osteoarthritis, Knee, Joint, Synovial joint, Joints, Stairway


BACKGROUND: The internal joint contact forces experienced at the lower limb have been frequently studied in activities of daily living and rehabilitation activities. In contrast, the forces experienced during more dynamic activities are not well understood, and those studies that do exist suggest very high degrees of joint loading. METHODS: In this study a biomechanical model of the right lower limb was used to calculate the internal joint forces experienced by the lower limb during vertical jumping, landing and push jerking (an explosive exercise derived from the sport of Olympic weightlifting), with a particular emphasis on the forces experienced by the knee. FINDINGS: The knee experienced mean peak loadings of 2.4-4.6×body weight at the patellofemoral joint, 6.9-9.0×body weight at the tibiofemoral joint, 0.3-1.4×body weight anterior tibial shear and 1.0-3.1×body weight posterior tibial shear. The hip experienced a mean peak loading of 5.5-8.4×body weight and the ankle 8.9-10.0×body weight. INTERPRETATION: The magnitudes of the total (resultant) joint contact forces at the patellofemoral joint, tibiofemoral joint and hip are greater than those reported in activities of daily living and less dynamic rehabilitation exercises. The information in this study is of importance for medical professionals, coaches and biomedical researchers in improving the understanding of acute and chronic injuries, understanding the performance of prosthetic implants and materials, evaluating the appropriateness of jumping and weightlifting for patient populations and informing the training programmes of healthy populations.

Concepts: Knee, Joint, Sartorius muscle, Knowledge, Synovial joint, Joints, Human leg, Popliteal artery


BACKGROUND: Rheumatoid arthritis is a disease affecting the extracellular matrix of especially synovial joints. The thickness of the synovial membrane increases and surrounding tissue degrades, leading to altered collagen balance in the tissues. In this study, we investigated the altered tissue balance of cartilage, synovial membrane, and connective tissue in collagen induced arthritis (CIA) in rats. METHODS: Six newly developed ELISAs quantifying MMP-derived collagen degradation (C1M, C2M, and C3M) and formation (P1NP, P2NP, and P3NP) was used to detect cartilage turnover in rats with CIA. Moreover, CTX-II was used to detect alternative type II collagen degradation and as control of the model. 10 Lewis rats were injected with porcrine type II collagen twice with a 7 day interval and 10 rats was injected with 0.05 M acetic acid as control. The experiment ran for 26 days. RESULTS: A significant increase in the degradation of type I, II, and III collagen (C1M, C2M, and C3M, respectively) was detected on day 22 (P = 0.0068, P = 0.0068, P < 0.0001, respectively), whereas no significant difference in formation (P1NP, P2NP, and P3NP) was detected at any time point (P = 0.2176, P = 0.8534, P = 0.5288, respectively). The CTX-II level increased strongly from disease onset and onwards. CONCLUSION: A nearly total separation between diseased and control animals was detected with C3M, making it a good diagnostic marker. The balance of type I, II, and III collagen was significantly altered with CIA in rats, with favour of degradation of the investigated collagens. This indicates unbalanced turnover of the surrounding tissues of the synovial joints, leading to increased pain and degeneration of the synovial joints.

Concepts: Bone, Collagen, Extracellular matrix, Rheumatoid arthritis, Cartilage, Tissues, Synovial joint, Connective tissue