Intra-Articular Pressure in Osteoarthritis of the Knee

Background: IAP (cid:0) intra-articular pressure (cid:0) of the knee has been extensively studied in the knee of rheumatoid arthritis 1.3 . the relationship between IAP and osteoarthrosis of knee rarely mentioned in the literature. The purpose of the study was to discover the pressure proles observed in OA(Osteoarthritis (cid:0) . The characteristics of osteoarthritis are multiple osteophytes, unstable chondral aps ,joint-space narrowing (cid:0) sclerosis. Whether these factors effect of osteoarthritis intra-articular pressure. Methods: Fifty three research subjects were studied. They were divided into two subgroups, group 1: Forty osteoarthritis (OA). group 2: Thirteen control knee of healthy volunteer. IAP was measured using the hand held portable water manometer. before operation of arthroscopic procedures in OAgroup . Research data were analyzed to identify IAP between the two groups. Results: The main ndingwasthat Resting IAP was positive pressure in all Osteoarthritis joints, otherwise subatmospheric or weakly atmospheric in normal subjects. Conclusions: The IAP rising is a feature of all patients with OAgroup. Therefore, These observations we recognize that signicantly increased resting IAP is major inuences by multiple osteophytes, joint-space narrowing (cid:0) sclerosis , loose bodies and denite deformity of bony ends.


Background
Through study a lot of literatures demonstrate that normal knee joint pressure is negative pressure also have con rmed that pressure in the patients with knee joint effusion in increased, so pressure in patients with osteoarthritis of the knee joint will be how? Through literature study our team recognizes that pressure may be within the knee and osteoarthritis relationship. Worthy of further research on the changes of osteoarthritis of knee joint pressure. Jayson has also been reported the intra-articular pressure, that is the pressure in the synovial uid (not that between the contact areas of the articulating surfaces), has been determined at rest. [1] In previous studies of IAP at rest and during exercise have shown that normal peripheral synovial joints have a subatmospheric pressure, commonly −2 to −4 mm Hg at rest. [2] [3] Baxendal has also been reported the normal human synovial joint has a subatmospheric or low atmospheric intra-articular pressure (IAP) at rest and during exercise. [4] IAP is very important to our knee. The cartilage is avascular because of the compressive forces it sustains, and its nutrition is dependent on synovial vessel perfusion. [5] Maintenance of synovial patency by mild distraction assists cartilage nutrition despite exercise or compressive forces. It has also been proposed that negative pressure will draw loose synovial tissues towards to each other during exercise, thus offering a stabilising in uence and promoting normal to joint tracking, [6] [7] Geborek showed clearly in their study that an increase of IAP as little as 20 mm Hg in patients with knees effusions can signi cantly decrease synovial blood ow suggesting the joint to be a system with a blood ow that is very sensitive to comparatively small changes in IAP. [8] when at low intra-articular pressures the blood supply to the synovium is unimpeded and at very high pressures the vessels are compressed and all vascular ow stops. These suggested that increased intra-articular pressure could interfere withthe circulation to the synovium. [9] Intra-articular pressure is central to the mechanism of hypoxic-reperfusion injury to the joint. [10] Thus there are several cases that may in uence the ability to generate high intra-articular pressures. Several types of synovitis were studied and the increase in intra-articular pressure is clearly not speci c to a particular disease. [11][12] [13] According to Blake so that the Rheumatoid arthritis with chronic knee effusions have signi cantly greater resting pressures. [14 -15] Geborek reported that Exercise of the joint causes the intra-articular pressure to rise above the capillary perfusion pressure, resulting in occlusion of the synovial capillary bed and hypoxia. [16][17] Simkin studies have con rmed the intra-articular pressure (IAP) rises signi cantly after isometric quadriceps contraction in patients. [6] Some scholars think that joint elasticity increases with increasing age, suggesting a greater ability to generate high intra-articular pressures. Conversely, the size and strength of quadricep muscles decline with increasing age, suggesting a decreased ability for the generation of intra-articular pressure. [18][19] Thus there are several associated factors that may in uence to generate high intra-articular pressures. We do not believe, as with previous studies, that the age difference is the cause of the different IAP pro les between the groups. [20] Although IAP has been extensively studied in the knee of several diseases, there is limited information available regarding human OA joints and the effect of IAP usage on OA is largely unknown. Measured IAP in a spectrum of OA and normal joints in order to evaluate the IAP dynamics, anddetermine whether a rising IAP is likely to occur at these OA patients and nd out the reason that cause highly IAP. The question allows us to hypothesis multiple osteophytes, joint-space narrowing, sclerosis, loose bodies and de nite deformity of bony ends are the major in uences on whether the joint sustains signi cant pressure responses. The purpose of our study was to discover the pressure pro les observed in OA(Osteoarthritis groups. The characteristics of osteoarthritis multiple osteophytes, unstable chondral aps; joint-space narrowing sclerosis, Whether these factors effect of osteoarthritis intra-articular pressure.

Materials And Methods
General information 40 clinically well de ned patients with OA were recruited to the study before operation. Fifty three research subjectswere studied. They were divided into two subgroups; group 1: 40 osteoarthritis the mean patient age was 56 years (45-72); group 2: 50 years (45-78) for 13 control knee of healthy volunteer.Specify the inclusion criteria for each group included patients with their clinical diagnosis was not in dispute on examination, capsular integrity, forty patients met these criteria. Exclusion criteria included knees with incomplete radiographic studies, synovitis, rheumatoid, rupturing the capsule, patients with a joint effusion with a positive bulge sign or positive patellar tap were also excluded. This study was conducted in accordance with the declaration of Helsinki. This study was conducted with approval from the Ethics Committee of the A liated No.2 Hospital of Harbin Medical University. Written informed consent was obtained from all participants.

Measurement of intra articular pressure
Measurements were performed on patients who agreed to these studies after detailed explanations before operation. We did not use subcutaneous tissues were in ltrated with 2% lignocaine taking care to avoid capsular or intra-articular contact. [21] We use the method of anesthesia is lumbar epidural anesthesia .The Measurements were performed after a spinal anesthetic was administered. A tourniquet was never used.In the picture g 1a might see the proximal thigh tourniquet but tourniquet is not in ated, when measuring, only after the measurement used in the operation. Patients were rested in a supine position for at least 15 minutes before the procedure. The subject was encouraged to relax completely with the knee extended. IAP was measured before operation of arthroscopic in OA , In this studies the techniques for cannulating the joint by using a parapatellar approach injection site with a water manometer in order to record the intra articular pressure, The tube was calibrated against a water manometer, After assembly, the water manometer is tted with a needle. A sterile disposable piezometer tube containing a pre-lled saline syringe The tube by slowly lling saline(solution of 0.9 percent sodium chloride,) through tube to the needle tip to ensure hydrodynamic communication with the joint lumen. The needle introduced into the joint cavity (parapatellar approachanteromedial), sterile precautions were observed throughout. Figure 1a shows us in the operation of intra-articular pressure measurement. Figure 1b the measured pressure tube local ampli cation. There was no infection of any specimens every steps were sterile. IAP was measured at rest, when a needle was attached to the water manometer to record the pressure were subatmospheric in group 2.In this studies the techniques for cannulating the joint, recording the intra-articular pressure , the lumen of the joint was placed in hydrodynamic communication with the water manometer. this methods we used are able to distinguish between atmospheric and subatmospheric (Positive and negative pressure)IAP recordings.

Statistical analysis
The mean resting pressure in the knees of patients with OA knees were positive and in control knees were negative. The two groups were compared by the t test. There is a clear difference in the generation of intra-articular pressure between the two groups. This is signi cant both at rest (P < 0.01). Statistical analysis was performed by using an SPSS (version 16.0; SPSS,) software.

Result
The result is group 1: 220 80-300cmH2O for the Osteoarthritis; group 2: demonstrates a subatmospheric negative pressure produced. We cannot measure the de nitely negative gure due to our appliance, but negative is sure. No negative phase of intra-articular pressure was found in the OA. Figure   2 shows IAP in the rst group produced very much higher pressures and the patients with control joints intra-articular pressure at rest was subatmospheric.
Adequate data was recorded on thirteen control knees and forty (OA) knees, the mean resting pressure in the knees of patients with OA knees were positive and in the 13 control knees were negative. The difference was statistically highly signi cant (P < 0.01).There is correlation was found between IAP and multiple osteophytes, joint-space narrowing sclerosis, loose bodies and de nite deformity of bony ends in the OA knees.

Discussion
Our experimental research and results are consistent with our original expectations. To compare the IAP of the Osteoarthritis and the control subjects nd out the IAP rise in OA group.The group of normal knee joint internal pressure measurement is negative pressure . IAP as an indicator to judge the severity of osteoarthritis, just like human blood pressure to judge the condition of people.By our experimental the hypothesis was con rmed that signi cantly increased resting IAP is major in uences by multiple entophytes, joint-space narrowing sclerosis , loose bodies and de nite deformity of bony ends. A lot of literatures demonstrate that normal human knee joint is negative, but the phenomenon of intra-articular pressure changes of OA patients is rarely mentioned, which is the difference between us and the other scholars. Measured IAP in a spectrum of OA in order to evaluate the IAP dynamics, anddetermine whether a rising IAP is likely to occur at these OA patients and nd out the reason that cause highly IAP. The IAP were found in normal knees were similar to those reported elsewhere, Muller (1929) found the pressure in normal living joints to be several cm. of water less than atmospheric pressure; Dixon (1966) similarly found that the pressure in the normal human knee fell below the atmospheric level by up to 30 mm. Hg; Reeves (1966) con rmed that the resting pressures in the knees of normal humans and of animals was usually between -2 and -10 mm. Hg. We cannot measure the de nitely negative gure due to our appliance, but negative pressure is sure. Our recording in group 1 is consistent with the ndings of above researcher 2 3 . Number of factors in uence the development of intra-articular pressure. Rheumatoid subjects with chronic knee effusions have signi cantly greater resting pressures 13 14 .Exercise of the joint causes the intra-articular pressure to rise above the capillary perfusion pressure, resulting in occlusion of the synovial capillary bed and hypoxia 15 16 .The intra-articular pressure (IAP) rises signi cantly after isometric quadriceps contraction in patients 6 . With increasing volumes of simulated effusion, joint use produced higher pressures 3 . thus synovitis, exercise, isometric quadriceps contraction, Rheumatoid, rupturing the capsule external injury),patients with a joint effusion with a positive bulge sign or positive patellar tap were also excluded by our study. During our study, the procedures were performed after a spinal anesthetic was administered; quadriceps contraction and stretching the unsupported parts of the synovium were avoided. Although this was somewhat arti cial, it enabled comparisons to be made under similar conditions. 1 Our experimental results showed that OA patients increased pressure within the knee. What causes increased? Pressure within the knee joint effusion, in ammation, unit four quadriceps contractionsare factors affecting intra-articular pressure, but we have no choice in these patients. From the X-ray and observe arthroscopic joint space narrowing, osteophyte formation, may be likely to be the main factors leading to joint increased pressure. The higher pressures in the OA knees may have been produced the mechanisms is reduced the joint space by multiple entophytes, joint-space narrowing, sclerosis, and de nite deformity of bony ends. Joint volume reduction leads to increased intra-articular pressure.We think that through the intra-articular pressure level, to judge the severity in patients with OA.
Intra-articular pressure increases judgments osteoarthritis severity index.Our studies question is to study the cases were too few, performed at rest and did not give further study about changes in intra-articular pressure during joint exercise.

Conclusions
We found thatthe IAP rising is a feature in OA group.The change of joint pressure was positively correlated with the severity of osteoarthritis.IAP as an indicator to judge the severity of osteoarthritis, just like human blood pressure to judge the condition of people.The higher pressures in the OA knees may have been produced the mechanisms is reduced the joint space. Joint volume reduction leads to increased intra-articular pressure. These observations we recognize that signi cantly increased resting IAP is major in uences by multiple osteophytes, joint-space narrowing sclerosis , loose bodies and de nite deformity of bony ends.
Abbreviations IAP:intra-articular pressure; OA:Osteoarthritis; Declarations Authors' contributions NK and HL Pan were responsible for the conception, design, and acquisition of data, NK drafted the initial manuscript and revised it critically for important intellectual content. HL Pan analyzed and interpreted the data. All authors read and approved the nal manuscript.   Typical X-ray shown narrowing of the joint space from OA subject. Typical pathology from OA patients was con rmed by the arthroscopy. Typical pathology from OA patients was con rmed by the arthroscopy.