Postoperative hemoglobin and recovery of hip muscle strength after total hip arthroplasty.

BACKGROUND: The presence/absence of postoperative anemia are presumed to have an impact on early recovery after surgery. This study was performed to compare hip muscle strength and hemoglobin during the perioperative period in 82 patients undergoing THA. METHODS: Evaluation of presence/absence of anemia was performed by calculating the 10-day postoperative/preoperative Hb ratio. Muscle strength was investigated before and 2 months after surgery. RESULTS: Postoperative SLR strength showed a significant difference between the patients whose 10-day postoperative/preoperative Hb ratio was <85% and ≧ 85%. CONCLUSION: We need to consider perioperative strategies to minimize anemia in order to improve patient outcomes.

Early clinical evaluation of total hip arthroplasty by three-dimensional gait analysis and muscle strength testing.

BACKGROUND: As improvement of gait is an important reason for patients to undergo total hip arthroplasty (THA) and they generally tend to evaluate its success based on postoperative walking ability, objective functional evaluation of postoperative gait is important. However, the patient's normal gait before osteoarthritis is unknown and the changes that will occur postoperatively are unclear. We investigated the change in gait and hip joint muscle strength after THA by using a portable gait rhythmograph (PGR) and muscle strength measuring device. PATIENT AND METHODS: The subjects were 46 women (mean age: 65.9 years) with osteoarthritis of the hip. Gait analysis and muscle strength testing were performed before THA, as well as 3 weeks and 3 months after surgery. We measured the walking speed, step length, and gait trajectory using PGR prospectively. PGR is attached to the patient's waist and records signals at a sampling rate of 100 Hz. Isometric torque of hip flexion and abduction were measured by using a hand-held dynamometer. RESULTS: There was no improvement at 3 weeks postoperatively, but the walking speed, stride length and muscle strength were clearly showed improvement at 3 months postoperatively. The walking trajectory was not normal preoperatively, since the trajectory was not symmetrical and did not intersect in the midline or form a butterfly pattern, and abnormality of the trajectory tended to persist postoperative 3 months despite resolution of hip joint pain after surgery. CONCLUSION: Since postoperative improvement of gait is an important consideration for patients undergoing THA, it seems relevant to evaluate changes in the gait after surgery and three-dimensional analysis with a PGR may be useful for this purpose.

Early clinical results of total hip arthroplasty assessed with the 25-question Geriatric Locomotive Function Scale and muscle strength testing.

BACKGROUND: We think that it is necessary to evaluate whether the patient after total hip arthroplasty has achieved age-appropriate locomotor ability by improvement in hip joint function. The 25-question Geriatric Locomotive Function Scale (GLFS-25) have been determined age-specific standard values for the general population. The aim of this study was to compare postoperative hip muscle strength and functional performance at 3 months after THA with preoperative levels, and to compare the outcomes at 3 months after THA with the function of age-matched adults without hip disease. METHODS: The GLFS-25 scores and muscle strength were investigated before THA and 3 months after surgery in 12 men and 75 women who underwent total hip arthroplasty. RESULTS: The mean preoperative and postoperative GLFS-25 score was 55.4 and 19.1, respectively. With regard to the influence of age, the mean scores before and after THA were respectively 52.0 versus 18.2 for patients aged 60-69 years and 61.2 versus 17.3 for those aged 70-79 years in the normal/mild OA group. When female patients from the normal/mild OA group and the implant group classified into levels 4-7 after THA were combined (n = 15), their mean preoperative and postoperative straight leg raising (SLR) strength was 0.56 Nm/kg and 0.75 Nm/kg, respectively. On the other hand, the mean preoperative and postoperative SLR strength was respectively 0.54 Nm/kg and 0.86 Nm/kg for patients classified into levels 1-3 after THA (n = 45). CONCLUSION: Before THA, 90% of the patients who has severe hip disturbance were in need of nursing care (levels 4-7), while the percentage decreased to 30% after surgery. There was a difference of SLR muscle strength between the patients in levels 4-7 and those in levels 1-3 after THA, suggesting that achieving levels 1-3 postoperatively might depend on whether SLR muscle strength shows improvement.

Rotational acetabular osteotomy for acetabular dysplasia and osteoarthritis: a mean follow-up of 20 years.

INTRODUCTION: Rotational acetabular osteotomy (RAO), a joint-conserving surgery in which the femoral head coverage by autologous cartilage is improved to achieve joint stability, is one of the most common joint-conserving surgeries for acetabular dysplasia of the hip in adult patients. Favorable outcome of RAO for pre- and initial coxarthrosis has been reported with middle- to long-term observation; however, surgery should be selected for advanced coxarthrosis. The objective of this study was to investigate the long-term clinical outcomes and radiological arthritis changes in patients who were treated with RAO and could be followed for 15 years or longer, and to investigate the joint conservation rate by preoperative arthritis stage. PATIENTS AND METHODS: The subjects were 156 patients (178 joints) treated with rotational acetabular osteotomy alone between January 1989 and June 2000. Of those, 106 patients (115 joints) were retrospectively investigated. The mean age at the time of surgery was 41.4 years (14-60 years), and the mean duration of follow-up was 20 years and 4 months (15-26 years and 7 months). RESULTS: There were no significant differences in the Harris hip score among the three groups before surgery; however, the score was significantly lower in the advanced than pre/initial coxarthrosis cases at final follow-up. The joint conservation rate with the end point defined as time of total hip arthroplasty was 70.4% at 20 years after surgery. By stage, joint conservation rates were 88.9, 78.9, and 59.3% in pre-, initial, and advanced coxarthrosis cases, respectively, demonstrating a significantly lower rate in the advanced coxarthrosis cases (p = 0.034). The mean time to conversion was 23, 14.5, and 13.7 years in the pre-, initial, and advanced coxarthrosis cases, respectively. CONCLUSION: The outcome of rotational acetabular osteotomy in most hips with pre- or initial coxarthrosis was satisfactory. Rotational acetabular osteotomy is an effective surgery for treating symptomatic developmental dysplasia of the hip in selected patients.

Cementless total hip arthroplasty for patients with rheumatoid arthritis: a more than 10-year follow-up.

BACKGROUND/PURPOSE: In this study, cementless THA was performed for RA patients, and its clinical outcomes, as well as radiographic findings and implant survival rates, were examined more than 10 years after surgery in comparison with the outcomes of the same procedure performed for patients with hip osteoarthritis (OA) during the same period. METHOD: We studied 28 cases of THA for RA clinically and radiologically at a minimum follow-up duration of 10 years. The patients consisted of 4 males and 22 females, with a mean age at the time of surgery of 53.1. The clinical and radiographic results were compared with an age-matched and sex-matched group of patients who had undergone THA for the diagnosis of primary or secondary OA. RESULTS: In the RA group, the mean Harris hip score was 48.3 before surgery, and improved to 76.8 at the time of the final survey. In the control group, the score also improved from 46.8 before to 86.5 after surgery, while revealing significant differences between the groups (p = 0.0002). In the RA group, 2 joints required revision THA on the acetabular side due to aseptic loosening, while such revision was not performed on the femoral side despite the presence of more than 2 mm of subsidence in 2 joints. The implant survival rate was 92.9 and 100 % in the RA and control groups, respectively, without significant differences (p = 0.493). CONCLUSIONS: Although its clinical outcomes were significantly different from those for OA, a satisfactory implant survival rate was achieved, at 92.9 % in RA patients.

Benefit and risk in short term after total hip arthroplasty by direct anterior approach combined with dual mobility cup.

PURPOSE: No previous reports have described the benefits and risks associated with the dual mobility cup (DMC) in primary THA via direct anterior approach (DAA). The aim of this study was to compare the safety and rate of early postoperative complication of the DAA with the DMC for THA with those of the DAA with a single standard cup, and to investigate the influence of the learning curve of the use of DMC on intra- and perioperative outcomes. METHODS: We retrospectively investigated 60 hips treated in the single-DAA group and 60 hips treated in the dual-DAA group. A primary/secondary outcome variable was the presence of any intra- or perioperative complication within the first 6 months/the operative time and hip function at 6 months postoperatively. We also analyzed influence of the learning curve of the use of DMC on intra- and perioperative outcomes. RESULTS: No intraoperative complications were observed in either group. One anterior dislocation and one periprosthetic hip fracture were occurred in the single-DAA group. The surgical times in the single-DAA and dual-DAA groups were 112.0 ± 20.9 and 121.0 ± 26.9 min (p < 0.001). There was no significant difference in the 6-month postoperative hip function scores between the two groups. There was no influence of the learning curve of the use of DMC on intra- and perioperative outcomes. CONCLUSION: We have demonstrated the short-term safety and lack of inferiority of using the DMC in the DAA compared with the standard single mobility cup.

Greater trochanter chip fractures in the direct anterior approach for total hip arthroplasty.

BACKGROUND: The direct anterior approach (DAA) for the treatment of total hip arthroplasty (THA) has gained popularity in recent years. Chip fractures of the greater trochanter are frequently seen, but the risk factors for such fractures are unknown. The study aimed to identify the risk factors for chip fractures in patients undergoing primary THA by the DAA during the surgeons' learning curve. MATERIALS AND METHODS: From November 2011 to April 2015, the first experiences of three surgeons who performed 120 THAs by the DAA (120 hips; 40 cases per beginner surgeon) were included. The incidence of chip fracture of the greater trochanter, the size of the greater trochanter as measured by computed tomography, and the patients' characteristics were retrospectively investigated. RESULTS: After exclusion of 11 hips, the remaining 109 hips were investigated. Chip fracture of the greater trochanter was identified in 32 hips (29.4 %). Univariate analysis with and without fractures showed that the width and depth of the greater trochanter were statistically significant risk factors (p = 0.02 and p < 0.001, respectively). Multivariate analysis using a logistic regression model demonstrated that the depth of the greater trochanter was an independent risk factor for chip fracture of the greater trochanter (OR 1.725; 95 % CI 1.367-2.177; p < 0.001). CONCLUSION: The size of the greater trochanter was identified as a risk factor for chip fracture of the greater trochanter. Novice surgeons should pay attention to the size of the greater trochanter when performing THA by the DAA.

Cementless total hip arthroplasty in patients aged ≥80 years.

BACKGROUND/PURPOSE: We evaluate the clinical and radiological results of cementless total hip arthroplasties (THAs) in patients aged ≥80 years. METHODS: We compared the clinical and radiological results of 30 cementless THAs done in patients aged ≥80 years (older group) and aged 60-69 years (control group). RESULTS: The Harris Hip score significantly decreased in the older group 1 year after the operation and at the final follow-up observation (p = 0.001), but no joints required revision surgery due to poor initial fixation or early loosening. CONCLUSION: Cementless THA in the elderly is safe and durable at the time of the follow-up.

Safety in early experience with a direct anterior approach using fluoroscopic guidance with manual leg control for primary total hip arthroplasty: a consecutive one hundred and twenty case series.

BACKGROUND AND PURPOSE: An encouraging result with direct anterior approach (DAA) is attractive for both patients and surgeons. However, the risks associated with beginning to use DAA require further analysis of the learning curve and better countermeasures to ensure safety. We ask whether the complication rate in the DAA by the inexperienced surgeon could be decreased with specific countermeasures. Our hypothesis was that the complication rate would be low even in early phase of the learning curve using the DAA with these particular countermeasures. PATIENTS AND METHODS: We investigated a consecutive series of 120 primary THA using the DAA with four specific countermeasures; 1) defined exclusion criteria for DAA; 2) no positioning table; 3) use of fluoroscopy as much as required; and 4) having an experienced assistant for DAA (one who has performed the procedure in more than 100 cases). The operative time, the time of fluoroscopic use during the operation, intra and post-operative complications, re-operation for any reason, and cup and stem alignment were investigated. RESULTS: Although the operation times were similar, the duration of fluoroscopy decreased with surgeons' experience. There were no intra-operative complications and no re-operations for any reason. One anterior dislocation was observed in one patient. The mean cup inclination and anteversion angle was 39.7° ± 7.6° and 30.3° ± 7.6°; 43.3 % of stems were positioned in flexion, 55.8 % in the neutral position on the lateral view. CONCLUSION: We demonstrated a lower complication rate during our early experience with the DAA using four countermeasures. Using these countermeasures for the first 40 cases may be useful for surgeons who are considering DAA.

Validation study of the Forgotten Joint Score-12 as a universal patient-reported outcome measure.

PURPOSE: The Forgotten Joint Score-12 (FJS-12) is for patients to forget their artificial joint and is reportedly a useful patient-reported outcome tool for artificial joints. The purpose of this study was to determine whether the FJS-12 is as useful as the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) or the Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ) in Japan. METHODS: All patients who visited our hospital's hip joint specialists following unilateral THA from August 2013 to July 2014 were evaluated. Medical staff members other than physicians administered three questionnaires. Items evaluated were (1) the reliability of the FJS-12 and (2) correlations between the FJS-12 and the total and subscale scores of the WOMAC or JHEQ. RESULTS: Of 130 patients, 22 were excluded. Cronbach's α coefficient was 0.97 for the FJS-12. The FJS-12 showed a significantly lower score than the WOMAC or JHEQ (p < 0.01). The FJS-12 was moderately correlated with the total WOMAC score (r = 0.522) and its subscale scores for "stiffness" (r = 0.401) and "function" (r = 0.539) and was weakly correlated with the score for "pain" (r = 0.289). The FJS-12 was favorably correlated with the total JHEQ score (r = 0.686) and its subscale scores (r = 0.530-0.643). CONCLUSION: The FJS-12 was correlated with and showed reliability similar to that of the JHEQ and WOMAC. The FJS-12, which is not affected by culture or lifestyle, may be useful in Japan.

Total hip arthroplasty after previous rotational acetabular osteotomy.

BACKGROUND/PURPOSE: Rotational acetabular osteotomy (RAO) is a joint-conserving surgery in which femoral head coverage is improved using autologous cartilage to stabilize the joint. For advanced coxarthrosis, it has been reported that radical surgery should be selected, compared to the pre- and early stages. The objective of this study was to determine the clinical outcomes of patients in whom coxarthrosis progressed after RAO and came to undergo total hip arthroplasty (THA). METHODS: We compared 24 total hip arthroplasties done in dysplastic hips after previous rotational acetabular osteotomy (RAO group) with a well-matched control group of 24 primary arthroplasties (control group) done during the same period at an average follow-up of 85 months (range 15-195). RESULTS: RAO group required significantly longer operative times and had more intraoperative blood loss. There was no significant difference between the two groups in terms of Harris Hip Score and radiographic outcome. Revision was performed in four and one joints in the RAO and control groups, respectively, showing no significant difference between the two groups (p = 0.165). CONCLUSION: THA after previous RAO leads to midterm results similar to those of other dysplastic hips. RAO does not seem to compromise the midterm clinical and radiographic outcome.

Prospective study on antimicrobial prophylaxis in total hip arthroplasty.

AIMS AND BACKGROUND: Prophylactic use of antibiotics against the pathogens likely to contaminate the procedure is considered beneficial to prevent surgical site infections. We asked that an increase in the effective blood concentration by increasing the administration dose immediately before the operation can decrease the incidence of surgical site infection and performed a prospective study in patients undergoing total hip arthroplasty. METHODS: The subjects consisted of 357 patients who underwent initial THA between January 2006 and June 2012. We compared 172 patients who received an initial dose of Unasyn-S 1.5 g (1.5-g group) and 185 treated after January 2010 when the initial dose alone was increased to 3.0 g (3.0-g group) in terms of the incidence and depth (superficial or deep layer) of SSI. RESULTS: SSI developed in 7 (1.96 %) of all patients, consisting of 5 (2.91 %) in the 1.5-g group and 2 (1.08 %) in the 3.0-g group. Its incidence did not differ between the two groups, but was slightly lower in the 3.0-g group. Deep infection was observed in 2 of the 5 patients in the 1.5-g group but neither of the 2 in the 3.0-g group. CONCLUSION: Although there is statistically no significant difference in the incidence of SSI, our data suggest that an increase of the preoperative antibiotics reduces the incidence of SSI and can be an effective measure for the prevention of infection.

Rapid hip osteoarthritis development in a patient with anterior acetabular cyst with sagittal alignment change.

Rapidly destructive coxarthrosis (RDC) is rare and develops unusual clinical course. Recent studies suggest multiple possible mechanisms of the development of RDC. However the exact mechanism of RDC is still not clear. The difficulty of the study on RDC is attributed to its rareness and the fact that the data before the onset of RDC is normally unavailable. In this report, we presented the patient having the radiographic data before the onset who had rapid osteoarthritis (OA) development after contralateral THA, which meets the current criteria of RDC. We thought that the increased posterior tilt of the pelvis after THA reinforced the stress concentration at pre-existed anterior acetabular cyst, thereby the destruction of the cyst was occurred. As a result the rapid OA was developed. We think that there is the case of rapid osteoarthritis developing due to alternating load concentration by posterior pelvic tilt on preexisting anterior acetabular cyst such as our patient among the cases diagnosed as RDC without any identifiable etiology. The recognition of sagittal alignment changes and anterior acetabular cyst may play important role in prediction and prevention of the rapid hip osteoarthritis development similar to RDC.

Is urinary incontinence the hidden secret complications after total hip arthroplasty?

INTRODUCTION: We hypothesized that posterior approach (PA) dissecting the short external rotators and anterior approach (AA) not dissecting these have different influences on the pelvic floor muscles and subsequently affect urinary incontinence. The objective of this study was to investigate whether AA advantageously influences symptoms of urinary incontinence. PATIENTS AND METHODS: The subjects were 76 female patients who underwent their primary total hip arthroplasty. The presence or absence of urinary incontinence before and after surgery was surveyed by a direct interview at the time of outpatient examination within a period from 1.5 year after surgery using the international consultation on incontinence questionnaire-short form. RESULTS: Urinary incontinence improved after surgery in eight patients (22.2%), slightly improved in one (2.8%), remained unchanged in 26 (72.2%), slightly aggravated in one (2.8%) in the AA group. In the PA group, urinary incontinence improved after surgery in one (2.5%), remained unchanged in 30 (75%), slightly aggravated in four (10%), and aggravated in five (12.5%). Symptoms of urinary incontinence were significantly improved in the AA group and aggravated in the PA group (Mann-Whitney U test, P = 0.0057). CONCLUSIONS: As the anatomical characteristic of the short external rotators, the root of the internal obturator muscle is connected to the levator ani muscle. Among the pelvic floor muscles, this levator ani muscle is closely involved in supporting the pelvic organs. Since the short external rotators may have been atrophied due to hip joint dysfunction before surgery, if the strength of this muscle group recovers, support of the pelvic organs and urinary incontinence may be improved. It was assumed that surgery through AA improved external rotation contracture of the hip joint and leg length, which increased tension of the internal obturator muscle, with which tension of the pelvic floor muscle also increased and improved urinary incontinence.

Mid-term clinical results of total hip arthroplasty using a Wagner standard cup for dysplastic hip.

BACKGROUND: The outcome of cementless total hip arthroplasty depends on many factors. We must not forget fundamental things those are design of outer surface of the component, that leads bone ingrowth into the prosthesis, better initial stability, and better insertional techniques. The purpose of this study was to review our experience with metal-on-metal total hip arthroplasty with a Wagner standard cup for patients who had acetabular dysplasia. PATIENTS AND METHODS: Fifty-four patients with 55 hips underwent primary metal-on-metal total hip arthroplasty (Metasul prosthesis) with a Wagner standard cup (44-48 mm in outer diameter) and were followed for a minimum of 10 years. All patients received the same type of cementless femoral component (Natural hip stem) and femoral head (28 mm in diameter). RESULTS: Seventeen of the 55 Wagner standard cups (30.9%) showed aseptic loosening over a mean period of 3.6 years after surgery, and there were no bone anchors on the outer surface of the 16 retrieved cups. CONCLUSION: From our experience, the small Wagner standard cup does not achieve sufficient osteointegration and we do not recommend the use of this cup, especially for patients with acetabular dysplasia and/or those with a small stature.

Surgical outcome for hip fractures in patients with and without Parkinson's disease.

PURPOSE. To compare surgical outcome of hip fractures (in terms of the ability to walk and complications) in patients with and without Parkinson's disease (PD). METHODS. Records of 207 patients who underwent surgery for femoral neck fractures were reviewed. Of whom, 9 men and 26 women with PD aged 58 to 89 (mean, 76.8) years underwent hemiarthroplasty for subcapital fractures (n=22) or internal fixation for intertrochanteric fractures (n=13). The remaining 36 men and 136 women with no PD aged 61 to 96 (mean, 81.8) years underwent hemiarthroplasty (n=108) or internal fixation (n=64) for subcapital (n=120) or intertrochanteric (n=52) fractures. None of the patients had pathological fractures, and all had been ambulatory prior to the fracture. According to the Columbia classification system, severity of PD was grade II in 11, grade III in 11, and grade IV in 13 patients. RESULTS. Respectively for the patients with and without PD at the one-year follow-up, 68.2% and 79.6% of those treated with hemiarthroplasty and 46.2% and 62.5% of those treated with internal fixation were able to walk with or without assistive devices. 81.8%, 63.6%, and 38.5% of the patients with grade-II, -III, and -IV PD, respectively, were able to walk at the one-year follow-up, compared to 73.3% of the patients without PD. CONCLUSION. Surgical treatment for hip fractures was appropriate for patients with grade-II or -III PD.

Chromium level of salvaged blood in patients undergoing revision hip arthroplasty.

PURPOSE. To evaluate the chromium level of the salvaged blood in patients undergoing revision total hip arthroplasty (THA). METHODS. Records of 7 women and one man aged 54 to 83 (mean, 64.3) years who underwent revision THA for aseptic loosening of the acetabular component (n=6), osteolysis of the acetabulum (n=1), or migration of the outer head (n=1) were reviewed, as were 2 controls who underwent primary THA. The initial THA entailed a metal-on-metal prosthesis (n=4), a metal-on-polyethylene prosthesis (n=3), and a bipolar head prosthesis (n=1). Chromium levels in the preoperative peripheral blood and intraoperative salvaged blood were measured using atomic absorption analysis. RESULTS. For controls and the patient with a bipolar head prosthesis, the mean chromium level in salvaged blood was 0.4 (range, 0.2-0.6) micrograms/l, which was significantly lower than that in the remaining 7 patients undergoing revision THA (mean, 5.6 micrograms/l; range, 1.2-9.8 micrograms/l). CONCLUSION. Salvaged blood of patients with a metal-on-metal prosthesis undergoing revision THA contained higher levels of chromium.

Intervertebral disc development is regulated by Wnt/ß-catenin signaling.

STUDY DESIGN: Histologic analysis of intervertebral disc (IVD) in three types of transgenic mice. OBJECTIVE: To investigate the role of Wnt/ß-catenin signaling in regulation of IVD development and organization. SUMMARY OF BACKGROUND DATA: ß-catenin dependent Wnt signaling is one of the central regulators in cartilage development during limb skeletal formation. Little is known, however, about the physiologic relevance of this signaling pathway to IVD development and organization. METHODS: Temporal-spatial distribution of Wnt/ß-catenin signaling activity was examined in IVD using Wnt/ß-catenin reporter (TOPGAL) mice. The structural changes in the mouse IVD components such as the nucleus pulposus (NP), endplate (EP), annulus fibrosus (AF), and the growth plate (GP) of the vertebral body were analyzed after transient activation of Wnt/ß-catenin signaling or deletion of ß-catenin in the mice. RESULTS: Activity of Wnt/ß-catenin signaling was high in EP, AF, and GP in the embryonic stages and decreased at the postnatal stage; it was undetectable in the embryonic NP but upregulated after birth. The transient activation of Wnt/ß-catenin signaling caused severe deterioration of the GP and the AF, whereas deficiency of ß-catenin accelerated bone formation in between EP and GP. CONCLUSION: The findings in this study suggest that proper regulation of Wnt/ß-catenin signaling is required for development and organization of IVD.

Transient activation of Wnt/{beta}-catenin signaling induces abnormal growth plate closure and articular cartilage thickening in postnatal mice.

Wnt/beta-catenin signaling is required for skeletal development and organization and for function of the growth plate and articular cartilage. To further clarify these roles and their possible pathophysiological importance, we created a new transgenic mouse model in which Wnt/beta-catenin signaling can be activated in cartilage for specific periods of time. These transgenic mice expressed a constitutive active form of beta-catenin fused to a modified estrogen receptor ligand-binding domain under the control of cartilage-specific collagen 11alpha2 promoter/enhancer. Transient Wnt/beta-catenin signaling activation in young adult mice by tamoxifen injections induced growth retardation and severe deformities in knee joints. Tibial and femoral growth plates displayed an excessive number of apoptotic cells and eventually underwent abnormal regression. Articular cartilage exhibited an initial acute loss of proteoglycan matrix that was followed by increases in thickness, cell density, and cell proliferation. In reciprocal studies, we found that conditional ablation of beta-catenin in postnatal mice using a Col2-CreER strategy led to hypocellularity in articular cartilage, growth plate disorganization, and a severe reduction in bone volume. Together, these data provide evidence that Wnt/beta-catenin signaling has important and distinct roles in growth plate and articular cartilage and that postnatal dysregulation of this signaling pathway causes diverse structural and functional changes in the two cartilaginous structures.