Chondroprotective Effect of PCSO‐524 (Green‐Lipped Mussel Extraction) Application Evaluated by Ultrasonography in Pomeranian and Chihuahua With Medial Patellar Luxation Grade II

ABSTRACT

Objective

This research evaluated the chondroprotective efficacy of PCSO‐524 in dogs with osteoarthritis (OA) secondary to medial patellar luxation (MPL) using ultrasonography − a non‐invasive technique recommended for early OA detection.

Materials and Methods

Animals: 25 dogs total (21 with MPL grade II, 50 stifle joints evaluated) divided into three groups, including control group: 10 dogs receiving placebo, treatment group: 11 dogs receiving PCSO‐524 (50 mg daily) and normal group: 4 healthy dogs (reference)

Duration: 16 weeks

Evaluations: Lameness scores, blood profiles, ultrasonographic findings, radiographic assessments and owner questionnaires at baseline, weeks 2, 4, 8, 12 and 16.

Results

The treatment group showed significant improvement in lameness scores within 8 weeks. The cartilage lesions improved within 4 weeks of PCSO‐524 administration. Synovial fluid scores decreased significantly by week 4 in the treatment group. Radiographic OA scores improved mildly at 12 weeks in the treatment group versus progression in the control group. Owners observed better gait and quality of life by week 2. No adverse effects on blood chemistry or organ function.

Conclusion

PCSO‐524 demonstrates effective cartilage protection in dogs with OA secondary to MPL, with improvements in clinical signs, ultrasonographic findings and radiographic outcomes. For dogs that cannot undergo surgical correction, PCSO‐524 supplementation combined with quadriceps muscle training and environmental management is recommended for improved quality of life.

Background: Medial patellar luxation (MPL) in small breed dogs leads to secondary osteoarthritis (OA). This study evaluated PCSO‐524 (Green Mussel lipid extract) as a non‐invasive chondroprotective treatment.

Study Design: 25 dogs (21 with MPL grade II) were divided into:

• Treatment group (n = 11): PCSO‐524, 50 mg/day

• Control group (n = 10): Placebo

• Reference group (n = 4): Healthy controls

Key Findings:

• ✓ Week 2: Improved gait and quality of life (owner‐reported)

• ✓ Week 4: Cartilage lesions improved; synovial fluid scores decreased significantly

• ✓ Week 8: Significant lameness score improvement

• ✓ Week 12: Radiographic OA scores improved in treatment versus progression in controls

• ✓ No adverse effects on blood chemistry or organ function

Conclusion: PCSO‐524 demonstrates effective cartilage protection in dogs with OA secondary to MPL. Combined with quadriceps training and environmental management, it improves clinical outcomes and quality of life in dogs unsuitable for surgical correction.

1. Introduction

Osteoarthritis (OA) is widely known as the most prevalent arthritic disease in dogs and cats. It is a common cause of chronic pain, leading to physical disability when progression occurs (Johnston 1997; Burnett et al. 2006). The varieties of medical therapies and physical managements for OA patients have been increasingly established and developed to treat human and animal suffering from OA, such as long‐term usage of non‐steroidal anti‐inflammatory drugs (NSAIDs), nutraceuticals, weight management and rehabilitation. Nutraceuticals play an interesting role due to their beneficial outcomes and less side effects after long‐term application. Jamikorn and Yibchok‐anun (2014) and Kwananocha et al. (2016) have reported that PCSO‐524, a New Zealand green‐lipped mussel extract, omega‐3 polyunsaturated fatty acids (n‐3 PUFAs) supplement, can reduce inflammation and articular cartilage degradation without any adverse effects. The clinical outcome of the application of PCSO‐524 has been evaluated in many different ways such as force plate gait analysis, lameness score, pain score, orthopaedic assessment score (OAS), radiographic findings and owner preferences and questionnaires (Mongkon and Soontornvipart 2012; Kwananocha et al. 2016). Unfortunately, there is no clinical study addressing the efficacy of PCSO‐524 on the articular cartilage degradation. The degradation of articular cartilage during arthritis is the key point to indicate the early stage of OA signs using ultrasonography techniques, which is recommended for the detection of an early OA signs in both humans and dogs (Okano et al. 2016; Ramírez‐Flores et al. 2017; Jain and Johar 2018) due to the less invasive technique and abilities to assess the cartilage and synovial capsule inflammation (Karatrantos et al. 2025). In Thailand, a large number of small breed dogs have been diagnosed with medial patellar luxation (MPL) disease, leading to the development of OA in the stifle joint (Martinez 1997; Alam et al. 2011). Although surgical treatment is the best way to cure this disease (Martinez 1997), some owners may refuse to let their pets undergo the surgical intervention due to being scared of the anaesthetic risks and lack of notification of lameness. The purpose of this study is to evaluate the chondroprotective effect of PCSO‐524, the omega‐3 PUFAs supplement, in dogs with OA secondary to MPL by using US.

2. Materials and Methods

2.1. Animals

Pomeranian and Chihuahua breed dogs, presented at the Small Animal Hospital, Faculty of Veterinary Science, Chulalongkorn University, were diagnosed with MPL of any severity. The severities of MPL were classified base on Piermattei et al. (2006). Twenty‐five dogs with the age of over 5 years old and weight between 2 and 6 kg were included in the study. MPL dogs (n = 21) were randomized and categorized into two groups, control and treatment groups. Moreover, the normal group (n = 4), which had the same criteria as both groups except being MPL, was selected to represent the normal appearance of the stifle joints in these breeds. All owners were informed and signed the consent form before enrolling in the study.

All dogs were examined thoroughly for both general physical and neurological examinations. The body condition score (BCS) was determined based on a 9‐point scale BCS system (Laflamme 1997). All dogs were fed commercial standard food only. In the control and treatment groups, the selected patients must not be received NSAIDs, nutraceuticals or pain control drugs at least 2 weeks before the study. Exclusion criteria were patients with a history of neurological deficit, systemic diseases or any orthopaedic diseases except MPL disease. This study was approved by the animal care and use committee of the Faculty of Veterinary Science, Chulalongkorn University Animal Care and Use Committee (CU‐IACUC), Bangkok, Thailand. The approval number was 1831085.

2.2. Study Designs

All normal stifle dogs underwent ultrasonographic and radiographic examinations to identify the normal stifle. In the treatment and control groups, all dogs (n = 21 dogs; 42 stifles) with any severity of MPL grade were divided into two groups by double blind randomized sampling technique. In the treatment group, 11 dogs (n = 22 stifles) were treated with PCSO‐524 at the recommended dose as 50 mg per animal once daily for 16 weeks. Ten dogs in the control group (n = 20 stifles) were fed with placebo (appearance same as PCSO‐524) once daily for 16 weeks. All caregivers in both groups were recommended to perform quadriceps muscle training (sit‐to‐stand exercise) and restrict excessive exercise for their MPL dogs. All dogs were evaluated for both stifles for clinical outcomes before treatment (D0) and post‐treatment program at week 2 (W2), 4 (W4), 8 (W8), 12 (W12) and 16 (W16). The clinical evaluations included lameness score, blood profiles, ultrasonographic findings, radiographic findings and owner questionnaires. In each visit, these patients were assessed for all clinical evaluations except the blood profiles, which were examined only at D0 and W16 for the evaluation of any adverse effects and health status. The endpoint to exclude the animals from the study included the worse clinical pain or lameness or any side effect detected. The rescue treatment, including pain management protocol and supportive treatment, would be applied.

2.2.1. Lameness Score

All dogs in the control and treatment groups were assessed, and abnormal gaiting was video‐recorded at each time point. The lameness videos were taken on the cranial, caudal, left and right lateral views. Lameness was scored during walking and trotting. The evaluation of lameness score was modified. All videos were evaluated and scored by three veterinarians who did not know about our trial.

2.2.2. Blood Profiles

The determination of haematology (complete blood count, CBC) and the standard serum chemistry parameters, including blood urea nitrogen (BUN), creatinine (Cr), alanine transaminase (ALT) or serum glutamate‐pyruvate transaminase (SGPT) and alkaline phosphatase (ALP), were performed at before (Day 0) and at the end of the study (Week16) for health status and adverse effects of the treatments.

2.2.3. Ultrasonographic Examination

To assess stifle joint alterations, US was performed with a real‐time 10‐MHz linear transducer (Mindray Z5 Ultrasound Machine) (Karatrantos et al. 2025; Kramer et al. 1999; Penninck and d'Anjou 2015; Ramírez‐Flores et al. 2017). It was used with 50 and 1.8 in gain and depth, respectively. Stifle joints were examined following an acoustic approach modified from Kramer et al. (1999) and Penninck and d'Anjou (2015). Some standard views were listed appropriately according to the objective of this study presented in Table 1 (Figure 1). The ultrasound (US) evaluation was analysed and scored (Tables 2 and 3) based on the modification of ultrasonographic scoring system modified from Goranov et al. (2013). The evaluation scores consisted of synovial fluid, articular cartilage and bone surface of the femoral condyles score. In each stifle, the femoral condyles were evaluated into four parts involving the proximal and distal of both the medial and lateral femoral condyles. Individual scores were ranged between 0 and 28 points, which were calculated for the ultrasonographic score. Moreover, the articular cartilage thickness of the femoral condyles was recorded in millimetres. The ultrasonographic and radiographic scores were blinded evaluated.

TABLE 1.

Ultrasonographic standard views for evaluating the stifle joint modified from Kramer et al. (1999).

Standard regions/views	Implementation
Suprapatellar region
(A) Parallel view on the femoral trochlea	Knee flexed at an angle of 45 degrees Parallel sagittal image
(B) Suprapatellar views on the femoral trochlea	Knee flexed as far as possible Transverse image
Infrapatellar region
(C) Infrapatellar view	Knee flexed at an angle of 90 degrees Sagittal image

FIGURE 1.

Drawings of stifle flexion in each position. (A) Stifle flexion from its axis at an angle of 45 degrees. (B) Maximum stifle flexion. (C) Stifle flexion from its axis at an angle of 90 degrees with ultrasound probe.

TABLE 2.

Ultrasonographic scoring system for OA stifle joint: Articular cartilage score modified from Goranov et al. (2013).

Articular cartilage score	Description
0	Normal appearance; anechoic band with smooth margin
1	Hypoechoic appearance of the hyaline cartilage with irregular margin
2	Hyperechoic appearance of the hyaline cartilage with irregular margin
3	Heterogeneous appearance of the hyaline cartilage with irregular margin

TABLE 3.

Ultrasonographic scoring system for OA stifle joint: Bone surface score modified from Goranov et al. (2013).

Bone surface score		Description
0	Normal appearance	Round bony margin
1	Mild	Minor irregular edge
2	Moderate	Some interruptions surface
3	Severe	Severe hyperechoic boundary of bones

2.2.4. Radiographic Examination

During the study, conventional radiographs of interested stifle joints were performed and recorded (FCR CAPSULA V VIEW workstation) in each visit. The radiographic examinations were obtained in two views, mediolateral and caudocranial, for classification of the OA score. This OA score was evaluated based on the modification of Wessely et al. (2017) and Frost‐Christensen et al. (2008). There were 15 assessment points in the stifle radiographs, including 11 points in the mediolateral view (Figure 2) and 4 points in the caudocranial view (Figure 2). Each point was graded on a numeric scale from 0 to 3 (Table 4). The overall OA scores were calculated in the range between 0 and 45.

FIGURE 2.

Radiographic image with assessment points in the mediolateral view of the stifle joint: 1, patellar apex; 2, patellar base; 3, proximal trochlear ridge; 4, distal trochlear ridge; 5, femoral condyle; 6, tibial tuberosity; 7, cranial aspect tibial plateau; 8, caudal aspect tibial plateau; 9, central aspect tibial plateau; 10, popliteal surface femur; 11, sesamoid bones. Radiographic image with assessment points in the caudocranial view of the stifle: 12, lateral tibial and femoral condyle; 13, medial tibial and femoral condyle; 14, intercondylar notch; 15, patella.

TABLE 4.

The radiographic scores of radiographic changes modified from Wessely et al. (2017) and Frost‐Christensen et al. (2008).

Grade	Severity	Radiographic changes
0	No	Radiographically normal or no evidence of osteophyte formation or subchondral sclerosis
1	Mild	Mild osteophyte formation and/or mild subchondral sclerosis (mild arthrosis)
2	Moderate	Moderate osteophyte formation and/or moderate subchondral sclerosis (moderate arthrosis)
3	Severe	Marked osteophyte formation and/or severe subchondral sclerosis (severe arthrosis)

2.2.5. Owner Questionnaires

The owner was requested to perform the questionnaires of Canine Brief Pain Inventory (Canine BPI, CBPI) by University of Pennsylvania, which was created by Dr. Dorothy Cimino Brown aimed to detect the severity of pain (Cleeland 1990, 2006). CBPI is a validated 11‐question owner‐completed survey used to evaluate chronic pain and quality of life (QoL) in dogs. It measures pain severity (PSS) (4 items) and pain interference (PIS) with daily function (6 items) on a 0–10 scale, alongside a global QoL rating (1–5 scale). Pain Degree was calculated through a direct additive approach, where the raw, unweighted scores of all 10 individual items from both the PSS and PIS sections were summed together for each individual dog at each designated time point. This cumulative mathematical calculation yielded a continuous baseline index with a minimum possible score of 0 (representing complete absence of pain and interference) and a maximum possible aggregate score of 100 (representing the most severe pain and total functional disability).

2.3. Data Presentation and Statistical Analysis

The demographic data, including breed, gender, age, body weight and the severity of MPL grades, were reported as descriptive statistics. D'Agostino & Pearson omnibus and Kolmogorov−Smirnov normality test with Dallal−Wilkinson−Lillie for p‐value were used to determine for normal distribution of age and body weight, respectively. Age, body weight, lameness score, CBC, blood chemistry parameters, ultrasonographic score, synovial fluid score, articular cartilage score, bone surface score, cartilage thickness and radiographic OA scores were reported as mean ± SD. Ordinary one‐way analysis of variance (ANOVA) was used to analyse age, body weight and cartilage thickness among normal, control and treatment groups. The Kruskal−Wallis test was used to analyse gender among groups. Mann−Whitney U test was used to assess differences in the severity of MPL, lameness score, CBC, blood chemistry parameters, ultrasonographic score, synovial fluid score, articular cartilage score, bone surface score and radiographic OA scores between control and treatment groups. Friedman tests were used to assess differences within groups, the lameness score, degree of pain, degree of life quality, ultrasonographic score, synovial fluid score, articular cartilage score, bone surface score and radiographic OA score. Repeated‐measures one‐way ANOVA was used to analyse the differences in cartilage thickness at across visit within each group. GraphPad Prism 8 (version 8.1.0) was used for the statistical analysis. The results were considered statistically significant at a p‐value < 0.05.

3. Results

Twenty‐five dogs (50 stifle joints) were enrolled in this study. The mean age, body weight and gender in each group are revealed in Table 5. The number of dogs with several degrees of patellar luxation is reported in Table 6.

TABLE 5.

Mean ± SD of age and body weight and the number of gender of dogs in control, treatment and normal groups.

Demographic data		Control group (N = 10)	Treatment group (N = 11)	Normal group (N = 4)	p‐value
Age (year)		6.40 ± 1.27	6.36 ± 1.80	5.0 ± 2.31	0.34 *
Body weight (kg)		3.49 ± 1.04	3.27 ± 1.08	3.73 ± 0.91	0.74 *
Gender (N)	Male (N)	4	5	3	0.498 **
	Female (N)	6	6	1

^* p‐value is obtained from ordinary one‐way ANOVA.

^** p‐value is obtained from Kruskal−Wallis test.

TABLE 6.

Number of dogs categorized from severity of MPL in control and treatment groups.

Groups	MPL II	MPL III	MPL IV	p‐value
Control group (n = 20)	(6/20) 30%	(13/20) 65%	(1/20) 5%	0.37 *
Treatment group (n = 22)	(3/22) 13.64%	(19/22) 86.36%	(0/22) 0%
All stifles	(9/42) 21.43%	(32/42) 76.19%	(1/42) 2.38%

^* p‐value is obtained from the Mann−Whitney U test.

3.1. Lameness Score

The evaluation of lameness score results revealed that the lameness score in the treatment group showed a significant decrease (p < 0.05) at W8−W16, while in the control group showed no difference in any week of the study. There was a significant decrease between groups after 12 weeks of the treatment (p < 0.05). Mean ± SD of lameness score in control and treatment groups are illustrated in Figure 3. The improvement in lameness score at least one degree between each visit is shown in Table 7.

FIGURE 3.

Mean ± SD of lameness score of the control group (green) in each monitoring week and the treatment group (red) in each monitoring week.

TABLE 7.

Percentage of the improvement of lameness score at least one degree between adjacent visits: D0−W2, W2−W4, W4−W8, W8−W12 and W12−W16.

Groups	D0−W2	W2−W4	W4−W8	W8−W12	W12−W16
Control group (n = 10)	(1/10) 10%	(0/10) 0%	(1/10) −10%	(1/10) 10%	(1/10) −10%
Treatment group (n = 11)	(9/11) 81.82%	(1/11) 9.10%	(1/11) 9.10%	(1/11) 9.10%	(0/11) 0%

Negative value percentage: worse than the time point assessment.

3.2. Blood Profiles

All dogs in the control and treatment groups were evaluated for CBC and the standard blood chemistry parameters before treatment (D0) and after treatment (W16). No significant differenceswerefound between D0 and W16 for any parameters in either group.

Though most of the parameters were in normal range at both D0 and W16 in the two groups, the value of ALT, the liver parameters, were mild elevated in some dogs at W16 in both groups.

3.3. Ultrasonographic Examination

From eight normal stifles, the ultrasonographic findings are shown in Figures 4, 5, 6, 7. The characteristics of the normal stifle joint were as described by Möller et al. (2008) and Penninck and d'Anjou (2015). In the suprapatellar region, the suprapatellar recess was seen above the femoral condyle with an average thickness was 2.4 mm (Figure 4). Synovial fluid was found as anechoic content with homogeneous echogenicity in the infrapatellar region (Figure 5A,B). Along the aspects of the femoral condyle of the suprapatellar and infrapatellar regions, the hyaline cartilage appeared as an anechoic band with a smooth and sharp hyperechoic margin (Figures 5B−7). The bone surface showed a uniform profile and a smooth boundary. In the transverse view of the suprapatellar region, the medial and lateral femoral condyles appeared; the average cartilage thickness of the medial, middle and lateral areas were 0.204 ± 0.013, 0.217 ± 0.026 and 0.213 ± 0.025 mm, respectively.

FIGURE 4.

Longitudinal view of the suprapatellar region of a normal stifle joint. Suprapatellar recess (arrows) was seen over the proximal of medial femoral condyle (PMFC). Patella (P) was used as a landmark.

FIGURE 5.

Ultrasonographic images of the infrapatellar region with sagittal view of the normal stifle joint. (A) Patella (P) and tibial tuberosity (TT) were used as landmarks for this view. Synovial fluid (SF) showed anechoic underneath the patellar ligament (arrowheads). (B) This region appeared distal aspect of medial femoral condyle (DMFC). An anechoic band with a smooth margin of the articular cartilage (arrows) was seen over its bone surface, which appeared as a hyperechoic smooth lining.

FIGURE 6.

Ultrasonographic image of suprapatellar region with sagittal view of the normal stifle joint. The proximal aspect of the medial femoral condyle (PMFC) was shown. Bone surface (arrowheads) and the articular cartilage (arrows) covering them were seen.

FIGURE 7.

Ultrasonographic image of suprapatellar region with transverse view of the normal stifle joint. The thickness of the articular cartilage of the medial and lateral femoral condyles were determined.

The evaluations of ultrasonographic scores and the thickness of articular cartilage are calculated as mean ± SD, shown in Tables 8 and 9, respectively. The ultrasonographic scores of the treatment group were significantly different between pre‐treatment and W4−W16 post‐treatment (p < 0.05), while no significant difference of these parameters was observed in the control group. Furthermore, a significant difference was observed between two groups of treatment after 4 weeks post‐treatment (p < 0.05).

TABLE 8.

Mean ± SD of ultrasonographic, synovial fluid, articular cartilage and bone surface score of the control and treatment groups.

Ultrasonographic parameters		Groups	Day 0	Week 2	Week 4	Week 8	Week 12	Week 16
Ultrasonographic score		Control group	9.10 ± 2.38a,A	9.10 ± 2.40a,A	9.40 ± 2.21a,A	9.65 ± 2.62a,A	9.30 ± 2.18a,A	7.65 ± 3.98a,A
		Treatment group	9.09 ± 2.91a,A	7.91 ± 2.89ab,A	6.82 ± 2.52bc,B	5.77 ± 2.20 cd,B	5.14 ± 2.17d,B	4.86 ± 1.93d,B
Synovial fluid score		Control group	2.40 ± 0.68a,A	2.45 ± 0.76a,A	2.60 ± 0.75a,A	2.75 ± 0.79a,A	2.55 ± 0.76a,A	2.60 ± 0.75a,A
		Treatment group	2.88 ± 0.66a,A	2.23 ± 0.61ab,A	1.91 ± 0.81b,B	1.82 ± 0.80b,B	1.59 ± 0.85b,B	1.59 ± 0.80b,B
Articular cartilage score	Proximal aspect of medial femoral condyle	Control group	2.95 ± 0.22a,A	2.90 ± 0.31a,A	2.95 ± 0.22a,A	2.85 ± 0.49a,A	2.90 ± 0.31a.A	2.95 ± 0.22a,A
		Treatment group	2.95 ± 0.21a,A	2.55 ± 0.67ab,A	2.00 ± 0.69bc,B	1.50 ± 0.67 cd,B	1.14 ± 0.35d.B	1.09 ± 0.53d,B
	Distal aspect of medial femoral condyle	Control group	1.10 ± 1.25a,A	1.15 ± 1.27a,A	1.15 ± 1.27a,A	1.30 ± 1.38a,A	1.15 ± 1.27a,A	1.20 ± 1.32a,A
		Treatment group	1.00 ± 1.38a,A	0.96 ± 1.33a,A	0.64 ± 1.00ab,A	0.50 ± 0.80ab,B	0.41 ± 0.73b,B	0.36 ± 0.66b,B
Bone surface score	Proximal aspect of medial femoral condyle	Control group	2.00 ± 0.56a,A	1.95 ± 0.61a,A	2.00 ± 0.56a,A	2.05 ± 0.61a,A	1.95 ± 0.61a,A	2.15 ± 0.59a,A
		Treatment group	1.64 ± 0.73a,A	1.64 ± 0.73a,A	1.64 ± 0.73a,A	1.50 ± 0.60a,A	1.45 ± 0.60a,A	1.36 ± 0.58a,A
	Distal aspect of medial femoral condyle	Control group	0.65 ± 0.75a,A	0.65 ± 0.75a,A	0.74 ± 0.80a,A	0.74 ± 0.80a,A	0.74 ± 0.80a,A	0.74 ± 0.80a,A
		Treatment group	0.50 ± 0.74a,A	0.50 ± 0.74a,A	0.50 ± 0.74a,A	0.46 ± 0.67a,A	0.41 ± 0.59a,A	0.41 ± 0.59a,A

Note: Values in the same row followed by different superscript lowercase letters differ significantly by Friedman test (p < 0.05). Values in the same ultrasonographic parameters between two groups followed by different superscript uppercase letters differ significantly by Mann−Whitney U test (p < 0.05).

TABLE 9.

Mean ± SD of the articular cartilage thickness of medial, middle and lateral of femoral condyles of the control and treatment groups.

Groups	Positions	Day 0	Week 2	Week 4	Week 8	Week 12	Week 16
Control group	Medial	0.235 ± 0.032	0.230 ± 0.038	0.231 ± 0.030	0.226 ± 0.024	0.237 ± 0.030	0.236 ± 0.035
	Middle	0.227 ± 0.046	0.222 ± 0.032	0.216 ± 0.025	0.227 ± 0.020	0.220 ± 0.019	0.220 ± 0.030
	Lateral	0.258 ± 0.13	0.217 ± 0.026	0.227 ± 0.034	0.224 ± 0.024	0.231 ± 0.038	0.226 ± 0.038
Treatment group	Medial	0.245 ± 0.045	0.235 ± 0.048	0.243 ± 0.042	0.244 ± 0.033	0.230 ± 0.036	0.229 ± 0.036
	Middle	0.226 ± 0.034	0.231 ± 0.031	0.266 ± 0.021	0.226 ± 0.036	0.222 ± 0.033	0.210 ± 0.020
	Lateral	0.211 ± 0.019	0.225 ± 0.034	0.230 ± 0.033	0.225 ± 0.029	0.224 ± 0.030	0.218 ± 0.029

Note: Values in the same row are not significantly different by repeated‐measures one‐way ANOVA (p > 0.05).

Lesions of the articular cartilage and bone surface were found on all medial ridges of femoral condyles, while none were detected on either the proximal ordistal aspects of the lateral femoral condyles.

There was no significant difference in the cartilage thickness between the two groups at any time point evaluation showed in Table 9.

Results revealed that the synovial fluid scores in the PCSO‐524 group showed a significant decrease in the treatment group at W4−W16 (p < 0.05), while no significant difference was observed in the control group. Synovial fluid score was significant different between two groups of treatment after 4 weeks post‐treatment (p < 0.05). Mean ± SD of synovial fluid scores of both groups are shown in Figure 8.

FIGURE 8.

Mean ± SD of the synovial fluid score of the control and the treatment groups in each monitoring week.

In the treatment group, the articular cartilage scores of proximal aspects of medial femoral condyle showed a significant decrease (p < 0.05) between pre‐treatment (D0) and post‐treatment at week 4−16, while nosignificant difference was observed in the control group. There was a significant difference after 4 weeks post‐treatment between control and treatment groups (p < 0.05). The improvement of the articular cartilage lesion between pre‐treatment (D0) and post‐treatment at week 4 is shown in Figure 9. Mean ± SD of the articular cartilage score of the proximal aspect of the medial femoral condyle of the control and treatment groups are shown in Figure 10.

FIGURE 9.

Ultrasonographic images of the suprapatellar region with sagittal view between pre‐treatment (D0) and post‐treatment at week 4. (A) The articular cartilage (arrows) showed heterogeneous hyperechoic with irregular margin (AC = 3) and bone surface (arrowheads) was moderate irregular hyperechoic lining (BS = 2). (B) The articular cartilage (arrows) was hypoechoic appearance with irregular margin (AC = 1) and bone surface (arrowheads) presented mild irregular hyperechoic lining (BS = 1).

FIGURE 10.

Mean ± SD of the articular cartilage score of the proximal aspect of the medial femoral condyle of the control and the treatment groups in each monitoring week.

The eroded cartilage of distal part of medial femoral condyle was found in 10 and 8 stifle joints from control and treatment groups, respectively. There were 42.8% of MPL stifles found to have erosion at the distal portion of the medial femoral condyle. The articular cartilage scores of distal aspects of medial femoral condyle showed a significant decrease (p < 0.05) between D0 and post‐treatment at weeks 12 and 16, while in the control group were not significant difference. There was significant difference after 8 weeks post‐treatment between two groups of treatment (p < 0.05).

The bone surface scores of both proximal and distal parts of the medial femoral condyle showed no significant difference in between the control and treatment groups. There was no significant difference between control and treatment groups.

3.4. Radiographic Examination

Radiography of the stifle joints were performed in two standard orthogonal views, including the mediolateral and the caudocranial views. The OA scores were calculated in the range between 0 and 45. The OA scores of control group were increased at W12 and W16 when compared with pre‐treatment at D0, without statistical difference. In treatment groups, the OA scores showed a mild decrease at W12 and W16 when compared with pre‐treatment at D0. Radiographic scoring was not significantly different between groups and time points. Mean ± SD of the radiographic OA score of control and treatment groups are shown in Figure 11.

FIGURE 11.

Mean ± SD of the radiographic OA score of the control and the treatment groups in each monitoring week.

3.5. Owner Questionnaire

The degrees of pain and life quality were statistically significant difference both in control and treatment groups. In control group, the difference of pain degrees showed between D0 and W12−W16 and the satisfaction of life quality found the difference between D0 and W4, W12 and W16. In the treatment group, the degrees of pain and the satisfaction of life quality were found significant increased after 4 weeks of the administration. There was no significant difference when a comparison was made between the control and treatment groups. Mean ± SD of pain and life quality degrees were compared between groups, as shown in Table 10.

TABLE 10.

Mean ± SD of the degrees of pain and life quality, which was evaluated by the questionnaire of Canine BPI within group.

Canine BPI parameters	Groups	D0	W2	W4	W8	W12	W16
Degree of pain	Control group	42.20 ± 13.36a	35.30 ± 13.97a	29.30 ± 17.22a	27.40 ± 15.31a	24.60 ± 15.01a	22.60 ± 15.21a
	Treatment group	52.45 ± 18.27a	35.55 ± 15.27ab	25.45 ± 12.02bc	20.82 ± 10.59bd	15.45 ± 5.91cd	13.73 ± 5.35d
Degree of life quality	Control group	2.9 ± 0.57a	3.4 ± 0.84ab	4.0 ± 0.82bc	4.0 ± 0.67acd,A	4.2 ± 0.79bd,A	4.5 ± 0.53 cd,A
	Treatment group	2.82 ± 0.75a	4.00 ± 0.63ab	4.36 ± 0.67b	4.81 ± 0.40b,B	4.91 ± 0.30b,B	5.0 ± 0b,B

Note: Values in the same row followed by different superscript lowercase letters differ significantly by Friedman test (p < 0.05). Values in the same Canine BPI parameters between two groups followed by different superscript uppercase letters differ significantly by Mann−Whitney U test (p < 0.05).

The CBPI revealed a better QoL score from fair to excellent in the treatment group and from fair to very good in the control group.

4. Discussion

MPL has been known as one of the most common developmental orthopaedic diseases in dogs, particularly in small and toy breed dogs (Roy et al. 1992; Alam et al. 2007). Abnormal biomechanics and repeated mechanical trauma to the articular cartilage are the main problems of this disease. It commonly leads to secondary OA of stifle joints due to the permanent joint instability and malalignment of the extensor mechanism (Hayes et al. 1994; Alam et al. 2011). Restoring normal stifle function is recommended to prevent progressive degeneration (Roy et al. 1992). However, several dogs suffering from MPL are not suitable candidate for surgery. Therefore, conservative treatment has been established. This study focuses on PCSO‐524, nutraceuticals which has potential in relieving OA pain, in the effectiveness in protection of the articular cartilage.

In this study, age, body weight and gender among the normal, control and treatment groups were not significantly different. Of all MPL dogs in the study, grade III MPL was mostly found as 76.19%, and grade II luxation was secondary found as 21.43%. The distribution of the luxation grades was not in accordance with recent studies, with grade II of MPL being the most prevalent luxation grade (Daems et al. 2009). The contrasting reports may be due to the differences in the breeds and age of dogs between these studies. The results of this study can be implied that Pomeranian and Chihuahua have a higher prevalence with MPL grade III more than others grade of MPL. Moreover, this study found only one stifle with grade IV luxation. The reason is that dogs with MPL grade IV mostly show more clinical signs, such as lameness and pain, which cause greater concern to owners. Conservative treatment or surgical correction is widely needed. Some of them may develop secondary diseases such as hip joint luxation, cranial cruciate ligament rupture (CCLR) or meniscal tear.

The results of lameness score in the treatment group were statistically found to have a significant improvement within 8 weeks after administration of PCSO‐524. However, all owners had observed an enhancement of dog's life quality since the second week. This is in accordance with the lameness score results. Over 80% of dogs (9/11 dogs) in the treatment group were found to have a better gait after 2 weeks of PCSO‐524 administration. Previous studies have also observed the improvement of lameness score and peak‐vertical force gait analysis after taking the supplement within 2 weeks in dogs with shoulder and hip OA (Soontornvipart et al. 2015). This is in agreement with the study of Kwananocha et al. (2016), who reported the effects of PCSO‐524 in hip and stifle OA. Since our study was breed‐specific, the number of patients in this study might not be large enough to obtain a significant difference within 2 weeks.

Regarding the questionnaire of Canine BPI, a significant improvement was observed in both groups. In the control group, pain degrees were significantly decreased after 12 weeks of placebo administration. On the contrary, the statistically significant results of dogs’ QoL fluctuated. Better results in some visits may be explained by the placebo effect and other conservative management, such as training quadriceps muscle and restriction of overexercise on slippery floor, which have been recommended to some owners who cooperated with the physical exercises. Furthermore, dogs with MPL show the variety degrees of clinical signs from asymptomatic, mild to moderate lameness, which can be occurred intermittent or continuous. A statistically significant improvement of both degrees of pain and life quality, in treatment group, were found after 4 weeks of the administration of PCSO‐524. The results are in accordance with the study in humans. Zawadzki et al. (2013) found that PCSO‐524 effectively cured the disease within 4 weeks by using the visual analogue scale for pain determination. However, as mentioned earlier, the owner opinions on dog's life quality had become a better improvement since the second week.

After administration of PCSO‐524 at the recommended dose for 16 weeks, there was no significant change in CBCs, liver and kidney function values. In accordance with previous studies, there was no change in these parameters when treated with the supplement for 24 weeks (Soontornvipart et al. 2015). The experiment of Jamikorn and Yibchok‐anun (2014) observed the same results, even though the dogs were treated with 10‐fold of the recommended dosage in healthy Beagles for 8 weeks. This study has also reported that some of the mean values of ALT in both treatment and control groups are higher than the normal range. However, a mild increasing of these liver function enzymes could be found in ageing patients without any observable changes in feed intake, clinical sings and behaviours.

US evaluation offers several advantages compared to other imaging modalities, including greater availability, quicker procedures, ease of repeat examinations and lower costs. It is a practical, dynamic and interactive assessment method that provides high‐resolution imaging (Karatrantos et al. 2025). According to the ultrasonographic findings, normal articular cartilage is characterized as a thin anechoic band with a sharp margin. The heterogeneous or hypoechoic appearance with an irregular surface of articular cartilage has been found at the medial femoral ridge. In this study, all MPL stifles were particularly noted to have cartilage erosions on the proximal part of medial femoral ridge. Of 42 MPL stifles, 18 stifles (42.8%) showed cartilage erosions on the distal part of the medial femoral condyle. There were no pathological findings on the lateral ridge of the femoral condyle. In agreement with the previous studies, the most area of eroded cartilage on femoral condyle were found on the medial trochlear ridge performing by gross examination (Alam et al. 2011; Boonsri et al., 2016; Jahrupatrakorn 2017). Cartilage lesions subsequently appeared due to the luxation of the patella (Daems et al. 2009; Vollnberg et al. 2012). When the stifle is extended, the patella slides proximally on the trochlear sulcus and glides out of the medial trochlear ridge. During in‐and‐out luxation of the patella, force is exerted between the articular patellar surface and the medial ridge of the femoral trochlea. Recently, there was a high prevalence of patellar erosion found in dogs and humans with MPL (Karatrantos et al. 2025). The eroded lesions were mostly presented on the articular surface of the patella (Nomura and Inoue 2005; Daems et al. 2009; Vollnberg et al. 2012). However, the lesion on the articular surface of the patella could not be observed in this study due to the limitations of US.

According to the analysed data, the ultrasonographic score in the treatment group showed significant improvement after 4 weeks of PCSO‐524 administration. Additionally, a significant difference in ultrasonographic score was found between control and treatment groups after 4 weeks of the treatment. Synovial fluid and articular cartilage scores of the proximo‐medial femoral condyle also showed a statistically significant difference after 4 weeks post‐treatment compared with the relevant time point. The disorder of synovial fluid always occurs in osteoarthritic dogs. It impairs the balance between synthesis and degradation of articular cartilage constituents. This leads to articular cartilage destruction, underlying bone remodelling, osteophyte formation and varying degrees of synovitis (Johnston 1997; Fujita et al. 2005). A reduction in degrees of synovial inflammation after treatment with PCSO‐524 has been reported in many studies (Mongkon and Soontornvipart 2012; Soontornvipart et al. 2015). Mongkon and Soontornvipart (2012) reported that serum IL‐1β level, a popular biomarker to detect joint inflammation, had been slowly declined over 14 days. Similar to the study of Soontornvipart et al. (2015), the level of OA biomarkers (chondroitin sulphate WF6 epitope) was lower within 14 days. The articular cartilage score of the distal aspect of the medial femoral ridge showed a significant increase in the treatment group after 12 weeks of PCCSO‐524 administration. This is not in accordance with the result in the proximal aspect of the medial femoral ridge. Eroded cartilage on the distal portion of the medial femoral condyle was found in 18 stifles (42.8%) of all MPL stifles. The lower quantity makes the results not statistically significant at the same week as the results of the proximal part.

All dogs were evaluated for cartilage thickness of the femoral condyle. The cartilage ththickness was measured at three distinct location; the medial, middle and lateral sites. After 16 weeks of treatment, there were no change in thickness of the cartilage when comparison to pre‐treatment. On the contrary, in a surgically induced OA rat model, significant histological changes including cartilage thinning were observed between 6 and 10 weeks post‐surgery (Hayami et al. 2006). However, the variations between species must be taken into account. It has taken more than a year to develop cartilage degradation and osteophyte formation in the dog model, while disease progresses at a faster rate in the rat models. According to the results, this study revealed that the average cartilage thickness of the femoral condyles in Pomeranian and Chihuahua dogs with MPL was 0.223 ± 0.092 mm. The average cartilage thickness of the distal femoral condyle at the medial, middle and lateral areas were 0.225 ± 0.051, 0.227 ± 0.112 and 0.228 ± 0.102 mm, respectively.

Magnetic resonance imaging, computed tomography and arthroscopy can detect cartilage damage in OA patients, but these methods are invasive, expensive and pose radiation risks to operators (Marino and Loughin 2010). US offers a safer alternative for diagnosis and monitoring cartilage destruction. However, proper scanning technique and understanding of normal joint anatomy are essential to minimize diagnostic errors. Key steps include using bone landmarks as reference points, ensuring proper patient positioning and restraint, and optimizing US settings and patient preparation.

US has clear advantages over radiography for evaluating joint pathology. It effectively detects soft tissue and bone abnormalities, including synovitis, cartilage lesions and bone surface damage. For example, US is particularly sensitive to mild synovitis in MPL − findings that radiography often misses. Ramírez‐Flores et al. (2017) demonstrated that US outperforms radiography for detecting joint effusion. Although US shows promise for identifying early‐stage OA, its application in canine medicine remains relatively novel. Success requires thorough knowledge of joint anatomy and precise probe positioning, yet standardized techniques and available evidence for stifle joint US in dogs remain limited. In ultrasonographic evaluation, the bone surface of the medial femoral condyle showed no significant change between before and after treatment in both groups. From the ultrasonographic findings, all MPL dogs were found to have subchondral lesions on the medial femoral condyle. It presented as an irregular hyperechoic lining with interrupted points.

After 12 weeks of treatment, the radiographic OA scores in the control group progressed, while a mild improvement was observed in the treatment group. Mongkon and Soontornvipart (2012) reported that dogs with hip, shoulder and stifle OA showed little improvement in radiographic OA evaluation score after administration of PCSO‐524 for 12 weeks. This controversy can be explained by the MPL model of this study. MPL dogs always encounter repetitive luxation of the patella, which contributes to abnormal joint motion and cartilage loading. The joint instability subsequently leads to OA progression (Roy et al. 1992). Therefore, MPL is identified as a low grade of OA progression. However, the radiographic evaluation was challenging due to the small size of joint; furthermore, MPL induced OA progression is generally less severe than that associated with cranial cruciate ligament disease.

In conclusion, this study demonstrated that PCSO‐524 has an effectiveness in cartilage protection in dogs with OA secondary to MPL. The cartilage lesion and synovial fluid were improved within 4 weeks of PCSO‐524 administration. After 2 weeks of the treatment, a better gaiting of dogs was observed by their owner with satisfaction. The radiographic OA evaluation improved mildly after 12 weeks of the treatment. In MPL dogs, surgical correction is suggested; otherwise, it probably leads to the development of progressive OA. MPL induces joint instability, which can lead to CCLR, meniscal tear and finally to chronic OA. Dogs with MPL are reluctant to stride with the stifle joints; they compensate by overusing of hip and hock joints, which results in hip joint luxation. Unexpectedly, none of these secondary abnormalities were found during 4 months of the study. However, Pomeranian and Chihuahua over 5 years old with MPL, which cannot undergo surgical procedures, should be recommended for other management. They were suggested for quadriceps muscle training and environmental managements with administration of PCSO‐524 for better QoL.

For further study, increasing the sample size is recommended for more significant and accurate results. Other techniques for determining pain and inflammatory status, such as platform gait analysis or biomarkers, are recommended to enhance the reliability of the data analysis.

Author Contributions

Kumpanart Soontornvipart: Conceptualization, methodology, data curation, formal analysis, supervision, writing – review and editing, funding acquisition, project administration, resources. Ratthanan Sathienbumrungkit: Methodology, data curation, investigation, validation, formal analysis, visualization, writing – original draft, software.

Funding

The authors have nothing to report.

Conflicts of Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. This clinical trial was conducted independently, and the evaluation of all ultrasonographic, radiographic and clinical outcomes was completed without financial or material bias from any commercial entity.

Ethics Approval Statement

This study was approved by the animal care and use committee of the Faculty of Veterinary Science, Chulalongkorn University Animal Care and Use Committee (CU‐IACUC), Bangkok, Thailand. (Approval number: 1831085).

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.