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As canine rehabilitation practitioners, understanding orthopedic comorbidities in small breeds directly informs post-surgical protocols and long-term joint management. A 2025 study in Veterinary and Comparative Orthopaedics and Traumatology reports arthroscopic findings on medial meniscal injury (MMI) in toy breed dogs (≤5 kg) with cranial cruciate ligament rupture (CrCLR).

Study Overview

•     Objective: Determine frequency of MMI in CrCLR cases in toy breeds and identify associated factors using arthroscopy.

•     Methods: Retrospective review of 202 stifles from 178 dogs (mean body weight 3.59 kg, median age 101 months). Recorded variables: age, sex, breed, body weight, medial patellar luxation (MPL) grade, lameness grade (0–3), lameness duration, tibial plateau angle (TPA). CrCLR classified as partial or complete; MMI graded as none, mild (minimal structural change), or severe (requiring partial meniscectomy). Ordered logistic regression with forward–backward stepwise selection.

•     Dominant breeds: Toy Poodles (58 stifles), Chihuahuas (50 stifles), Yorkshire Terriers (45 stifles).

Main Findings

     •  Overall MMI incidence: 74/202 stifles (36.3%).  

          *  Mild damage: 50 stifles (67.6% of MMI cases) — mostly small radial tears.  

          *  Severe damage: 24 stifles (32.4% of MMI cases) — 19 bucket-handle tears, 5 flap tears.

     •  CrCLR Classification: Partial tears in 58 stifles (28.7%); complete ruptures in 144 stifles (71.3%). MMI was more common with complete ruptures (31.9% mild and 15.3% severe) compared to partial tears (6.9% mild and 3.4% severe).

     •  Breed-Specific Observations:

          *  Yorkshire Terriers had the highest MMI rate (55.6%) and complete CrCLR (86.7%).

          *  Toy Poodles: 36.2% MMI, 70.7% complete CrCLR.

          *  Chihuahuas: 30.0% MMI, 70.0% complete CrCLR.

     •  Significant factors (multivariable ordered logistic regression):

          *  Complete CrCLR: coefficient 1.72, p < 0.001 (vs. partial tear)

          *  Grade 3 lameness (non-weight-bearing): coefficient 1.45, p < 0.001 (vs. grade 1)

          *  Higher body weight (within ≤5 kg range): coefficient 0.405, p = 0.043

          *  Non-significant: age, sex, breed (despite trends), MPL grade, lameness duration, TPA (mean 27.6°).

     •  Additional findings: Lateral meniscal tears in 12 stifles (6.8%, all small radial); caudal cruciate superficial fraying in 13 stifles (7.3%).

Clinical Implications for Rehabilitation Practitioners

     1)  Complete CrCLR and severe (grade 3) lameness are strong predictors of concurrent MMI.  Prioritize careful meniscal assessment in these cases.

     2)  Yorkshire Terriers showed notably higher complete rupture and MMI rates; consider breed-specific biomechanical differences when planning loading progression.

     3)  Higher body weight (even within toy range) correlated with increased MMI detection — possibly due to greater joint forces or easier arthroscopic visualization.

     4)  Arthroscopy remains the gold standard for meniscal evaluation in small joints; underdiagnosis risk is higher with open arthrotomy in ≤5 kg dogs.

     5)  Post-TPLO/arthroscopy rehab should emphasize early controlled weight-bearing, joint stability work, and monitoring for signs of residual or progressive meniscal pathology.

This research affirms that medial meniscus injury is a notable comorbidity in toy breed cranial cruciate ligament rupture cases, emphasizing the need for targeted evaluation. From a personal, clinical perspective, I tend to find that the presence of a meniscal tear is also an indication that conservative management will yield unfavourable outcomes in cruciate tear cases.  While arthroscopy may be the gold standard for identification, clinical tests can also help to point towards that diagnosis as well, making knowledge of such quite important.

Reference:

Kikuchi Y, Shimada M, Honnami A, Akagi H, Takahashi F, Yamaguchi S. Incidence of Medial Meniscus Injury Detected by Arthroscopy in Toy Breed Dogs (≤5 kg) with Cranial Cruciate Ligament Rupture. Vet Comp Orthop Traumatol. 2025 Sep;38(5):249-253.