Medial femoral condylar cartilage focal defects in association with medial meniscal tears in dogs: A multi-institutional retrospective case series

Abstract

The objective of this report was to describe arthroscopic findings in dogs with concurrent cranial cruciate ligament rupture (CCLR) and medial meniscal tears in which severe, focal articular cartilage pathology was identified on the medial femoral condyle (MFC). Medical records, radiographic findings, and arthroscopic images of dogs with cartilage lesions of the MFC and medial meniscal tears were reviewed retrospectively. Outerbridge scores were retrieved from operative reports and confirmed by the authors via review of arthroscopic images. Twelve dogs with 13 affected stifles were included in this study. All stifle joints had complete CCLRs, medial meniscal tears, and focal grade III to IV cartilage lesions of the MFC. Twelve stifles had a displaced vertical longitudinal tear (bucket handle tear) and 1 stifle had a displaced complex tear of the medial meniscus. The cartilage lesions appeared to be in direct contact with the displaced portion of the meniscal tear. It was concluded that medial bucket handle and complex meniscal tears may be associated with an increased risk of focal cartilage defects. An association between meniscal tears and severe cartilage lesions of the MFC would emphasize the importance of evaluating the stifle joint and debriding the torn meniscus during surgical repair of CCLR. Rapid diagnosis and management may limit the amount and severity of cartilage damage.

Key clinical message:

This case series demonstrated severe focal cartilage defects on the MFCs of 13 stifles with concurrent CCLR and medial meniscal tears.

Cranial cruciate ligament rupture (CCLR) is the leading cause of hind-limb lameness in dogs (1–7). Loss of the cranial cruciate ligament leads to destabilization of the stifle, affecting the biomechanical forces acting on the soft tissues, cartilage, and bones composing the joint (3). Changes in the biomechanical forces of the canine stifle joint after CCLR predispose the articular surfaces of the femoral condyles and tibial plateau to injuries resembling degenerative joint disease (5,8). Previous studies evaluating arthroscopic findings from canine stifle joints after CCLR have reported articular cartilage pathology in up to 100% of cases at least 12 wk post-CCLR (9,10).

The menisci within the stifle joint are paired fibrocartilaginous structures on the medial and lateral surfaces of the joint that function to increase joint congruency and redistribute pressure across the articular cartilage surfaces (8,11,12). Concurrent medial meniscal injury was identified in 10 to 80% of dogs with complete CCLR (1,3–5,13–15). Studies have shown varied results regarding the possible correlation between meniscal tears and articular cartilage damage. Pozzi et al showed in cadaveric studies that meniscal injuries result in greater loading stresses on the articular cartilage of the femur and tibia and suggested that the increased mechanical stress may be associated with increased articular cartilage damage (11,12,15). Those cadaveric studies were further supported by findings from Saban et al and Fung et al of higher Outerbridge scores and an increase in radiographically assessed arthritis in stifles with meniscal tears (7,16). Most recently, in a 2025 study by Campbell et al, an increased likelihood of cartilage damage at the medial femoral condyle (MFC) was noted in stifles with concurrent bucket-handle medial meniscal tears (17). However, other recent retrospective studies failed to identify an association between meniscal injury and articular cartilage damage (5,9,10,15).

The purpose of this case series was to report the findings in 12 dogs (13 stifles) of severe focal cartilage lesions of the MFC in association with complete CCLR and displaced medial meniscal tears.

CASE DESCRIPTIONS

We conducted a multi-institutional retrospective case series consisting of dogs treated at 4 veterinary specialty centers in the United States. Medical records and operative reports for dogs from participating institutions that had been diagnosed with concurrent CCLR, displaced medial meniscal tears, and severe articular cartilage damage were identified. Arthroscopic images were reviewed by a Board-certified veterinary surgeon, and dogs with severe articular cartilage damage limited to the MFC were included. Dogs were excluded if they did not have complete medical records, preoperative radiographs, or images saved from the arthroscopic procedures or if they had evidence of bipolar or diffuse degenerative joint disease. Data retrieved included breed, sex, age at time of arthroscopic diagnosis of stifle pathology, weight, body condition score, duration of lameness, grade of lameness, orthopedic examination findings (including crepitus, effusion, drawer, and meniscal click), condition of the cranial cruciate ligament, condition of the medial meniscus, and Outerbridge classifications of the joint compartments. Descriptive statistics were reported using medians and ranges.

Conditions of the cranial cruciate ligament and medial meniscus were assessed by Board-certified veterinary surgeons by visual inspection and probing during the surgical procedures. The articular cartilage of the stifle joint and the MFC in particular was scored during the surgical procedures using the modified Outerbridge grading scale, in which 0 = normal, grade 1 = softening of the cartilage based on probing, grade 2 = minor fraying or fragmentation, grade 3 = severe fraying or fragmentation, and grade 4 = complete erosion of articular cartilage with subchondral bone exposed (9,14). The medial meniscal tears were classified. In addition, to decrease intraoperative observer variability, arthroscopic images were reviewed and Outerbridge scores assigned for each stifle by author K.S.S. No Outerbridge scores assigned by K.S.S were discordant from those recorded in the operative reports.

To identify radiographic changes consistent with severe cartilage damage or lesions similar to primary osteochondrosis dissecans (OCD), 2-view, standard, orthogonal preoperative tibial plateau leveling osteotomy radiographs from each affected stifle were reviewed retrospectively by a Board-certified veterinary radiologist uninformed as to the nature of the study. In addition, the radiologist scored the osteoarthritis of each dog’s stifle according to the criteria set by DeLuke et al (18).

Medical records from a total of 12 dogs with 13 damaged stifles were analyzed for this report. Five dogs (41.6%) were castrated males and 7 (58.3%) were spayed females. Represented breeds included German shepherd (n = 3), Siberian husky (n = 2), golden retriever (n = 2), Labrador retriever (n = 1), and mixed-breed (n = 4). The median age was 8.5 y (range: 4 to 11 y). The median weight was 30.5 kg (range: 11 to 51 kg) (Table 1). The median duration of lameness was 8 wk (range: 1 to 28 wk). The median grade of lameness was 3/4 (range: 1/4 to 4/4). On orthopedic examination, all 13 stifles had positive drawer sign, 5 (38.5%) had crepitus, 11 (84.6%) had effusion, and 6 (46.2%) had a meniscal click (Table 2).

TABLE 1.

Patient population and Outerbridge scores (12 dogs, 13 affected stifles).

Dog	Sex	Breed	Agea (y)	Weight (kg)	BCS	Outerbridge scoreb Femoropatellar compartment	Medial compartment	Lateral compartment
1	Female spayed	German shepherd	5	35	4.5/9	Grade 0	Grade IV	Grade 0
2	Male neutered	Golden retriever	11	29	5/9	Grade 0	Grade III	Grade 0
3	Male neutered	German shepherd	9	44	4.5/9	Grade 0 bilaterally	Grade IV bilaterally	Grade 0 bilaterally
4	Female spayed	Siberian husky	9	28	7/9	Grade 0	Grade IV	Grade 0
5	Female spayed	Siberian husky	4	18	5/9	Grade 0	Grave IV	Grade 0
6	Female spayed	Mixed	7	39	5/9	Grade 0	Grade III	Grade 0
7	Female spayed	Mixed	6	11	5/9	Grade 0	Grade III	Grade 0
8	Female spayed	German shepherd	8	32	5/9	Grade 0	Grade IV	Grade 0
9	Female spayed	Golden retriever	10	51	9/9	Grade 0	Grade IV	Grade 0
10	Male neutered	Labrador retriever	9	48	6/9	Grade 0	Grade IV	Grade 0
11	Male neutered	Mixed	6	25	5/9	Grade 0	Grade IV	Grade 0
12	Male neutered	Mixed	11	13	5/9	Grade 0	Grade IV	Grade 0

BCS — Body condition score.

^aAge at diagnosis of cranial cruciate ligament rupture.

^bGraded by a Board-certified veterinary surgeon using the modified Outerbridge cartilage grading score, in which 0 = normal, grade 1 = softening of the cartilage based on probing, grade 2 = minor fraying or fragmentation, grade 3 = severe fraying or fragmentation, and grade 4 = complete erosion of articular cartilage with subchondral bone exposed.

TABLE 2.

Owner-reported duration of lameness and orthopedic examination findings.

Dog	Duration of lameness (wk)	Grade lameness	Drawer	Crepitus	Stifle effusion	Meniscal click
1	28	1/4	Present	Present	Present	Present
2	1	3/4	Present	Present	Present	None
3 Ra	4	3/4	Present	Present	Present	None
3 La	12	2/4	Present	Present	Present	None
4	12	4/4	Present	Present	Present	Present
5	6	2/4	Present	Unknownb	Unknownb	Present
6	8	4/4	Present	Unknownb	Present	Present
7	1	3.5/4	Present	Unknownb	Present	Present
8	4	3/5	Present	Unknownb	Present	None
9	Unknownb	4/5	Present	Unknownb	Present	None
10	Unknownb	Unknownb	Present	Unknownb	Present	Present
11	20	Unknownb	Present	Unknownb	Unknownb	Unknownb
12	Unknownb	2/5	Present	Unknownb	Present	None

^aDog 3 had bilateral cranial cruciate ligament rupture. Duration of lameness and orthopedic examination findings are listed separately for the right (R) and left (L) stifles.

^bData listed as “Unknown” were not reported in the available medical records.

Each of the 13 stifles had a complete CCLR and a medial meniscal tear confirmed during stifle arthroscopy by a Board-certified veterinary surgeon. Each of 12 stifles had a displaced vertical longitudinal tear (or “bucket-handle” tear) and 1 stifle had a displaced complex tear. All 13 stifle joints had grade III to IV cartilage lesions in the MFC, scored according to the Outerbridge grading scale (Table 1, Figure 1). All other stifle compartments were graded 0. On examination of the arthroscopic images, the displaced portion of the medial meniscus appeared to be in direct contact with the MFC at the site of the lesion (Figure 2). There were no articular cartilage lesions identified on the lateral femoral or tibial condyles or the caudal tibial plateau in any of the 13 stifle joints analyzed (Figure 2).

FIGURE 1.

Arthroscopic images of the medial femoral condyle cartilage lesions identified in each of the 12 dogs. Image numbers correlate to the signalments for individual dogs in Table 1. Dog 3 had bilateral stifle disease. Here, 3A represents the right stifle and 3B represents the left stifle. Blue arrows indicate the demarcation between articular cartilage and exposed subchondral bone.

FIGURE 2.

Representative arthroscopic images from Dog 1, left stifle. A — Articular cartilage lesion on medial femoral cartilage. Grade IV: subchondral bone exposure. Blue arrow indicates demarcation between articular cartilage and exposed subchondral bone. B — Displaced portion of medial meniscus bucket-handle tear appears to be in direct contact with medial femoral cartilage lesion. C — Caudal tibial plateau shows no evidence of cartilage damage.

On analysis of preoperative radiographs, all 13 stifles had mild to severe joint effusion and 8 of 13 had stifle joint space narrowing (61.5%). None of the stifles had radiographic evidence of subchondral bone erosion. The median total osteoarthritis score was 10 (range: 4 to 31) (Table 3; Table S1, available online from: Supplementary Materials).

TABLE 3.

Radiographic findings on tibial plateau leveling osteotomy preoperative radiographs.

Dog	Stifle joint effusion	Erosion of subchondral bone	Stifle joint space narrowing	Total stifle OA scorea
1	Moderate to severe	None	None	11
2	Mild to moderate	None	None	9
3 Rb	Moderate to severe	None	Present	7
3 Lb	Severe	None	Present	10
4	Moderate	None	None	8
5	Severe	None	None	9
6	Mild	None	Present	4
7	Moderate	None	Present	3
8	Severe	None	Present	16
9	Severe	None	Present	31
10	Severe	None	Present	18
11	Moderate	None	Present	12
12	Moderate	None	Present	12

^aStifle radiographs were evaluated by a Board-certified veterinary radiologist according to the criteria set by DeLuke et al (18). The individual osteoarthritis (OA) scores for each criterion are available in Table S1 (available online from: Supplementary Materials).

^bDog 3 had bilateral cranial cruciate ligament rupture. Radiographic findings are listed separately for the right (R) and left (L) stifles.

DISCUSSION

This report documents 12 dogs, from 4 veterinary hospitals, with concurrent CCLR and medial meniscus tears in which severe focal cartilage lesions of the MFC were confirmed arthroscopically. Focal femoral condyle cartilage lesions have been attributed to altered joint biomechanics, cartilage trauma, or primary osteochondrosis. We were unable to associate any of these as causes of the cartilage lesions in this case series. Subsequently, we theorized that these focal lesions were due to abrasion against the torn portion of the medial meniscus fixed in a cranially displaced position or the torn portion of the meniscus repeatedly displacing and reducing (meniscal click).

Altered joint biomechanics leading to femoral condyle cartilage lesions may include angular limb deformities, joint instability subsequent to cruciate ligament rupture, and altered cartilage pressure secondary to meniscal injury and compartmental overload. Angular limb deformities can lead to overloading of the medial or lateral compartment of the stifle joint, in turn leading to bipolar (femoral and tibial) cartilage lesions. Angular limb deformities and bipolar cartilage lesions were not identified in any of the cases in the present report.

In cases of complete CCLR, in which severe cranial tibial displacement occurs, the femoral condyles may abrade the caudal tibial plateau during weight-bearing movement. These biomechanical changes would promote erosion of the articular cartilage on both the femoral condyles and extreme caudal aspect of the tibial plateau (6). Cartilaginous pathology was not identified on the caudal aspect of the tibial plateau in any of the cases reported herein, although lesions on the caudal tibial plateau might be difficult to identify due to the location under the caudal meniscal rim.

Primary osteochondrosis can lead to focal cartilage lesions of the femoral condyles. None of the cases in the present report had the typical signalment or radiographic or arthroscopic findings of OCD. When OCD is present in the canine stifle, it is most commonly identified in the lateral femoral condyle, but it has also been reported in the MFC (19,20). The 12 dogs we described did not match the classic signalment of OCD: giant-breed dogs diagnosed at < 1 y of age. The dogs in this report were all diagnosed with cartilage lesions at > 4 y of age and lacked histories of lameness beginning as juveniles. In addition, OCD-type subchondral bone lesions were not evident on preoperative radiographs in any of these cases. There was no history or evidence of direct cartilage trauma in any of these cases.

In this case series, severe focal cartilage lesions of the MFC were identified only in dogs with concurrent CCLR and medial meniscus tears. In those cases, when the stifle joint was evaluated arthroscopically, the displaced portion of the torn medial meniscus appeared to be in direct contact with the identified cartilage lesion on the femoral condyle (Figures 1, 2). This contact was apparent throughout the range of motion of the stifle joint, with internal and external rotation of the tibia, varus, and valgus of the stifle joint and with the tibia in a neutral and thrusted position (thrust was achieved with an internal stifle lever). Although arthroscopy cannot accurately reproduce the kinematics of the stifle joint during daily activity, our findings suggested there was contact between the torn portion of the meniscus and the cartilage lesion throughout a wide range of stifle positioning.

Campbell et al recently reported a significantly greater chance of moderate to severe cartilage wear of the MFC in stifles with a displaced medial meniscal tear compared to those with normal menisci or a non-displaceable meniscal tear (17.2% compared to 4.8%, respectively) (17). The authors theorized a primary mechanical abrasive process is occurring between the displaced medial meniscal tear and the medial femoral condylar articular cartilage. This may be a subacute process of cartilage damage primarily affecting the cranial surface of the MFC, in contrast to the more chronic medial compartment osteoarthritis proposed by Pozzi et al (11) and commonly identified in human knees with chronic instability and degenerative meniscal injury (21). Similarly, in a past study, Hulse et al identified severe focal cartilage lesions of the MFC in second-look arthroscopies (median time to second look: 35.5 mo), including on the cranial surface of the femoral condyles. The authors noted contact between the lesions and the cranial soft tissues and theorized that the cartilage damage was caused by abrasion between the cartilage and the cranial soft tissues (6). The cases in these reports suggest that abnormal contact between the displaced fibrocartilaginous meniscal tear and the cranial surface of the MFC could lead to severe cartilage lesions.

Limitations of this case series include its retrospective nature, the small number of cases included, and the inherent subjectivity of the Outerbridge cartilage grading system (9,22). All cases evaluated from the 4 institutions involved both CCLRs and medial meniscal tears. As this was a descriptive study, arthroscopic review was not conducted on dogs that had only medial meniscal tears. Last, the authors were unable to accurately measure the exact sizes of the MFC cartilage lesions. Due to the locations and angles of the arthroscopic portals, curvature of the MFC, and large size of many of the lesions, it was not possible to position a measuring device into the proper location to make accurate measurements (23,24). Moreover, the ratio of animal weight to femur size was not calculated, preventing standardization of measurement data across varied dog sizes.

Several retrospective studies have failed to identify an association between meniscal injury and focal articular cartilage damage in the canine stifle (9,15,25). However, the 12 cases described in this report are in agreement with recent studies from Saban et al and Campbell et al, providing further evidence that medial meniscal tears may contribute to severe cartilage pathology of the MFC. This mechanism is in addition to other causes of generalized cartilage damage in canine cruciate disease, including translational and rotational instability leading to abnormal shear forces, alterations in compressive forces secondary to loss of meniscal support, and possible abrasion between the femoral condyle and cranial soft tissues, as proposed by Hulse et al (6). An association between meniscal tears and condylar cartilage lesions would increase the importance of thorough intra-articular stifle inspection and removal of damaged meniscal tissue before surgical treatment of CCLR. The importance of these lesions to outcomes in canine cases is uncertain. In human orthopedics, articular cartilage lesions are associated with increased pain, increased arthritis development, slower return to exercise, and decreased quality-of-life scores (26,27). It is likely that the large, high-grade cartilage lesions reported herein would contribute to more rapid progression of osteoarthritis, increased pain, and impaired postoperative function in dogs. Future research studies are needed to elucidate a causative relationship between medial meniscal tears and severe focal cartilage lesions of the MFC of the canine stifle, as well as the importance to clinical outcomes. CVJ