Aetiology and pathogenesis of cranial cruciate ligament rupture in cats by histological examination

Abstract

Objectives The aim of this study was to examine histologically intact and ruptured cranial cruciate ligaments in cats, in order to evaluate whether degeneration is a prerequisite for rupture. Methods We performed a histological examination of 50 intact and 19 ruptured cranial cruciate ligaments in cadaver or client-owned cats, respectively, using light microscopy. Cats with stifle pathology were further divided into five age groups in order to investigate the relationship of changes in the ligament with lifespan. Cats with ruptured cranial cruciate ligaments were divided into two groups according to medical history (with presumed history of trauma or without any known history of trauma) in order to investigate the relationship of ligament rupture with a traumatic event. Data from 200 healthy cats were selected randomly and reviewed to make a statistical comparison of cats with and without cranial cruciate ligament rupture (reference group). Results On histological examination, the intact cranial cruciate ligaments showed basic parallel arrangement of the collagen fibres, with no relation to age. While cats of a more advanced age showed fibrocartilage in the middle of the cranial cruciate ligament - a likely physiological reaction to compression forces over the lifespan - degenerative changes within the fibrocartilage were absent in all cases, regardless of age or rupture status. Cats suffering from cranial cruciate ligament rupture without history of trauma were significantly older than cats in the reference group. Conclusions and relevance This study showed that differentiation of fibrocartilage in the middle of the cranial cruciate ligament is likely a physiological reaction to compressive forces and not a degenerative change associated with greater risk of rupture in advanced age. This finding in cats is distinct from the known decrease in differentiation of fibrocartilage in dogs with cranial cruciate ligament rupture. Furthermore, the histological examination of cats revealed no other signs of degeneration in the cranial cruciate ligaments. Thus, degeneration is likely not an aetiological factor for cranial cruciate ligament rupture in cats.

Cranial cruciate ligament disease in cats: an epidemiological retrospective study of 50 cats (2011–2016)

“…The age of the cats in our study is comparable to earlier reports, 6,14,17 and the weight is similar to that of randomly selected healthy controls in two earlier studies of CCLD in cats. 5,6 A greater proportion of cats in our study was insured vs the general insurance coverage (35.7% in 2012) of cats in Sweden. 28 This discrepancy in insurance coverage could indicate that owners of insured cats are more likely to seek veterinary advice in cases of CCLD.…”

“…A degenerative process in the ruptured CCL has been reported in dogs, 30,31 and there is an ongoing discussion about the aetiology of CCLD in cats. 5,6 A recent study by Wessely et al 5 found no histological evidence of a degenerative process in the CCL of cats, while a study by Harasen 6 supported both a traumatic and a degenerative aetiology of the disease. However, only a single CCL was examined histologically in the latter study.…”

“…Even though the exact aetiopathogenesis of canine CCLD is unknown, multiple risk factors -including breed, sex, age and body weight -have been identified. [1][2][3][4] The aetiopathogenesis of CCLD in cats is unclear, 5,6 and although the disease is reported less frequently in cats than in dogs, 7 epidemiological studies are lacking. In dogs with CCLD, bilateral rupture is reported in approximately 20-50% of cases.…”

Tibial tuberosity transposition advancement for treatment of concomitant cranial cruciate ligament rupture and medial patellar luxation in four feline stifles

“…Cranial cruciate ligament (CrCL) rupture is reported far less commonly in cats than in dogs. 1 Potential explanations for this include the CrCL being larger than the caudal cruciate ligament in cats, 2 – 4 the lower amount of differentiation of fibrocartilage in the cat 5 and the potential for many cats with CrCL rupture never being evaluated by a veterinarian. 2 Historically, a traumatic event has been assumed to be the main cause for CrCL rupture in cats; 1 , 6 however, the actual cause is not entirely clear in every case.…”

“… 2 Indeed, a recent study showed that up to 14% of cats appear to develop bilateral disease. 11 In addition, although one study 5 failed to confirm any histologic evidence of degeneration as a contributing factor to CrCL rupture, other studies have demonstrated the presence of degenerative changes such as calcification in the CrCL prior to complete rupture, 12 and moderate-to-severe stifle osteoarthritis (OA), despite an acute onset of lameness. 13 These latter findings would tend to support a degenerative process in at least a subset of cats with CrCL injury.…”