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Upward patellar luxation/fixation, also known as locking patella, is an uncommon condition in cattle where the patella becomes temporarily displaced on the medial aspect of the upper region of the femoral trochlea.
Affected cattle usually present with intermittent lameness, reluctance to move, and an abnormal gait. The gait of the affected animal appears jerky, during which the affected limb remains extended backwards for an extended period but then jerks forwards and upwards as the patella is released from the point of fixation on the upper region of the femoral trochlea.
The condition is progressive with some affected cattle displaying an abnormal gait for a few steps before returning to a normal gait. On rare occasions the patella may become permanently fixed on the upper region of the femoral trochlea, resulting in the limb extending backwards and the claws of the hoof dragging on the ground. In chronic cases, there will be excessive wear on the dorsal surface of the toes of the affected limb. In some animals the condition may occur bilaterally.
The cause of upward patella luxation/fixation is not known but there are a number of theories including increased ligament laxity (particularly in late pregnant cows), reduced fat between the patella ligaments (through body condition loss), or as a heritable condition. Working animals, such as draught animals, seem to be overrepresented and this may be related to repeated hyperextension of the stifle joint or dragging limbs through mud.
Upward patella luxation/fixation resembles the condition of ‘stringhalt’ observed in horses. However, stringhalt in horses is associated with grazing pastures which contain certain plants that are considered toxic resulting in the condition being neurological in origin.
‘Linda’, brand number 67, is a mature aged Holstein milk cow, who presented for examination for intermittent lameness affecting her right hind limb. The cow was ambulatory with a gait consistent with the condition of upward patella luxation/fixation as described.
A thorough lameness examination was carried out to rule out other causes of lameness. Differential diagnoses included sciatic nerve paresis, pathology of the hoof, rupture of the cranial cruciate ligament, rupture of a collateral ligament of the stifle, meniscal injury and injury of the coxo-femoral joint.
It was decided to monitor the cow’s progress and if the condition progressed, surgical intervention would be sought. Just over a month later, the cow presented again for re-examination with the prospect of surgical intervention as the abnormal gait was occurring more frequently, and the cow was not keeping up with the milking herd.
The condition was treated surgically by performing a medial patella ligament desmotomy. The cow was restrained within a crush and head bale, and sedated with xylazine (Ilium Xylazil 20, Troy) 0.02mg/kg IV.
The medial patella ligament was identified by digital palpation on the medial aspect of the stifle. The area over the medial patella ligament was clipped, surgically prepped and the skin over the medial ligament was infiltrated with approximately 10ml local anaesthetic (Ilium lignocaine 20, Troy) followed by infusion of local anaesthetic beneath the ligament.
A scalpel bald was used to make an incision, approximately 3cm long, anterior to the medial ligament. The blade was then used to sever the medial ligament approximately 4-6cm from its insertion on the tibia (it is recommended a tenotome is used to perform the desmotomy procedure due to the risk of scalpel blade breakage).
Once the ligament had been severed, there was an obvious palpable depression over the area where the medial ligament was located. The surgical wound was then closed with a single skin suture non-absorbable #3 polyamide (Supramid, Braun) suture material using a cruciate suture pattern. Post operative treatments included Meloxicam (MeloxxiTM injection, Abbey Animal Health) 0.5mg/kg SC once off and Procaine penicillin (Depocillin, MSD Animal Health)12mg/kg IM once daily for 3 days.
The procedure allowed immediate return to normal function of the right hind limb for the cow.
The skin suture was removed by the farm owner approximately 14 days after the procedure. The cow continued to recover uneventfully, conceived at the next mating period, and remained in the milking herd until the farm was sold the following year.
The reported long-term outcome for cattle that undergo the standing medial ligament desmotomy is 95.23%. The procedure could be carried out in recumbent animals, but this has been shown to have a lower success rate, 83.33%. Reasons for treatment failure include incorrect diagnosis (such as lateral patella luxation), incomplete severing of the medial patella ligament and delayed intervention (> 1 year of clinical signs).
The current clinical case is an example of a successful outcome of the field procedure, medial ligament desmotomy, for the correction of upward patella luxation/fixation (‘locking’ patella).
References:
Desrochers, André. “Diagnosis and prognosis of common disorders involving the proximal limb.” Veterinary Clinics: Food Animal Practice; 2017; 33(2): 251-270.
Frei, S. & Nuss, K. Intermittent upward fixation of the patella in 12 cows: A retrospective study of treatment and long-term prognosis. Schweiz Arch Tierheilkd. 2015; 157(10): 553-8.
Mahla, J., Dabhi, P., Amin, A. et al. Studies on evaluation of close method patellar desmotomy in standing method verses lateral recumbency in cattle: A review of 84 cases. The Pharma Innovation Journal. 2023; 12(6): 3965-3967.
Parkinson, T. J., Vermunt, J. J., & Malmo, J. Diseases of Cattle in Australasia: a comprehensive textbook. 2nd edn. New Zealand Veterinary Association Foundation for Continuing Education. New Zealand, 2019: 968-967.
Pentecost, R., & Niehaus, A. Stifle Disorders: Cranial Cruciate Ligament, Meniscus, Upward fixation of the Patella. Vet Clin Food Animal. 2014; 30, 265-281.
Dr Ashley Phipps, Registered Veterinary Specialist,
BVSc (HonsI) GradCertVPH (EAD) MVS MVSc (Clinical) FANZCVS (Dairy Cattle Medicine and Management)
Rochester Veterinary Practice
Dr Ashley Phipps graduated in 2011 from the University of Melbourne with a Bachelor of Veterinary Science, with first class honours. He has worked at Rochester Veterinary Practice since graduation.
He completed a three-year residency (2013-2016) in Dairy Medicine with the University of Melbourne, which included completing a Master of Veterinary Science (Clinical), a Master of Veterinary Studies and a graduate certificate in Veterinary Public Health.
Dr Phipps achieved membership to the Cattle Chapter of the Australia and New Zealand College of Veterinary Scientists in 2015 (Dairy Cattle Medicine). After this he undertook a Fellowship Training Program in Dairy Cattle Medicine and Management whilst based in rural practice, in conjunction with the University of Queensland, Production Animal Services. He successfully completed the fellowship examinations in November 2020 and is now a Fellow with the Australia and New Zealand College of Veterinary Scientists in Dairy Cattle Medicine and Management.
Dr Phipps created Cattle Vet AU, an online resource for veterinary student and cattle veterinarians and self-published The Veterinary Field Guide to Cattle Medicine in 2023.
