Last week we operated on Poppy’s knee. Poppy is a charcoal, medium-sized chihuahua, first brought into the clinic about a week ago. Despite being only one-and-a- half years old, Poppy’s owner said her dog had been, on and off, suffering from a limp for most of her life and that the problem seemed to be concentrated around her right hind leg.
During the clinical discussion, I learnt that the on-and-off episodes afflicting Poppy were intermittent – to the extent that she might be absolutely fine and then suddenly lift her leg up high and walk on only three legs. These episodes seemed to last only a few minutes and once she’d recovered, she would go back to walking on all fours legs as if nothing had ever happened.
Poppy is one of those dogs with a pleasant disposition and very happy to cooperate. She cheerfully paraded her walk and stood to attention while being weighed. All throughout, her gait was absolutely fine. Moreover, Poppy’s owners have kept her at a very good weight of 4.5kg and so her problem could not be attributed to being overweight or underweight.
With all else seeming to be perfectly fine, the indications were that Poppy was suffering from subluxation of the patella of her right leg – a problem fairly common, especially in small to medium breeds of dogs.
The patella, or knee-cap as it is commonly known, is the largest of sesamoid bones. Sesamoid bones are small bones embedded within the tendons or muscles that support them. They tend to be found close to various articulated joints and function as pulleys. They also provide a smooth surface over which tendons can slide around and transmit forces more efficiently.
As in Poppy’s case, the patella is a sesamoid located on the front of the knee. It is embedded among the major tendons surrounding the knee, the slides inside a groove which is situated on the front surface of the lower end of the femur or thigh bone. The main purpose of the patella is to increase the leverage exerted by the front muscles of the thigh to be able to fully extend the knee joint.
However, abnormalities do occur where the patella dislocates from the groove in the central position of the knee joint. When it dislocates, in the majority of cases it does so medially, that is, it will rotate inward towards the inner thigh area. While the patella is out of place, the leg cannot perform its normal function and is usually held up high.
When the dislocation is temporary and the patella can spontaneously return back in place, this is referred to as subluxation of the patella. Dogs of small and medium breeds such as Pomeranians, Pekinese or, as in Poppy’s case, chihuahuas, are more predisposed to such conditions.
To prevent long-term arthritic crippling further aggravating any underlying subluxation, a good evaluation needs to be done by your veterinarian early during the occurrence of the condition
The causes of subluxation of the patella can be various as can the severity of the condition. Your veterinary surgeon will examine your dog to test the stability of the joints and the alignment of the bones involved.
To assist both dog breeders and potential dog owners alike, the various dog breed associations utilise what is known as the Putnam Patellar Luxation Grading System to be able to recognise whether or not a particular dog suffers from this condition and to which degree it is affected.
This is again part of the clinical examination performed by a veterinary surgeon who, according to the degree of possible subluxation of the patella, would assess the dog from zero to grade four – zero representing a normal patella, with four indicating that the condition is at its most severe. Every dog so afflicted would need to be examined individually before an opinion can be given as to whether or not surgery is recommended.
Left uncorrected, the patellar ridges may wear, the groove may become even shallower and the dog will become progressively more lame. So, whenever surgery is recommended, this should be performed, especially since with advancing years, arthritis can prematurely affect the joint, causing a permanently swollen knee with poor mobility.
To prevent long-term arthritic crippling further aggravating any underlying subluxation, a good evaluation needs to be done by your veterinarian early during the occurrence of the condition.
There are various surgical techniques used, depending on the anatomical conditions, the surgeon’s preference, as well as the size of the dog, yet all have the same aim – firstly to prevent the patella from slipping out of place and, secondly, to restore the full function of the knee joint and leg.
According to the Putnam grading system, Poppy had a Grade 1 patellar subluxation in her right leg. Surgery was indicated and duly carried out. Poppy recovered from surgery without incident and we now look forward to following her progress in the coming weeks.
thisweekwiththevet@gmail.com
Dr Martin Debattista is a veterinary surgeon.