Extracapsular stabilisation (ES) using lateral fabel-lotibial tuberosity sutures is commonly performed, but there are many errors that must be avoided in order to achieve maximal patient comfort and function. First, failure to place the ES suture external to the joint capsule results in excessive pain and poor limb function as the suture rubs upon bone. If a lateral arthrotomy is performed, it is important to separate the overlying biceps fascia from the underlying joint capsule before performing the arthrotomy. This separation is done primarily by blunt dissection and should be to the level of the lateral fabella. Then, the arthrotomy is performed medially or laterally as preferred by the surgeon. If lateral parapatellar arthrotomy is performed, secure anatomical closure of the joint capsule ensures that subsequent placement of the ES is external to the joint capsule.

Second, the stabilising suture must be firmly anchored around the lateral fabella. To do so, the lateral fabella and fabellofemoral ligament are identified at the approximate proximodistal level of the patella (occasionally, veterinary surgeons will become disorientated and pursue the fibular head thinking it is the lateral fabella. Recognition that the fibular head is quite distal to the patella makes this error easy to avoid). The fabellofemoral ligament can be identified as a short, stout band of white-coloured fibres fanning out cranially from the lateral fabella to the supracondylar femur. Next, the surgeon places a cruciate needle from the caudodistal aspect of the fabella, along its deep (axial) margin and penetrates the fabellofemoral ligament cranioproximally. Use of purpose-specific cruciate needles that are strong, 'fishhook' shaped needles, make this much simpler than when using simple half-circle needles. A folded, single strand of suture in the cruciate needle is passed around the fabella and then cut to produce two strands of suture. Alternatively, cruciate needles with two swaged-on strands of monofilament nylon suture are commercially available. Failure to distinctly identify the fabella prior to suture placement may cause poor suture anchorage or inadvertent injury to the peroneal nerve, which passes slightly caudal and distal to the fabella.

Third, failure to anchor the suture to the tibial tuberosity in an approximate isometric position causes the suture to cycle through a range of stifle motion and may lead to premature suture breakage or elongation. Lack of suture isometry may also lead to limited range of motion or loss of stability in portions of the weightbearing stride. Placement of the tibial tuberosity bone tunnel proximal and caudal to the insertion of the patellar ligament (immediately cranial to the extensor sulcus of the tibia) approximates isometry. The tibial tunnel is frequently misplaced too far distally along the tibial crest.

Fourth, selection of an inappropriate ES suture risks fixation failure and/or suture infection because not all materials have adequate tensile strength or biocompatibility. Monofilament nylon fishing line is commonly used; however, not all products have predictable tensile strength, especially after steam or ethylene oxide sterilisation. One brand of monofilament nylon fishing line has been extensively studied for ES use (Hard type nylon leader line (HTNLL), Mason Tackle Co., Otisville, Michigan, USA). When using knots to secure the ES, suture breakage under loading tends to occur at or near the knot. Even if suture breakage does not occur, knot tightening under load causes suture loop elongation. In fact, 27 kilogram-test (kgt) HTNLL is superior to 36 kgt, presumably due to the tightening of the knot or stress concentration near the knot. Alternatively, crimp clamp systems can be used instead of knots. When properly used, these systems allow for less knot bulk, less suture loop elongation and greater load to failure when compared to knots. However, the size of crimp clamp must be designed for a specific diameter of suture and a specific crimping instrument. Lack of this calibration may result in poor mechanical performance as the crimp clamp either fails to adequately grip the suture (if the crimp is too loose) or disrupts the material (if the crimp is too tight). The calibration and design of the Securos^TM crimp clamp system appears to outperform other brands especially when inherent variations in surgeon grip strength (which are substantial) are taken into account.

Finally, it is presumed that all ES techniques ultimately fail by suture breakage or stretching and they should be seen as a 'bridge' facilitating the transition from an unstable stifle to a stifle stabilised by organised fibrous connective tissue. It is clear that in the best of circumstances, the ES repair likely elongates even at the relatively low loads incurred during walking. As the patient activity becomes more vigorous, further elongation of the ES occurs. It is, therefore, essential that a slow, methodical programme of activity restriction combined with physical therapy be tailored to an individual's anticipated soft tissue healing period. Failure to adequately restrict patient activity in the early postoperative period risks ES failure due to suture breakage/elongation.