Knee Brace Hinges
Choosing a knee brace can be difficult and confusing. Lots of technical language is thrown around with little or no explanation of what it actually means, or advice on which would really work best for you and your injuries. Hinged knee braces provide the best support, however, did you know that there are five different types of hinge? Each offering different benefits and levels of support. We decided that it would be helpful to put together a blog post explaining these different hinges to hopefully make your shopping experience easier.
We will start with the least complex of the hinge types and work through to the more complicated and higher lever support hinges.
Pot Rivet Hinge
Pot rivets are the simplest hinge. They feature one or more often two points of pivot, and are restricted to 180 degrees of vertical movement and do not bow horizontally meaning that they prevent any twisting or unnatural movement. The two hinges are not connected meaning that they work independently of each other. They offer support for the knee, but they do not offload any of the pressure away from the joint, simply support and correct the knees natural movement, making them an ideal choice for supporting a general imbalance or weak joint.
Triaxial or Three Point Hinge
The construction of this is identical to the pot rivet hinge, the only difference being that the hinge features three points of pivot, this gives it a slightly more natural movement than the standard hinge, meaning that they will feel less restrictive whilst essentially offering the same level of support to the joint. Again these tend to only allow 180 degrees of movement so if you suffer with hyper extension (hyper meaning too much, extension meaning straightening) where your knee gives way when it is fully straight or goes past being straight, then a hinge with a definite end point is for you.
Non-axial leaf springs work differently to a conventional hinge. It is formed using sandwiched layers of metal and plastic which can freely bend vertically forwards and backwards at any point, but will not bend side to side, this makes them popular as they do not feel restrictive but do keep the knee straight. The springing action gives the feeling of pushing the knee and helping to complete a step. The downside of this free movement forwards and back is that it is not limited to the natural 180 degree movement of the knee so it does not prevent hyper extension of the knee in a forward motion. Taking these properties into consideration braces including this system are suitable for use on knees with medial or lateral weakness, that makes it prone to collapsing inwards or outwards and hyper extension is not an issue. The non-axial leaf spring is unique to the Push braces, perfect for everyday use, or during low impact sports such as walking, golf and jogging.
Offloading or Geared Hinges
Offloading hinges have just one point of pivot (but often widened over what looks like 2 points) around a gear mechanism, meaning that both sides work in tandem with each other. If you were to hold the centre and move one “arm” the other will move to match. It is this connection between the gears that causes weight to offload from the knee through the hinge where it is then dispersed through the thigh and calf muscles. The offloading hinge provides a higher level of support than the triaxial hinges, however, the movement does not feel as natural so some people may find this restrictive. An offloading hinge is recommended for use with high level ligament injuries, as they keep the knee in line and prevent bowing, twisting, hyperextension and any other unnatural movement. This rigidity makes them ideal for higher impact sports such as skiing.
Fourcepoint is a type of hinge unique to the Donjoy range. The Fourcepoint hinge gives an offloading effect similar to the offloading hinge. When you straighten out a Fourcepoint hinge, rather fully extending to 180 degrees straight away, the hinge slows and softens for the final part of the movement, providing a cushioning effect through the joint. It achieves this through a combination of geared hinges and springs. This softening action be can set to come into effect at different stages of extension, depending upon which ‘level’ is selected. Level one is the least cushioning, so only engages at 175 degrees, level 2 engages at 169 degrees and level 3 at 160 degrees. The hinge is designed to never quite reach the full 180 degree extension, this prevents the knee from locking in the straight position.
The Fourcepoint has the additional feature of being able to adjust the angle to which the knee can be bent by inserting flexion stops, they can be set at 90, 75, 60 and 45 degrees making this an ideal alternative to NHS braces post-surgery or treatment, as the brace can be adjusted to your stage of rehabilitation.
This hinge provides maximum relief to the joint, and for that reason it is recommended for high impact sports such as skiing and motocross.
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