Orthotics part 3

Please note: The following text cannot and should not replace advice from the patient's healthcare professional(s). Any person who experiences symptoms or feels that something may be wrong should seek individual, professional help for evaluation and/or treatment. This information is for guidance only and is not intended to provide individual medical advice.

Nicci is based at Westminster and Chelsea NHS Trust. She works for Opcare which is one of the biggest NHS providers of orthotic, prosthetics and wheelchair services. Opcare pride themselves on being innovative and at the forefront in patient care. Opcare’s mission statement is ‘Our mission is to provide professional services in a caring and informative manner. We seek to continually develop our understanding of the needs of each individual user and apply our knowledge to optimise their quality of life’.

Knee braces are used for a range of reasons, which may include to control a range of motion, maintaining alignment or to offload injuries. To understand the principles of knee braces you first must understand the anatomy of the knee.

Anatomy of the knee

The knee is a joint located between the lower and upper part of the leg, also known as the largest joint in the body. There are three specific bones: above your knee is your femur, below your knee is your tibia and in between is your patella (also known as the kneecap). Your patella lies in a small groove called the trochlear groove. The ends of the bones are covered with a layer of cartilage. In between the tibia and femur there are two crescent-shaped pads of cartilage called menisci. The meniscus’s role is to reduce friction and evenly distribute weight across the joint.

The bones are held together by a capsule, which secretes fluid to lubricate the joint. Ligaments and tendons support the outside of the capsule:

• Medial collateral ligament (MCL) – provides stability to the inner part of the knee
• Lateral collateral ligament (LCL) – provides stability the outer part of the knee
• Anterior cruciate ligament (ACL) – prevents excessive forward movement
• Posterior cruciate ligament (PCL) – prevents excessive backward movements of the knee.

Knee braces

Knee braces are separated into two categories  – bespoke and stock. They are then further categorised into function. The main types of knee braces are:

• Fracture knee braces – for immobilisation and to hold a joint in specific alignment to aid healing.
• Post op knee braces – to provide protection post-surgery and to control the range of motion during recovery.
• Osteoarthritis (OA) knee braces – these may apply compression to tissues to stabilise your knee and/or redistribute your weight.
• ACL, PCL, LCL and MCL – use depends on which ligament is damaged and your rehabilitation needs and these control the range of motion of the knee.
• Patella stabilisation – used to treat patella mal tracking, where the patella is misaligned and runs too far over to one side.
• Buttress – used for patella stabilisation and meniscus tears.
• Hyperextension – to help manage excessive backwards motion of the knee joint (also called genu recurvatum)
• Compression /proprioception braces – these then vary between: Hinged and non-hinged, range of motion stop, pull on and wraps

Mechanisms

Depending on the type of knee brace and the type of condition, knee braces use a variety of mechanisms:

1. Changing the movement directly at the joint – by changing this movement we can effectively redistribute pressure
2. Changing shear forces – forces acting in a direction which is parallel to a surface or cross section of the body
3. Changing axial/loading forces – compression or tension
4. Three point pressure – to provide a corrective force
5. Increase the surface area – the larger the surface area, the greater control.
6. Increase the lever arm – allow for bigger forces to be used, to allow greater offloading or correction.

When assessing the knee, it is important to think about correction vs deformity, aims of the treatment, long term or short term solutions and hand dexterity (are patients able to out on and take off the device). As most of the above braces are for injury or post-operative management and as the list of injuries is endless, this article will focus on the use of braces for stabilisation. This will mostly centre around mal tracking and proprioception.

Patellofemoral syndrome (patella mal tracking) and EDS

Some people are born with a certain variation within their anatomy such as the trochlear groove being too shallow, therefore the patella is likely to dislocate or lateralize. In conditions such as EDS and Marfan’s syndrome where ligaments have more laxity, there is a greater risk of instability. In most of these cases buttress or patella stabilisation braces are used. Buttress braces are doughnut shaped circles around the patella to provide stabilisation I find that due to the ligament laxity within EDS, in some cases having too much anterior pressure on top of the knee can also increase chances of mal tracking. For this reason, I find that knee braces which focus the forces more laterally have a higher success rate.

Proprioception and EDS

Proprioception is your body’s awareness of where it is in space. It is the sense that lets us perceive location, movement and actions of body parts. For example, proprioception enables a person to close their eyes and touch their nose with their index finger. EDS patients are likely to have poor proprioception, making a person appear to be clumsy. There are a range of knee braces which focus on using compression to aid proprioception and in turn allow for greater awareness, thus making the wearer feel more stabilised. When thinking about a hypermobile joint, the braces I have found to provide my patients with a greater sense of proprioception are braces which use a range of compressive materials. For this I use three zones of compression strategically placed around the knee. The silicone ones offer support and antimigration.

This is a short overview of some knee braces and their different types of function. There are many more!