KNEE BRACING

Prophylactic and functional braces can essentially be combined into the same cat- egory since the design of the brace is not dependent on whether there is injury or no injury. The design is dependant on how the brace should influence the joint kinematics and kinetics.

Most braces have a unilateral or bilateral hinge support, and the ‘hinge’ system maybe a simple unicentric device or a more complex polycentric device which takes into account the complex axis of move- ment during knee flexion and extension. The hinges may be free or have blocks so the brace can limit certain degrees of flex- ion and/or extension. Thigh and tibial straps are adjustable on one side and may be fixed on the other depending on where the points of force application are required to be (see Fig.1). Most functional braces for knee ligament injuries are made from lightweight carbon and can be obtained ‘off the shelf’ or custom fitted. The latter is obviously more expensive.

INDICATIONS FOR USE Prophylactic bracing There is little evidence to date that pro- phylactic knee braces are able to prevent or minimise the severity of knee ligament injuries in sport. In addition to this, in many high risk sports such as football or rugby where prevention may be desirable, braces that might be substantial enough in their construct to withstand injury are banned. Currently the American Academy of Orthopaedic Surgeons does not recom- mend the regular use of a prophylactic knee brace at any level of competition.

Rehabilitation bracing Rehabilitation braces typically have longer femoral and tibial components with all round leg support and with hinges that can be locked off at more frequent intervals. The indications for post-surgical/injury bracing tend to be surgeon-dependant. For instance, in 2001 a survey of orthopaedic surgeons in the UK revealed 30% braced their patients following ACL reconstruc- tion, regardless of the type of operation performed, and of these 93% braced them for 6 weeks (5).

Functional bracing These are the braces that as clinicians working with people wanting to return to sport we probably get asked most fre- quently about. This may be following an

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ACL, MCL, PCL or LCL injury or a combina- tion injury. The efficacy of these braces has been evaluated in different ways: ■ Mechanical stabilisation ■ Proprioceptive facilitation ■ Psychological support.

These braces aim to mechanically stabilise the knee and minimise one or a combina- tion of the following movements: ■ Varus/valgus movement - for MCL and LCL injury

■ Anterior and posterior tibial movement - for ACL and PCL injuries

■ Tibial rotation - and particularly medial rotation in the case of ACL injury, and lateral rotation for posterolateral ligament injury.

While studies have shown that bracing is capable of minimising some of these move- ments and decreasing the strain in the ACL under low load (6, 7), it is debatable as to whether they are capable of doing this under the high loads and physiological strain rates that are incurred during most sports. It is hard to conceive that even the most sophisticated custom-made braces would be able to prevent the subtle tibial rotation that is involved in ACL instability.

But bracing may not just work in terms of mechanical restraint. By nature of being in contact with the knee, they also have a role to play in proprioceptive facilitation. This was first shown in studies investigat- ing elastic bandages such as tubigrip and neoprene sleeves. While knee sleeves provide no protection in terms of mechan- ical restraint they do improve knee joint proprioception in normal knees (8). Furthermore, it has been shown that braces can improve proprioception in knees following ACL reconstruction (9). The difficulty in interpreting some of this literature is the method used to assess proprioception. A commonly used tool is the ability to reproduce knee joint position in non-weight bearing. While this might be a valid laboratory test, it is not known how this, or if this correlates to functional performance.

In a recent randomised clinical trial, a braced and an unbraced group were com- pared following ACL reconstruction with a minimum 2 year follow up. The outcomes included functional testing, and no differ- ences were reported between the two groups (10). However, studies have shown

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that ACL deficient subjects felt bracing protected their knees and improved their performance (11, 12). So there seems to be a conflict between subjective reporting and objective measurements of knee stability and performance in the literature. It would appear that there is a stronger case for those who experience knee insta- bility, and the use of functional braces in these cases may be an adjunct to rehabili- tation and assist in bringing the knee back into a ‘window of control’ during activity.

SELECTING A FUNCTIONAL BRACE There are several considerations for select- ing and fitting a functional brace: 1. Appropriateness for activity If the client is asymptomatic during activ-