Braces for ligament protection can be:
- prophylactic - used to prevent injury
- rehabilitative - to protect the repair after surgical correction
- functional - to protect a joint after ligament damage
These are used during sports activity where there is a high risk of knee ligament damage, with the aim of protecting the knee from both direct and indirect injury. They may be single-hinged or double-hinged (a hinge on one side of the knee joint only, or a hinge on both the outer and the inner side). The design aim is to prevent excessive anterior or posterior translation (i.e. the thigh bone moving forward or backward relative to the shin bone), excessive rotation (the thigh bone cork-screwing relative to the shin bone), or excessive varus or valgus angulation (being forced into a bow-leg or knock-knee angulation).
There is obviously a great deal of interest by professional athletes in this group of braces, but the literature suggests that there is insufficient evidence of any real efficacy in reducing the incidence or the severity of ligament damage, and some studies have shown increased knee injury in brace wearers, as well as an associated increase in ankle and foot injuries on the same side.
Rehabilitative braces are designed to allow the surgeon to dictate after surgery the degree of motion allowable at the extremes of range in order to decrease the strain on the knee ligaments, particularly the operated one.
Again, however, the literature to date suggests that there is no significant difference between the results in post-operative patients who use such braces and those who do not.
Functional knee braces are designed to minimise external and internal rotation ('foot rotating outwards or inwards') and anterior and posterior translation in patients who have mild to moderate anterior cruciate ligament instability and who are waiting for surgery or who refuse surgery.
Functional knee braces may come 'off-the-shelf' or be custom-fitted. Custom braces are generally advocated for asymmetrically-proportioned legs, high-intensity activities and maximal comfort, while off-the-shelf braces are advocated for patients with minimal symptoms of instability or fluctuating leg circumference (e.g. during rehabilitation).
Both types of brace are generally of similar design and use either a 'hinge-post-shell' (which incorporates moulded shells of plastic and foam connected by lateral hinges - i.e. hinges on the outer side) or 'hinge-post-strap' (which relies on bilateral - i.e. on the outer and inner side - hinged supports attached to leg and thigh straps). The hinge-post-shell design seems to provide enhanced control, durability, rigidity and flesh contact.
It is in the area of functional bracing that the literature abounds with issues and controversies -
- A study on patients with intact cruciates showed no difference in efficacy between custom and off-the-shelf braces (1).
- Braces from different manufacturers vary considerably in the effectiveness of their restraint (2, 3).
- Laboratory studies using models (4) and physical studies using patients performing controlled movements (5) show that functional knee braces do limit rotation and translation, but the former study showed that this protection disappears during actual use during sport.
- There are differences in the effectiveness of braces in different positions on the field even within the same sport (6) and some studies suggest that in braced patients there is a greater likelihood of injury during sport when wearing a functional brace (7).
- There is controversy about whether the all-important proprioception ('position sense') of the knee is improved (8) or not (9) with the use of functional braces.
- Increased muscle fatigue is an issue in the braced leg, due to increased muscle pressure and decreased blood flow (10).
- After anterior cruciate ligament reconstruction using identical surgical technique, the post-operative use of a functional brace seems to make no significant difference to recovery (11).
- Some studies go so far as to claim that prophylactic and functional bracing may inhibit performance or even cause serious adverse effects (12).
- A good review which is worth reading (incidentally published by a leading brace manufacturer) highlights that the available research is unlikely to help a doctor much in selecting an effective functional brace, and that manufacturers should assume more responsibility in the validation of both existing and future brace design (13).
There are a great many models of functional brace and many manufacturers, but leaders include -
- Defiance CI (Donjoy)
- Lenox Hill (Lenox Hill Brace Shop)
- Performer (Ortho-Tech)
- Air Townsend (Townsend Design)
- CTi (Innovation Sports)
'Off-the-shelf' functional braces from Amazon include -
- Beynnon B.D., Pope M.H., Wertheimer C.M. et al. The effect of functional knee-braces on strain on the anterior cruciate ligament in vivo. J Bone Joint Surg. 1992, 74-A (9), 1298-1312.
- Wojtys E.M., Looubert P.V., Samson S.Y. et al. Use of a knee-brace for control of tibial translation and rotation. A comparison, in cadavera, of available models. J Bone Joint Surg. 1990, 72-A (9), 1323-1329.
- Lunsford T.R., Lunsford B.R., Greenfield J. et al. Response of eight knee orthoses to valgus, varus and axial rotation loads. Journal of Prosthetics and Orthotics. 1990, 2 (4), 274-228.
- Liu S.H., Lunsford T., Gude S. et al. Comparison of functional knee braces for control of anterior tibial displacement. Clin Orthop. 1994, 303, 203-210.
- Beynnon B.D., Johnson R.J. et al. The effect of functional knee bracing on the anterior cruciate ligament in the weightbearing and non-weightbearing knee. Am. Orthop, Society for Sports Med. 1997, 25 (3), 353-359.
- Albright J.P., Powell J.W., Smith et al. Medial collateral ligament knee sprains in college football. Soc. for Sports Med. 1994, 22 (1), 12-18.
- Butler P.B., Evans G.A., rose G.K. et al. A review of selected knee orthoses. British J Rheumatol. 1983, 22, 109-120.
- Liu S.H., Mirzian R. Current review: Functional knee bracing. Clin Orthop. 1995, 317, 273-281.
- Risberg M.A., Beynnon B.D., Peura G.D. Proprioception after anterior cruciate ligament reconstruction with and without bracing. Knee Surg., Sports Traumatol., Arthrosc. 1999, 7 (5), 303-309.
- Styf J.R., Lundin O., Gersguni D.H. Effects of a functional knee brace on leg muscle function. Am. Orthop. Soc for Sports Med. 1994, 22 (6), 830-834.
- McDevitt E.R., et al. Post operative braces after ACL reconstruction: A prospective randomised study, presented at the annual meeting of the American society for Sports Medicine, Sun Valley, 2000.
- Styf J. The effects of functional knee bracing on muscle functional performance. Sports Medicine. 1999, 28 (2), 77-81.
- Kartus J., Stener S., Kohler K et al. Is bracing after anterior cruciate ligament reconstruction necessary? Knee Surg., sports Traumatol., Arthrosc. 1997, 5, 157-161.