Knee injuries - how to prevent them

Knee injuries among young basketball players are worryingly common, but Quinette Louw has found ways of making amends. ELMIEN WOLVAARDT reports.

Basketball has become an increasingly popular sport amongst South Africa's youth, and such regular physical activity is one of the key weapons available against chronic disease and rising public health costs.

But knee injuries have proven to be a major problem, forcing some players to stop all forms of exercise very early in their careers.

In her physiotherapy practice, Quinette Louw saw many basketball players with knee injuries. This prompted her to conduct ten case studies which could potentially lead to a research project. One of the players Quinette studied had become, at the age of 20, the youngest player to be selected for the national basketball team.

Sadly, the bilateral knee pain he had developed at the age of 16 worsened and forced him to retire soon after his selection. The pain was so bad that he couldn't even jog more than a hundred metres.

Quinette realised that the answer lay in improving players' ability to avoid knee injuries - both by strengthening the muscles, and by 'teaching' the muscles how to stabilise the knee during impact.

She designed a programme of knee injury prevention exercises to do just that, and tested it on young basketball players, with excellent results.

The retired basketball player and his 16-year-old brother, who is still playing basketball, later assisted with this research project to highlight the importance of young players not retiring from sport early due to injury.

Being a relatively new sport in South Africa, basketball has poor medical support structures. The particular community in which Quinette conducted her study consists mainly of low- and middle- income groups and parents in these communities cannot always afford the injury management expenses that would enable their children to continue enjoyable and safe physical activity.

Fortunately, as an increasing number of coaches adopt her exercise programme, Quinette hopes to see more and more young people enjoying basketball for many years to come.

Feedback or feed-forward?
The exercise programme Quinette developed consists of 20 neuromuscular control exercises to prevent knee injuries or reduce the severity of knee injuries.

In general there are two motor control mechanisms involved in the interpretation of sensory information from the joints and coordinating the muscle responses responsible for joint control. The first way in which our muscles receive the information they need to respond to movement (such as landing from a jump) is via sensory feedback information received from the joints.

However, this information has to travel via numerous reflex loops and takes a great deal of processing time: approximately 240 microseconds from the moment the joint registers a movement to the moment the muscles move to stabilise the knee.

This is usually too late to prevent injury, as the duration of impact when landing after a jump is usually only about 43 milliseconds.

The second system involves the brain anticipating a movement and feed-forwarding a plan of action to the relevant muscles.

When the muscles receive this information, they are pre-programmed with the appropriate muscle activation patterns.

The good news is that these pre-activated muscles can react very quicly to any external, destabilising load on a joint (again, such as the load experienced by the knee when landing). This takes between 30 and 80 milliseconds. Since the muscle reaction time is much faster, the knee may be stabilised before an injury occurs.

The goal of the exercises designed for this project was thus to improve a player's feed-forward control system. This is done by simulating the movements players experience during game play: gently at first, and then gradually increasing the intensity of the loads experienced as the players become more experienced. experienced.

The following risk factors for knee injury were identified in Quinette Louw's study of the movement patterns of injured and uninjured players:

• Landing with the knee in a relatively straight position
• High and long duration of impact forces imparted on the knee when landing
• Ineffective knee muscle control that cannot adequately stabilise the knee joint.

Study results
Two groups of basketball players participated in the study. The first group continued with usual basketball training while the second group also performed the knee injury prevention exercises during training sessions. In both cases, players' movements were periodically measured using motion analysis equipment. The group that performed the knee injury prevention exercises demonstrated the following improvements in knee control when landing:

• The size and duration of the impact forces on the knee were reduced, imparting less strain to the knee structures.
• Players landed with the knee more bent and this assisted with shock absorption.
• Knee muscles showed a significantly increased ability to stabilise the knee joint.

No changes in knee control were noted in the players who continued with the usual training.

• Nearly 30% of Cape Town's adolescent basketball players have had knee injuries.
• Landing from a jump was the most common injury mechanism (it was responsible for 40% of the knee injuries).

Beginning stage exercises Single leg standing balance exercises Stand on one leg with the knee slightly flexed to about 20 degrees (stand 6 seconds on each leg). Maintain good alignment of the hip, knee and ankle joints while performing exercises 1- 3. Exercises 1- 3 are what players usually start out with. Please note that they form part of a full exercise programme which is available, free of charge, from Quinette Louw: Tel +27 (0) 21 959-2542, Fax +27 (0) 21 930-8370, qlouw@uwc.ac.za.		Exercise 1 Bounce a ball while interchanging the left and right hand.
Exercise 2 Partners face each other four steps apart and bounce a ball to each other.
Coaches can remind players to: Land as softly as possible Maintain good alignment of the trunk and lower limb(s) and keep the knees over the toes when landing Absorb shock by bending the knees sufficiently.		Exercise 3 While the player bounces a ball the coach performs gentle perturbations to the shoulder of the player.