Originally published in Hard2Guard Player Development Newsletter 5.22
Preventing or limiting injuries is one of the primary goals of strength and sports coaches. After all, if a player is injured, he or she cannot help the team. The problem is often the lack of sophisticated, practical knowledge in terms of evaluating movement that can help spot a potential injury before it becomes a reality.
I worked an elite college camp years ago and sat with the athletic trainer as she pointed out girl after girl who was at risk because of her basic movement skills. I grew frustrated when she said that the coach said there was no time to do a session on movement skills at the camp, even though the camp was playing a time-waster (Land-See-Air) at the time.
We rely heavily on volunteer or near-volunteer coaches, so we will never reach a point where coaches have the expertise of athletic trainers in these manners. However, a recent study published by Stensrud et al. (2011) in the British Journal of Sports Medicine suggests that a subjective assessment to determine poor knee control is as effective as a two-dimensional (2D) test of frontal plane knee motion. A previous study (McLean et al., 2005) identified three-dimensional motional analysis as the gold standard, but found a high correlation between 3-D and 2-D analysis. Therefore, a subjective assessment can be used to evaluate poor knee control in athletes.
The study used three tests: single-leg squat (SLS), single-leg vertical drop jump (SLVDJ) and two-leg vertical drop jump (VDJ). The SLVDJ used a 10cm box, but found poor results. The VDJ used a 30cm box jump. Interestingly, the SLS and VDJ identified different participants who showed poor knee control.
On the subjective assessment, the participants were scored 0 to 2:
“The score 0 indicated (A) no significant lateral tilt of the pelvis, (B) no obvious valgus motion of the knee and (C) no medial/lateral side-to-side movements of the knee during the performance. Players rated as 1 displayed (A) some lateral tilt of the pelvis, and/or (B) the knee moving slightly into a valgus position and/or (C) some medial/lateral side-to-side movements of the knee during the performance. Players rated as 2 displayed (A) lateral tilt of the pelvis, and/or (B) the knee moving clearly into a valgus position and/or (C) clear medial/lateral side-to- side movements of the knee” (Stensrud et al., 2011; p. 590).
Based on this rating scale, a coach could use a SLS or VDJ to evaluate his or her athletes. What does it mean or what to look for?
In this video of a VDJ, look at her knees when she lands: her knees are in a clear valgus position at landing. I would rate her a 2, and she is someone who would be termed “at-risk” in my non-medical opinion.
Depending on her training history and strength, she either needs to re-learn how to jump and land, or she needs to develop more strength through her quadriceps, hamstrings and glutes or both. If she has good lower-body strength in the weight room, then she needs to learn to land properly and increase her elastic strength through plyometrics. Regardless, through the VDJ, a coach can identify her as “at-risk,” and if he or she lacks the knowledge to put together a program to correct the issues, the coach can direct her parents to a knowledgeable strength coach or physical therapist.
On the SLS, the coach watches for the same limitations. The first tell-tale sign is the athlete putting down her other foot. This shows a lack of balance and/or a lack of strength, either of which are worrying. To rule out balance, the coach could do a simple single-leg balance test – stand on one leg with the other leg raised and count how long the player can hold the position without wobbling; if the player cannot get to 20 seconds, balance is an issue. If balance is ruled out, you are looking at a strength deficiency. Also, the coach wants to monitor the knee control as the player descends. The knee should track over the foot. I have seen athletes who end up with their hip pointing the opposite direction of their knee – I don’t even know how they can get to that position! I have tried to demonstrate it, and I cannot do it. Again, if the knee moves inward into a valgus position, the athlete lacks the strength to control the movement and would be termed “at-risk.”
The study showed that different athletes failed different tests, meaning that using both tests is probably best to capture all the potential at-risk athletes. Also, the tests should give an idea of the major limitation: the SLS is primarily strength and balance, while the VDJ could be technique, strength or elastic strength.