A Focus on Injury: Ski Knees

There's nothing quite like skiing in the Rockies...

History of Knee Pain

It's about this time of year, every year, that people living in north of California think about strapping on skis for the winter.  The most common concern is regarding knee integrity and readiness to ski.
 
I like to group the concern into three groups:

1. I currently have knee pain,
2. I have had pain in the past but currently do not, and
3. I’ve never had concerning knee pain.

 
Chances are that if you fall into group 3, you will likely ski and have an injury-free season (but unfortunately there is always a first time for everything…). If you fall into group 1 or 2, you’ll likely appreciate the remainder of the article.   Knowledge is power – use the following information to shape your training and awareness!

Mechanism of Ski Injuries

Fact
The knee has two joints – the tibiofemoral joint and the patellofemoral joint. Skiing loads both joints tremendously, in different ways.
The two most common knee injuries from skiing include ACL (anterior cruciate ligament) tears, and patellofemoral dysfunction (knee cap pain).
 
ACL Tears
ACL tears are acute, and often a result of catching an edge, crashes or poor landings.  They often fall into one of three categories:

1) Slip Catch: Commonly seen while turning when the inside edge of the outer ski catches the snow surface, forcing the knee into a valgus collapse and internal rotation position (2).

2) Dynamic Snow Plow: When one of the ski edges accidentally engages the inside edge of the skis, and forces the lower leg to jerk inwards (valgus collapse).  The tibia rapidly moves across the middle of the body and cause the valgus collapse of the knee. (1).

3) Landing Back-Weighted: A tactical error in jumping / landing and technique that leads to landing on the tails of the ski, which will stress the knee joint in an anterior/posterior shearing nature (1).

Patellofemoral Pain
 
Patellofemoral pain often comes on from an accumulation of poor or excessive loading.  The most common fault (and easiest to identify) is a valgus collapse of the knee.

You can also identify this by watching someone squat or lunge, or squat / jump, as seen below.  If the knee has a tendency to collapse inwards, the hip is usually doing a poor job stabilizing the knee.

Other possible reasons for patellofemoral pain include overuse of the quads (anterior chain dominance, too much skiing too soon), tight quads (causing compression of the patella) or weak quads (causing poor stabilization of the knee cap for the load being placed). 

Training for Healthy Knees and an Injury-Free Ski Season

An entire training program for proper knee function is outside of the scope of this article, however a couple good examples include:

1. http://www.shape.com/fitness/workouts/gym-pro-skier-paula-moltzan
2. http://www.onthesnow.ca/news/a/107241/u-s--ski-team-s-5-essential-ski-training-exercises

 
General loading principles to abide by include:

1. Mobility and Strength: Work on joint mobility and muscle flexibility, while building a base level of fitness. Spend at least 1 month in this phase before moving forward to any jumping / plyometric exercises.  Being able to squat and deadlift your own body weight with good form, is a great goal (and minimum requirement by athletic standards) for controlling your body in dynamic and variable conditions.  As your knees allow move into exercises including lunges, step ups, single leg squats, and Bulgarian split squats.  For all lower body strengthening exercises, focus on engaging the glutes and hamstrings (not just quad focused).  Ensure your knees stay in neutral alignment (not allowing them to collapse inwards).
   
2. Plyometrics: Introduce plyometric exercises at least 3 weeks in advance to the start of your ski season.  Find the level which challenge you to complete 3 sets of 30 seconds (with 3 minute breaks in between sets) and gradually progress forwards.
   

A reasonable list of exercises (from basic to advanced) include:
 
Two Leg Focused Exercises
Hopping (forward/backwards, side to side, diagonals)
Squat Jumps
Burpees (with jump)
Box Jumps
Lateral Box Jump Overs (side to side)
Hurdle Bounds
 
Single Leg Focused Exercises
Ski Hops
Jumping Lunge
Single Leg Hopping (forward/backwards, side to side, diagonals)
Single Leg Hopping (through cones or agility ladder)
Single Leg Hurdle Bounds

Perfecting Your Technique

During the early part of the ski season, spend the first few ski days working on your technique.  Perhaps some pointers from your friends or a ski instructor would be helpful?  As you scroll up and review the possible injury mechanisms, remember that strength and, more importantly, technique are to blame for most ski injuries. 

Pre-Season Stoke

Now is the time to make a game plan. If you are excited for ski season, let this fuel your training!
Any level of commitment to pre-season strengthening is better than nothing!  The ideal goal would be to get into the gym 3 times a week for strength training, but start with whatever you can commit to.
If you currently have pain, and aren't sure where to start, make an appointment with a physiotherapist or sports medicine physician.

See you out there!

References

1) Bere, T., Flørenes, T. W., Krosshaug, T., Nordsletten, L., & Bahr, R. (2011). Events leading to anterior cruciate ligament injury in World Cup Alpine Skiing: a systematic video analysis of 20 cases. Br J Sports Med, bjsports-2011.

2) Bere, T., Mok, K. M., Koga, H., Krosshaug, T., Nordsletten, L., & Bahr, R. (2013). Kinematics of anterior cruciate ligament ruptures in World Cup alpine skiing: 2 case reports of the slip-catch mechanism. The American journal of sports medicine, 41(5), 1067-1073.