by Kim Hewson, MD
In medicine, a syndrome is a group of signs and symptoms that are consistently observed that are characteristic of a single condition. As a retired orthopaedic surgeon and a ski instructor, I am often sought out for consultation on injuries suffered by friends, clients and fellow instructors. Over the past two seasons, a symptom of medial (inside) knee pain has emerged in some skiers with a common pattern of fat ski use on groomed terrain.
The common sign observed has been tenderness over and below the joint line of the knee associated with mild soft tissue swelling and tenderness. The skier symptoms are complaints of progressive soreness and difficulty initiating turns on the inside edge of the outside ski. After skiing, walking and nighttime discomfort are common. Some report temporary pain relief with ice and anti-inflammatory agents. The skier often will not return to skiing for several days and upon return uses a narrow waisted ski.
This syndrome with fat ski use occurs only when using fats on groomed or rough terrain, not in powder terrain. We define fat skis as skis >100mm underfoot.
Biomechanics of Inversion stress and varus thrust: a two-phase oscillating micro-trauma to the knee.
Phase I – Compression: The leveraged outside foot is forced into inversion stress. As a result, the outside ski flattens on the snow and the leg rotates slightly externally. The medial boot cuff adds subtle pressure [varus thrust] to the inside lower leg creating a varus stress or bowing compression force at the knee joint.
Phase II – Strain: In repeated attempts to recover the flattening ski, the skier corrects ski inversion by active foot eversion and internal leg rotation. As a result, medial hamstring muscle insertions just below knee are repeatedly put under strain resulting in tendonitis and bursitis.
Kim Hewson is an Orthopaedic Surgeon and former Director of Orthopaedic Sports Medicine and Team Physician at the University of Arizona. He is currently a veteran Telluride Ski School Alpine Instructor in his 15th season and Staff Trainer in the Biomechanics of Alpine Skiing.