KneeHab: Anatomy of an ACL injury, from Grade I to Grade III |

KneeHab: Anatomy of an ACL injury, from Grade I to Grade III

Olympic freeskier and multi-time X Games medalist Keri Herman of Breckenridge slides down a rainbow rail at Keystone's A51 Terrain Park in 2014. On March 13 of this season, Herman blew her MCL on a rail at Breckenridge and is finished for the final weeks of winter.
Sebastian Foltz / Summit Daily file photo |

KneeHab 101 series

Knee injuries are a part of sporting life in the mountains. Over the next few weekends, the Summit Daily sports section will print weekly articles about ACL/MCL injury, surgery, rehab, recovery and prevention, featuring interviews with local doctors, physical therapists and pro athletes. They’re the only knees you’ve got — show them some love.

Have a suggestion for the series? Email sports editor Phil Lindeman at

Week 1 — “A club I never wanted to join,” injury column

Week 2 — Anatomy of an ACL/MCL injury

Week 3 — Yoga for ACL/MCL recovery, video

Week 3 — ACL surgery 101

Week 4 — “Slice, dice, make it nice,” pre-surgery thoughts and fears column

Week 5 — Myth-busting for knee injuries

Week 6 — Post-surgery recovery, rehab and physical therapy

Week 7 — Man on the street: Summit locals talk knee injuries, video

Week 8 — “Long, hard road,” recovery column


Know your knee

Like all joints in your body, the knee is an intricate spiderweb of bones, ligaments, tendons and muscles. Here’s an introduction to the bits and pieces that make up your knees.

Ligaments — Tough, fibrous tissues that connect bones to other bones or cartilage and essentially hold joints together. These are your ACL, MCL, LCL and PCL, and they’re usually the most susceptible to sports injuries.

Tendons — Flexible, corded tissues that connect bones to muscles. Leg tendons, such as the quadriceps tendon, are generally used to repair ligament tissue during ACL reconstruction.

Quadriceps, gastrocnemius and soleus — The major muscles of your leg. The quadriceps surrounds your femur and makes for big, strong thighs, while the gastrocnemius and soleus surround your tibia and fibula to form the calf.

Tibia, fibula and femur — The bones of your leg. The femur runs from your hips to your knee joint, while the tibia and fibula combine to make the lower leg from your knee to ankle.

Meniscus — A C-shaped cushion of cartilage between the femur and tibia. As a pair, menisci form a cushion for joint stability and shock absorption.

Patela — The kneecap.

ACL — Short for anterior cruciate ligament, the ACL sits inside the knee behind the patella and prevents the tibia from moving forward in relation to the femur.

MCL — Short for medial collateral ligament, the MCL runs along the inside of the knee and outside of the knee joint. It works with the LCL to provide side-to-side stability.

LCL — Short for lateral collateral ligament, the LCL is located on the outside of the knee joint and works in sync with the MCL for side-to-side stability.

PCL — Short for posterior cruciate ligament, the PCL also sits inside of the knee like the ACL and connects the femur to the tibia. It’s much larger and stronger than the ACL, making it more difficult to damage.

Source: Howard Head Sports Medicine.


Acute knee protocol

You’ve just busted your ACL. Bummer. Between injury and surgery, doctors recommend keeping the knee and surrounding muscles active to maintain mobility — and make recovery go smoother. Here are knee exercises from Howard Head designed to protect and strengthen a wounded knee.

Patellar mobilization — Move the kneecap on the injured knee side to side for 2-3 minutes, then up and down for 2-3 minutes. This helps with inflammation and stiffness.

Calf stretching with strap — With a towel or strap around your toes, sit with legs straight and gently pull back on toes until you feel a stretch in your calf and hamstring. Hold for 20-30 seconds and repeat 3-5 reps, 2-3 times per day.

Seated flexion and extension — Sit on chair or other raised surface with legs on the ground. Extend your injured leg until it’s straight with help from your uninjured leg, if needed. Repeat for 10-15 minutes, 3-4 times per day.

Ankle pumps — Sit on a flat surface with legs extended in front of you. Flex and point your toes back and forth. Repeat 5-15 minutes, 3-4 times per day.

Wall slides — Lying flat on your back about 1-2 feet from a wall, place your injured leg straight against the wall and support with you uninjured leg from beneath. Slowly slide the injured leg down the wall until your knee is close to 90 degrees, and then slide back up the wall. Repeat for 10-15 minutes, 3-4 times per day.

Stationary bike sets — Using both legs, bike for 5-20 minutes daily (up to twice) and use your good leg to guide the injured leg. Do not use resistance and go as slow or fast as needed.

Source: Howard Head Sports Medicine.

Editor’s note: This article is part of an eight-week series about ACL, MCL and other knee injuries, featuring professional and first-hand info on surgery, rehab, recovery and prevention. See the Summit Daily sports section every Friday or Saturday for the next installment, and head online to for past articles.

“See ya later MCL!” reads the caption with Keri Herman’s Instagram video from March 13. “At least I went out grabbin’. Who wants to go to the beach?”

In the video, the Breckenridge pro skier — the same 32-year-old Minnesota native who’s claimed 16 medals at X Games, Dew Tour and the Grand Prix over the past decade — is going for a hard-way 270 off a shooter rail at her home mountain. She spins, she grabs, and then she lands just a touch short of the full 270, wrenching her left knee under her body at an angle anyone would describe as wrong. Hours later, she had the diagnoses: a blown MCL and the end of her ski season.

This year’s MCL tear is just the latest in a long line of injuries for Herman. She’s missed full near-complete seasons due to concussions and past knee injuries, and she’s hardly alone. Knee ligament tears — otherwise known as blowing out a knee — are the No. 1 injuries for skiers, according to Rick Cunningham, an orthopedic surgeon with Vail Summit Orthopedics. In more than a decade with the office, Cunningham has repaired hundreds of ACLs, MCLs and other ligaments that hold the knee together and make sports like skiing, basketball, baseball and tennis possible.

Those kind of kinetic, fast-moving sports are the most dangerous for knee joints, and it all comes down to the twisting, jerking, high-impact movements that even novices have to endure. Some injuries, like Herman’s MCL, will heal naturally with enough downtime and a strict physical therapy regimen. Others, like an ACL tear — the most common of the skiing-related knee injuries — require surgery to fully heal, especially if a skier or snowboarder ever wants to ride again.

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“Unfortunately, I’ll see some patients in November who tore their ACL the first week of the season,” Cunningham said. “They’re usually guys in their 20s who are here for the season. I’ll explain that they’ll feel better day by day — the swelling will go down, the pain will go down, within a week you have improved range of motion — and they’ll say, ‘I feel good. I’m here for the winter, let me try to get back out there.’”

Meet your ACL

But an ACL tear isn’t as simple as rest and relaxation. The ACL (full name: anterior cruciate ligament) sits inside the knee behind the kneecap. It holds the tibia in your lower leg to the femur in your upper leg and prevents one from jutting out in front of the other. It’s why most people who tear their ACL hear or feel a large pop: that’s your knee joint twisting in a way it shouldn’t.

Like all knee injuries, ACL injuries come in three levels, according to Cunningham and local physical therapy offices. Grade I trauma is relatively minor and is often referred to as a sprain. Grade II injury is more serious and includes partial tearing to the ACL fibers, which makes it weaker and more prone to injury. Grade III is the end all, be all, when a ligament is fully torn in half.

“In other parts of the U.S., where you have a patient who does little more than walk or ride their bike, they might not need surgery,” Cunningham said of ACL injuries. “Maybe they just need to protect the knee and avoid impact sports. You only need surgery absolutely if you’re doing cutting and pivoting sports that expose your knee to those movements.”

The winter sports connection

Why, then, are ACL and MCL injuries so common with skiers and snowboarders, while other knee ligament tears are rare? It comes down to the natural movements of both sports. Skiers are more prone to knee injuries — they’re wearing two enormous sticks, or levers, and barreling down hills, after all — while snowboarders are more prone to upper-body injuries, including broken wrists and dislocated shoulders. A 2012 study in the American Journal of Sports Medicine found that 28 percent of snowboard injuries involve the wrist, while 17 percent of skiing injuries involve the ACL.

“People fall in lift lines and tear their ACLs all the time,” said Paula Ashbaugh, a physical therapist with Avalanche Physical Therapy who works part-time at the Breckenridge Medical Center on Peak 9. The ACL is the weaker of two ligaments inside the knee, and Ashbaugh said it’s often ruptured when the knee twists out of alignment in relation to the thigh. Because snowboarders have two feet attached to one piece of equipment, their knees are more protected against the buckling and bowing motion of skiing — even if they’re more likely to fall completely off-balance.

If skiers are more prone to knee injuries simply because of their equipment, then how do snowboarders blow a knee? Simple: flat landings and strong quads. A 2009 study in another medical journal compared knee injuries for snowboarding and alpine skiing, showing that all 35 of the included snowboard injuries came from landing flat after a jump. Of those 35, 31 injuries were to the front leg. Researchers found that these snowboarder’s quad muscles were strong enough to rip the ACL after a hard, flat landing.

Over time, researchers and doctors have found that ACL injuries (and other knee ligament tears) also tend to be more prevalent with women. It comes down to anatomy: Women’s hips grow wider than men’s during puberty, which leads to a natural bowing of the legs at the knee. This puts some women’s knees under pressure long before they even step into a pair of ski boots.

Roads to recovery

Surgery or no, knee recovery is vital for anyone who lives an active life, or even simply wants to walk stairs comfortably years from now. Ashbaugh and Eric Dube, a PT with Howard Head Sports Medicine, recommend three things immediately after injury: manage the swelling, return to a normal range of motion and work your quad.

“It’s all about stability: What can you do to stabilize the knee?” Ashbaugh said. “And it starts with the quad. It’s going to help you walk better, it’s going to help you keep you range of motion and it’s going to help you walk when you get done.”

PTs and doctors suggest rehab after any knee injury or surgery, and the trick is to continue strengthening the muscles and joints long after you’re back to normal. It isn’t guaranteed to ward off another injury, but it can help.

“That’s like saying if you’re a totally fit athlete and train properly, you won’t tear your ACL,” Ashbaugh said. “But what about Lindsey Vonn and Bode Miller? We see professional, world-class skiers tearing their ACLs. It might help you ski longer and last longer.”

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