The term hip impingement has become a very common term for anterior hip pain in hockey players. Hip impingement in hockey players stems from the combined flexion and internal rotation of skating and goalie maneuvers. The idea behind hip impingement is that the femoral neck contacts the acetabular rim, impinging on the labrum and other tissues of the anterior hip. We often use tests like FADDIR (combined flexion, adduction, internal rotation of the hip) to identify players with hip impingement. Theoretically, this makes sense – players are reaching end range flexion and internal rotation while skating and we can reproduce their pain off-ice using a similar end range flexion and internal rotation maneuver suggesting repetitive impingement irritating the anterior hip structures. But if we look deeper into the research behind skating and goalie mechanics, this might not be the case.
The Problem with Hip Impingement Research in Hockey
One of the more prevalent issues in the research of hip impingement in skating mechanics is that we aren’t measuring a baseline of hip range of motion where the hip is reaching end range flexion and internal rotation. So we are claiming players are reaching an impingement point without knowing what that point is. For example, Stull et al (2013) studied sprint starts in peewee hockey players to identify at risk positions for impingement in youth players. They determined that players are getting into positions that can lead to contact between the femoral neck and acetabulum. However, the degrees of flexion and internal rotation they found should fall within normal, especially for 12 year old kids who we could assume don’t yet have any degenerative changes.
We can also look at other skating studies and find that the degrees of hip flexion and internal rotation are not that extreme considering what normal hip motion should be. From Robbins et al (2018), at max hip flexion of 60-70 degrees at ice contact there is conjunct adduction of less than 10 degrees and less than 20 degrees of internal rotation.
Similar issues can be found in goalie studies. Whiteside et al (2015) looked at hip mechanics of goalies for 3 different maneuvers. They found similar ranges as Stull and Robbins. Yet, goalie maneuvers are often thought to be the cause of hip impingement.
Additionally, Frayne et al (2015) studied different pad configurations on hip internal rotation during the butterfly. As you can see below with the upright triangles representing end range hip internal rotation at 90 degrees of hip flexion, none of the goalies tested reached end range internal rotation based on off-ice measurement of hip internal rotation.
Now, there are goalie maneuvers that haven’t been studies, like the RVH. This position clearly is a lot of flexion and internal rotation. But does it meet the requirements for being end range? Maybe for some. Most goalies tend to have greater hip range of motion than the majority of players and most people. They also might have shallower acetabulums according to some research (here, here), which would allow them to have greater internal rotation without the femur abutting the acetabulum. I think out of all the movements discussed so far, this one is the most likely to lead to hip impingement.
When does hip impingement occur?
Now that we know the depths of hip range of motion with skating and some goalie maneuvers, we can compare them to the ranges at which hip impingement actually occurs. In a recent study by Han et al (2019), they looked at what hip movements were limited by soft tissue restrictions and bony impingement in hip cadaver models. They found that the only position of anterior bony impingement occurred at 120 degrees of hip flexion, full hip adduction and max hip internal rotation. That’s twice as much hip flexion as we’ve seen in any player or goalie movement in combination with end range adduction and internal rotation.
Comparing to some of the positions found in skating and goalie studies, max internal rotation at 45 degrees of hip flexion was 37 degrees, similar to the goalie skating position found by Whiteside and more internal rotation than both Stull and Robbins in similar positions of hip flexion. Han et al found that in this position of combined mid-range hip flexion and max internal rotation, soft tissue was the limiting factor. This suggests that hip ligaments/capsule and muscle will stop the femur from contacting the acetabulum in forward skating, butterfly and goalie skating.
Then why do hockey players appear to get hip impingement?
Some of you are likely thinking that none of this makes sense because the majority of hockey players who come in with anterior hip pain have impingement symptoms. They have positive FADIR tests which is supposed to tell us that they are repetitively impinging on some anterior hip structures but yet the research shows that they probably aren’t. First, I don’t think our impingement tests are very sensitive or specific because a lot of asymptomatic people will also get pain on something like a FADIR or hip scour tests. Second, whereas there are definitely goalie maneuvers that could lead to anterior impingement of hip structures, I think there is a different mechanism that is leading to irritation of the anterior hip in both players and goalies.
We’ve discussed the recovery and glide phase of skating but haven’t brought up the push off phase. The push off in forward skating is a combination of hip extension, abduction and external rotation. This repetitive motion has shown to increase strain on the anterior labrum and capsule/ligaments, the same structures potential impinged with a FADIR or hip scour. There is research that suggests repetitive extension with external rotation torque will create shearing of the anterior labrum (here) and lead to deformation of the iliofemoral ligament of the anterior hip. Further research has demonstrated when the anterior labrum and iliofemoral ligament lose their integrity, there is an increase in motion of the femoral head inside the acetabulum (here, here, here). This turns into a cycle of increased femoral head motion, repetitive strain on the labrum and iliofemoral ligament and an irritated anterior hip. Then when we do our impingement tests on someone with anterior hip pain, we are impingement on tissues that are already irritated from repetitive shearing and stretching leading to a positive impingement test.
Take Home Message
In conclusion, I think there is need for a paradigm shift in how we think about hip impingement in hockey players, and whether or not it truly is an issue in the sport or a just symptom from the repetitive extension and external rotation of skating. How does this change what we do in terms of training and treatment? For me, having a deeper understanding of the actual mechanics of anterior hip pain in hockey players has helped me better educate my clients on movements to avoid to allow their hips to calm down, has helped me choose more appropriate exercises for them to continue training and for rehab, as well as helped me improve my clinical reasoning and being more specific with my provocative tests. I hope this also helps you do the same.