As a sophomore in college, I tore my ulnar collateral ligament for the fourth time and my baseball career came to an early end. At this point in time, I had been in and out of physical therapy for nearly seven years for several throwing related injuries but had struggled to stay healthy. Now that my baseball career was over, I took time to reflect on my struggles and noticed a pattern in my therapists’ rehab approaches; they only ever looked at my shoulder and elbow. A significant amount of emphasis was placed on improving shoulder range of motion and rotator cuff strength, but the rest of my body was largely ignored.
There is an inherent weakness to this approach. With an angular velocity of nearly 7,000 degrees per second, throwing a baseball is the fastest motion in all of sports (2). The human body is obviously incapable of achieving these speeds with the shoulder alone. These elite level speeds are achieved by transferring momentum from proximal segments to more distal segments, before ultimately transferring force to the baseball (7). This is a concept known as kinetic linking. The more body segments that contribute to the throwing motion, the greater potential velocity the individual has (8).
Hip range of motion and elbow injuries
The hips play a crucial role in force development during the pitching motion. Not only are they important for improving performance, but they may also play a role in injury prevention. Saito et al found that youth baseball players who complained of elbow pain demonstrated a decrease in hip internal rotation, when measured in the position of 90 degrees of hip flexion, compared to their healthy counterparts (36 degrees vs. 47 degrees) (5). This was true for both the trail leg and lead leg in the painful group.
What’s interesting about this study is that they also measured hip internal rotation in the prone position and observed no difference between the painful group and the non-painful group. In other words, the painful group demonstrated a difference of about 10 degrees of hip internal rotation when measured in a position of 90 degrees of hip flexion versus neutral, while the non-painful group demonstrated similar ranges of motion in each position. These findings were replicated in a separate study that demonstrated no correlation between hip internal rotation and elbow pain when measured in the prone position (3). Unfortunately, hip internal rotation at 90 degrees of hip flexion was not measured in the second study.
These findings have led to two questions that are worth investigating:
Why would a hip internal rotation deficit correlate with elbow pain?
Why would hip internal rotation be more limited in the position of 90 degrees of hip flexion?
Why would a hip internal rotation deficit correlate with elbow pain?
There are six phases to a baseball pitcher’s throwing motion; the wind-up, stride, arm cocking, arm acceleration, arm deceleration and follow through (8).
The wind-up begins with the first motion the pitcher makes and ends when the pitcher reaches maximum knee lift. As the pitcher reaches the end of the wind-up phase, the pitcher’s torso and pelvis are oriented in a negative direction, pointing more towards second base than home plate (7). After maximal knee height is achieved, the pitcher enters the next phase of the throwing motion, the stride phase. This phase starts when the lead leg begins to move towards home plate and concludes as the lead leg first contacts the ground.
Achieving proper positioning of the lead leg as it contacts the ground at the end of the stride phase is a significant moment during the pitching delivery. Ideally, the pitcher will land with a closed-shoulder position, meaning the torso is still oriented in a negative direction relative to the pelvis (7). In order to achieve the closed-shoulder position, the pitcher must possess adequate hip internal rotation in order to sink into their trail leg while maintaining a closed position (8). Achieving this position allows for optimal hip, pelvis, and trunk rotation to occur (5). As the pitcher’s lead leg contacts the ground, the energy stored in the trail leg is transferred to the baseball by first internally rotating the trail leg, then rotating the torso towards home plate, and finally releasing the baseball (7). This is the kinetic linking concept that we alluded to earlier.
But what happens when a pitcher is limited in hip internal rotation? Pitchers with limited hip range of motion tend to land with an open-shoulder position at foot contact (5). This landing position results in the pelvis rotating towards home plate too early. This throws off the timing of the pitching delivery and leads to an over-reliance on the arm for force production since the energy generated from the pelvis has been dissipated (8). Not only is this an inefficient way to throw a baseball, but it also leads to increased stress being placed on the throwing shoulder and elbow. Research has shown that if a pitcher is unable to achieve the closed-shoulder position, the valgus load at the elbow increases (1).
Why would hip internal rotation be more limited in a position of 90 degrees of hip flexion?
It is likely that the factors limiting hip internal rotation at 90 degrees of hip flexion are either femoroacetabular impingement or stiffness in the muscles that extend and externally rotate the hip (ligaments could also play a role, but that is the beyond the scope of this post) (5,6). An easy way to differentiate between these two potential causes is to perform the double knees to chest test. Have the subject lie on their back and pull both knees to towards their chest. Next, ask the individual what they feel.
If the individual complains of a pinching at the front of their hip during this test, it is likely that they are experiencing femoroacetabular impingement. Research has shown a relationship exists between high-level sports participation and osseous changes at the femoral head-neck junction (3). If a cam-type lesion is present at the head-neck junction, the odds of developing hip impingement are increased (6). In these individuals, it is important to not push through the pinching sensation in the front of the hip, as this can lead to irritation of the labrum.
One of my favorite exercises for addressing femoroacetabular impingement is quadruped rocking with banded distraction. Start on all fours with a super band pulling the proximal thigh laterally. This creates space in the joint and decreases the risk of the femur impinging on the acetabulum. Next, sink your butt towards your heels and slowly exhale before returning to the starting position. Repeat this motion 10-20 times. Always retest by performing the double knees to chest test to see if the intervention performed had a positive effect on the pinching sensation.
If the individual reports that they feel a stretch in the glutes during the double knees to chest test, it is likely that the culprit is muscular stiffness of the hip extensors and external rotators. Putting the hip in a position of 90 degrees of hip flexion would put these stiff muscles on stretch, further limiting the hip’s ability to internally rotate. One of my favorite ways to decrease tone in the gluteal region is by performing the pigeon pose slide. Start on all fours. Extend one leg and place it on a slider while you cross the opposite leg under the extended leg. Sink your chest towards the ground as you push the slider back. Slowly exhale before returning to the starting position. Repeat this movement 8-10 times.
Summary
The pitching delivery is extremely complex and has been shown to elicit some of the fastest velocities in all of sports. These elite level speeds are achieved by generating force through our proximal muscles before transferring this force more distally. Dysfunctional proximal movement can lead to energy leaks, causing negative downstream effects. For example, it has been shown that baseball pitchers demonstrating a difference in hip internal rotation greater than 10 degrees in a seated position when compared to hip internal rotation in a prone position may be predisposed to elbow pain (5). This is why we must take a global approach to evaluating our athletes rather than simply looking to the site of the symptoms for answers. The throwing shoulder and elbow still deserve our attention, however, investigating how an athlete moves on a more global level can help us to a paint a more detailed picture and better understand why the injury may have happened in the first place.
Disclaimer: The majority of studies used in this blog to assist in the prediction of injury risk examined youth and adolescent baseball pitchers (aged 9-18) as test subjects. Although I still hold a strong belief that hip range of motion needs to be considered in throwers at every level, the specific ranges of motion listed in these studies may not be transferrable to the adult population. While I tend to use the 35 degrees of hip internal rotation recommended by the Selective Functional Movement Assessment, I believe more research is needed to establish these norms in the baseball population.
References:
1. Davis JT, Limpisvasti O, Fluhme D, Mohr KJ, Yocum LA, Elattrache NS, Jobe FW. The effect of pitching biomechanics on the upper extremity in youth and adolescent baseball pitchers. Am J Sports Med. 2009 Aug;37(8):1484-91.
2. Dillman CJ, Fleisig GS, & Andrews JR. Biomechanics of pitching with emphasis upon shoulder kinematics. J Orthop Sports Phys Ther. 1993;18(2):402-408.
3. Garrison JC, Hannon J, & Conway J. No difference in hip range of motion exists between baseball players with an ulnar collateral ligament tear and healthy baseball players. Int J Sports Phys Ther. 2019;14(6):920-926.
4. Laudner KG, Moore SD, Sipes RC, & Meister K. Functional hip characteristics of baseball pitchers and position players. Am J Sports Med. 2010;38(2):383-387.
5. Saito M, Kenmoku T, Kameyama K, et al. Relationship between tightness of the hip joint and elbow pain in adolescent baseball players. Orthop J Sports Med. 2014;2(5):1.
6. Siebenrock KA, Behning A, Mamisch TC, & Schwab JM. Growth plate alteration precedes cam-type deformity in elite basketball players. Clin Orthop Relat Res. 2013;471(4):1084-1091.
7. Stodden DF, Fleisig GS, McLean SP, Lyman SL, & Andrews JR. Relationship of pelvis and upper torso kinematics to pitched baseball velocity. Journal of Applied Biomechanics. 2001;17:164-172.
8. Wilk KE, Meister K, Fleisig G, & Andrews JR. Biomechanics of the overhead throwing motion. Sports Medicine and Arthroscopy Review. 2000;8(2):124-134.