Femoroacetabular Impingement (FAI) series, Part 2: Differential Diagnosis and Assessment

In this post, I will be covering some differential diagnosis and key aspects of the assessment when treating athletes with anterior groin pain that may be FAI. As mentioned in the previous post, there are a number of things that can cause “anterior groin pain” including athletic pubalgia (sports hernia) and trigger point referral patterns. So in order to differentiate FAI from these other diagnoses, you have to understand these other pathologies as well. I won’t be going into detail with each of the diagnoses but will provide succinct information as to the etiology of each.

Athletic pubalgia, also known as a sports hernia, is not a true “hernia” by medical definition. It can be a result of multiple injuries but most commonly it involves micro tearing in the rectus abdominis (lower portion, near attachment on public symphysis) and adductors (again, near their attachment on the pubis). Athletic pubalgia has commonly been viewed as sport and position specific, with the three more common sports being football, soccer, and hockey. Clients often will present with groin pain (often chronic), that increases with any exertional activity, and subsides with rest. Males are more commonly affected than females.

Muscle trigger points (MTrPs) can also cause referred pain patterns into the anterior hip. Due to their proximal attachments, the iliopsoas group/adductor longus and magnus can refer pain into the anterior groin. These can be present in an athlete with FAI as well due to their inefficient movement patterns and over compensation with certain muscles. However, it will be important to perform an in-depth assessment and not stop when you find MTrPs so that you don’t miss something more serious like athletic pubalgia or FAI.

iliopsoas-referral-pattern

adductor-longus-referral-pattern

Often times FAI can be traced by to some sort of non-specific groin strain, leading to muscular imbalances later in life, though there can be an acute precipitating episode as well. The athlete may recount “not being as flexible for as long as they can remember”. Though Dr. Byrd found that rarely is the flexibility a true impairment, as the lumbosacral and pelvic motions are increased to compensate for hypomobile hip joints. Most commonly athletes will use the “C sign” to describe the location of their pain when it’s deep.

c-sign
C sign. When asked to locate their pain, the athlete often times will describe it as a wrapping discomfort from lateral to anterior and deep.

I have mixed feelings about objective/special tests and the data that I can gather from them. I still perform them during my assessment because I feel that the more data you can gather on the initial visit, the better tailored your POC will be for that specific client. However, if a client comes in with an irritated hip, almost any test will surely increase their pain. Another thing to keep in mind is that while the client may have unilateral symptoms, the bony morphology may also be present on the asymptomatic side. The biggest deficit that should be spotted upon initial assessment is that the athlete will lack IR on the symptomatic side – however since I mentioned that the structural changes may also be present on the asymptomatic side, there will be cases where you will find no change side to side. You will need to continue to ask leading questions and find out if it reproduces THEIR pain or if the movement is just uncomfortable. Special tests that can be useful in cases of suspected FAI are the hip scour (if there is intra-articular damage already), passive flexion/adduction/IR (FADDIR), log roll test (IR and ER), ASLR*, as well as AROM/PROM and palpation.

log-roll
Log roll test. Positive test when ER > IR. No stress is placed on the femoralacetabular joint in the supine position, therefore should not be painful unless intra-articular damage has already occurred (muscle guarding and acuity will dictate pain levels as well).

ASLR has an * next to it because I don’t use it the way others do and it’s not necessarily validated by research (at least I haven’t found any – but who knows, I haven’t been looking too hard for that), just a clinical pearl. The classic ASLR test usually tests for lumbar disc pathology and/or posterior chain tension. Now, as I mentioned earlier, with any hip pathology that’s acute or moderate/highly irritable, movement WILL create pain for the athlete. I’ve found that those who aren’t symptomatic at rest but have some sort of FAI confirmed with other tests later, will have a positive ASLR with pain onset between 30-90 deg (large range based on severity and acuity of symptoms). It’s similar to the shoulders when you get an athlete with shoulder impingement and a painful arc. Now this is just something I’ve noticed in the clinic, so don’t quote me in your next presentation with this information, but give it a try and see what happens on your next assessment.

Some other things you may find upon initial evaluation is that they don’t really want to load the hip that is affected. With FAI, if it is in it’s early stages, the athlete may not have much trouble with weight bearing activities like walking but more explosive activities such as running and jumping may increase irritation. Therefore, the athlete may not have much pain when walking into your clinic. But in later stages the athlete may ambulate with an antalgic gait because they do not want to load the hip and want to get on and off of it quickly – effectively creating a functional leg length discrepancy during gait and can lead to lumbar spine problems if not corrected early on.

In athletes playing high risk sports (i.e. hockey, soccer, football etc…) some leading questions I like to ask include “when does the pain come on” during activity as well as “what movements exacerbate it”. Often times, the pain comes on during the swing phase of running (due to hip flexion ROM) or cutting away from the painful side. For hockey players pain can come on during their push off while skating AND when they bring the leg through. Pain during push off is usually noted when they are skating around a corner in the direction towards their painful side – i.e. L hip pain, when they push off to skate around a corner to their L. This is because they are adducting and IR their inside leg to stay in line while skating and can increase pain/pressure on that hip. Often times I will also ask the athlete to demonstrate the movement that brings on their pain.

hockey IR hip.jpg
Forced Hip IR/Adduction while going around a corner on skates. In this image, if the R side were painful, the player would have pain during push off while going around this corner.

If the patient has had radiographic imaging, you may be able to identify the lesion and type from the X-ray. You may also find other signs on the radiograph like the “cross-over sign”. The cross over sign indicates acetabular retroversion and is present when the anterior/superior border of the acetebulum extends more laterally past the posterior/superior border.

cross over sign
Cross over sign on radiographic imaging. The white line traces the anterior portion of the acetabulum and the black line traces the posterior aspect of the acetabulum. As you can see, the anterior/superior border extends laterally past the posterior superior aspect.

However – with all of these tests, no single test will tell you that the athlete has FAI, you will need to utilize a combination of tests, ROM, palpation, and most importantly history. If you ask the right questions, the athlete will, with out knowing, point you in the right direction. Palpation can often times help localize tender areas, but as mentioned before, your athlete may have a combination of impairments contributing to their symptoms, not just FAI (MTrPs, strain, articular damage etc…).

References:

Ames, P. S. PT, SCS and Heikes, C., S. MD. Femoroacetabular impingement in the running athlete. JOSPT 40(2). Feb 2010

Austin, A. B. DPT, Souza, R. DPT, Meyer, J. L. DPT, Powers, C. M. PT, PhD. Identification of abnormal hip motion associated with acetabular labral pathology. JOSPT 38 (9). Sept. 2008

Byrd, J. W. T. MD. Femoroacetabular impingement in athletes Part 1: Cause and Assessment. SportsHealth 2(4) 2010

Rabe, S. B. MS, ATC, LAT et al Athletic pubalgia: Recognition, Treatment, and Prevention. ATSHC 2(1) 2010

 

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