Pain in the front of the hip when squatting is a common complaint, and is often diagnosed as a hip flexor problem, or hip impingement. A lesser known pathology is called subspine impingement (SSI), or anterior inferior iliac spine (AIIS) impingement. The AIIS is the bottom bony bump you can feel in the front of your pelvis and serves as a muscle attachment point. In some cases, the neck of the femur abuts against this point causing pain. 

This is slightly different from femoroacetabular impingement (FAI) in that FAI is intra-articular, meaning it occurs inside the capsule, and SSI is extra-articular. It has been described as an avulsion of the rectus femoris and its attachment to AIIS. An avulsion is when the bone pulls at the attachment site causing inflammation. It is common for patients with FAI to also have SSI (Hetsroni et. al, 2012). 

Pain will typically be provoked with both active and passive hip flexion, and the patient will tend to move the hip into external rotation as the hip flexes to avoid pain. Straight leg raises will usually elicit pain, and in the early stages of rehab, a hip spica wrap may be helpful. Patients will also usually have pain with hip internal rotation and groin pain (Bech & Havercamp, 2018). 

Another source of complication can be a little muscle called iliocapsularis. It lies over the front of the hip capsule and its function is unknown, but it has been theorized that its role is as a hip stabilizer. Some have described it as pulling the capsule in a superior and medial direction, and may prevent pinching in the front of the hip. Weakness in this muscle may allow for capsular pinching. One of the attachment points is the AIIS and may contribute to osteophyte (bone spur) formation, causing SSI (Sato et. al, 2016). 

If you want to assess it, here is how it’s done:

References: 

Bech, N. H., & Haverkamp, D. (2018). Impingement around the hip: Beyond cam and pincer. EFORT Open Reviews, 3(2), 30-38. doi:10.1302/2058-5241.3.160068

Hetsroni I, Larson CM, Dela Torre K, et al. Anterior inferior iliac spine deformity as an extra-articular source for hip impingement: a series of 10 patients treated with arthroscopic decompression. Arthroscopy. 2012; 28:1644–53.

Nabhan, D. C., Moreau, W. J., McNamara, S. C., Briggs, K. K., & Philippon, M. J. (2016). Subspine hip impingement. Current Sports Medicine Reports, 15(5), 315-319. doi:10.1249/jsr.0000000000000291

Sato T, Sato N, Sato K (2016) Review of the Iliocapsularis Muscle and its Clinical Relevance. Anat Physiol 6:237. doi: 10.4172/2161-0940.1000237