The diagnostic gold standard to differentiate FAI (femural acetabular impingement) from other muscular-tendinous pathologies is, actually, the injection of intra-articular anesthetic (lidocaine), with a pre- and post- evaluation of pain scale.

If, after injection, the pain disappears, the pain is probably due to an articular problem (FAI). This kind of differential diagnosis test has a sensibility of 100% and a specificity of 81%.

C-terminal telopeptide of type II collagen (CTXII) as cartilage degradation index, could be a marker, simply detectable, to assess the healthy of the cartilage status and could be measured in serum and urine.

This study is observational-analytical and cross-sectional, because the same patient will receive both the diagnostic iter.

For the rules of Evidence-based Medicine (Brown et al., 2006), the definition of this study PICO is:

P (population)= all the patients with suspected FAI afferent to Orthopaedic-Traumatology and Prosthetic surgery and revisions of hip and knee implants

I (intervention)= enzyme-linked immunosorbent assay (ELISA) for C-terminal telopeptide of type II collagen (CTXII) in serum and urine

C (comparison)= intra-articular lidocaine injection

O (outcome)= sensibility/specificity of ELISA test

From a literature analysis the C-terminal telopeptide of type II collagen (CTXII) seem to be the best candidate for this kind of comparison. Some previous studies (Scarpellini et al, 2008) demonstrated that this marker could be used in this way, and, for this reason, the aim of this study is to investigate the sensibility and specificity of this marker in serum and urine, vs the actual diagnostic gold standard (anesthetic intra-articular injection).

If the marker will be equal or better than the actual gold standard, the clinical practice will have an improvement, because this kind of analysis is simply performing and less invasive for the patient.

The study will enroll 20 patients with suspected FAI between 18-45 years and of both the gender.

Inclusion Criteria:

• Patients with clinical diagnosis of suspected FAI
• Patients with clinical addressing to arthroscopy

Exclusion Criteria:

• Patients referring articular rheumatic pathologies
• Patients referring traumatic events in hip
• Patients wearing other hip prosthesis

20 male and female, age range 18-45 recovered for suspicious FAI