Following hip arthroscopy for femoroacetabular impingement syndrome (FAIS) decreased hip muscle strength for adduction, extension, flexion, and external rotation including impaired functional performance have been observed. However, no studies are lacking on more demanding muscular and functional parameters such as hip muscle rate of force development and reactive strength index. Information on such muscular properties following hip arthroscopy for FAIS may help guide future planning of post-operative rehabilitation strategies.

This is a cross-sectional study with an embedded prospective non-randomized study. The aim of the cross-sectional study is to investigate hip muscle function and functional performance in patients who have undergone hip arthroscopy for FAIS during the preceding 6-30 months.

The aim of the prospective non-randomized study is to investigate the effect of a 12-week structured and supervised physiotherapy-led intervention aiming at improving hip muscular function on self-reported hip and groin function including hip muscle function and functional performance.

Forty-five subjects from the Capital Region with an age of 18-40, who have undergone a hip arthroscopy for FAIS during the last 6-30 months, will be included in the cross-sectional study. Additionally, all included subjects will be offered to take part in the prospective non-randomized study consisting of 12 weeks of supervised and structured physiotherapy-led treatment.

The below measures will be obtained at baseline, and at 12-weeks follow-up if subjects are included in the prospective study. All testing, and supervised physiotherapy-led treatment, will be performed at Hvidovre Hospital:

1. Hip muscle function
2. Single leg jump performance
3. Self-reported hip and groin function
4. Evaluation of return to sport
5. Evaluation of satisfaction regarding usual-care post-operative rehabilitation

Inclusion Criteria:

• Male/female at the age of 18-40 years at the time of surgery
• Undergone hip arthroscopy for FAIS during the previous 6-30 months (surgical procedure: cam resection and labral surgery)
• Pre-operative cam morphology specified as an alpha angle ≥55°

Exclusion Criteria:

• Pre-surgery joint space width <3 mm
• Any of the following surgical procedures at any time: extra articular surgery of the hip joint (except capsular closure), microfracture, periacetabular osteotomy, and surgery of the ligamentum teres; previous hip arthroscopy in the same hip joint; previous hip pathology such as Perthes' disease, slipped upper femoral epiphysis, hip dysplasia (Lateral Center Edge Angle <25°), and/or avascular necrosis; Any rheumatoid disease in the hip joint such as synovial chondromatosis.

Subjects who have undergone hip arthroscopy for femoroacetabular impingement syndrome during the preceding 6-30 months in the Greater Copehangen Area