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Osteoarthritis develops secondary to the action of hostile biomechanics upon susceptible cartilage. Cam morphology describes a loss of concavity at the femoral head-neck junction resulting in femoral impaction against the acetabular rim within a functional range of movement. This impaction is termed femoroacetabular impingement and can result in pain and cause damage to adjacent articular cartilage that progresses to osteoarthritis. Cam morphology is a target for joint preservation strategies. The first study in this thesis compares hip development in academy football players with controls from local schools. The results provide strong evidence that cam morphology can develop in response to intense sporting activity during adolescence. At present, it is not possible to recommend activity modification as the cardiovascular benefits of exercise are likely to outweigh potentially detrimental effects on hip morphology. Nevertheless, individuals participating in high-level sports during youth may represent a high risk cohort for osteoarthritis warranting surveillance. Diagnostic tools currently available only allow identification of late joint degeneration when disease is irreversible. Advances in the field of disease biomarkers may overcome this challenge. The second study of this thesis explored the prognostic value of compositional MRI. Baseline delayed gadolinium-enhanced MRI of cartilage was able to predict the development of radiographic hip osteoarthritis in asymptomatic individuals within five years. As well as identifying individuals who are likely to benefit from intervention, compositional MRI may allow the evaluation of treatment efficacy within short timeframes. A number of interventions aimed at joint preservation are under investigation for treating cam morphology femoroacetabular impingement. Arthroscopic surgery is increasingly performed to restore the concavity at the femoral head-neck junction and prevent impaction against the acetabular rim. A feasibility study was performed for a proposed randomised controlled study comparing operative and non-operative treatment. The study protocol was developed for the 'Femoroacetabular Impingement Trial' (FAIT).

The initial recommendation for the postoperative regime after uncemented total hip arthroplasty (THA) was 6-12 weeks of partial weight bearing (PWB) to obtain a stable implant position during bone ingrowth. In recent years patients with uncemented THA have increasingly practiced full weight bearing (FWB) after surgery, which has largely been based on clinical experience rather than on scientific evidence. The aim of this thesis was to investigate the effects of FWB versus PWB for 3 months on the stability of the implants and on bone mineral density (BMD), as well as body composition (BC) of the lower extremities. We used radiostereometric analysis (RSA) to measure implant micromotion and dual X-ray absorptiometry (DXA) to measure BMD and BC. Forty-six patients with strictly unilateral osteoarthritis of the hip (OAH) received uncemented THA. These patients were then randomized to the FWB or PWB groups and followed for 5 years. In a preoperative cross-sectional study the BMD of the hip and heel were compared between the OAH-affected side and the healthy side. The study showed an increase of BMD at the femoral neck and a decrease at the total hip and trochanter. The results of a RSA study of cup stability showed that there might be minimal movement in medial and proximal directions during the first postoperative week. These results indicate that the RSA baseline investigation of uncemented cups should be performed as early as possible after the first postoperative day. FWB had no adverse effects on the stability of the uncemented press-fit cups or the uncemented cementless Spotorno (CLS) femoral stems after a 5-year follow-up. There was no difference in periprosthetic BMD around the CLS stem regardless of the postoperative weight bearing regime. All zones around the femoral stem indicated a recovery in BMD toward baselines, except the calcar region, which showed progressive loss in BMD to -22% at 5 years post-surgery. FWB had no effect on the changes in BC after surgery. In conclusion, FWB is safe in uncemented THA in terms of stability, BMD and BC. Furthermore, THA apparently counteracts age-related changes in BC but not in BMD.