This study is to compare scans of the knee performed using new software designed specifically to look at the knee joint with those performed using approved software designed for scans of the hip.

Inclusion Criteria:

1. Adult (>30 years) males and females.
2. Have had a hemi knee replacement of one knee at least 8 weeks ago.
3. Patello-femoral osteoarthritis is not a contraindication if person does not have symptoms from the patello-femoral joint.
4. Able to provide informed consent.
5. In good general health.

Exclusion Criteria:

1. Neuromuscular or vascular disease in the affected leg.
2. Found to be unsuitable for hemi knee arthroplasty (KA) before or at surgery.
3. Preoperative extensions defect greater than 15 degrees.
4. Preoperative maximal flexion of less than 100 degrees.
5. Symptomatic patello-femoral osteoarthritis.
6. Insufficiency of anterior cruciate ligament (ACL)
7. Fracture sequalae (Intraarticular fracture and all tibial condyle fractures).
8. Previous osteotomy.
9. Previous extensive knee surgery.
10. Metabolic bone disease including osteoporosis with a T score of <-2.5.
11. Rheumatoid arthritis.
12. Postmenopausal women on systemic hormone replacement therapy (HRT).
13. Long-term treatment with oral corticosteroids and/or bisphosphonates.
14. Inability to consent (such as Alzheimer's Disease).
15. Misuse of drugs or alcohol.
16. Serious psychiatric disease.
17. Disseminated malignant disease and treatment with radiotherapy or chemotherapy.