AN2.1-6 | General features of bones & Joints — Part 4

CLINICAL PEARL

A common scenario in PHC and casualty settings: a 70-year-old woman presents with knee pain after a minor fall. Knee X-ray shows mild degenerative changes. She is discharged with analgesics for 'knee arthritis'. Six weeks later she returns — she can barely walk. A hip X-ray reveals an undisplaced subcapital femoral neck fracture with early avascular necrosis.

Why did she feel knee pain? Hilton's law: the obturator nerve supplies both the hip joint and the medial knee skin. The missed fracture compressed this nerve, producing referred pain at the knee.

The rule to prevent this: always X-ray the joint above AND below the pain. This is standard emergency medicine protocol and directly derived from Hilton's law.

SELF-CHECK — Quick Check — Joints & Hilton's Law

The saddle joint at the base of the thumb (1st carpometacarpal joint) allows all of the following movements EXCEPT:

A. Flexion and extension

B. Abduction and adduction

C. Circumduction

D. Axial rotation

According to Hilton's law, why might a patient with hip joint pathology complain of knee pain?

A. Because the knee and hip bones are directly connected

B. Because the same nerve (obturator nerve) supplies both the hip joint and the medial knee skin

C. Because falling on the hip always damages the knee ligaments

D. Because the femoral nerve supplies only the knee, not the hip

Which component of a synovial joint produces synovial fluid?

A. Articular cartilage

B. Fibrous capsule

C. Synovial membrane

D. Intra-articular ligaments