Thirty degrees of knee flexion means the knee is bent 30° from full extension — a slight bend. Normal knee flexion ranges roughly from 0° (full extension) to about 135°; 30° is limited and usually insufficient for tasks like climbing stairs or deep sitting. Clinically it’s measured with a goniometer and used to track recovery, stiffness, or contracture during rehabilitation.

A standing AP and lateral (lat) knee X‑ray are two X‑ray views taken while the patient stands and bears weight. The AP (anteroposterior) view assesses joint space narrowing, alignment and medial/lateral compartments; the lateral view evaluates the patellofemoral joint, posterior structures, effusion and fractures. Weight‑bearing images better reveal osteoarthritis and joint instability. The exam uses low‑dose ionizing radiation and is quick.

AP knee central ray is generally angled 0–5°. Use approximately 5° cephalad when the ASIS-to-table distance is >24 cm, perpendicular (0°) when 19–24 cm, and about 5° caudad when <19 cm. The goal is to make the CR perpendicular to the tibial plateau to open the joint space. Adjust angulation for patient habitus and comfort.

Normal knee flexion in a healthy adult is full extension (0°) to about 135–150° of flexion. Most daily activities require roughly 0–120°: walking needs about 60°, climbing stairs around 90–100°. Flexion under 120° can limit squatting or sitting cross‑legged. Individual variation occurs with age, flexibility, prior injury, or surgery.

Yes. Arthritis—especially osteoarthritis and inflammatory types—can reduce knee flexion by causing pain, swelling, stiffness, cartilage loss and joint-space narrowing. Bone spurs (osteophytes), synovial inflammation and muscle weakness further limit bending and cause crepitus. Targeted treatments—physiotherapy and strengthening, weight loss, pain relief or injections, and surgical options for advanced disease—can improve range of motion and function.

The varus stress test at 30° assesses the lateral (fibular) collateral ligament. With the patient supine and the knee flexed about 30°, the examiner stabilizes the distal thigh and applies a varus force (adduction of the lower leg). Excess lateral joint opening or pain compared with the opposite knee indicates LCL injury; at 30° the test isolates the LCL from other stabilizers.