What could cause pain in my knee when crouching or climbing the stairs?
Cartilage - meniscus
Crouching and climbing increase the load across the patellofemoral joint under the knee cap and cartilage damage in the area of the patella and trochlear groove would cause pain when crouching or climbing stairs.
A meniscal tear would also likely be more symptomatic with crouching or climbing stairs. Orthopaedic evaluation is indicated.