The knee joint is one of the body's largest and most complex joints, hence why we think it's the bee's knees! Though its movements are relatively simple, bending (flexion), straightening (extension), and minimal amounts of rotation, the composition of the knee is a vast network of ligaments and muscles.
The primary bony structures of the knee joint are:
Femur (thigh bone)
Tibia (shin bone)
Patella (knee cap)
Fibula (lateral lower leg bone)
The primary soft tissues of the knee joint are:
The Menisci (Medial Meniscus and Lateral Meniscus)
The menisci function increases the contact area between the femur and the tibia and provides cushioning and shock absorption. The menisci also help to guide motion in the knee and help with stability.
MCL (Medial Collateral Ligament)
Attaches the end of the femur on the leg's inside to the tibia, providing stability to the knee against forces acting from the outer surface of the knee.
LCL (Lateral Collateral Ligament)
Attaches the lateral (outside) aspect of the femur to the head of the fibula; the primary role is to stabilize against forces acting from the inner surface of the knee.
ACL (Anterior Cruciate Ligament)
Located inside the knee joint, it is an important structure that provides stability to the knee, explicitly resisting anterior translation (forward movement) of the tibia on the femur.
The ACL and PCL are named cruciate ligaments because they form a cross in the middle of the knee joint.
PCL (Posterior Cruciate Ligament)
It is also located inside the knee joint and provides stability by resisting posterior translation (backward movement) of the tibia on the femur.
Muscles in the region and their function:
Quadriceps: 4 muscles that work as knee extensors
Hamstrings: 3 muscles that work as knee flexors
Semitendinosus (flexor and internal rotator)
Semimembranosus (flexor and internal rotator)
Biceps femoris (flexor and external rotator)
Other muscles in this region:
Gracilis: a flexor and internal rotator of the knee
Sartorius: a flexor and internal rotator of the knee
Popliteus: a flexor and internal rotator of the knee, also a knee stabilizer
Gastrocnemius: a calf muscle that assists with knee flexion
Most of us have heard of ACL or meniscus injury due to a ski crash, slide tackle, or another trauma-related incident. Commonly, acute injury to the knee damages one of the structures mentioned above. However, in contrast, generalized knee pain that is of gradual onset progresses over time, and becomes chronic, is often a symptom of a problem elsewhere (typically at the hip or the ankle!). Please note these statements are generalizations, and the cause of knee pain or dysfunction is mainly individual and person dependent! When working to rehab the knee from both acute and chronic injury, it is essential to look at the areas above and below to ensure optimal mechanics and strength are restored!
We hope you learned some new information about your knees, and if you have a cranky one or two, reach out. We are here to help. Helping you live and feel your best, Nicole and the OMPT team Want workouts specific to your activity? Reach out for a customized plan.