Knee joint is the largest joint in human body.1 Knee joint is the common site for chronic pain in older patients. Knee joint is the most common joint to get injured during contact sports.
Knee Joint Movements-2
Body weight is carried through the knee joint. Knee joint movements are flexion (bend) and extension (straightens). Flexion and extension occurs between tibia and femur bone while patella slides over the femur bone. Knee joint flexion and extension occurs every time a step is taken forward or backward. Patella bone is located anterior or in front of the knee joint. Patella slides over femur bone while knee is bent or extended. Patella protects the front of the joint and also anterior dislocation of knee joint.
Cause of Chronic Knee Pain During Knee Joint Movement-
- Degeneration of cartilage causes knee pain during flexion and extension.
- Conditions that can cause chronic pain when taking a step forward or backward are fragments in knee joint or patellar subluxation or dislocation.
- Knee joint tendonitis or bursitis causes severe pain with knee joint movements.
Articulating cartilages covers the inner joint surface of end of femur, tibia, and patella. Articular cartilages are surrounded by lubricant fluid within knee joint.3 The cartilage and the viscous fluid within knee joint functions as shock absorber during knee joint movements. In addition smooth inner surface of the cartilage also supports smooth bending of knee joint.
Knee Joint Cartilage Abnormalities Causing Chronic Knee Pain-
- Osteoarthritis causes deterioration of knee joint articulating cartilages resulting in severe pain.
- Floating fragment of cartilages in knee joint causes severe pain
- Psoriatic arthritis causes degeneration of cartilage resulting in severe pain.
- Wear and tear causes thinning of cartilage and grinding pain while walking or standing in place.
Knee Joint Menisci
The menisci are the cartilages located on inner (medial) and outer (lateral) side of knee joint. Sports injury or slip and fall causes meniscus tear. Meniscus also supports function of shock absorption during knee joint activities.
Cause Of Chronic Knee Pain Secondary To Menisci Abnormalities-
- Inflammation of menisci as seen in rheumatic arthritis.
- Tear or fracture of menisci seen after trauma or injury.4
- Wear and tear of menisci causes thinning of menisci resulting in severe pain during ambulation (walking).
Knee Joint and Bones
Knee joint is formed by femur, tibia, fibula and patella.
Bones of Knee Joint-
- Femur– Lower end of the femur (thigh bone).
- Tibia– Upper end of the tibia (shin bone).
- Patella (kneecap)– Patella is located in front of knee joint.
Knee Joint-This Consist of Two Joints.
- Major knee joint is Femoro-Tibial Joint, which links femur and tibia.
- Minor joint is Femoro-Patellar Joint, which links femur and patella.
Chronic Knee Pain Caused By Abnormalities Of Knee Joint And Bones Of The Knee Joint-
- Knee Joint Dislocation- Dislocation between femur and tibia or dislocation between patella and femur.
- Knee Joint Fracture- Fracture of lower end of femur, upper end of tibia, upper end of fibula and patella.
- Knee Joint Hematoma
- Knee Joint Abscess
Ligaments of The Knee Joint-
There are four ligaments. Injury of any of the four ligaments causes joint instability and severe pain with knee joint movements.
Cruciate Ligaments– Located at the center of the joint, one on each side.
- Anterior Cruciate Ligament– Limits forward movement and dislocation of knee joint, and also restricts rotation of knee joint.
- Posterior Cruciate Ligament– Limits backward movement and dislocation of the knee joint, and also restricts rotation of knee joint.
Collateral Ligaments- Located at the inner (medial) and outer (lateral) side of the knee joint.
- Medial Collateral Ligament– Stabilizes knee on medial (inner) side.
- Lateral Collateral Ligament– Stabilizes knee on outer side.
Chronic Pain Caused By Abnormality or Disease Of Knee Joint Ligament-
- Inflammation of Ligaments.
- Partial or Complete Tear of Ligaments.
Tendons of The Knee Joint-
A tendon is tough cord of fibrous tissue located at the end of muscles and connects muscle to bone. Tendinitis is caused by inflammation of tendon, which results in severe pain.
The Quadriceps Tendon
- Spreads over the patella.
- Muscle is attached to patella and tibia.
- Muscle contraction results in extension of knee joint.
The Patellar Tendon
- Connects the patella to the tibia.
- Protects patella and prevents patellar dislocation.
Chronic Pain Caused By Abnormality Or Disease Of Knee Joint Tendon
- Tendonitis- Inflammation of tendons associated with knee joint.
- Partial or complete tear of ligaments following auto accident, work accident or fall.
Muscles Associated With Knee Joint-
Muscle contraction and relaxation results in joint flexion (bend) and extension (straightening) of the leg at knee joint. Muscle contraction pulls the nonflexible tendon attached to the bone resulting in either flexion or extension of the knee joint. Contraction of quadriceps muscle causes extension of knee joint and contraction of hamstring causes flexion of knee joint.
The Quadriceps Muscle Groups-
- Lies in front of the upper leg.
- Muscles contracts when leg is straightened from a bent position. Muscle is relaxed when the leg is bent (flexion of knee joint).
The Hamstring Muscle Group-
- Lies on the back of the upper leg.
- Muscles contract when the leg is bent at knee joint.
- Muscle is relaxed when the leg is straightened from a bent position.
Chronic Knee Pain Caused By Abnormality or Disease of Knee Joint Muscles.
- Muscle Spasm.
- Partial or Complete Tear of Muscles.