There are three parts to the knee joint. The joint between the femur and the tibia is divided into two parts - the medial and the lateral joint.
There is a joint between the patella, the kneecap, and the femur. The kneecap slides in the groove. Then there are four major ligaments. ACL and PCL, which are inside the knee. And the MCL, the medial collateral ligament, and the LCL, the lateral collateral ligament.
Those ligaments can get injured. Different mechanisms of injury can cause different problems.
It is important for people who are active to keep their muscles strong, to stretch and to avoid sudden movements. If you are going to be exercising on a regular basis you do not want to change your routine very quickly. You want to build up activity so that your muscles and joints and the ligaments all stay stable rather than having them react to the quick stress that can cause a problem.
ACL Injury
The ACL injury occurs in various sports, such as basketball, soccer or baseball when there is a sudden stop or a jumping injury. With an ACL injury there is acute pain and swelling right away. The patients may hear a pop and they may have difficulty putting weight on their leg right away. It is important to see a doctor right away. A classic symptom of an ACL injury is a hemarthrosis or bloody fluid in the knee.
In young people, most ACLs need to be fixed surgically. It is not an emergency but should be done within a few weeks followed by about a six-month rehab.
Meniscal Tear
A more common injury than the ACL is a meniscal tear. The meniscus is the cartilage between the bones of the knee. A twisting injury shears the meniscus. The meniscus does not have a blood supply to it, so it tears, and it just sits there and slips in and out of the joint and causes pain. If it slips in and out, it can cause the knee to lock. When trying to straighten the knee out it gets stuck. Diagnosis is with an MRI. If symptoms continue, the patient would require arthroscopic surgery to take the torn part of the meniscus out of the knee joint.
Chondromalacia
Chondromalacia, sometimes called runner's knee, is due to an irritation of the undersurface of the kneecap. The knee cap does not track properly because the quadriceps are weak. Chondromalacia is usually treated conservatively with physical therapy to strengthen the quadriceps.