The knee is a hinge joint that allows for bending and straightening, or flexion and extension. It is also a weight-bearing joint, and because it is both articulating and weight-bearing, it is the one joint most prone to suffering damage from trauma and overuse.
Overuse injuries can include or involve the following:
- Patellofemoral pain: This is pain that comes about from overuse of the knee, which is the most common cause of pain in the knee. Pain is in the front of the knee or behind the kneecap.
- Bursitis: The lining of the joint, the bursa, lubricates the joint, but with overuse, it can cause inflammation.
- Patellar tendonitis (“jumper’s knee”): This is strain caused by weak upper leg muscles, hamstring, and gluteal muscles.
- Osteoarthritis: This is degeneration caused by wear-and-tear.
Acute injuries can include or involve the following:
- Muscle strain: In particular, this can occur in the front (quadriceps) or back (hamstring) of the thigh.
- Meniscus tear: The meniscus, a tendon that serves as a cushion between the thigh (femur) and shin bones (primarily the tibia), can tear. Menisci that are already compromised by wear-and-tear can become weak enough to tear with lesser challenges.
- Ligament sprain or tear: In particular, this can occur in the medial and lateral collateral ligaments and the crossing cruciate ligaments.
What about the back of the knee?
The back of the knee is called the popliteal area. In any of the above injuries, an inflammatory response can cause the bursa to overreact with excessive fluid production. At some point the excess fluid bulges out of the tissue behind the knee in the popliteal area. It can be seen as a pouch-like fluid collection. This phenomenon is called a Baker’s cyst or a popliteal cyst. Usually, a popliteal cyst is caused by another condition, so simply draining the fluid with a needle will probably result in failure and a re-occurrence until the primary cause is treated. Left alone, it may resorb over time, stay the same, or get larger. It causes a stiffness in the back of the knee and/or a painful sensation of fullness.
Aside from a Baker’s cyst, what are causes of pain at the back of the knee?
- Hamstring tendonitis (biceps femoris tendonitis): This is the most common injury to the back of the knee from overuse. The hamstring muscles go from the pelvic bones to the side/back of the knee joint, and where they attach at the knee can become inflamed.
- Gastrocnemius tendinitis: This is overuse that causes inflammation to the calf muscle’s attachment to the knee. If the inner head of the gastrocnemius tears, it can cause “tennis leg.” Overuse is most common with runners and sprinters.
- Posterolateral Corner injury: This is usually caused by sporting injuries or auto accidents. The posterolateral corner has many parts, including tendons, ligaments, nerves, and fascia.
- Popliteus injury: This is an injury to the small muscle at the back of the knee. It can be from trauma or overuse.
It doesn’t take shrewd diagnostics to determine the cause of knee pain at the back of the knee: if it’s not from a recent injury, then it is from overuse. Also, a seemingly insignificant injury can create a significant injury when it occurs to an already overused and compromised knee.
What are symptoms of knee pain?
In short, if the knee cannot perform its function as a hinge joint while bearing weight without pain, this indicates an injury.
Any activity involving motions of the knee that results in pain can be helpful in determining its origin. The type of pain—sharp, dull, aching, and tearing, etc.—and the position of the pain—central, anterior, or posterior—are all helpful in making the diagnosis. The back of the knee has its own special conditions that can cause pain, as listed above. Sometimes, a popliteal cyst is the first indication there is something wrong.
How can pain of the back of the knee (and of the knee in general) be treated?
Physical therapy, including icing, stretching, and muscle strengthening. Stretching exercises should begin the very next day after an injury when the knee pain is acute.
Hamstring stretches, quadriceps stretches, and runner’s stretches should be used. This should progress to straight leg raises, hip abduction (extending the leg away from center lying side), and hip adductions (extending the leg toward the center lying on side).
Limit activity: Undue strain on an already-compromised knee joint should be avoided. This includes squatting, kneeling, pivoting, running, dancing, aerobics, sports, and some swimming exercises. Instead, fast walking, elliptical machines, soft platform treadmills, and/or any exercise that consists of a smooth motion for the knee should be introduced.
Where does muscle strengthening end and limiting activity begin? The compromise between strengthening exercises and the limitation of activity is best determined and coordinated by a physical therapist who can objectively measure the risks and benefits.
- Acetaminophen or NDAIDs, such as ibuprofen (Advil, Motrin); meloxicam (Mobic); and ketorolac (Toradol), can be used.
- Compounded combinations of transdermal creams or patches can also be used. A compounding pharmacy can mix a cream that can allow the area to locally absorb an NSAID, possibly an anesthetic, and even other ingredients that are prescribed by a physician.
The knee, when it gives out, can be very disabling; unlike back pain, where a stoic posture can get you by, any ambulation or position involving standing is compromised if not outright prohibited when it comes to a damaged and painful knee. It is fortunate, however, that the knee joint is very transparent about its condition, quickly showing itself to be suffering from an identifiable injury or, if not that, the wear-and-tear of overuse.