We have previously discussed knee pain, including in the last issue when we discussed the injuries to the medial side of the knee. Today we discuss the final area of the knee, the posterior knee.
Let us first look at the anatomy of the posterior knee.
If we consider all the anatomical structures on the posterior side of the knee, we will find there are 7 muscles, 4 ligaments, 3 bones, 4 bursas, 2 mensicus, and multiple arteries, veins and nerves. There are also three surfaces of bone lined with cartilage. All of these structures are potential sources of pain and subject to injury.
The following are common causes of posterior knee pain:
- Knee joint effusion
- Baker’s Cyst
- Referred pain (from lumbar spine, patellofemoral joint, or neural compression)
- Biceps femoris tendinopathy
Less common causes of posterior knee pain:
- Popliteus tendinopathy
- Gastrocnemius tendinopathy
Rare causes of posterior knee pain, but not to be missed, would include Deep Vein Thrombosis, Claudication, and Posterior cruciate ligament sprain/tear. If you ever have a hot, red, area behind the knee, swelling or discolouration that does not look normal, this warrants a trip to the emergency room. Don’t delay what could be a vascular issue.
As we have previously discussed tendinopathies and joint effusion can be the result of multiple different causes, we will only take a closer look at posterior knee pain from Baker’s Cysts and the different sources of Referred Pain.
Baker’s Cysts
These are fluid filled sacs that form in the posteromedial knee joint. In adults, these cysts form as a result of chronic knee joint effusion, or excessive fluid, often from something else happening within the joint like a medial meniscus tear, ACL injury, cartilage degeneration or arthritis. In some people, the cyst will spontaneously burst or become reabsorbed and in others the size may fluctuate, so at times they appear smaller or larger. Due to the high association with other joint injuries/pathology, it is very important that the knee is fully assessed to look for these other potential knee joint injuries.
Patients with a Baker’s Cyst will present with:
- Palpable and sometimes tender mass in the posteromedial compartment of the knee
- Decreased knee flexion
- Pain on deep squats or kneeling
Diagnosis:
- Can be made on ultrasound of the area and give the approximate size of the cyst, however ultrasound does not assess the structures of the internal knee, like the meniscus and cruciate ligaments well so further imaging will need to be done to find the source of the problem
- MRI is considered the gold standard for diagnosis, both of the cyst and the underlying causes
Conservative treatment would involve:
- Addressing the underlying cause, i.e., if a medial meniscus tear is the cause of the excessive knee swelling, the torn meniscus needs to be addressed.
- Aspiration combined with a steroid injection may be used for temporary relief
- Surgery to remove the cyst completely. Usually only done for very large and painful cysts.
Keep in mind that although removal may help with the decreased knee flexion or may allow an athlete to perform, Baker’s cysts will likely reform until the underlying cause is addressed.
Referred sources of posterior knee pain
When posterior knee pain is unable to be reproduced on examination, we need to look at other structures as a potential source for referred pain. Often, patients with referred posterior knee pain, cannot isolate the pain to a particular structure. There may be other sensations, like numbness/tingling or a deep ache.
Structures which refer to the posterior knee:
- Lumbar spine, usually nerve root irritation
- Piriformis syndrome
- Sciatic nerve entrapment at piriformis or hamstring
- Muscular trigger point
Examination:
When a knee structure cannot be identified as the source of the pain, the examination should include lumbar spine range of motion, joint palpation and compression tests as well as, neural tensioning tests. A very mild low back injury may present with leg pain, making the patient feel that only the knee is the source of the problem. Neural tensioning tests tend to be very sensitive to reproducing pain. In addition, the muscles of the buttocks and the posterior thigh need to be fully palpated looking for areas of tightness that may reproduce the pain.
Treatment will then need to address the source of the problem. If it is lumbar disc herniation, for example, treatment would include relieving compression on the nerve root, via chiropractic manipulation, exercise and pain management. Once the pain is under control, then looking at making biomechanical changes, either through specific exercises or creating new movement patterns, can help to prevent further injury down the road. Make sure to discuss with your healthcare provider options for treatment, regardless of the source of the problem.
This sums up our series on knee pain. Chiropractors can definitely diagnosis and treat most knee injuries and if we can’t treat it, we can help direct you to another professional that can. If you have questions regarding knee pain or any health issues, please contact us at MMD Chiropractic Health Centre, 905.529.2911.