Ross Hauser, MD
The questions this article’s research is going to answer are:
“Why is my knee unstable?,” and
“How did I get such a bad knee?”
The answer to both questions are simple. The supporting structures in your knee have weakened and the weakened structures have caused your knee to become loose.
Knee Instability is a problem of the entire joint
A heavily referred to and cited British study suggests that stability of the knee joint is maintained by the shape of the condyles (bones), their relationship with the meniscus and cartilage combination with passive supporting structures (the ligaments of the knee).1 That sounds obvious, however the core message is that stability of the knee joint is maintained by the entire knee working in concert. This concept is easily lost during a physical examination by doctors who see a torn meniscus and want to operate without realizing the damage to the bone, articular cartilage and ligaments the removal of the meniscus can cause. This is discussed at length in my article on meniscus repair without surgery.
Anatomy of knee instability
The knee condyles (medial for the middle and lateral for the outside) are bony structures that sit in the bottom of the thigh bone in the knee joint that assist in keeping the knee from hyperextending (bending too far.) The medial condyle is larger bone structure because it bears more weight. As we age, and a lifetime’s stress impact our knees, these bones wear away. Their degeneration has been clearly associated with meniscus degeneration.
The meniscus is the cartilage padding that acts as a shock absorber. When it is damaged, the protective articular cartilage that covers the thigh and shin bones are now stressed. What we have here is the beginnings of bone-on-bone knee. Meniscal and articular cartilage generation factors working against each other.
The above process is a multi-fold attack on knee stability.
- First the boney structure that prevent excessive movement wear away causing excessive or hypermobile movement.
- That hypermobility as well as surface pressure (impact loads of our body weight on our knees) cause meniscus damage, the meniscus damage causes articular cartilage damage.
So the simple understanding is – knee stability is maintained by the the shape of the condyles and menisci, and knee instability occurs when these structures suffer degenerative wear and tear or osteoarthritis. Now it gets worse, let’s introduce ligament laxity or ligament damage to the knee instability equation.
So now we have an osteoarthritic effect on the knee. Back to the paper cited above. The four major ligaments of the knee are: the famous anterior cruciate ligament (ACL), the posterior cruciate ligament (PCL), the medial collateral ligament (MCL), and the lateral collateral ligament (LCL).
The medial collateral ligament and posterior cruciate ligament are attached to the medial condyle, the lateral collateral ligament is attached to the lateral condyles. Now we have ligaments that are compromised by the bone degeneration and begin to loose their characteristic tautness because their bone attachments are degenerating.
Conversely, working backwards in a different patient scenario, it is instability in these ligaments that may have started the degenerative cascade of the condyles and menisci. Wear and tear, past impact injuries, everything in the knee affects the ligaments and the ligaments effect everything in the knee.
Knee ligament instability
Sports medicine doctors in German suggest that when dealing with knee instability in patients doctors should be wary that “the interpretation of multidirectional knee laxity (the knee overextends in multiple directions) is complex and suggests the necessity for individualized care of knee diseases and injuries.”2 What they are saying is let’s get a good physical examination and look at the knee. Please see my article Is My MRI Accurate? This includes looking for ligament laxity.
The following studies demonstrate how important the ligaments are to the stability of the knee, and when compromised will result in subluxation (misalignment or dislocation) of the tibia and femur of the knee.
In the first study concerning posterior cruciate ligament laxity, the researchers note, “Knees with underlying physiologic cruciate ligament laxity had the greatest lateral tibial plateau subluxation.” In other words when the ligaments were compromised the knee became misaligned – displaced. 3
The second study reporting on anterior cruciate ligament laxity states, “After anterior cruciate sectioning alone, both the lateral and medial tibial condyles displaced (subluxed) anteriorly.”4
In other words a partial tear of the ACL resulted the condyles being displaced. See above the medial collateral ligament and posterior cruciate ligament are attached to the medial condyle, the lateral collateral ligament is attached to the lateral condyles. And again concerning the ACL, the third research team reports, “Significant increases in internal rotation occurred in seven knees when only the anterior cruciate ligament had a partial tear.” 5
The subject of ligament damage and joint instability is covered at length in my article on this website.
Knee cap instability
Patellofemoral subluxation is one of the most common knee problems seen. The kneecap is not tracking properly (staying in the groove in the femur), and often times tracks laterally (wanders to the side). Sometimes recurrent knee cap instability may require surgical intervention as suggested by structural anatomical defects, i.e., under developed bones especially in children in adolescents.
Wear and tear injuries, which is the focus of this article, are increased tibial tubercle–trochlear groove distance (the knee cap is floating away from the joint), and insufficiencies in the medial retinacular structures (medial patellar retinaculum tendon damage).
Again, traditional medicine likes to treat this condition with surgery. One author states, “Repair of the medial patellofemoral ligament in cases of patellar dislocation has considerably lowered the incidence of recurrent instability.” 6 The author goes on to discuss various surgical procedures for patellar subluxation, even arthroscopic debridement if arthritis is found.
Surgery, however, means cutting and removing. And cutting through important knee structures will eventually lead to more instability and degeneration of the joint. This is confirmed by research that says the surgery to correct the instability is a leading cause of instability. “Medial patella subluxation is a disabling condition typically associated with previous patellofemoral instability surgery.” 7
“Nonoperative treatment, such as focused physical therapy and patellofemoral stabilizing brace, is often unsuccessful.”8
Prolotherapy, on the other hand, can be utilized as a non-surgical option. Prolotherapy injections to the medial side of the patella, to strengthen the attachment of the vastus medialis to the patella, will pull the patella back into the groove. Comprehensive Prolotherapy will also be given to all of the unstable ligaments and structures of the knee for complete healing of the knee.
Please also see our article on Patellofemoral Instability or Patellofemoral Pain Syndrome
Comprehensive Prolotherapy used in some cases with Platelet Rich Plasma Therapy and Stem Cell Therapy works at the root of the problem, the ligament or soft tissue damage. A series of injections are placed at the tender and weakened areas of the affected structures of the knee. These injections contain a proliferant to stimulate the body to repair and heal by inducing a mild inflammatory reaction. The body heals by inflammation, and Prolotherapy stimulates this healing. The localized inflammation causes healing cells to arrive at the injured area and lay down new tissue, creating stronger ligaments and rebuilding soft tissue. As the ligaments tighten and the soft tissues heal, the knee structures function normally rather than subluxing and moving out of place. When the knee functions normally, the pain goes away.
Watch this video
1 Kakarlapudi TK, Bickerstaff DR. Knee instability: isolated and complex.Western Journal of Medicine. 2001;174(4):266-272.
2 Mouton, C., Seil, R., Meyer, T. et al. Combined anterior and rotational laxity measurements allow characterizing personal knee laxity profiles in healthy individuals Knee Surg Sports Traumatol Arthrosc (2015) 23: 3571. doi:10.1007/s00167-014-3244-6
3. Noyes FR, Stowers SF, Grood ES, Cummings J, VanGinkel LA. Posterior subluxations of the medial and lateral tibiofemoral compartments. An in vitro ligament sectioning study in cadaveric knees.Am J Sports Med 1993 May-Jun;21(3):407-14.
4. Noyes FR, Grood ES, Suntay WJ. Three-dimensional motion analysis of clinical stress tests for anterior knee subluxations. Acta Orthop Scand 1989 Jun; 60(3):308-18.
5. Lipke JM, Janecki CJ, Nelson CL, McLeod P, Thompson C, Thompson J, Haynes DW. The role of incompetence of the anterior cruciate and lateral ligaments in anterolateral and anteromedial instability. A biomechanical study of cadaver knees. J Bone Joint Surg Am. 1981 Jul; 63(6):954-60.
6. Boden BP, Pearsall AW, Garrett WE Jr, Feagin JA Jr.Patellofemoral Instability: Evaluation and Management. J Am Acad Orthop Surg.1997; 1(5): 47-57.
7. McCarthy MA, Bollier MJ. Medial Patella Subluxation: Diagnosis and Treatment. Iowa Orthop J. 2015; 35: 26–33.